Abstract:

Developing a superior heterostructured composite, optimizing performance through synergies from complementary advantages in diverse materials, remains an ongoing challenge. The rise in organic contaminants in freshwater bodies possesses a major threat to human health. Various dyes such as Rhodamine B, Eosin Y and Methylene Blue are found in excess concentration due to industrial usage and their removal is important for environmental remediation and contaminant-free water. In this study, we report synthesis and fabrication of Bi2MoO6/g-C3N4 (BM/CN) composite photocatalyst and Rhodamine B photodegradation studies. The composite photocatalysts have been characterized using XRD, TGA, FT-IR, UV–Vis, TRPL, SEM, TEM, XPS, electrochemical, and BET studies over g-C3N4, Bi2MoO6, and Bi2MoO6 (10–40 wt%) supported on g-C3N4 photocatalysts. The photocatalytic studies are performed using various composite photocatalysts of BM/CN show 30%-Bi2MoO6 supported on g-C3N4 (30BM/CN) exhibits maximum visible light activation for dye degradation with 3.6 and 2.4-fold higher rate of degradation than bare g-C3N4 and Bi2MoO6, respectively. Higher surface area, broad light absorption, enhanced lifetime, lower charge transfer and higher transient photocurrents of the composite photocatalysts compared to g-C3N4 and Bi2MoO6. Moreover, study is aided with scavenger tests to support the proposed mechanism.The increased photoactivity of 30BM/CN is due to the synergistic interplay of improved charge generation and a reduction in the electron-hole (e−/h+) recombination rate. 

Abstract:

The utilization of the dielectric barrier discharge (DBD) plasma process presents a promising avenue for transforming carbon dioxide (CO2) into valuable compounds. In this research, we explore the integration of DBD plasma with a NiOx/γ-Al2O3 catalyst to amplify the efficiency and selectivity of CO2 conversion into carbon monoxide (CO). A series of NiOx-loaded on γ-Al2O3 catalysts were synthesized through wet impregnation and employed in the DBD plasma reactor. The synergy between non-thermal plasma and NiOx/γ-Al2O3 resulted in a significant enhancement in CO2 conversion, particularly demonstrating a notable increase in the energy content of produced carbon monoxide (CO). Enhanced conversion rates and selectivity were observed. Notably, the NiOx/γ-Al2O3 catalyst with a 15wt% loading exhibited the highest CO2 conversion of approximately ~ 9% at an applied voltage of 22 kV, accompanied by an energy efficiency of 1.13 mmol kJ-1. This study provides a comprehensive analysis of the impact of plasma-catalyst coupling on CO2 conversion into CO, showcasing the potential of hybrid DBD reactor systems for large-scale CO2 conversion and contributing to sustainable and value-added fuels production. The superior performance of the hybridized system is attributed to enhanced charge deposition and modified gas-phase chemistry resulting from the integration of the catalyst. Furthermore, we employed BOLSIG + software to calculate the mean electron energy and electron energy distribution function for different packing conditions, enhancing our understanding of the system's behavior and contributing valuable insights to the overall study.

Abstract:

The rational design of nitrite sensors has attracted significant research interest due to their widespread use and the associated risks of methemoglobinemia and carcinogenicity. The undisclosed nitrite sensing performance of the spinel cobaltite MnCo2O4 (MCO) prepared by an oxalate-assisted coprecipitation method has been reported in this study. Spectroscopy and microscopy investigations revealed the formation of uniform MCO nanorods with a high aspect ratio. The electrocatalytic nitrite oxidation at MCO-coated GCE (MCO/GCE) indicated the promising performance of the synthesized material for nitrite sensing. MCO/GCE detects nitrite in a concentration range of 5 µM to 3 mM and has an LOD of 0.95 µM with a higher sensitivity of 857 μA mM−1 cm−2 in a response time of 4 s. In MCO, the mixed-valence states of Co2+/Co3+ confer a high electrical conductivity and higher valent redox couples of Mn and Co impart remarkable electrocatalytic activity towards nitrite oxidation. MCO spinel undergoes facile and ultrafast faradaic reactions to mediate nitrite oxidation. Additionally, the mesopores of MCO nanorods facilitate the rapid diffusion of electrolyte and nitrite ions. Employing the electrode in sensing nitrite in milk, lake, and tap water samples further validates its potential application in real-life testing. MCO spinel nanorods showcase promising scope for utilization in the electrochemical sensing of nitrite and inspire further exploration of transition metal oxide-based mixed spinel materials. 

Abstract:

This study describes the synthesis of amino-functionalized carbon nanoparticles derived from biopolymer chitosan using green synthesis and its application towards ultrasensitive electrochemical immunosensor of highly virulent Escherichia coli O157:H7 (E. coli O157:H7). The inherent advantage of high surface-to-volume ratio and enhanced rate transfer kinetics of nanoparticles is leveraged to push the limit of detection, without compromising on the selectivity. The prepared carbon nanoparticles were systematically characterized by employing CO2 -Thermal programmed desorption (CO 2 -TPD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible (UV-visible), and transmission electron microscopy (TEM). The estimated limit of detection of 0.74 CFU/mL and a sensitivity of 5.7 ((ΔR ct /R ct )/(CFU/mL))/cm 2 in the electrochemical impedance spectroscopy (EIS) affirms the utility of the sensor. The proposed biosensor displayed remarkable selectivity against interfering species, making it well-suited for real-time applications. Moreover, the chitosan-derived semiconducting amino-functionalized carbon shows excellent sensitivity in a comparative analysis compared to highly conducting amine-functionalized carbon synthesized via chemical modification, demonstrating its vast potential as an E. coli sensor.

Abstract: 

Sustainable energy harvesting has emerged as a frontier research area and relentless efforts are being put in to tackle the tenacious issues of global warming and energy crisis. Photoelectrochemical (PEC) water splitting is regarded as a promising technology to produce H2. In this study, we report facile fabrication of ZnS modified SrTiO3/Bi2S3 (STO) heterojunction photoanode for PEC water splitting. Ternary heterojunction photoanode was fabricated using sol-gel followed by SILAR methods. Coupling of wide band gap STO with narrow band gap Bi2S3 photosensitizer extends the absorption edge while the ZnS passivation layer improves electrode stability by preventing direct contact of Bi2S3 with electrolyte and providing an active energy state for facile charge transfer to improve charge separation. Decreased rate of recombination and elongated lifetime of photogenerated charge carriers resulted in enhanced charge carrier dynamics. STO/Bi2S3/ZnS photoanodes displayed a photocurrent density (J) of 1.89 mA.cm-2 at 1.23 V vs RHE and HC-STH of 1.19% at 0.42 V vs RHE in neutral medium while the corresponding values in basic medium were J = 5.08 mA cm-2 at 1.23 V RHE and HC-STH 4.8% at 0.71 V vs RHE; considerably higher than bare STO and binary STO/Bi2S3 electrodes. The superior performance in basic medium could be attributed to the presence of hole scavengers. The improved photostability >3000 s was attributed to ZnS deposition. To better under the role of hole scavengers the quantification of O2 and H2 was undertaken. 

Abstract: 

Fairy chemicals (FCs), such as 2-azahypoxanthine (AHX), are a potential new class of plant hormones that are naturally present in plants and produced via a novel purine metabolic pathway. FCs support plant resilience against various stresses and regulate plant growth. In this study, we developed a four-step method for synthesising AHX from 2-cyanoacetamide, achieving a good yield. Oxime was obtained from 2-cyanoacetamide via the oximation reaction. Cascade-type one-pot selective Pt/C-catalysed reduction of oxime, followed by a coupling reaction with formamidine acetate, yielded intermediate 5-amino-1H-imidazole-4-carboxamide (AICA). For the synthesis of AICA from oxime, we used modern fine bubble technology, affording AICA in 69% yield. Subsequently, we synthesised 4-diazo-4H-imidazole-5-carboxamide (DICA) from AICA via the diazotisation reaction. Notably, the synthesis of DICA from AICA was achieved, and the stability of previously known less stable DICA in the solid state was confirmed. Finally, PhI(OAc)2 (0.5 mol%) catalysed the intramolecular cyclisation of DICA in the green solvent water to yield AHX (overall yield of 47%). This study's innovative techniques and substantial discoveries highlight its potential influence and significance in FCs science, thereby establishing a new standard for subsequent research.

Abstract

E-Glass/epoxy prepregs are undisputedly a great advancement in processing and fabrication technology. They offer immense advantages over conventional composite manufacturing processes in terms of waste reduction and efficient manufacturing times. These prepregs are used in several industries including but not limited to automobile, construction, defence and aerospace. Their versatility and wide applicability however is shadowed by intricate storage and handling requirements. Prepregs usually need to be stored at below freezing temperatures and hence lose their chemical integrity during transportation if not handled properly leading to a lot of wastage and scrap generation. Therefore, it is essential to develop a rigorous regime in order to determine the shelf-life and usability of these prepregs. Hereby, we report an extensive experimental design for assessing shelf-life of commercially available prepregs using techniques like DSC and IR and corelating the findings with mechanical data. The degree of pre-cure increased to 30% as a result of exposure to moisture over prolonged time and a substantial decrease in mechanical strength was observed. The shelf-life was found to be about 7 weeks and a strong agreement between analytical and mechanical data was observed.

Abstract

The present work studied the decomposition of isopropyl alcohol (IPA), widely used in chemical industries and households, in a packed-bed dielectric barrier discharge (DBD) plasma reactor. Metal oxide (MOx) coated on γ-Al2O3 (M = Cu, Mn, Co) was utilized for packing. The plasma-packed mode was a likely alternative to the conventional removal techniques, as it aids the conversion of dilute concentrations of IPA to CO and CO2 at ambient conditions (room temperature and atmospheric pressure). The mean electron energy calculations suggest that electrons with higher energy are generated when the discharge zone is packed with catalysts. When comparing IPA conversion (input concentration of 25 ppm) for no packing mode and MOx/γ-Al2O3 coupled plasma mode, the latter method enhances conversion to greater than 90% at an applied voltage of 18 kV. Also, MOx/γ-Al2O3 showed the highest selectivity to CO2 (70%) compared to plasma-only mode (45%). The metal-oxide layer provides the necessary catalytic surface facilitating the oxidation of IPA to COx through active oxygen species or the interaction of surface hydroxyl groups. The use of MOx/γ-Al2O3 resulted in about 90% carbon balance and reduced ozone generation, demonstrating the significance of integrating metal oxide to achieve efficient conversion and maximal selectivity towards the desired products. 

Abstract

The requirement of green, sustainable, and prudent chemical procedures is one of the bottlenecks in synthetic organic chemistry. Nanostructured materials have the promise to fill the gap between homogeneous and heterogeneous catalysis and can offer benefits without compromising the selectivity in forming the desired products. Advancement of sustainable and green chemical processes under environmental benign conditions is one of the immense interests in modern organic chemistry. Significantly, the hydrogenation of nitroarenes is one of the most important useful catalytic processes in the fine and bulk chemical industry. The most recent advancement of catalysts with supported metal nanoparticles has prompted their enormous accomplishments in the course of the most recent years, provoking their noteworthy applications as “standard” catalysts. Currently, this topic has gotten a lot of consideration. However, despite the fact that support materials have a great diversity in the catalysts for the reactions and modifications, a systematic rationalization of the field is lacking. In this review, we cover and categorize the recent progress in support materials tuning strategies to enhance catalytic performance for the hydrogenation of nitroarenes. Also, importance of support materials in the heterogeneous catalytic hydrogenation of nitroarenes is discussed. 

Abstract

Removal of Arsenic, a potent carcinogen from aqueous environments is imperative to ensure the provision of potable water and to mitigate the risks associated with its exposure. In this study, we explore a composite based on biochar derived from coconut-shell loaded with Cerium Oxide for the removal of Arsenic (As(V)) by adsorption. The synthesized adsorbent combines the characteristic high specific surface area of carbon materials with high adsorption affinity of CeO2 towards Arsenic to create a synergistic effect. Various parameters such as initial concentration, adsorbent dosage, presence of coexisting anions etc., were investigated to determine the kinetics and thermodynamics of adsorption. The effect of initial pH on the adsorption was also investigated and maximum removal efficiency of around 99 % was observed. A very high adsorption capacity was observed and highlighting the genesis of a highly effective adsorbent for the removal of As(V) incorporating an inexpensive and ecologically acceptable approach. 

Abstract

Zero-dimensional hybrid copper(I) halides (HCHs) are attractive due to their interesting photoluminescence (PL) properties and the high abundance and low toxicity of copper. In this study, we report green–red dual emission from rhombic 1-butyl-1-methyl piperidinium copper bromide [(Bmpip)2Cu2Br4] microcrystals (MCs) prepared on borosilicate glass. The structure and elemental composition of the MCs are characterized by single crystal X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Interestingly, MCs prepared on an ITO-coated glass plate show an intense green emission compared to the dual emission on a bare glass or plastic substrate. Furthermore, the intensity of the green emission from the MC is enormously increased by powdering using a conductive material, suggesting the deactivation of the red-emitting state by a charge transfer interaction with the conductor. These findings open a new strategy to suppress the self-trapping of excitons by longitudinal optical phonons and control the dual emitting states in HCHs. 

Abstract

Ground granulated blast furnace slag (GGBS) is a primary industrial waste product of iron production, and its improper disposal has been a serious environmental problem. This study aims to modify the GGBS using oxalic acid (GGBS-Ox) for the adsorption of tetracycline (TC) from an aqueous solution. GGBS-Ox was synthesized and characterized via FTIR, XRD SEM, XPS, BET, and DLS. The effects of process parameters, involving initial solution pH, stirring speed, and contact time, are evaluated by utilizing response surface methodology (RSM), artificial neural network (ANN), and random forest (RF) based models. The experimental results indicate that the removal efficiency of TC is significantly affected by the initial pH of the solution. The RSM, ANN, and RF models accurately simulated the experimental data, as indicated by the high coefficient of determination (R2), which was 0.98, 0.95, and 0.98, respectively. Additionally, kinetics, isotherm, and thermodynamic models were evaluated for the adsorption of TC onto GGBS-Ox. The findings of this study demonstrated the utilization of GGBS-Ox as an efficient and sustainable adsorbent for the treatment of TC and can be considered as a potential adsorbent for wastewater treatment. 

Abstract

Emerging contaminants in wastewater are one of the growing concerns because of their adverse effects on human health and ecosystems. Adsorption technology offers superior performance due to its cost-effectiveness, stability, recyclability, and reliability in maintaining environmental and health standards for toxic pollutants. Despite extensive research on the use of traditional adsorbents to remove emerging contaminants, their expensiveness, lack of selectivity, and complexity of regeneration remain some of the challenges. Industrial wastes viz. blast furnace slag, red mud, and copper slag can be used to develop efficacious adsorbents for the treatment of emerging contaminants in water. Advantages of the use of such industrial wastes include resource utilization, availability, cost-effectiveness, and waste management. Nevertheless, little is known so far about their application, removal efficacy, adsorption mechanisms, and limitations in the treatment of emerging contaminants. A holistic understanding of the application of such unique industrial waste-derived adsorbents in removing emerging contaminants from water is need of the hour to transform this technology from bench-scale to pilot and large-scale applications. This review investigates different water treatment techniques associated with industrial waste-based adsorbents derived from blast furnace slag, red mud, and copper slag. Besides, this review provides important insights into the growing trends of utilizing such novel types of adsorbents to remove emerging contaminants from water with an emphasis on removal efficacy, controlling measures, adsorption mechanisms, advantages, and limitations. The present timely review brings the current state of knowledge into a single reference which could be a strong platform for future research in understanding the latest advancements, decision making, and financial management related to the treatment of wastewater using industrial waste-based adsorbents.

Abstract

Photoelectrochemical water splitting has been envisaged as a promising green technology for efficient solar-to-fuel conversion. Graphitic carbon nitride (g-C3N4 ) demands prime focus amongst the emerging class of potential 2D materials for energy harvesting and storage on account of its high chemical/thermal stability and metal-free nature. The unique characteristics of the material enables its application both as a photocathode or photoanode. However, the low photocurrent density of pristine g-C3N4 curbs its possible commercial application. Considerable attempts to modify the electrodes via nano-structuring, heteroatom doping, heterojunction formation, etc. are in progress. The current review offers insight into the potential and limitations of g-C3N4 as a photoanodic/cathodic material.

Abstract

Developing an efficient photocathode system from earth abundant materials is essential for effectual Photoelectrochemical (PEC) water splitting. Charge transfer between heterojunctions is important in fabricating a novel photocathode, keeping cost-effectiveness, abundance, and PEC performance in mind. The p-type narrow band gap photocathode, CuO (Eg = 1.5 eV) synthesized by hydrothermal method, was decorated with Sb2S3 Nanospheres (NSs) by adopting a facile chemical bath deposition (CBD) procedure to fabricate CuO/Sb2S3 NSs heterojunction. Fabricated heterojunction showed better PEC performance contrary to bare CuO, improvement in photocurrent density CuO/Sb2S3 NSs (J = -1 mA.cm-2) than CuO (J = -0.3 mA.cm-2) photoelectrode at 0 VRHE  in 0.5 M Na2SO4 (pH 6.85) is due to enhanced charge carrier generation/separation. The photostability of CuO/Sb2S3 remains intact for 2.5 h with no degradation in photocurrent density. Sb2S3 works as a sensitizer, diminishing the recombination rate of the e-/h+ in CuO/Sb2S3 NSs. UV-Visible and photoluminescence(PL) emission spectra results suggested CuO/Sb2S3 enhanced absorption spectrum and reduced rate of recombination. Electrochemical impedance spectroscopy studies show less charge transfer resistance for CuO/Sb2S3 NSs than CuO. This finding will pave new path in developing novel photocathodic material configurations and heterojunction with Cu-based binary oxides/chalcogenides for solar harvesting. 

Abstract

Detecting gram -ve bacterial colonies is crucial in addressing the clinical challenges associated with chronic wounds and delayed healing. These bacteria can exacerbate wound conditions, hindering natural healing and potentially leading to infections. The electrochemical sensing platform presented in this study serves as a valuable tool for healthcare professionals to make timely and targeted treatment decisions. Towards this, we developed a cost-effective electrochemical sensing platform leveraging the TLR4/MD-2 complex to detect gram -ve bacterial colonies. Our biosensors were meticulously fashioned using Polyaniline (PANi) and Hollow-Polyaniline (HPANi) nanofibers. Notably, the HPANi-based sensors, owing to their distinctive hollow structure, facilitated amplified responses under comparable experimental conditions compared to PANi-based counterparts. The designed sensing platform demonstrated exceptional accuracy in identifying Escherichia coli (gram -ve), showcasing a theoretical detection limit of 0.215 CFU/mL for PANi and a remarkably improved 0.14 CFU/mL for HPANi. These sensors displayed outstanding selectivity for gram -ve bacteria, even amidst gram +ve bacteria and fungi. Moreover, our platform demonstrated remarkable sensitivity, yielding 3.04 ((ΔR/R)/CFU/mL)/cm² for the HPANi-based sensor, surpassing the performance of the PANi-based sensor at 1.98 ((ΔR/R)/CFU/mL)/cm². 

Abstract

Bacterial biofilms in chronic wounds are primarily responsible for delayed wound healing and affect a person’s life quality. A patient’s recovery depends on the treatment based on the speedy diagnosis of the wound or bacteria responsible for biofilm formation. Identification plays an essential role in the best recovery of a patient, and electrochemical techniques are best suited. In this work, we utilized the cost-effective and in-house developed carboxylic-terminated carbon paste electrode’s surface immobilized with TLR-4 to identify gram-ve bacteria, i.e., E.coli. A miniaturized electrochemical cell was used to accommodate these electrodes, which also helped in reducing sample wastage and improving the detection limit. The fabricated electrodes detected E.coli with a very low detection limit of 0.13 CFU/mL. When tested with nonspecific bacteria and fungi, the proposed platform demonstrated excellent specificity and selectivity towards gram -ve bacteria and the mixture of both gram +ve/-ve bacteria and fungi. The bioelectrodes stored for more than two weeks were tested on various days, and the results indicated an excellent shelf-life for the proposed platform. 

Abstract

The comprehensive study on the impact of different synthesis techniques on the structural, electrical, and photocatalytic properties of perovskite ferroelectric ceramics K0.5Na0.5NbO3 (KNN). The solid-state reaction and hydrothermal methods are used to prepare the KNN ceramics, and the effects of grain size on the physical characteristics these ceramics are examined. The KNN-S prepared by solid-state method have significantly larger grain size as compared to that for KNN-H prepared by hydrothermal method. Furthermore, the KNN-S is found to exhibit higher dielectric, piezoelectric and ferroelectric properties as compared to KNN-H. On the other hand, the increased photocatalytic activity is observed in KNN-H as compared to KNN-S. As compared to the hydrothermal synthesis, the solid-state synthesis causes an increase in the relative dielectric permittivity from 2394 to 3286, remnant polarization from 15.38 to 20.41 μ μC/cm2, planer electromechanical coupling factor from 0.19 to 0.28 and piezoelectric coefficient  from 88 to 125 pC/N. The KNN-S ceramics are also found to have a lower leakage current density, and higher grain resistance than KNN-H ceramic. The enhanced photocatalytic activity of KNN-H is attributed to relatively smaller particle sizes. The KNN-S and KNN-H samples are found to have degradation efficiencies of RhB solution of 20% and 65%, respectively. The study highlights the importance of synthesis methods and how these can be exploited to tailor the dielectric, piezoelectric and photocatalytic properties of KNN. 

Abstract

Engineering low-cost and efficient materials for sensing Hydrazine (HA) is critical given the adverse effects of high concentrations on humans. We report an efficient electrode made up of rod-shaped Co3O4/g-C3N4 (Co3O4/GCN) coated fluorine doped tin oxide as a desirable electrode for the detection of HA. GCN is synthesized by thermal decomposition of melamine, Co3O4, and the heterostructure is grown by a hydrothermal process. The as-prepared materials were characterized by using spectroscopic and microscopic techniques. The voltammetric studies showed that HA can be oxidized at a lower onset potential of 0.24 V vs. reference Ag/AgCl, and the composite yielded a significantly enhanced oxidation peak current than the pure components because of the high electrocatalytic activity and the synergy between Co3O4 and GCN. By employing chronoamperometry, the proposed sensor can detect HA in a wide range with a high sensitivity of 819.52 µAmM-1cm-2 and a detection limit of 3.14 µM. The high conductivity of Co3O4, enhanced electroactive surface area, the rich redox couples of Co2+/Co3+, and the additional catalytic sites from GCN are responsible for the high performance of the heterostructure. 

Abstract

The rise in demand for biomass as a renewable energy source is being seen as an alternative energy source to conventional fossil fuels. Blending of biodiesels and bioethanol in gasoline is the initial step towards complete utilization of biomass fuels. Glycerol is a byproduct generated in vast quantities during biodiesel production. Glycerol on further oxidation can produce several value-added products in conjunction with hydrogen (H2) through photo-/electrocatalysis (PEC/EC). The valuable products from glycerol include 1,3-dihydroxyacetone, glyceraldehyde, tartronic acid, formic acid, and glyceric acid. Glycerol can be used as a feedstock in PEC/EC cells along with water. An intriguing strategy unfolds by combining the oxidation of biomass-derived compounds at the anode with the hydrogen evolution reaction taking place at the cathode, all contained within a biomass electrolysis or photo-reforming reactor. This approach allows for the simultaneous production of high-value chemicals and hydrogen, while minimizing energy consumption and reducing CO2 emissions. This review seeks to integrate essential insights into photo and electro-assisted catalysis, with the objective of offering a holistic comprehension of the overall reaction mechanisms involved in the photo-/electrocatalytic oxidation of glycerol. At the same instance, various transition metal-based photo-/electrocatalysts for glycerol valorization are reviewed and discussed in great details. Moreover, this evaluation carefully examines the potential regarding the obstacles and possibilities in the advancement of photo-/electrocatalytic glycerol oxidation, aligning with the future demands for sustainability in the global energy landscape. 

Abstract

In this report, CuBi2O4 and CuBi2O4/MnO2 are synthesized using coprecipitation and hydrothermal methods respectively. CuBi2O4/MnO2 has been extensively used for the electrochemical detection of hydroxylamine. CuBi2O4 and CuBi2O4/MnO2 are well characterized by XRD, XPS, FESEM to reveal the structural and morphological features of the material. Electrochemical measurements like CV, chronoamperometry, impedance is studied to reveal the electrochemical behavior of CuBi2O4/MnO2 towards hydroxylamine. Stability, reproducibility and interference studies are performed to reveal the suitability of CuBi2O4/MnO2 as an electrode material for electrochemical detection of hydroxylamine.

Abstract

Chronic wounds caused due to bacterial biofilms are detrimental to a patient, and an immediate diagnosis of these bacteria can aid in an effective treatment, which is still an unmet clinical need. An instant and accurate identification of bacterial type could be made by utilizing the Toll-Like Receptors (TLRs) combined with Myeloid Differentiation factor 2 (MD-2). Given this, we have developed an electrochemical sensing platform to identify the gram-negative (gram-ve) bacteria using TLR4/MD-2 complex. The nonthermal plasma (NTP) technique was utilized to functionalize amine groups onto the carbon surface to fabricate cost-effective carbon paste working electrodes (CPEs). The proposed electrochemical sensor platform with a specially engineered electrochemical cell (E-Cell) identified the Escherichia coli (E. coli) in a wide linear range of 1.5×10° - 1.5×106 C.F.U./mL, accounting for a very low detection limit of 0.087 C.F.U./mL. The novel and cost-effective sensor platform identified gram-ve bacteria predominantly in a mixture of gram positive (gram+ve) bacteria and fungi. Further, towards real-time detection of bacteria and point-of-care (PoC) applications, the effect of the pond water matrix was studied, which was minimal, and the sensor could identify E. coli concentrations selectively, showing the potential application of the proposed platform towards real-time bacterial detection. 

Abstract

We employed a solvothermal and thermal pyrolysis approach to prepare a heterojunction of oxide perovskite (Bi2MoO6) dispersed on polymeric carbon nitride (PCN) sheets. The introduction of Bi2MoO6 particles onto PCN sheets improved the light absorption characteristics of the Bi2MoO6/PCN heterojunction. As synthesized Bi2MoO6/PCN heterojunction exhibited a larger surface area of 24.5 m2/g, compared to the individual Bi2MoO6 (18.2 m2/g) and PCN (7.3 m2/g), respectively. This enhanced surface area provided newer catalytic sites for the heterojunction. The resulting heterojunction was employed as a photocatalyst for the reduction of a series of toxic mono, di, and tri-nitrophenols, namely 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4,6-trinitrophenol, into industrially important amino phenols. By utilizing visible light irradiation and NaBH4 as a reducing agent, the Bi2MoO6/PCN photocatalyst demonstrated accelerated reduction kinetics than individual catalysts. This enhanced performance was attributed to the larger surface area and suppressed charge carrier recombination of Bi2MoO6/PCN heterojunction, which facilitated efficient photoreduction. Overall, this study sheds light on the promising application of oxide perovskite/PCN heterojunction systems in photocatalytic reduction reactions, offering a viable solution for mitigating emerging pollutants. 

Abstract

Hydrogen has tremendous potential as a sustainable energy source for the future. Unassisted photoelectrochemical water splitting is a promising approach to producing hydrogen fuel from sunlight and water. To economically produce hydrogen, efficient, low-cost, environmentally friendly, and long-term stable photocathodes and photoanodes are needed. In this study, we have fabricated CuBi2O4 (CBO) photocathodes using drop-casting, hydrothermal, and electrodeposition methods. The resulting photocathodes have nanoparticle, nanosphere, and flake-like structures. The drop-casted CBO (D-CBO) exhibits an impressive onset potential of 0.9 V with a photocurrent density of −3.0 mA·cm–2 at 0 V vs reversible hydrogen electrode (RHE) and a solar to hydrogen (STH) efficiency of 0.61% at 0.23 V vs RHE, which is higher than hydrothermal CBO (H-CBO) and electrodeposited CBO (E-CBO). The high onset potential of the D-CBO photocathode results in a good unbiased operating photocurrent of −1.8 mA·cm–2, which is assisted by the BiVO4 (BVO) photoanode. The BVO photoanode has a photocurrent density of 1.6 mA·cm–2 at 1.23 V vs RHE. This study demonstrates hydrogen production from a BVO-CBO tandem cell and highlights the importance of photovoltage in tandem devices for overall water splitting, particularly in devices with CBO photocathodes 

Abstract

Hydrogen is gaining significant attention as a clean fuel option due to its high energy density, which can be produced through solar water splitting. In this study, S-TiO2 photocatalyst has been synthesized using the sol-gel method. Analysis revealed that cation substitution S+4 and S+6 of Ti+4 in the TiO2 lattice resulted in the formation of S=O bond and S-Ti-O bond. The S-TiO2 was then coated with BiSbS3 using the chemical bath deposition (CBD) method, followed by the deposition of FeOOH using the similar technique. The resulting photoelectrode, S-TiO2/BiSbS3/FeOOH, exhibited a photocurrent density of 4.36 mA.cm−2 at 1.23 V vs reverse hydrogen electrode and a solar-to-hydrogen efficiency of 1.31% at 0.6 V vs RHE, outperforming other electrodes. The improved photoactivity was attributed to the synergetic effect of heterojunction and cocatalyst loading. This study provides insight into the potential applications of cocatalysts in (photoelectrochemical) PEC water splitting.

Abstract

Climate change and its detrimental effects on the environment have led to an urgent need for a transition toward a fossil-free energy future. To achieve this goal, renewable energy sources, especially hydrogen, will play a crucial role. However, to make them more viable, various sectors like Power, Industrial, Mobility, etc., are looking for ways to store and transport the energy generated from hydrogen. The advancement of Power-to-X (PtX) technologies has caught attention, as it offers a solution for converting renewable energy into chemical or fuel forms that can be used in various applications and overcome the problem of storage associated with hydrogen. This concept is being looked at as a potential game-changer in the energy sector. This review focuses on two key areas within the Power-to-X (PtX) technology that holds significant potential for transitioning towards a fossil-free energy future: eFuels synthesis and Direct Air Capture (DAC) technology. efuels provide an opportunity for nations to increase energy independency or reduce greenhouse gas emissions by supplying energy-dense fuels which are miscible with conventional fossil fuels. DAC technology, on the other hand, captures Carbon dioxide (CO2) from the air and converts it into efuels. By reducing the amount of CO2 in the atmosphere, DAC technology can help to slow the effects of climate change. Overall, both eFuels synthesis and DAC technology have the potential to play a vital role in the transition toward a fossil-free energy future. They offer solutions to both stationary and mobile applications while also making a substantial reduction in greenhouse gas emissions, thereby helping to alleviate the impacts of climate change. In this paper, we intend to provide a summary on efuels synthesis, DAC, and their impact on the existing energy equipment. 

Abstract

Transition metal-catalyzed tandem reactions are highly prominent in organic synthesis. Especially, palladium-catalyzed biscarbofuctionalization of alkenes is remarkable. However, enabling this type of tandem reaction through heterogeneous catalysis is the most desirable. In this context, silica-supported Pd nanoparticles catalyzed tandem Heck followed by Suzuki coupling reaction has been developed via a dual C–C bond formation. The significance of silica support has also been examined. Excellent catalytic performance was shown by the designed catalyst and enabled the construction of dihydrobenzofurans and oxindoles in good to excellent yields and with good functional group tolerance. Despite being recycled numerous times, the catalyst maintained its catalytic efficiency. 

Abstract

Halide vacancies cause lattice degradation and nonradiative losses in halide perovskites. In this study, we strategically fill bromide vacancies in CsPbBr3 perovskite nanocrystals with NaBr, KBr, or CsBr at the organic–aqueous interface for hydrophobic ligand-capped nanocrystals or in a polar solvent (2-propanol) for amphiphilic ligand-capped nanocrystals. Energy-dispersive X-ray spectra, powder X-ray diffraction data, and scanning transmission electron microscopy images help us confirm vacancy filling and the structures of samples. The bromide salts increase the photoluminescence quantum yield (98 ± 2%) of CsPbBr3 by decreasing the nonradiative decay rate. Single-particle studies show the quantum yield increase originates from the poorly luminescent nanocrystals becoming highly luminescent after filling vacancies. Furthermore, we tune the optical band gap (ultraviolet–visible–near-infrared) of the hydrophobic ligand-capped nanocrystals by halide exchange at the toluene–water interface using saturated NaCl or NaI solutions, which completes in about 60 min under continuous mixing. In contrast, the amphiphilic ligand accelerates the halide exchange in 2-propanol, suggesting ambipolar functional groups speed up the ion-exchange reaction. The bromide vacancy-filled or halide-exchanged samples in a toluene–water biphasic solvent show higher stability than amphiphilic ligand-capped samples in 2-propanol. This strategy of defect passivation, ion exchange, and ligand chemistry to improve quantum yields and tune band gaps of halide perovskite nanocrystals can be promising for designing stable and water-soluble perovskite samples for solar cells, light-emitting diodes, photodetectors, and photocatalysts. 

Abstract

Cu-doped TiO2 with different weight percentages of Cu loading (1% to 4%) were synthesized by the sol–gel technique and characterized by powder XRD, SEM and TEM. 1 and 2 wt% Cu2+ doping, Cu -TiO2 has a major anatase phase with a minor rutile phase, and with increasing Cu loading to 3% and 4%, rutile phase increasing were observed. UV–Vis absorption spectroscopy confirmed that with Cu doping, the band gap of TiO2 decreased. PL and XPS was used to understand the optical properties and the surface elemental composition and the oxidation state of the elements of the prepared catalysts. Photocatalytic activity of synthesized materials was assessed for the visible light assisted removal of Rhodamine B and Cr (VI) individually and simultaneously. The mineralization of the pollutant was confirmed by the TOC analyzer. 3% Cu-doped TiO2 shows the highest degradation and mineralization when compared to other TiO2 materials. The radicals trapping experiments were conducted to determine the mechanism and it was found that O2–• and e- are the active radical species for the photocatalytic degradation of Rhodamine B and Cr (VI). The simultaneous removal of Rhodamine B and Cr (VI) was higher compared to the removal of individual pollutants.

Abstract

The unique and highly tunable photophysical, photochemical and photoredox properties of porphyrins contribute to their versatile applications in alternate energy generation, sensing, and therapeutic fields. The synthetic route for meso substituted porphyrins involves acid-catalysed condensation of aldehyde and pyrrole followed by oxidation. Herein, we report an environmentally benign novel approach for the synthesis of substituted tetraaryl porphyrins using acetonitrile as the solvent and Keggin type phosphovanadotungstic acid as the catalyst. The simple one-pot strategy completely avoids the usage of acidic/chlorinated solvents and expensive oxidising agents. A reasonable spectroscopic yield of around 12–39% could be obtained for various derivatives under the optimised conditions. 

Abstract

Eco-friendly carbothermal techniques were used to synthesize nanocomposites of biowaste-derived Ni/NiO decorated-2D biochar. The use of chitosan and NiCl2 in the carbothermal reduction technique was a novelty to synthesize the Ni/NiO decorated-2D biochar composite. Potassium persulfate (PS) was found to be activated by Ni/NiO decorated-2D biochar, which is thought to oxidize organic pollutants through an electron pathway designed by the reactive complexes formed between PS and the Ni/NiO biochar surface. This activation led to the efficient oxidation of methyl orange and organic pollutants. Analyzing Ni/NiO decorated-2D biochar composite before and after the methyl orange adsorption and degradation procedure allowed us to report on the process of its elimination. The Ni/NiO biochar with PS activation showed higher efficiency than Ni/NiO decorated-2D biochar composite as this material was able to degrade over 99% of the methyl orange dye. The effects of initial methyl orange concentration, dosages effect, solution pH, equilibrium studies, kinetics, thermodynamic studies, and reusability were examined and evaluated on Ni/NiO biochar. 

Abstract

The design and development of inexpensive, and extremely sensitive sensors for Hydroxylamine (HYA) are imperative due to its toxicity to animals, plants, and aquatic life. This work proposes a high-performance enzyme-free electrochemical sensor for HYA based on its oxidation on Nickel cobaltite (NCO) spinel-modified fluorine doped tin oxide (FTO) electrode. Hydrothermally grown irregularly shaped NCO nanoparticles (NPs) of size around 10 nm are characterized by XRD, XPS, UV–visible, BET, and TEM to evaluate the structural and morphological characteristics. NCO-modified FTO (NCO@FTO) electro-oxidizes HYA at a potential of 0.66 V vs. Ag/AgCl, delivering 1.7 times the current response than bare FTO. The rich catalytically active redox couples of Ni and Co, high conductivity, and high surface area of the NCO NPs contribute to the superior electrochemical response of NCO@FTO. As an amperometric sensor, NCO@FTO detects HYA in a wide range of 10 to 4000 µM concentration with a high sensitivity of 408 μA mM−1 cm−2. The sensor has a detection limit of 0.47 μM (S/N = 3), faster response of less than 3 s, excellent selectivity, and good stability. The practical feasibility of the proposed sensor is investigated by employing it in the monitoring of real samples. This study demonstrates NCO@FTO as an efficient low-cost sensor for HYA and extends the use of spinel metal oxides in bioanalysis.

Abstract

A coaxial dielectric barrier discharge (DBD) reactor was used to perform catalytic non-thermal plasma for CO2 conversion under ambient conditions. A systematic study was made to understand the role of basic oxides in activating weakly acidic CO2. For this purpose, MO/γ-Al2O3 (M = Mg, Ca, Sr, and Ba) catalysts were synthesized and integrated with the DBD reactor. The applied voltage was varied from 16 kV to 22 kV to determine the effect of applied voltage on CO2 conversion. Plasma discharge generates high-energy electrons that activate the basic oxides. Integration of basic metal oxides with the non-thermal plasma reactor resulted in a higher CO2 conversion. The adsorption of weakly acidic CO2 on the basic sites is responsible for the higher conversion of catalytic plasma reactor over plasma reactor alone. Among the basic metal oxides studied, SrO loaded γ-Al2O3 resulted in the best conversion, where CO2 conversion of ∼ 12% and energy efficiency of ∼ 1.46 mmol kJ−1 was attained at a power of 1.8 W. The concentration of O2 and O3 was measured during the reaction. The hybridized system's superior performance may be due to increased charge deposition and altered gas-phase chemistry because of catalyst integration. BOLSIG + software was used to compute the mean electron energies and electron energy distribution function for various packing conditions. 

Abstract

A set of mono and bimetallic Cu–Ni systems supported on γ-alumina catalysts were synthesized using γ-radiation instead of conventional calcination and reduction. Using a variety of characterization approaches, the structural and surface characteristics of catalysts were determined and their properties were compared with their counterparts prepared using the conventional method. The efficiency of these catalysts for the vapour phase selective hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was investigated. The catalysts prepared by γ-irradiation contain Cu in its metallic state with high dispersion. γ-Radiation is advantageous because it enables the preparation of metal-supported catalysts in a single step by avoiding post-reduction. The catalysts prepared by γ-irradiation presented a higher activity compared to the conventional catalysts. Among all, the catalysts with 10%Cu–7%Ni on γ-Al2O3 demonstrated the highest conversion (94.5%) and selectivity (97%). The enhanced activity of the γ-irradiated catalysts was mostly attributable to the existence of a high surface area and copper dispersion. The γ-irradiated catalyst showed stable activity during the time of stream analysis. The desired reaction conditions to achieve a high yield of γ-valerolactone were also optimized. 

Abstract

Bandgap-engineered inorganic and hybrid halide perovskite (HP) films, nanocrystals, and quantum dots (PQDs) are promising for solar cells. Fluctuations of photoinduced electron transfer (PET) rates affect the interfacial charge separation efficiencies of such solar cells. Electron donor- or acceptor-doped perovskite samples help analyze PET and harvest photogenerated charge carriers efficiently. Therefore, PET in perovskite-based donor–acceptor (D–A) systems has received considerable attention. We analyzed the fluctuations of interfacial PET from MAPbBr3 or CsPbBr3 PQDs to classical electron acceptors such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 1,2,4,5-tetracyanobenzene (TCNB) at single-particle and ensemble levels. The significantly negative Gibbs free energy changes  of PET estimated from the donor–acceptor redox potentials, the donor–acceptor sizes, and the solvent dielectric properties help us clarify the PET in the above D–A systems. The dynamic nature of PET is apparent from the decrease in photoluminescence (PL) lifetimes and PL photocounts of PQDs with an increase in the acceptor concentrations. Also, the acceptor radical anion spectrum helps us characterize the charge-separated states. Furthermore, the PL blinking time and PET rate fluctuations (108 to 107 s−1) provide us with single-molecule level information about interfacial PET in perovskites. 

Abstract

Developing efficient photocathodes with novel design is essential for enhancing the functioning of photoelectrodes in photoelectrochemical (PEC) water splitting. The efficiency of solar-to-fuel conversion has been proven to be improved by using a suitable structural composition to create heterostructures. Apart from surface reactions, charge transfer between heterojunction interfaces is critically important. We report the first-ever novel and rational design of a hybrid photocathode using a CuBi2O4 based absorber material with a Sb2S3 heterojunction and evenly dispersed plasmonic Au nanoparticles (NPs) sandwiched between CuBi2O4 and Sb2S3. The heterostructure comprising CuBi2O4/Sb2S3 revealed an enhanced photoactivity due to ameliorated light absorption and charge separation showing a photocurrent density of −2.25 mA cm−2 at 0 V vs. RHE at pH 6.65. The crucial dual role of sandwiched Au NPs, as an electron relay mediator, facilitates the electron transfer at the heterojunction interface. Secondly, a plasmonic sensitizer enhances light absorption and charge carrier concentration via charge injection in CuBi2O4/Au/Sb2S3. The CuBi2O4/Au/Sb2S3 photocathode displayed a remarkable photocurrent density of −3.2 mA cm−2 at 0 V vs. RHE (0.85% HC-STH at 0.45 V vs. RHE) at pH 6.65, two-fold enhancement compared to CuBi2O4 (−1.5 mA cm−2 at 0 V vs. RHE, 0.27% HC-STH at 0.3 V vs. RHE). The high-performance CuBi2O4/Au/Sb2S3 photocathode achieves the highest photocurrent and HC-STH efficiency for a heterojunction to the best of our knowledge. Our findings will pave the way for developing new photoelectrodes with metal NPs sandwiched between semiconductor heterostructures and increasing PEC performance for solar-driven PEC water splitting.

Abstract

Biogas is a renewable energy produced due to the anaerobic decomposition of plants and animals. Biogas contains a high amount of methane (CH4), carbon dioxide (CO2), and trace amounts of hydrogen sulfide (H2S). It is naturally released in the environment, and the composition varies depending on the source it is generated. The primary focus of the study is to understand the influence of H2S on CH4 and CO2 conversion during syngas production. The effect of applied voltage on biogas reforming reaction with different dielectric materials (glass beads, γ-Al2O3, ZrO2, and quartz wool) packed in a discharge zone was investigated by using a dielectric barrier discharge (DBD) non-thermal plasma reactor. The influence of gas composition and packed bed on the efficiency of the biogas reforming reaction was investigated. After that, the biogas reforming reaction with packed dielectric material was performed without H2S and subsequently with H2S (blended with N2) while keeping the residence time constant. It was observed that H2S has a significant effect on the conversion. The CH4 conversion drastically dropped from 23% (without H2S) to 9% (with H2S), and CO2 conversion dropped from 18% to 11 % at 22 kV with quartz wool packed DBD. Energy efficiency decreased from 3.12 mmol/kJ (without H2S) to 1.78 mmol/kJ (with H2S) with glass beads packed DBD. Moreover, H2S has more effect on CH4 conversion than CO2. 

Abstract

Developing cost-effective noble metal-free co-catalysts as alternatives to platinum group metals is an impeccable strategy to enhance photoelectrochemical (PEC) water splitting. In this report, we successfully fabricated CuInS2 nanosheet array-based photocathode modified with CdS and co-catalyst MoS2 in a green approach to improve water splitting under solar irradiation. The visible light absorption of the modified hybrid photocathode (CIS/CdS/MoS2) was significantly enhanced due to introducing CdS and MoS2. Photoluminescence, impedance spectroscopy, and Mott–Schottky analysis depicted improved separation of excited electron–hole pairs, minimized resistance of charge transfer, and increased excited-state charge carrier concentration, resulting in increased photocurrent. Typical results indicated that composite photoelectrodes delivered higher photocurrent (−1.75 mA/cm2 at 0 V vs RHE) and HC-STH conversion efficiency (0.42% at 0.49 V vs RHE) than those of CIS and CIS/CdS photoelectrodes. This improved PEC performance is accredited to the synergetic impact of CdS in charge generation and transfer and MoS2 as a cocatalyst with active surface sites for proton reduction. This study not only reveals the promising nature of CuInS2-based light absorber photocathodes for solar energy utilization but also recommends the use of MoS2 as a cocatalyst for the proton reduction reactions for widespread applications in solar to hydrogen conversion. 

Abstract

The development of efficient H2O2 sensors is crucial because of their multiple functions inside and outside the biological system and the adverse effects that a higher concentration can cause. This work reports a highly sensitive and selective non-enzymatic electrochemical H2O2 sensor achieved through the hybridization of Co3S4 and graphitic carbon nitride nanosheets (GCNNS). The Co3S4 is synthesized via a hydrothermal method, and the bulk g-C3N4 (b-GCN) is prepared by the thermal polycondensation of melamine. The as-prepared b-GCN is exfoliated into nanosheets using solvent exfoliation, and the composite with Co3S4 is formed during nanosheet formation. Compared to the performances of pure components, the hybrid structure demonstrates excellent electroreduction towards H2O2. We investigate the H2O2-sensing performance of the composite by cyclic voltammetry, differential pulse voltammetry, and amperometry. As an amperometric sensor, the Co3S4/GCNNS exhibits high sensitivity over a broad linear range from 10 nM to 1.5 mM H2O2 with a high detection limit of 70 nM and fast response of 3 s. The excellent electrocatalytic properties of the composite strengthen its potential application as a sensor to monitor H2O2 in real samples. The remarkable enhancement of the electrocatalytic activity of the composite for H2O2 reduction is attributed to the synergistic effect between Co3S4 and GCNNS. 

Abstract

Toluene is a common solvent used in paints, pesticides, resins, etc. Although toluene is found in low concentrations in an indoor environment, long-term exposure to it is hazardous. This research aims to study toluene oxidation in a catalyst-packed dielectric barrier discharge (DBD) reactor designed to withstand high flow rates. The DBD reactor was packed with commercially available Al2O3 first and then with Mn and Co oxide-coated Al2O3. The surface modification of Al2O3 with transition metal oxides significantly improved the reactor's performance. At a power input of 20.3 W (equivalent to 13.0 J/l), MnO2/Al2O3 efficiently decomposed 50 ppm toluene (93%), and the corresponding CO2 selectivity was 57%. The in-situ breakdown of ozone, which leads to the formation of more reactive oxidants such as atomic oxygen, appears to make MnO2/Al2O3 better among the catalysts studied. The mean electron energies and the energy electron distribution function were calculated using the BOLSIG+ program. 

Abstract

The current research is focused on the decomposition of carbon dioxide (CO2) into carbon monoxide (CO) and oxygen (O2) in a non-thermal plasma reactor using dielectric barrier discharge (DBD) at ambient conditions. Pure CO2 was injected into the DBD reactor at a flow rate of 30 mL min-1, and the voltage was varied between 16 kV to 22 kV. The filamentary micro discharges generated during plasma has a significant effect on CO2 conversion. The effect of packing materials on CO2 conversion was investigated by packing non-catalytic materials such as quartz wool, glass capillary, glass wool, and glass beads in the discharge zone of the DBD reactor. Among the studied packing materials, quartz wool exhibited a maximum CO2 conversion of 9.3 % at a discharge power of 2.0 W and specific energy input (SEI) of 4.0 J mL-1. However, glass capillary exhibited the highest energy efficiency of 1.2 mmol kJ-1 at an SEI of 3.5 J mL-1. 

Abstract

Despite being the most favorable ammonia (NH3) gas sensors, metal oxide semiconductors fail to deliver high selectivity and room temperature (RT) sensing. Tuning the metal oxide with doping is an attractive way of overcoming these disadvantages. Herein, we report Mn-doped ZnO microspheres as promising sensors for highly sensitive and selective RT sensing of NH3. ZnO and 2 wt% Mn-doped ZnO microspheres were synthesized by a low-cost and fast solution combustion synthesis, and their structure, morphology, and gas sensing properties were investigated. Mn-doping resulted in a change in the lattice parameters, an increase in the oxygen vacancies, and surface acidity of ZnO as confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Temperature programmed desorption (TPD), respectively. Mn-doped ZnO showed a response (Ra/Rg) of 20.2 in 100 ppm NH3, which is significantly higher than ZnO. The sensor showed high selectivity, three times higher than that of ZnO, and good stability. Improvement in the sensing performance of Mn-doped ZnO is attributed to the increase in the defects and surface acidity with Mn-doping. 

Abstract

In this report, copper bismuth oxide (CuBi2O4), a ternary oxide is used for the electrochemical detection of 4-nitrophenol (4-NP). 4-NP is an organic pollutant which is extremely toxic and hazardous to environment. Herein, CuBi2O4 nanorods are prepared hydrothermally followed by electrode fabrication using drop casting method. Structural, morphological studies of CuBi2O4 and electrochemical characterizations pertaining to its performance for electrochemical detection of 4-NP are performed. The electrode has displayed the sensitivity of 56.16 μA μΜ−1 cm−2 with limit of detection (LoD) of 0.61 μM. It displayed high selectivity against several organic and inorganic interferences. The feasibility of CuBi2O4 modified electrode for real water samples is tested and obtained good recovery values. The detailed mechanism involved in the electrochemical detection of 4-NP is proposed and validated with computational studies. Density functional theory (DFT) calculations are performed on the optimized molecules involved in the electrochemical detection of 4-NP confirming CuBi2O4 acting as electron donor while 4-NP as electron acceptor. Further, natural bond orbital (NBO) calculations of 4-NP show a charge of − 0.251 a.u. on -NO2 group and + 0.251 a.u. on the rest of the molecule indicating 4-NP undergoes facile nucleophilic attack. The electrostatic potential (ESP) mapping of 4-NP blue shaded regions justifies its favorable behavior towards nucleophilic attack. Apart from this, UV-Vis spectroscopy is used to study the catalytic reduction of 4-NP using NaBH4. This study reveals that CuBi2O4 is promising material for the electrochemical detection of 4-NP. Also, further modifications of CuBi2O4 can be explored for electrochemical sensing and catalytic performance. 

Abstract

This study investigates the durability and leachate behaviour of an alkali-activated fly ash (FA) as a binder to stabilise expansive soils in deep-mixing applications. To activate FA, a liquid alkali activator (LAA) to binder ratio (LAA–FA) was introduced and varied from 1.0 to 1.5. The effects on swelling–shrinkage, consolidation and unconfined compressive strength (UCS) characteristics under wetting–drying cycles (durability) were studied on deep-mixed expansive soils. Leachate studies were conducted to determine the environmental impact of alkali-activated FA. Heavy metal and sodium ion concentrations were measured in each leachate cycle. To examine the permanent microstructural and phase changes in the mixes, scanning electron microscopy (SEM) and x-ray diffraction (XRD) studies were conducted. The swelling–shrinkage behaviour of soil could be marginally controlled for LAA/FA = 1.0 and 1.25 due to heavy weight loss during the wetting–drying cycles. However, even after 12 durability cycles, the UCS of soil with LAA/FA = 1.5 retained 1.0 MPa and showed non-critical swelling–shrinkage behaviour. The heavy metals and sodium ion concentrations were in acceptable range for LAA/FA = 1.25 and 1.5. XRD and SEM studies revealed that soil treated with a binder ratio of LAA/FA = 1.5, showed high crystalline peaks and aggregated structures 

Abstract

In chronic wounds, rapid identification of the bacterial type is critical for immediate clinical assessment. A novel, cost-effective, and label-free electrochemical nanobiosensor was developed with the help of an indigenously fabricated carbon paste working electrode to rapidly identify the bacterial type. The proposed platform made use of gold nanoparticles (AuNPs) to boost electrochemical activity, and the strong affinity of boronic acid moieties for diols allowed for detection and differentiation of gram + ve and gram -ve bacteria on the same platform. A scalable and robust miniaturized Electrochemical Cell (E-Cell) designed for the developed electrodes assisted in reducing sample waste, detection time, and Limit of Detection (LOD). Within 15 min, the proposed nano biosensing platform identified Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria with an excellent recovery rate for the blind samples. Because of its size and the extra lipopolysaccharides (LPS) layer containing diols, the bioelectrode demonstrated a superior response to E. coli, effectively distinguishing it from S. aureus. Furthermore, the proposed biosensing platform demonstrated an excellent shelf-life and reproducibility with acceptable selectivity and exhibited an excellent specificity towards bacteria, making it an ideal candidate for rapid identification of the bacterial type. 

Abstract

This paper reports a facile approach for the synthesis of graphene stabilised zero valent iron (nZVI) via carbothermal reduction method using bio-waste materials. X-ray photoelectron spectroscopy confirmed the formation of nZVI, which was further supported by magnetic susceptibility measurements. The process of Cr(VI) removal was revealed by analysing nZVI/graphene before and after the Cr(VI) adsorption process. nZVI/graphene reduces Cr(VI) to Cr(III), which was adsorbed on the graphene sheet, avoiding the passivation of nZVI. Graphene provides good electrical conductivity, skeletal support, and has long-term electron releasing characteristics, which can accelerate the reduction of Cr(VI) to Cr(III) and demonstrates a quick and high removal capacity of Cr(VI) from an aquifer. The influence of Cr(VI) initial concentration, adsorbent dosages, equilibrium studies, solution pH, kinetics, adsorption isotherms, and thermodynamic parameters was also investigated. 

Abstract

Hydrogen production through solar-driven water splitting is a promising approach and an alternative to the conventional steam reforming of natural gas and coal gasification. The growing energy demand and environmental degradation through carbon-emitting fossil fuels urge a transition in the usage of non-renewable to renewable sources of energy. The photocathodes in a photoelectrochemical (PEC) water-splitting cell are essential for the direct evolution of hydrogen. Among the known photocathodes, Cu-based p-type semiconducting materials are the most promising photo-absorber materials owing to their low-cost, low toxicity, natural abundance, suitable bandgaps, and favorable band edges for reduction. Moreover, the chemical stability and the rate of recombination significantly limit the longevity, the PEC performance, and practical applicability of Cu-based photocathodes. To overcome these problems, it is critical to have a thorough understanding of the constraints, improvement strategies, and an assessment of current developments in order to construct and design highly stable and efficient photocathodes. Here, in this review we have summarized the development of Cu-based metal oxide and sulfide photocathodes with the significant operational challenges and strategies that have successfully been employed to enhance the PEC performance. Furthermore, the emphasis is placed on recent reports and future perspectives regarding emerging challenges. 

Abstract

Environmental degradation due to the carbon emissions from burning fossil fuels has triggered the need for sustainable and renewable energy. Hydrogen has the potential to meet the global energy requirement due to its high energy density; moreover, it is also clean burning. Photoelectrochemical (PEC) water splitting is a method that generates hydrogen from water by using solar radiation. Despite the advantages of PEC water splitting, its applications are limited by poor efficiency due to the recombination of charge carriers, high overpotential, and sluggish reaction kinetics. The synergistic effect of using different strategies with cocatalyst decoration is promising to enhance efficiency and stability. Transition metal-based cocatalysts are known to improve PEC efficiency by reducing the barrier to charge transfer. Recent developments in novel cocatalyst design have led to significant advances in the fundamental understanding of improved reaction kinetics and the mechanism of hydrogen evolution. To highlight key important advances in the understanding of surface reactions, this review provides a detailed outline of very recent reports on novel PEC system design engineering with cocatalysts. More importantly, the role of cocatalysts in surface passivation and photovoltage, and photocurrent enhancement are highlighted. Finally, some challenges and potential opportunities for designing efficient cocatalysts are discussed. 

Abstract

In this report, CuBi2O4/Co3O4 has been used for the electrochemical detection of glucose. Herein, CuBi2O4 nanorods and Co3O4 has been hybridized with CuBi2O4 to form CuBi2O4/Co3O4 nanocomposite hydrothermally. CuBi2O4 and CuBi2O4/Co3O4 electrodes are fabricated by using drop casting method. Structural, morphological studies of CuBi2O4/Co3O4 and electrochemical characterizations pertaining to its performance in comparison to CuBi2O4 for electrochemical detection of glucose are performed and discussed elaborately. The detailed mechanism involved in the electrochemical detection of glucose is proposed. The electrode has shown the sensitivity of 49 μA mM−1 cm−2 with a limit of detection (LOD) of 0.136 μM. DFT calculations are performed on the optimized molecules involved in the electrochemical detection of glucose confirming CuBi2O4/Co3O4 acting as electron donor while glucose as electron acceptor. Further, natural bond orbital (NBO) for charge distribution calculations and ESP mappings for the optimized molecules are performed to understand nucleophilic/electrophilic positions. This study reveals that CuBi2O4 and its modifications are promising materials for the electrochemical detection of glucose. Further, the role of Co3O4 in improving the sensitivity and electrochemical performance for detection of glucose has been discussed. 

Abstract

The development of efficient and novel p-n heterojunctions for photoelectrochemical (PEC) water splitting is still a challenging problem. We have demonstrated the complementary nature of (p-type) BiSbS3 as a sensitizer when coupled with (n-type) TiO2/CdS to improve the photocatalytic activity and solar to hydrogen conversion efficiency. The as-prepared p-n heterojunction TiO2/CdS/BiSbS3 exhibits good visible light harvesting capacity and high charge separation over the binary heterojunction, which are confirmed by photoluminescence (PL) and electrical impedance spectroscopy (EIS). The ternary heterojunction produces higher H2 than the binary systems TiO2/CdS and TiO2/BiSbS3. This ternary heterojunction system displayed the highest photocurrent density of 5 mA·cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) in neutral conditions, and STH of 3.8% at 0.52 V vs. RHE is observed. The improved photocatalytic response was due to the favorable energy band positions of CdS and BiSbS3. This study highlights the p-n junction made up of TiO2/CdS/BiSbS3, which promises efficient charge formation, separation, and suppression of charge recombination for improved PEC water splitting efficiency. Further, no appreciable loss of activity was observed for the photoanode over 2500 s. Band alignment and interfaces mechanisms have been studied as well. 

Abstract

A dielectric barrier discharge reactor (DBD) was employed as a non-thermal plasma (NTP) source for non-oxidative conversion of methane at ambient condition. The reactor was later operated as packed-bed DBD and also served with catalyst coupling. In the bed, dielectric materials (glass beads, BaTiO3) as well as some catalytic support materials (TiO2, SiO2 and γ-Al2O3 beads) were introduced in order to find out the non-catalytic reaction mechanism. Typical results indicated that the non-catalytic mode could favorably activate the strong C-H bond to produce H2 and light hydrocarbons without applying any oxidant or thermal energy. Apart from the materials property (shape, size, surface area, dielectric constant) different plasma parameters has a strong influence on the reaction performance. The existence of highest methane conversion and products yield was experimentally observed form the catalyst coupled plasma mode which could be reasonably described by their dominant catalytic surface properties. Moreover, the present reactor model found to be able enough in limiting the solid coke formation on catalyst surface. 

Abstract

Nonthermal plasma, a nondestructive, fast, and highly reproducible surface functionalization technique, was used to introduce desired functional groups onto the surface of carbon powder. The primary benefit is that it is highly scalable, with a high throughput, making it easily adaptable to bulk production. The plasma functionalized carbon powder was later used to create highly specific and low-cost electrochemical biosensors. The functional groups on the carbon surface were confirmed using NH3-temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) analysis. In addition, for biosensing applications, a novel, cost-effective, robust, and scalable electrochemical sensor platform comprising in-house-fabricated carbon paste electrodes and a miniaturized E-cell was developed. Biotin–Streptavidin was chosen as a model ligand–analyte combination to demonstrate its applicability toward biosensor application, and then, the specific identification of the target Escherchia coliO157:H7 was accomplished using an anti-E. coliO157:H7 antibody-modified electrode. The proposed biosensing platform detected E. coliO157:H7 in a broad linear range of (1 × 10–1–1 × 106) CFU/mL, with a limit of detection (LOD) of 0.1 CFU/mL. In addition, the developed plasma functionalized carbon paste electrodes demonstrated high specificity for the target E. coliO157:H7 spiked in pond water, making them ideal for real-time bacterial detection. 

Abstract

W-Mo/Mo-V/V-W co-doped TiO2 photocatalyst for the effective degradation of MB (methylene blue) dye under sunlight irradiation was successfully prepared by one-step Plasma Electrolytic Oxidation (PEO) process. The XRD, XPS, and EDS results revealed that W/Mo/V were co-doped in the TiO2 lattice. The highest redshift in the light absorption edge is recorded for the sample MV (Mo-V co-doped TiO2) with a bandgap of 2.51 eV, whereas the bandgaps for WM (W-Mo co-doped TiO2) and VW (V-W co-doped TiO2) are recorded as 2.96 eV and 2.58 eV, respectively. The co-doped photocatalysts show a typical PEO structure with a high degree of porosity favouring the dye adsorption ability. EIS, LSV, and PL analysis confirmed that the co-doped coatings pose a high degree of charge separation, suppressed charge carriers' recombination, and increased the ability to produce photocurrent. Under direct sunlight irradiation, the sample MV showed the highest photocatalytic efficiency, confirmed by MB dye degradation, then the other co-doped and undoped TiO2. This can be attributed to the synergetic effects of intense visible light absorption in the solar spectrum and the reduced charge carriers' recombination rate by acting as the trapping sites for photogenerated electrons and holes. Finally, this immobilised co-doped photocatalyst developed by the PEO process is a promising system in the quest to establish a renewable energy-assisted strategy for textile wastewater treatment application.  

Abstract

In this study, the ability of ozone to oxidise toluene present in low levels into CO and CO2 was studied. The catalytic ozonation of toluene was carried out in a micro-fixed bed reactor. The oxidation was done in two steps: toluene adsorption on the catalyst followed by sequential ozone desorption. Toluene breakdown by ozone at low temperature and atmospheric pressure was achieved using γ-Al2O3 supported transition metal oxides impregnated with a reduced noble metal. The catalyst Ag–CoOx/γ-Al2O3 efficiently oxidised and transformed toluene into products (52.4% COx yield). This catalyst has a high surface area, more acidic sites, and lattice oxygens for better toluene oxidation. The addition of Ag to the CoOx/γ-Al2O3 catalyst surface improved toluene adsorption on the catalyst surface, resulting in improved product yield, selectivity, and carbon balance. 

Abstract

The requirement of green, sustainable, and prudent chemical procedures is one of the bottlenecks in synthetic organic chemistry. Nanostructured materials have the promise to fill the gap between homogeneous and heterogeneous catalysis and can offer benefits without compromising the selectivity in forming the desired products. Advancement of sustainable and green chemical processes under environmental benign conditions is one of the immense interests in modern organic chemistry. Significantly, the hydrogenation of nitroarenes is one of the most important useful catalytic processes in the fine and bulk chemical industry. The most recent advancement of catalysts with supported metal nanoparticles has prompted their enormous accomplishments in the course of the most recent years, provoking their noteworthy applications as “standard” catalysts. Currently, this topic has gotten a lot of consideration. However, despite the fact that support materials have a great diversity in the catalysts for the reactions and modifications, a systematic rationalization of the field is lacking. In this review, we cover and categorize the recent progress in support materials tuning strategies to enhance catalytic performance for the hydrogenation of nitroarenes. Also, importance of support materials in the heterogeneous catalytic hydrogenation of nitroarenes is discussed. 

Abstract

The present work reports the decomposition of a model volatile organic compound (VOC), toluene, in a packed-bed dielectric barrier discharge (DBD) plasma reactor. For this purpose, 2.5 wt% MO x / γ-Al 2 O 3 (M = Mn and Co) catalysts prepared by the wet impregnation method were utilized for packing. The influence of varying input toluene concentration (between 50 and 200 ppm) and different packing conditions (surface modifications of γ-Al 2 O 3 with Mn and Co oxides) on the conversion of toluene, product selectivity of CO and CO 2 , and ozone formation were studied. Surface-modified γ-Al 2 O 3 showed improved CO 2 selectivity compared to γ-Al 2 O 3 and bare plasma. CoO x / γ-Al 2 O 3 effectively decomposed 50-ppm toluene (95% at 3.8 W) with about 70% CO 2 selectivity. MnOx/ γ-Al 2 O 3 and CoO x / γ-Al 2 O 3 displayed the similar conversion effect at higher toluene input. Almost 98% carbon balance and suppressed ozone formation were observed using surface-modified γ-Al 2 O 3 , signifying the necessity of integrating metal oxide to achieve effective conversion and maximum selectivity towards the desired products. The mean electron energies and electron energy distribution function were also calculated using BOLSIG+ software. The high-performance packed-bed DBD system packed with supported 2.5% MO x / γ-Al 2 O 3 offers a promising approach using highly active transition metal oxide-based catalysts for VOCs removal. 

Abstract

An atmospheric-pressure plasma jet (APPJ) was directly irradiated at a gas-liquid interface under ambient conditions. The reactive oxygen species (ROS) like hydroxyl radicals (•OH), hydrogen peroxide (H2O2) and ozone (O3) and also reactive nitrogen species (RNS) such as nitrogen oxides (NOx) and nitric acid (HNO3) formed during the plasma discharge were quantified under various experimental parameters. In a chemical dosimetry method, terephthalic acid (TA) was employed for the quantification of •OH and titanium sulfate was used to quantify the H2O2. Quantitative determination of NO3− was carried out by using Ion chromatography (IC). The changes in the solution pH were studied during the plasma treatment. Strong acidification along with the production of dominant reactive nitrogen species and ozone formation were observed with air. The effect of various gases, gas flow rate, various applied voltage and catalyst were studied to optimize the experimental conditions for the best performance. The influence of catalyst Fe2+ salt, TiO2 on the formation of reactive species were studied. The efficiency of the plasma device for the degradation of crystal violet (CV) was also investigated with TiO2 and Fe2+ salt. 

Abstract

Mechanically modulating optical properties of semiconductor nanocrystals and organic molecules are valuable for mechano-optical and optomechanical devices. Halide perovskites with excellent optical and electronic properties are promising for such applications. We report the mechanically changing excitons and photoluminescence of self-assembled formamidinium lead bromide (FAPbBr3) quantum dots. The as-synthesized quantum dots (3.6 nm diameter), showing blue emission and a short photoluminescence lifetime (2.6 ns), form 20–300 nm 2D and 3D self-assemblies with intense green emission in a solution or a film. The blue emission and short photoluminescence lifetime of the quantum dots are different from the delayed (ca. 550 ns) green emission from the assemblies. Thus, we consider the structure and excitonic properties of individual quantum dots differently from the self-assemblies. The blue emission and short lifetime of individual quantum dots are consistent with a weak dielectric screening of excitons or strong quantum confinement. The red-shifted emission and a long photoluminescence lifetime of the assemblies suggest a strong dielectric screening that weakens the quantum confinement, allowing excitons to split into free carriers, diffuse, and trap. The delayed emission suggests nongeminate recombination of diffusing and detrapped carriers. Interestingly, the green emission of the self-assembly blueshifts by applying a lateral mechanical force (ca. 4.65 N). Correspondingly, the photoluminescence lifetime decreases by 1 order of magnitude. These photoluminescence changes suggest the mechanical dissociation of the quantum dot self-assemblies and mechanically controlled exciton splitting and recombination. The mechanically changing emission color and lifetime of halide perovskite are promising for mechano-optical and optomechanical switches and sensors. 

Abstract

Energy production and environmental pollution are the two major problems the world is facing today. The depletion of fossil fuels and the emission of harmful gases into the atmosphere leads to the research on clean and renewable energy sources. In this context, hydrogen is considered an ideal fuel to meet global energy needs. Presently, hydrogen is produced from fossil fuels. However, the most desirable way is from clean and renewable energy sources, like water and sunlight. Sunlight is an abundant energy source for energy harvesting and utilization. Recent studies reveal that photoelectrochemical (PEC) water splitting has promise for solar to hydrogen (STH) conversion over the widely tested photocatalytic approach since hydrogen and oxygen gases can be quantified easily in PEC. For designing light-absorbing materials, semiconductors are the primary choice that undergoes excitation upon solar light irradiation to produce excitons (electron-hole pairs) to drive the electrolysis. Visible light active semiconductors are attractive to achieve high solar to chemical fuel conversion. However, pure semiconductor materials are far from practical applications because of charge carrier recombination, poor light-harvesting, and electrode degradation. Various heteronanostructures by the integration of metal plasmons overcome these issues. The incorporation of metal plasmons gained significance for improving the PEC water splitting performance. This review summarizes the possible main mechanisms such as plasmon-induced resonance energy transfer (PIRET), hot electron injection (HEI), and light scatting/trapping. It also deliberates the rational design of plasmonic structures for PEC water splitting. Furthermore, this review highlights the advantages of plasmonic metal-supported photoelectrodes for PEC water splitting. 

Abstract

Solar induced water splitting with semiconductor photoelectrodes has been recognized as a sustainable alternative for addressing the energy crisis and pollution by creating hydrogen as a clean fuel. Insufficient light absorption and quick recombination of excitons are the most major bottlenecks in the emergence of semiconductor-based photocatalysts. The major challenge to the commercialization of this technique is the development of photoelectrodes that fulfill the PEC water-splitting requirements. In this study, As a photoanode for PEC water splitting, BiSbS3 NRs were grown on TiO2 films using a simple chemical bath deposition method. Such heterojunctions were chosen to amplify and expand the absorption of visible light, charge transport, charge separation and electrical conduction. The results show that the TiO2/BiSbS3 heterojunction photoanode exhibits relatively low charge transfer resistance, a highest current density of 5.0 mA.cm−2 and STH conversion efficiency of 4.5% at 0.3 V vs RHE. The system's long-term stability was also evaluated for a period of 10,000 s and hydrogen evolution was carried out for 9000 s. Photoluminescence (PL) spectroscopy confirms that TiO2/BiSbS3 heterojunction exhibits stronger light absorption and efficient charge transfer compare to bare TiO2 and BiSbS3. Composite exhibits larger Brunauer − Emmett − Teller (BET) surface area compare to bare TiO2 and BiSbS3 which have contributed in excellent PEC performance compare to bare materials. 

Abstract

A novel, cost-effective carbon paste working electrode (CPE) was developed and was utilized for label-free, non-enzymatic glucose sensing using the inherent affinity of Boronic Acid moieties towards glucose. The electrodeposited gold nanoparticles (AuNPs) onto the surface of CPE offered the enhanced active surface area and rate kinetics, thereby improving the sensitivity of glucose detection. The bioelectrodes showed a significantly low detection limit, high sensitivity, excellent stability, and shelf-life indicating the applicability of the proposed biosensor for non-enzymatic glucose monitoring. 

Abstract

A sustainable method was used to produce aromatic ketones by the solvent-free benzylic oxidation of aromatics over mesoporous Cu(II)-containing propylsalicylaldimine anchored on the surface of Santa Barbara Amorphous type material-15 (CPSA-SBA-15) catalysts. For comparison, mesoporous Cu(II)-containing propylsalicylaldimine anchored with Mobil Composition of Matter-41 (CPSA-MCM-41) was assessed for these reactions under similar reaction conditions. The washed CPSA-SBA-15(0.2) (W-CPSA-SBA-15(0.2)) catalyst was prepared using an easy chemical method for the complete removal of non-framework CuO nanoparticle species on the surface of pristine CPSA-SBA-15(0.2) (p-CPSA-SBA-15(0.2) prepared with 0.2 wt% of Cu, and its catalytic activity was evaluated with different reaction parameters, oxidants and solvents. In order to confirm the catalytic stability, the recyclability was assessed, and the performance of hot-filtration experiments was also evaluated. All the catalysts used for these catalytic reactions were characterized using many instrumental techniques to pinpoint the mesoporous nature and active sites of the catalysts. The proposed reaction mechanism has been well documented on the basis of catalytic results obtained for solvent-free oxidation of aromatics. Based on the catalytic results, we found that W-CPSA-SBA-15(0.2) is a very ecofriendly catalyst with exceptional catalytic activity. 

Abstract

To date, photoanodes containing bimetallic alloy nanoparticles (ANPs) are exposed good photoelectrochemical (PEC) performance for hydrogen production owing to their optoelectronic properties. In this work, low-cost, visible light active and environmental-friendly BiVO4/Bi–Cu nanocomposite photoanode is fabricated via organic decomposition and electrodeposition process. Transmission electron microscope images reveals that Bi–Cu ANPs are uniformly distributed on BiVO4 which can enhance the PEC performance. Typical results originate that BiVO4/Bi–Cu nanocomposite exhibits a high photocurrent density of 10.31 mA cm−2 at 1.23 V and solar-to-hydrogen conversion efficiency of 3.55%, which is higher than other electrodes. In addition, this composite shows excellent long-term stability over 5 h and low charge transfer resistance. These results suggest the introduction of Bi–Cu ANPs enhances the broadband light absorption of BiVO4 due to the excitation of localized surface plasmons at different wavelengths and also improves the charge transportation in the photoanode. Thus, BiVO4/Bi–Cu photoelectrode reports here is superior PEC performance for hydrogen generation providing an economical and feasible route to fabricate surface plasmon resonance (SPR)-enhanced composites as photocatalysts using earth-abundant Bi and Cu metals instead of noble-metals. 

Abstract

Metal sulfide photoanodes emerge into an efficient platform for converting light energy into hydrogen by water splitting. Herein, we demonstrate the facile fabrication of a ternary photoanode (TiO2/Ag2Se/CdS) by decorating a TiO2/Ag2Se electrode with CdS quantum dots. The ternary electrode exhibits low charge transfer resistance, and high-density photocurrent (24.6 mAcm−2 at 1.23 V). We estimate the photon-to-hydrogen conversion efficiency at 14% (at 0.43 V) due to sulfite oxidation. Also, Ag2Se improves the electrode stability, highlighting the promising nature of the electrode for practical applications. These excellent photocatalytic properties of TiO2/Ag2Se/CdS are achieved by the favorable band-edges positions of CdS and Ag2Se quantum dots, the broad absorption of solar photons in the UV-to-NIR region, and the separation and transport of charge carriers. 

Abstract

This paper deals with an in-depth analysis on the role of the microstructure phase of titanium dioxide (TiO2) precursor in sodium bismuth titanate (Na0.5Bi0.5TiO3, hereafter represented as NBT) ceramics prepared through the hydrothermal method. The comparison of the grain size, microstructure, crystal structure, and electrical properties of the NBT ceramics is carried out using anatase and rutile TiO2. NBT ceramics with anatase TiO2 (denoted by NBTA) displayed superior dielectric and ferro/piezoelectric properties along with the additional functionality in terms of photocatalysis. Systematic studies of functional properties such as piezoelectric, ferroelectric, and dielectric stressed the far-reaching influence of effects on grain size. The mechanisms and functional properties of grain quantitative effects are also discussed. Grain boundaries volume fraction increment has decreased the dielectric peak but increased the diffusiveness in the case of the NBT with rutile TiO2 precursor (denoted as NBTR). Similarly, elastic stiffness increment restricts the movement of the domain wall and led to a decrement in remnant polarization along with an increase in the values of the corresponding piezoelectric coefficient in fine-grain NBTR samples. 

Abstract

An NTP hybrid system was designed in combination with metal oxide (MOX)-coated glass beads (GB) to synthesize value-added fuels and chemicals directly from methane. The combined plasma-packed mode was found to be a promising alternative to thermal catalysis, as it successfully enabled the single-step partial oxidation of methane to produce liquid oxygenates at atmospheric pressure and room temperature. When comparing plasma without packing (58%) and MOX/GB coupled plasma mode, the later method enhances the liquid selectivity to 74% with the introduction of C2 oxygenates in addition to C1 chemicals. Among the coated materials applied, NiO-coated GBs showed the highest liquid yield of ∼10%, including the maximum methanol yield of ∼5%, while coupled with NTP-DBD mode. Gas discharge-promoted methane conversion was observed in the presence of GB and MOX/GB, which can be attributed to the enhanced electric field generated as a result of the improved plasma strength created by the beads. Also, the oxide layer of metal oxide nanoparticles provides a catalytic base for adsorption/desorption of methane and other gas phase active species, which can facilitate the partial oxidation process of methane either by the gas-phase active oxygen species or through the interaction of surface hydroxyl groups. 

Abstract

We report for the first-time copper bismuth oxide (CuBi2O4) as an electrochemical sensor for the oxidation of uric acid and reduction of hydrogen peroxide. CuBi2O4 films are prepared on FTO via electrodeposition and used as a working electrode. Structural and morphological studies of CuBi2O4 were done by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron microscopy, tunneling electron microscopy (TEM). Electrochemical studies were performed using cyclic voltammetry (CV), chronoamperometry with CuBi2O4 electrode for the detection of uric acid (UA) and hydrogen peroxide (HP). High sensitivities of 206.7 and 280.6 μA mΜ-1 cm−2 were achieved for the detection of UA and HP. Therefore, CuBi2O4 can be a potential candidate to explore for sensing applications. 

Abstract

Visible-light-active photoelectrodes are more responsive to high-energy conversion efficiency in photoelectrochemical (PEC) water splitting. In this work, we fabricated a bismuth sulfide@reduced graphene oxide (Bi2S3@rGO) nanocomposite photoanode via facile synthetic methods. Typical results show that the Bi2S3@rGO nanocomposite exhibited a high photocurrent density of 6.06 mA cm–2 and a maximum applied bias photon-to-current efficiency (ABPE) of 4.2% at 0.32 V. Moreover, Bi2S3 nanorods have more uniform dispersion on the surface of rGO sheets in the Bi2S3@rGO composite as demonstrated in the transmission electron microscopy images. In addition, photoluminescence and impedance studies reveal the enhanced charge-transfer properties in the Bi2S3@rGO photoelectrode. The enhanced PEC performance of the composite could be attributed to the effective visible-light absorption of Bi2S3 and the good electron-transfer properties of highly conductive rGO nanosheets, facilitating the charge separation and transportation, leading to the inhibition of charge recombination. 

Abstract

In this study, pure ZnO and g-C3N4 were synthesized using coprecipitation and simple calcination methods, respectively. Further, ZnO is impregnated on a g-C3N4 surface with 10, 20 & 30 weight percentages, respectively. Besides, these materials are characterized by various physicochemical techniques such as PXRD, UV-Vis-DRS, TEM, PL, and FT-IR, etc. Vitally, as-prepared materials, catalytic activity was tested for removal of Rhodamine B and 4-nitrophenol from the wastewater under visible light irradiation. Among all these catalysts, 20 wt% ZnO/g-C3N4 showed better activity and showed 67% and 75% mineralization. 

Abstract

Catalysts of zirconium-exchanged proton-containing tungstophosphoric acid (TPA) supported on β-zeolites were prepared by an impregnation method for the selective alcoholysis of furfuryl alcohol into ethyl levulinate. The prepared catalysts were characterized by different spectroscopic techniques. The results indicated the existence of a Keggin ion structure of TPA after its modification with Zr ions and successive dispersion on β-zeolites. The introduction of Zr in TPA generated Lewis acidic sites in the catalyst. Pyridine-adsorbed FT-IR confirmed the presence of both Brønsted and Lewis acidic sites in catalysts. The catalytic activity for the alcoholysis of furfuryl alcohol depends on the strength of both Brønsted and Lewis acids of the catalyst. Among these catalysts, 20%Zr0.75TPA/β-zeolite was active for the alcoholysis of furfuryl alcohol with a 96% yield of ethyl levulinate. Optimal conditions were established to obtain maximum yield. A plausible reaction mechanism was also proposed. The catalyst was reused without any appreciable loss of activity. 

Abstract

The present study investigates the applicability of Fenton's oxidation for the treatment of a highly refractory, viscous, bulk drug industry effluent. The effluent is found to behave as a Newtonian fluid, thrice as viscous as water. Fenton's oxidation experiments on the undiluted effluent are conducted in accordance with central composite design (CCD), considering the operating factors of pH (3–11), FeSO4 dosage (3–15 g L−1), H2O2 dosage (7–19 mL L−1), and treatment time (30–150 min). The treatment yielded a maximum total organic carbon (TOC) reduction of 28% at neutral pH, FeSO4, and H2O2 dosages of 9 g L−1 and 13 mL L−1, respectively, for 150 min of operation. The maximal treatment efficacy observed at neutral pH is explained by the non-radical mechanism of Fenton's oxidation, and further correlated with viscosity and type of fluid (here, Newtonian), as judged from the generated viscosity profiles. Upon comparison with previous effluent samplings, differing treatment efficacies are observed for different fluid types, that is, Newtonian and non-Newtonian (shear thinning), with the latter obtaining twice the TOC reduction, under similar experimental conditions. Hence, the effect of viscosity and fluid type on the effectiveness of Fenton's oxidation treatment is experimentally validated and discussed.  

Abstract

The long-term integrity of fly ash (FA) geopolymer-stabilized high-percentage reclaimed asphalt pavement (RAP) in the pavement base layer was investigated in this research. The FA geopolymer-stabilized RAP and virgin aggregate (VA) mixes were studied as an economical and durable alternative to 100% VA bases, with an emphasis on the influence of curing time. The maturity age of FA is usually set as 28 days, similar to traditional portland cement. However, due to partial pozzolanic reactions, though geopolymerized, the dilution of partial FA particles does not fully play its role at 28 days of curing time. Hence, this is not a realistic reference time for predicting the service life of FA geopolymer-stabilized aggregate blends. Therefore, a detailed experimental investigation was undertaken to evaluate the ultimate strength, durability, and microstructural characteristics of four distinct FA geopolymer-stabilized RAP:VA blends for a long-term ambient curing time up to 270 days. In this study, the long-term cured specimens showed significant improvement in mechanical strength and stiffness, yielding lower permanent deformations. It was noticed that only about 12% and 40% average unconfined compressive strength (UCS) could be achieved in 7- and 28-day cured specimens, respectively, with reference to their ultimate strength at 270 days. Hence, to examine the microstructural characteristics of powdered FA geopolymer blends, X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), and Fourier transform-infrared spectroscopy (FT-IR) studies were performed. The test results revealed that the consumption of reactive metal ions was continued for an extended period under a controlled curing regime, which resulted in improved mechanical strength and durability of the solidified product. 

Abstract

Direct conversion of methane into chemicals and fuels under mild conditions has been considered as a ‘holy grail’ of chemistry and catalysis in the 21st century. Plasma-catalytic partial oxidation of methane (POM) to higher-value liquid fuels and chemicals over supported transition metal catalysts (Ni/γ-Al2O3, Cu/γ-Al2O3 and Fe/γ-Al2O3) has been investigated in a co-axial dielectric barrier discharge (DBD) reactor at room temperature and atmospheric pressure. The selectivity of oxygenates was 58.3% in the plasma POM reaction without a catalyst, while the combination of DBD with the catalysts enhanced the selectivity of oxygenates up to 71.5%. Of the three catalysts, Fe/γ-Al2O3 showed the highest methanol selectivity of 36.0% and a significant methanol yield of 4.7%, while the use of Cu/γ-Al2O3 improved the selectivity of C2 oxygenates to 9.4%, which can be attributed to the presence of more acid sites on the surfaces of the Cu catalyst. The possible reaction pathways in the plasma-catalytic POM reaction have been explored by combined means of plasma electrical and optical diagnostics, analysis of gas and liquid products, as well as comprehensive catalyst characterization. The plausible reaction routes for the production of major oxygenate (methanol) on the Fe/γ-Al2O3 surfaces have been proposed. The surface CHx species are found to be critical for methanol synthesis; they can be formed through the direct adsorption of CHx radicals generated in the plasma gas-phase reactions or through the dissociation of adsorbed CH4 on the catalyst surface. 

Abstract

The direct activation of undiluted CO2 is carried out in a co-axial dielectric barrier discharge (DBD) reactor. The variation of the electrical discharge parameters and their influence on CO2 decomposition is investigated with the integration of 15 % MO/γ-Al2O3 (M = Ni, Cu) catalyst in the discharge zone. The electrical discharge is found to shift from the filamentary to a combination of surface and micro filamentary discharge on catalyst integration to NTP and also leads to the higher conversion of CO2 than DBD alone. The highest conversion of CO2 (15.7 %) with the energy efficiency of 1.597 mmol/kJ is achieved under CuO/γ-Al2O3 integrated NTP system, whereas the maximum of carbon balance (94.4 %) reaches with 4% CeO2 addition to CuO/Al2O3 catalyst. The oxygen vacancy of the catalyst plays a vital role in improving the performance, especially, the oxygen buffer property of CeO2 facilitates the recombination reaction and contributes to obtaining the highest carbon balance. 

Abstract

Semiconducting photoelectrodes emerge as an efficient platform for converting light energy into hydrogen by photoelectrochemical (PEC) water splitting. The present study reports the improvement in PEC performance using metal oxide photoelectrodes sensitized with a narrow-band-gap semiconductor Bi2Se3, which extends the light response beyond the visible region and generates and transports charge carriers. When Bi2Se3 nanoflowers (NFs) were incorporated into the TiO2 electrode, the extent of hydrogen production was found to be increased by an order of magnitude. The binary electrode TiO2/Bi2Se3 nanocomposite exhibited a decent photocurrent density of 1.76 mA cm–2 at 1.23 V, which is three times superior to that of pure Bi2Se3 NFs. Moreover, the binary TiO2/Bi2Se3 electrode delivers the highest solar-to-hydrogen conversion efficiency of 1.01% at 0.6 V and incident photon-to-current conversion efficiency of 10.5%. Furthermore, both Bi2Se3 and TiO2/Bi2Se3 electrodes show superior photostabilities for over 6 h. The enhanced PEC activity is attributable to the facile transportation of photoelectrons from Bi2Se3 to TiO2 electrodes, thereby minimizing the charge recombination. 

Abstract

The Prins cyclization of styrene (SE) with paraformaldehyde (PFCHO) was conducted with mesoporous ZnAlMCM-41 catalysts for the synthesis of 4-phenyl-1,3-dioxane (4-PDO) using a liquid phase heterogeneous catalytic method. For a comparison study, the Prins cyclization reaction was also conducted over different nanoporous catalysts, e.g. mesoporous solid acid catalysts, AlMCM-41(21) and ZnMCM-41(21), and microporous catalysts, USY, Hβ, HZSM-5, and H-mordenite. The recyclable mesoporous ZnAlMCM-41 catalysts were reused in this reaction to evaluate their catalytic stabilities. Since ZnAlMCM-41(75) has higher catalytic activity than other solid acid catalysts, washed ZnAlMCM-41(75)/W-ZnAlMCM-41(75) was prepared using an efficient chemical treatment method and used with various reaction parameters to find an optimal parameter for the highly selective synthesis of 4-PDO. W-ZnAlMCM-41(75) was also used in the Prins cyclization of olefins with PFCHO and formalin (FN, 37% aqueous solution of formaldehyde (FCHO)) under different reaction conditions to obtain 1,3-dioxanes, which are widely used as solvents or intermediates in organic synthesis. Based on the nature of catalysts used under different reaction conditions, a reasonable plausible reaction mechanism for the Prins cyclization of SE with PFCHO is proposed. Notably, it can be seen from the catalytic results of all catalysts that the W-ZnAlMCM-41(75) catalyst has higher 4-PDO selectivity with exceptional catalytic activity than other microporous and mesoporous catalysts. 

Abstract

In this study, the microwave-absorption characteristics of multi-layered radar-absorbing structures (RASs) were investigated. Electrical-grade glass (e-glass)/epoxy composites containing modified multi-walled carbon nanotubes (MWCNTs) were fabricated. The poly aniline (PANI) coated MWCNTs was obtained by in-situ polymerisation of aniline in the presence of MWCNTs. The PANI-coated MWCNTs (PCNTs) were then used as reinforcements in the polymer matrix, and their morphologies, microstructures, thermal stabilities, and microwave-absorbing properties were investigated. The complex permittivity and permeability of the composites were measured and found to have increased with increasing filler concentration. Microwave absorbing properties were analysed via waveguide measurement. The three-layered RASs reinforced with PCNTs having a thickness of 4 mm exhibited a RL of –5 dB over the entire X-band and a reflection peak of –24.53 dB at 10.0 GHz. Hence, the epoxy/PCNTs composites are suitable for use in microwave-absorption applications. 

Abstract

A dual-function non-thermal plasma system was successfully employed for the Pd nanoparticles preparation, followed by in- plasma catalytic methane partial oxidation to liquid oxygenates and fuels. Non-thermal plasma treated catalyst (P-Pd/SBA-15) was found to possess better surface characteristics to provide the best liquid oxygenates selectivity of 70%, while it restrained to only 58% in only plasma mode. 

Abstract

The development of new radar-absorbing structures (RASs) with strong microwave absorption, fine thickness and adequate structural performance is imperative. Herein, nanocrystalline Ni0.5Zn0.5Fe2O4 was synthesised by a facile and effective sol–gel autocombustion technique. The structural and magnetic properties of ferrite were determined by various characterisation techniques, and E-glass/epoxy-based nanocomposites with different weight percentages of ferrite were fabricated by in-situ polymerisation. Further, electromagnetic properties were investigated to elucidate the possible absorption mechanism of the fabricated structures. The 4-mm-thick double-layered E-glass/epoxy/nickel–zinc ferrite composites exhibited reflection loss (RL) of <−10 dB for a bandwidth of 2.4 GHz and a maximum RL of −33 dB at 9.6 GHz. This performance was attributed to the larger magnetic loss and sufficient matching of electromagnetic parameters. This study provides a unique insight into the utilisation of Ni0.5Zn0.5Fe2O4 for producing lightweight and relatively thin RASs in the X-band at a low cost. 

Abstract

The present study investigates the oxidative technique of hydrodynamic cavitation (HC) for the treatment of a highly refractive, bulk drug industry effluent with an initial total organic carbon (TOC) content of 69960 mg/l. A qualitative insight into the pharmaceutical industry, drug production, and effluent characteristics is presented. Experiments on the undiluted effluent were conducted in accordance with central composite design (CCD). For the venturi-based HC studies, variation of pH (3.63-10.36), inlet pressure (2.95-13.04 bar), and treatment time (26.36-93.63 min.) were studied, besides investigating their effects on treatment efficiency. HC treatment yielded a maximum 25% reduction in TOC with a cavitational yield of 65.69 × 10-3 mg/J for an optimum combination of pH 7, inlet pressure 8 bar, cavitation number of 0.242, and treatment time 60 minutes (17 recirculations). Furthermore, synergetic effects of increasing inlet pressure and effluent temperature were quantified, and found to effectuate a maximum increase of 1781% in vapour pressure, and decrease of 77% in cavitation number. Lastly, effects of operating factors on treatment efficacy and the success of HC system were summarized. 

Abstract

This study aims to provide non-biological treatment solutions to the pharmaceutical industry, depending on the quantitative and qualitative aspects of the wastewater. Commonly overlooked aspects of industrial wastewater such as its fluctuating characteristics, selection of suitable sampling points, and adopting an appropriate treatment methodology are addressed. Different units in a drug-producing industry and chief ingredients at each stage were identified. An appropriate sampling point was finalized following a series of systematic and repeated samplings of prominent industrial locations, at different periods. High organic and solids strength industrial wastewater samples were characterized and subjected to various physico-chemical and oxidative techniques, namely electrocoagulation (EC), chemical coagulation, photocatalytic oxidation, electro-Fenton’s (EF), Photo-Fenton’s (PF), and Fenton’s oxidation. The highest total organic carbon (TOC) reduction efficiencies about 47, 23, and 62 % were obtained from Fenton’s oxidation for distinct samplings. The variation in quality of effluent heavily influences the treatment efficacies of individual treatment schemes. Hence, rigid treatment protocols are inadvisable to propose for industrial perspectives to handle diurnal variations in effluent characteristics. Rather, industry-specific solutions may be provided, depending on the type of wastewater generated. 

Abstract

Copper bismuth oxide (CBO), modified with cobalt as dopant has been prepared by coprecipitation and the electrode was prepared by doctor blade method. The cobalt doped copper bismuth oxide (Co-CBO) has been extensively used for selective glucose sensing and photoelectrochemical activity. Physical characterizations like X-ray diffraction, field-emission scanning electron microscopy are studied to confirm the formation of desired electrode. Linear sweep voltammetry, chronoamperometric and impedance studies explain about the electrocatalytic nature of cobalt doped CBO. Oxidation peak for glucose was observed for CBO at 0.54 V while for Co-CBO it occurred at 0.46 V. The reduction in potential is explained through synergistic catalytic enhancement due to cobalt doping. Further, Co-CBO was used for photoelectrochemical application, the electrode has shown current density of −0.80 mA cm−2 while that for CBO is −0.20 mA cm−2. Therefore, CBO has formed a desirable phase with cobalt which resulted in the enhancement of electrocatalytic performance. 

Abstract

Dry reforming of methane is conducted in a catalyst packed-bed dielectric barrier discharge (DBD) reactor aiming to improve the reaction efficiency. The MgO- and CeO2-promoted Ni/γ-Al2O3 catalyst is tested to carry out the reaction. An interesting observation is that Ni/MgO_Al2O3 integration provides ∼35 and 13% conversion of CH4 and CO2, respectively. The highest syngas ratio of 0.94 is obtained with Ni/MgO_Al2O3, whereas the ratio is only 0.57 with Ni/CeO2_Al2O3 and 0.64 with bare DBD. In addition, Ni/CeO2_Al2O3 offers the highest selectivity (68%) of CO due to the oxygen buffer property of CeO2. Finally, the optimal acid/base property is highly desirable for the dry reforming reaction. 

Abstract

A facile method for the synthesis of ultra-small palladium (Pd) nanoparticles by polyol method is described. Pd nanoparticles are stabilized/caped by poly(N-vinylpyrrolidone) (PVP) and PVP capped Pd nanoparticles encapsulated by polystyrene. The resulting nanocatalyst was investigated for catalytic reduction of 4-nitrophenol under ambient conditions. Optimized reactions conditions showed that 20 mg of the catalyst and 1.0 M NaBH4 are the ideal conditions to achieve the best activity. 

Abstract

The present study accomplishes the partial reduction of CO2 to carbon monoxide in a dielectric barrier discharge (DBD) reactor packed with g-C3N4 and TiO2 or ZnO mixed with g-C3N4. Typical results indicate that the ZnO + g-C3N4 packed reactor provides ~12% CO2 conversion at SIE of 4.8 J/mL, whereas DBD yields only ~7.5% conversion under the same experimental conditions. The best performance of the ZnO integrated system is due to the presence of more basic sites than those of the TiO2 packed system, which enables effective adsorption of acidic CO2 on its surface. The highest energy efficiency of 1.106 mmol/kJ is achieved with 5% ZnO + g-C3N4 at SIE of 4.8 J/mL, whereas DBD exhibits only 0.746 mmol/kJ under the same conditions. Notably, catalyst packing also enables the highest carbon balance of ~97%. 

Abstract

Plasmonic metal nanoparticles containing photoanodes are known to exhibit stable photoelectrochemical (PEC) performance due to their optical and electronic properties. In this work, we report the application of plasmonic Bi nanoparticles supported over a g-C3N4/Bi2S3 photoanode for PEC water splitting. Typical results indicated that g-C3N4/Bi2S3/BiNPs ternary composite photoanode showed a high photo-current density of 7.11 mA cm−2 at 1.23 V under solar irradiation, which was ∼ 5 and 10 times higher than g-C3N4/Bi2S3 and g-C3N4 photoanodes, respectively. Further, the composite electrode also demonstrated superior solar to hydrogen efficiency and long-term stability. It was concluded that Bi nanoparticles play a major role in enhancing the PEC performance for hydrogen evolution reaction. Thus, g-C3N4/Bi2S3/BiNPs has superior PEC performance and proved to work as an alternative to noble metal based photo-electrodes for solar-water splitting reactions. 

Abstract

We report a WO3/Cu/Bi2S3 wherein incorporation of Cu nanoparticles (Cu NPs) to enhance the photoelectrochemical activity over WO3/Bi2S3. Cu NPs effectively harvest the light energy upon plasmon excitation and transfer the energy to contacted WO3, thereby improving the photoelectrochemical (PEC) performance. The WO3/Cu/Bi2S3 composite was characterized by scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD) to analyze the morphology and interfacial contact between the semiconductors. The photocurrent density and Solar-to-Hydrogen conversion efficiency for this composite is 10.6 mA cm−2 at 1.23 V (versus RHE) and 3.21% at 0.81 V (versus RHE), which are much higher than WO3/Bi2S3 with 4.02 mA cm−2 at 1.23 V (versus RHE) and 2.46% at 0.81 V (versus RHE) respectively. Moreover, the stability and photo-response of WO3/Cu/Bi2S3 were carried out through chronoamperometric studies. The composite retained its stability over 50 cycles without decay in PEC performance. High incident photon conversion efficiency (IPCE) value of about 51% is achieved which is evident from the high photocurrent density. Incorporation of Cu NPs increase the photoactivity which is evident from the photocurrent value. The increased activity of Cu NPs sandwiched composite is attributed for the quick electron transfer to semiconductor due to surface plasmon resonance (SPR) effect. 

Abstract

In this study, we synthesized a robust and sustainable Pd/SiO2 nanospheres catalyst. Further, its catalytic activity was demonstrated for the direct reductive coupling of nitroarenes under mild conditions. While the reaction with Pd nanoparticles on other supporting materials such as modified carbon materials and TiO2, under similar conditions, resulted formation of amines exclusively. Therefore, it was confirmed that the SiO2 was found to be the best supporting material towards the selective reductive coupling of nitroarenes. Also, the catalyst could be recycled up to five cycles with a marginal loss of product yield (< 2% yield). 

Abstract

Aromatic acylation is an indispensable chemical transformation in organic synthesis in affording aryl ketones. In this manuscript, we have described the synthesis of aromatic ketones utilizing graphene oxide (GO) supported PdO nanoparticles (PdO/GO), as heterogeneous transition metal catalyst. The [Pd]-heterogeneous catalyst enabled the coupling between iodoarenes and aromatic aldehydes. The acylation was carried out by eliminating toxic CO gas as the source of the carbonyl. Further, practicality of this strategy was also demonstrated by fusing 1,3-dihydroisobenzofurans. 

Abstract

A wide range of technologies has been developed for producing hydrogen economically and in greener ways. Photoelectrochemical water splitting using photoelectrodes submerged in a bath electrolyte forms a major route of hydrogen evolution. The efficacy of water splitting is improved by sensitizing metal oxide photoelectrodes with narrow bandgap semiconductors that efficiently absorb sunlight and generate and transport charge carriers. Here we show that the efficiencies of photocurrent generation and photoelectrochemical hydrogen evolution by the binary TiO2/Sb2S3 anode increase by an order of magnitude upon the incorporation of the earth-abundant plasmonic bismuth nanoparticles into it. The ternary electrode TiO2/Bi nanoparticle/Sb2S3 illuminated with sunlight provides us with a photocurrent density as high as 4.21 mA cm−2 at 1.23 V, which is fourfold greater than that of the binary electrode and tenfold greater than that of pristine TiO2. By using bismuth nanoparticles, we estimate the incident photon to current conversion efficiency at 31% and solar power conversion efficiency at 3.85%. Here the overall impact of bismuth nanoparticles is attributed to increases in the open-circuit voltage (860 mV), which is by expediting the transfer of photogenerated electrons from Sb2S3 nanoparticles to the TiO2 electrode, and short-circuit current (9.54 mA cm−2), which is by the plasmonic nearfield effect. By combining the cost-effective plasmonic bismuth nanoparticles with the narrow bandgap Sb2S3 on the TiO2 electrode, we develop a stable, ternary photoanode and accomplish high-efficiency photocurrent generation and hydrogen evolution. 

Abstract

The increased production of semiconductor nanomaterials such as heavy metal quantum dots and perovskites for applications such as in energy harvesting, optoelectronic devices, bioanalysis, phototherapy and consumer health products raises concerns regarding nanotoxicity. After disposal, these materials degrade upon interaction with the environment, such as rain and surface waters, soil and oxygen, and solar irradiation, leading to the release of heavy metal ions in the environment with exposure to aquatic and terrestrial animals and plants, and humans. Researchers are in the early stages of understanding the potential toxicity of such nanomaterials by quantifying the amount of heavy metal ions released due to environmental or biological transformation. Here, we evaluate the toxicity of environmentally transformed nanomaterials by considering PbS quantum dots as a model system. Using metal ion sensors and steady-state fluorescence spectroscopy, we quantify the amount of Pb2+ released by the photochemical etching of quantum dots. Furthermore, with the help of cytotoxicity and comet assays, and DNA gel electrophoresis, we evaluate the adverse effects of the released metal ions into the cultured lung epithelial (H1650), and neuronal (PC12) cells. These studies reveal higher levels of cell proliferation and DNA damage to PC12 cells, suggesting the neurotoxicity of lead due to not only the downregulation of glutathione, elevated levels of reactive oxygen and nitrogen species, and a calcium influx but also the proactivation of activator protein 1 that is correlated with protein kinase c. This research shows the significance of molecular biology studies on different cells and animals to critically understand the health and environmental costs of heavy metal-based engineered nanomaterials. 

Abstract

A non-thermal dielectric barrier discharge (DBD) plasma reactor was integrated with an M/SBA-15 (M = Pd, Pt, Ag and Au) catalyst, where metal reduction was achieved by H2 plasma treatment. Subsequently, the plasma-catalytic combination mode was tested for the methane partial oxidation reaction to liquid oxygenates, and the results were compared with the plasma-only system in terms of reactant conversion, energy efficiency and product distribution. The results from the characterization of the catalysts confirmed that the plasma treatment improved the surface characteristics of the catalysts and also modified or expanded the discharge on the catalytic surface. The plasma energetic species generally helped to flatten the metal nanoparticles over the support surface, which resulted in a better dispersion with the formation of smaller nanoparticles. A total liquid selectivity of 70% was achieved for the plasma-treated Pt/SBA-15-DBD system with almost 12% CH4 conversion compared to 58% total liquid at 7% CH4 conversion with the plasma-only system. 

Abstract

A very green catalytic method has been introduced for the synthesis of alkylaromatic ketones by solvent-free benzylic oxidation of alkylaromatics with molecular oxygen (O2) over hexagonally mesostructured MnSBA-15 catalysts synthesized with a variety of manganese (Mn) contents using a pH-adjusting direct hydrothermal (pH-aDH) method. For example, the solvent-free oxidation of ethylbenzene (EB) over different mesoporous MnSBA-15 catalysts and uniform pore sized MnMCM-41(31) prepared by an alkaline hydrothermal method has been systematically evaluated. Washed MnSBA-15(4) (W-MnSBA-15(4)) or green mesoporous MnSBA-15(4) obtained after the removal of the non-framework octahedral Mn2O3 species deposited on the active surface of MnSBA-15(4) using a promising chemical treatment method is used for this reaction to evaluate its catalytic activity. Meanwhile the recyclability and hot-filtration experiments for this reaction have been also studied. The catalytic activities obtained from the above catalytic results prove that the W-MnSBA-15(4) has higher EB conversion and APO selectivity than the other mesoporous catalysts used in this reaction. Therefore, in order to find the optimal reaction parameters for this reaction, various reaction parameters with W-MnSBA-15(4) have been thoroughly evaluated. Using W-MnSBA-15(4), the catalytic results obtained with different oxidants used in this reaction have also been discussed clearly. The catalytic results of solvent-free benzylic oxidations with W-MnSBA-15(4) conducted with different alkylaromatic molecules have been obviously discussed. All the mesoporous catalysts used in this reaction have been characterized using several instrumental techniques to confirm them as the standard mesoporous catalysts. The plausible reaction mechanism for the solvent-free oxidation of EB has been successfully reported based on the characterization results of the catalyst and catalytic results. The ESR and UV-vis DRS results of the W-MnSBA-15 catalyst used in these reactions corroborate that the disordered octahedral divalent (Mn2+) and tetrahedral trivalent (Mn3+)-species have been successfully incorporated on the silica surface of the catalysts. Based on the catalytic results, it is noteworthy to observe that mesoporous W-MnSBA-15(4) is a highly active, green and promising heterogeneous catalyst for the selective synthesis of alkylaromatic ketones, since the catalyst produces the best catalytic activity among the other mesoporous Mn silicate catalysts. 

Abstract

A very green catalytic method has been introduced for the synthesis of alkylaromatic ketones by solvent-free benzylic oxidation of alkylaromatics with molecular oxygen (O2) over hexagonally mesostructured MnSBA-15 catalysts synthesized with a variety of manganese (Mn) contents using a pH-adjusting direct hydrothermal (pH-aDH) method. For example, the solvent-free oxidation of ethylbenzene (EB) over different mesoporous MnSBA-15 catalysts and uniform pore sized MnMCM-41(31) prepared by an alkaline hydrothermal method has been systematically evaluated. Washed MnSBA-15(4) (W-MnSBA-15(4)) or green mesoporous MnSBA-15(4) obtained after the removal of the non-framework octahedral Mn2O3 species deposited on the active surface of MnSBA-15(4) using a promising chemical treatment method is used for this reaction to evaluate its catalytic activity. Meanwhile the recyclability and hot-filtration experiments for this reaction have been also studied. The catalytic activities obtained from the above catalytic results prove that the W-MnSBA-15(4) has higher EB conversion and APO selectivity than the other mesoporous catalysts used in this reaction. Therefore, in order to find the optimal reaction parameters for this reaction, various reaction parameters with W-MnSBA-15(4) have been thoroughly evaluated. Using W-MnSBA-15(4), the catalytic results obtained with different oxidants used in this reaction have also been discussed clearly. The catalytic results of solvent-free benzylic oxidations with W-MnSBA-15(4) conducted with different alkylaromatic molecules have been obviously discussed. All the mesoporous catalysts used in this reaction have been characterized using several instrumental techniques to confirm them as the standard mesoporous catalysts. The plausible reaction mechanism for the solvent-free oxidation of EB has been successfully reported based on the characterization results of the catalyst and catalytic results. The ESR and UV-vis DRS results of the W-MnSBA-15 catalyst used in these reactions corroborate that the disordered octahedral divalent (Mn2+) and tetrahedral trivalent (Mn3+)-species have been successfully incorporated on the silica surface of the catalysts. Based on the catalytic results, it is noteworthy to observe that mesoporous W-MnSBA-15(4) is a highly active, green and promising heterogeneous catalyst for the selective synthesis of alkylaromatic ketones, since the catalyst produces the best catalytic activity among the other mesoporous Mn silicate catalysts. 

Abstract

Halide perovskites have emerged as a class of most promising and cost-effective semiconductor materials for next generation photoluminescent, electroluminescent and photovoltaic devices. These perovskites have high optical absorption coefficients and exhibit narrow-band bright photoluminescence, in addition to their halide-dependent tuneable bandgaps, low exciton binding energies, and long-range carrier diffusion. These properties make these perovskites superior to classical semiconductors such as silicon. Most importantly, the simple synthesis of perovskites in the form of high quality films, single crystals, nanocrystals and quantum dots has attracted newcomers to develop novel perovskites with unique optoelectronic properties for optical and photovoltaic applications. Here, we comprehensively review recent advances in the synthesis and optoelectronic properties of films, microcrystals, nanocrystals and quantum dots of lead halide and lead-free halide perovskites. Followed by the classification of synthesis, we address the ensemble and single particle properties of perovskites from the viewpoints of the confinement and transport of charge carriers or excitons. Further, we correlate the charge carrier properties of perovskite films, microcrystals, nanocrystals and quantum dots with the crystal structure and size, halide composition, temperature, and pressure. Finally, we illustrate the emerging applications of perovskites to solar cells, LEDs, and lasers, and discuss the ongoing challenges in the field. 

Abstract

We report a novel catalyst Pd/SOS that catalyzes the dual C–C bond forming coupling of an iodoarene moiety with an internal alkene and an external alkyne via an intramolecular Heck reaction, followed by an intermolecular Sonogashira reaction, respectively. The catalyst was characterized using XRD, IR, XPS, SEM and TEM analyses. Notably, for the first time, cheap and readily available new silica [nanosilica on microsilica (SOS)] material-supported ultra-small Pd nanoparticles (2.20 nm) are employed for the efficient synthesis of dihydrobenzofuran and oxindole derivatives in a domino one-pot reaction. Significantly, a sub-molar quantity of Pd (0.3 mol%) was found to be sufficient to furnish the products in very good to near quantitative yields. Gratifyingly, the catalyst could be recycled up to five cycles with a marginal loss (∼no loss) of the product. 

Abstract

A bio-adsorbent was derived from the coconut shells and surface modification of the adsorbent was done by physical activation by using carbon dioxide (CO2), ozone (O3) and steam (H2O). The consequence of physical activation on the physicochemical properties was analyzed by N2 adsorption, thermogravimetric analysis (TGA) and temperature programmed decomposition (TPD). Typical results indicated that the physical activation of carbon is an efficient approach for the removal of heavy metal Cr(VI) from the aqueous solution and the best adsorption was achieved at pH 2.0. The equilibrium studies indicated that Cr(VI) adsorption follows Langmuir adsorption isotherm and pseudo-2nd-order kinetics. 

Abstract

Control measures against antimicrobial resistant bacterial pathogens are important challenges in our daily life. In this study, we discuss the sensitivity and resistance of four bacterial pathogens, Vibrio alginolyticus, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, to silver-silica hybrid nanoparticles. Successively, by combining with an efflux pump blocking agent Verapamil, we find that these hybrid nanoparticles induce complete mortality to even the most resistive S. aureus. The above pathogens are selected from a pool of 100 bacterial strains resistant to silver nitrate. While S. aureus shows increased resistance to the nanoparticles, the cell wall integrity and genetic stability of V. alginolyticus and E. coli are compromised in the presence of the hybrid nanoparticles. These studies suggest that the antimicrobial properties of the nanoparticles against Gram-negative pathogens originate from increased oxidative stress, which is confirmed by the blocking of reactive oxygen species (ROS) using scavengers such as ascorbic acid and observing DNA damage. The antimicrobial property of the nanoparticle when combined with its nontoxic nature to mammalian cells makes it a promising agent for controlling drug-resistant Gram-negative pathogens. 

Abstract

The CO2 reforming of CH4 to synthesis gas is performed in a dielectric barrier discharge (DBD) plasma coupled with g-C3N4, g-C3N4/TiO2, g-C3N4/ZnO and g-C3N4/mixed oxide (2.5 wt% ZnO and 2.5 wt% TiO2) catalysts. For CH4 and CO2 gases, the highest conversion is obtained with 5 wt% TiO2 + g-C3N4 and 5 wt% ZnO + g-C3N4, respectively. The g-C3N4 and 5 wt% TiO2 + g-C3N4 catalysts shows poor selectivity towards H2 and CO formation. Whereas, 5 wt% ZnO + g-C3N4 exhibits the highest H2 and CO selectivity. However, with increasing SIE the CO selectivity decreases over 5 wt% ZnO + g-C3N4. The selectivity towards H2 and CO are found to be optimal over 5 wt% MO (1:1) + g-C3N4 and the combination of TiO2 + ZnO coupled with g-C3N4 significantly improves the carbon balance. This optimum performance by 5 wt% MO (1:1) + g-C3N4 in providing the best carbon balance is due to the combination of electronic and acid-base characteristics of the catalysts. The generation of various active species is evidenced by emission spectroscopic study. 

Abstract

Comprehensive investigations on the effect of mechanical and chemical processing techniques on structural, electrical and photocatalytic properties of single phase lead-free Na0.5Bi0.5TiO3 (NBT) and their correlations are presented here. NBT is synthesized using solid-state (NBT-SSR), sol-gel (NBT-SG), combustion (NBT-C) and hydrothermal (NBT-H) techniques. The structural analysis confirmed the rhombohedral (R3c) phase stabilization in the solid-state synthesized sample whereas a minor monoclinic (Cc) phase coexisted with R3c phase in chemically synthesized samples. The robust relaxor feature along with slanted ferroelectric hysteresis loop (for energy storage) was observed in hydrothermally synthesized NBT samples (NBT-H). The ferroelectric hysteresis loop gradually became slanted due to the multi-domain to the mono-domain transformation that eased the domain reversal and switching which was observed through lower coercive field (Ec) values. NBT ceramics synthesized using combustion technique (NBT-C) appeared to be the best target catalyst to probe the influence of ferroelectricity on the decolorization of Rhodamine B dye under simulated visible light. 

Abstract

Partial oxidation of methane to methanol is one of the best routes for liquid oxygenates preparation. The present study describes the application of a non-thermal plasma reactor operated under dielectric barrier discharge mode with/without catalyst addition for a single stage methane conversion to methanol. Air has been chosen as the oxidant for methane partial oxidation. It is found that both the reactant conversion and product distribution are strongly dependent on the reactor configuration, feed gases composition and also catalyst addition. A series of γ-Al2O3 supported Cu catalyst with metal oxide promoters (ZnO, ZrO2 and MgO) were integrated with plasma zone as to obtain in-plasma catalytic reactor. Typical results show that the synergistic effect due to plasma activation and catalytic action, significantly improves both CH4 conversion and CH3OH selectivity. The best methanol selectivity of ∼28% is achieved over the CuZrAl catalyst with a CH4 conversion of ∼11%, while plasma reactor provides only ∼18% CH3OH selectivity. The possible reaction mechanism of methanol formation inside the plasma reactor has been discussed, which highlights that the catalyst facilitates the adsorption of plasma excited species and improves the performance of the reactor. 

Abstract

For the global environmental problem, development of sustainable photocatalysts possess major scientific challenge. In this context, we developed a series of Zn1-xCuxO (x = 0.01, 0.02, 0.03, 0.04) nanocatalysts (via co-precipitation method) for photocatalytic abatement of Bisphenol-A from the water. As-prepared photocatalysts characterized by using various physicochemical techniques like PXRD, XPS, TEM, UV-VIS-DRS and PL spectroscopy. Notably, among all photocatalysts Zn0.99Cu0.01O furnished the better activity under visible light and observed 74% of abatement with rate constant 0.0076 min−1 and 66% of mineralization.  

Abstract

CuO/γ-Al2O3 promoted partial oxidation of methane to methanol was carried out in a non-thermal plasma DBD reactor operating under ambient conditions. The catalysts were synthesized by wet impregnation method, characterized systematically and tested for a single step methane partial oxidation to methanol under ambient conditions. Typical results highlighted the complementary effect of plasma and catalyst, where integration of catalyst in plasma zone improved both conversion of methane and selectivity to methanol. The influence of specific input energy and feed gas composition was studied and the intermediate species formed in plasma catalytic reaction was monitored by an optical emission spectroscopy. The best CH3OH selectivity of ˜37% was achieved over 5 CA catalyst against the ˜27% CH3OH selectivity with plasma system. The improved performance of the hybridized system was asserted due to high charge deposition and modified gas phase chemistry due to catalyst integration.  

Abstract

This work reports the elimination of the emerging contaminant cefixime, an active pharmaceutical ingredient (API) from Indian based drug effluent. A sequential two step electrocoagulation (EC) and photocatalytic oxidation treatment is proposed to eliminate the API below its minimum inhibitory concentration (MIC). This study is prominent due to the treatment of high strength crude drug effluent, with total organic carbon (TOC) of 7395 mg/l, in order to reduce the organic load with complete elimination of pre-existing microbial population. Treatment processes were conducted in batch reactors, in which, EC was carried out by two electrodes viz. Aluminum and Iron. On optimization, at 10 V and 24 V for aluminum and iron electrode, TOC was found to reduce by 14% and 22% respectively. By Fenton’s reaction with iron electrode, 41% TOC removal was observed, with reduction of cefixime to 0.01 mg/l. On step two EC with H2O2, a further 2% TOC removal facilitated in reduction of cefixime to 0.001 mg/l, determined by HPLC-MS (High Performance Liquid Chromatography-Mass Spectrometry). The sequential EC treated-diluted effluent, subjected to TiO2 and H2O2 assisted photocatalytic oxidation by natural sunlight and UV source, separately, resulted in further TOC reduction of 30% and 33% respectively. EC treatment effectively reduced the API below MIC (6 mg/l), determined by antimicrobial activity and EC-Fenton’s reaction allowed elimination of pre-existing bacteria in effluent, below the lower limit of detection (LOD) i.e., 0.5 colony forming units (CFU)/ml. Thus, this work highlights the significance of non-biological treatments of drug effluents to prevent microbial drug resistance in environment. 

Abstract

Cobalt oxide visible light-active photo-catalysts supported on TiO2 nanoparticles with varying amount of cobalt oxide [3% CoOx/TiO2 (A), 4% CoOx/TiO2 (B), 5% CoOx/TiO2 (C)] were synthesized by solid-state method followed by calcination. The as-synthesized catalysts were characterized by various techniques such as powder XRD, TEM, EDX, UV-Vis-DRS and XPS analysis. The photocatalytic activity of the as-synthesized materials was studied for the reduction of nitroarenes to the corresponding amines using hydrazine monohydrate as the reductant. Cobalt(II) oxide is responsible for the reduction of nitroarenes and then, cobalt(III) is reduced back to the original compound by hydrazine hydrate, thus ascertaining the catalytic nature of this hydrogenation process. XPS suggests the presence of Co(II) in CoOx/TiO2. 

Abstract

Herein we report the synthesis and photocatalytic evaluation of heterostructure WO3/g-C3N4 (WMCN) and CeO2/g-C3N4 (CMCN) materials for RhB degradation and photoelectrochemical studies. These materials were synthesized by varying the dosages of WO3 and CeO2 on g-C3N4 individually and were characterized with state-of-the-art techniques like XRD, BET surface area, FT-IR, UV–Vis DRS, TGA, SEM, TEM and XPS. A collection of combined structural and morphological studies manifested the formation of bare g-C3N4, WO3, CeO2, WO3/g-C3N4 and CeO2/g-C3N4 materials. From the degradation results, we found that the material with 10 wt% WO3 and 15 wt% CeO2 content on g-C3N4 showed the highest visible light activity. The first order rate constant for the photodegradation performance of WMCN10 and CMCN15 is found to be 5.5 and 2.5 times, respectively, greater than that of g-C3N4. Photoelectrochemical studies were also carried out on the above materials. Interestingly, the photocurrent density of WMCN10 photoanode achieved 1.45 mA cm−2 at 1.23 V (vs.) RHE and this is much larger than all the prepared materials. This enhanced photoactivity of WMCN10 is mainly due to the cooperative synergy of WO3 with g-C3N4, which enhanced the visible light absorption and suppresses the electron–hole recombination. 

Abstract

Present study reports the application of non-thermal plasma approach for the partial oxidation of methane to methanol. The target was achieved by employing oxygen under ambient condition in a dielectric barrier discharge (DBD) reactor, which was later operated as a packed bed DBD. A variety of packing materials of different nature (Al2O3, TiO2, CeO2 and glass beads) are tested and corresponding reaction pathways also have been shown. In addition, the influence of the feed gas composition, total flow rate and specific input energy has been investigated. Formation of CH3OH, H2, CO, CO2, C2H6, and HCHO has been identified. Typical results indicated that the plasma reactor operating under a packed bed configuration showed better performance than the reactor without packing. Among the packing materials used, glass beads packing provided the best selectivity of ~35% to methanol, whereas, it was around 25% with DBD reactor without packing. In a similar manner, the yield of methanol increased to 5.4% with glass beads packing against 1.7% with DBD reactor with no packing. The good performance with glass beads packing is due to the uniform distribution of the microdischarges and improved filed strength. 

Abstract

A non-thermal atmospheric pressure plasma jet has been used for the green synthesis of highly dispersed colloidal silver nanoparticles. The reducing species such as hydrogen radicals and hydrated electrons are identified, and the change in the solution pH is studied during AgNP formation. The structural properties and size of the plasma-reduced silver nanoparticles are characterized via X-ray diffraction, ultraviolet-visible spectroscopy, fluorescence spectroscopy and transmission electron microscopy. The size of the colloidal AgNPs is tuned by adjusting the initial concentration of AgNO3. The effect of terephthalic acid, a hydroxyl radical scavenger, on the reduction of Ag+ ion is studied. The typical catalytic activity data indicate the better performance of the plasma-reduced colloidal Ag nanoparticles than that obtained from the chemical reduction method. The antibacterial activity of the plasma-reduced Ag nanoparticles also shows a better performance than that of the chemically reduced AgNPs, highlighting the potential of the plasma reduction approach for the synthesis of metal nanoparticles, which are stable even after 30 days without a stabilizing agent. Additionally, the effects of hydroxyl scavengers (isopropyl alcohol) and Fenton's reagent (Fe2+ salt) on CV degradation are studied. 

Abstract

Pd/CuFe2O4 nanowire-catalyzed cross coupling transformations are described. Notably, these reactions showed excellent functional group tolerance. Further, the protocol is applied to a one-pot synthesis of benzofurans via a Sonogashira coupling and intramolecular etherification sequence. The catalyst was reused and found to maintain its activity and stability. 

Abstract

Monoclinic Bismuth vanadate (BiVO4) nanomaterial is an attractive, efficient photoanode for photoelectrochemical (PEC) water splitting due to excellent visible light activity and good photo-chemical stability. However, poor charge separation and low charge carrier mobility hinder the improvement of PEC performance of BiVO4. In this work, molybdenum (Mo)-doped BiVO4@reduced graphene oxide (rGO) nanocomposites are fabricated and their potential to serve as photoanodes for PEC water splitting is evaluated. This composite, by the introduction of Mo-dopant and rGO in BiVO4 enhances the PEC performance for water oxidation for they assist in reducing charge recombination and enhancement of photocurrent. As a result, the Mo-BiVO4@rGO composite photoanode exhibited a photocurrent density of 8.51 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE), which is two and four times greater than that of Mo-BiVO4 (5.3 mA cm-2 at 1.23 V versus RHE) and pristine BiVO4 (2.01 mA cm−2 at 1.23 V versus RHE) photoactive electrodes. In addition, good photo-conversion efficiency, low charge transfer resistance and good external quantum efficiency (EQE) are achieved for this ternary nanocomposite. These studies reveal the improved PEC activity for water splitting by the Mo-doped BiVO4@rGO, and indicated that this approach can be used to design more efficient photoanodes for PEC water splitting. 

Abstract

This study reports the potential of non-thermal atmospheric pressure plasma jet for the bacterial inactivation in an aqueous medium. All experiments were conducted in a reactor containing aqueous solution i.e., water, pre-inoculated with bacterial suspensions and after plasma exposure solution is inoculated in Petrifilm to know the viable count. The plasma jet exposure to the bacterial aqueous solution was carried out under various gases such as helium, argon, air and also in combination as Argon + Air and Helium + Air. In each case, the oxidizing species such as hydrogen peroxide, nitric acid, hydroxyl radicals and ozone formed in the reactor during the plasma exposure were quantified. The effect of applied voltage and gas flow rate were studied to optimize the conditions for its efficacy. The solution pH plays a prominent role in bacterial inactivation, as the process is effective at low pH exhibiting 7 log reduction of bacterial population. The bacterial inactivation is efficient at below the critical pH (<4.7) and the inactivation process becomes less effective if the pH goes above 4.7. Plasma treatment of deionized water produces some reactive species such as hydrogen peroxide and nitrates, this plasma treated water is used to test the bacterial inactivation. Addition of Fe2+ salt to the plasma treated water improves the efficacy by converting hydrogen peroxide to hydroxyl radicals, which serves to be a major contributor to the bacterial inactivation. Especially, Non-thermal plasma offers an alternative way to sterilize vacuum sensitive and thermo-labile living tissues. 

Abstract

The partial oxidation of methane to methanol was performed in a non-thermal dielectric barrier discharge (DBD) plasma reactor. The influence of various parameters on the conversion of methane, product selectivity and energy efficiency has been studied. Typical results indicate that the discharge gap has a marked influence on methane conversion and product distribution. The best selectivity to CH3OH and HCHO was ~25% and ~17% at a discharge gap of 4.5 and 5 mm, respectively, and the highest corresponding energy efficiency was ~0.9 mmol kJ−1. At a later state, the DBD reactor was operated under a packed-bed configuration by integrating the discharge gap with zero surface glass materials having different geometry: glass beads (spherical), glass capillary (hollow cylindrical) and glass wool (spongy honeycomb) to understand the influence of material geometry on the plasma discharge and finally on the formation of products such as CH3OH, HCHO, CO, CO2, H2, C2H6. Typical results indicated that the morphology of the packing materials affects the discharge characteristics, and hence the product distribution. It is concluded that the better performance of the packed-bed plasma reactor is due to the improved electrical field strength. Among the geometries studied, glass wool showed the highest CH4 conversion due to the improved field strength/surface corona, whereas glass-bead packing improved the CH3OH selectivity to ~32%. 

Abstract

The conversion of greenhouse gases, H2 and CO selectivity, H2/CO ratio, and carbon formation in the dry reforming reaction over Ni-supported ZSM-5, Al2O3, and TiO2 are tested under thermal, plasma, and plasma–thermal conditions. It is observed that the dielectric nature, specific surface area, and acid-base properties of the support influence the performance during the DRM reaction. Typical results indicate that the best activity and syngas yield are achieved with 15Ni/Al2O3 under plasma conditions, possibly due to the high dielectric constant and surface area of Al2O3 and nanosize of Ni. In the thermal condition, the highest conversion of 73% and 68% for CH4 and CO2, respectively, is achieved over 15Ni/ZSM-5 at 500 °C. Plasma-assisted thermal conditions provide the highest conversion due to the activation of reactants and their partial conversion in the plasma zone before entering into the catalytic zone. The plasma-assisted thermocatalytic conversions of CH4 and CO2 reach the best values of 76% and 71%, respectively, on 15Ni/ZSM-5. Under the same conditions, 68% and 65% conversion of CH4 and CO2, respectively, is achieved with 15Ni/Al2O3 where the selectivity for H2 and CO is 45% and 58%, respectively. 

Abstract

Anilines are one of the important chemical feedstocks and are utilized for the preparation of a variety of pharmaceuticals, agrochemicals, pigments, and dyes. In this context, the catalytic reduction of nitro functionality is an industrially vital process for the synthesis of aniline derivatives. Herein, we report an efficient nanosized bimetallic Pd–Au/TiO2 nanomaterial which is proved to be quite efficient for rapid catalytic hydrogen transfer reduction of nitroarenes into corresponding amines. Significantly, the reduction process is successful under solvent-free and mild green atmospheric conditions. Bimetallic Pd–Au nanoparticles served as the active center, and TiO2 played as a support in hydrogen transfer from the source hydrazine monohydrate. Typical results highlighted that the reactions were very rapid and the products were obtained in good to excellent yields. Significantly, the process was successful in the presence of a very low amount catalyst (0.1 mol %). Furthermore, the reaction showed good chemoselectivity and compatiblity with double or triple bond, aldehyde, ketone, and ester functionalities on the aromatic ring. Typical results indicated the true heterogeneous nature of the Pd–Au/TiO2 nanocatalyst, where the catalyst retained the activity, without loss of its activity.