Publications

Abstract: In this work, the electronic structure and optical properties are investigated within the framework of the density functional theory (DFT) for different Na-H co-doping scenarios to find out the suitability of H co-doping technique for achieving p-type conductivity in ZnO. Very low formation energies were found for the H co-doped systems compared to others which suggests that they can suppress other n-type impurities and increase the effect of p-type NaZn defects in the lattice. From the electronic structure calculations, we have found that NaZn doped structures with 50% H co-doping produces the best p-type behavior indicating importance of controlling annealing time. Moreover, from the optical calculations, it has been found that NaZn creates impurity states 174 meV above the valence band and electron concentration in these states can be controlled by H co-doping concentration. H co-doping has not produced any substantial lattice strain as compared to other dopants and structures with Na-H co-doping is transparent in the visible light range. 

Abstract: Co3O4 decorated MoS2 nanoflower (MoS2/Co3O4) has been successfully synthesized by a simple hydrothermal method. A combined experimental and theoretical investigation was performed to comprehend the effect of Co3O4 on the structural, optical, and electronic properties of MoS2 nanoflowers. A number of characterization techniques have been used to study the surface morphologies, structural properties, chemical constitution, and optical properties of the nanocomposites including, FE-SEM, TEM, XRD, XPS, and UV–VIS spectroscopy. Flower-like structures of MoS2 and MoS2/Co3O4 have been observed from the FE-SEM and TEM images. The Rietveld refinement of the X-ray diffraction (XRD) pattern was used to estimate the various structural parameters of the nanoflowers which also confirms the phase purity of the MoS2 nanoflower. X-ray photoelectron spectroscopy (XPS) results revealed strong electronic interaction between Mo–S and Co–O in the nanocomposites. The optical bandgap of the as-prepared samples was estimated using diffusive reflectance spectra and was found to be varied between 1.44 eV to 1.27 eV nanostructure due to the incorporation of Co3O4 nanoparticle. To fully understand and validate the structural, optical, and electrical characteristics of the samples, density functional theory (DFT) calculations were carried out. DFT results revealed that the Mo-4d and Co-3d orbital-orbital interactions occur due to the incorporation of Co3O4 into MoS2, leading to a decrease in the band gap. Moreover, a charge redistribution occurred between MoS2 and Co3O4 interface, creating more active sites for electro and opto-catalytic reactions. Among the results, the red shift of the optical absorbance spectra is the most obvious one enabling our synthesized nanocomposite to absorb in the near-infrared range. This study will offer a new insight into the fabrication of transition oxide-based hetero-interface influenced MoS2 functional devices for diverse applications.

Abstract: A comprehensive investigation of the gas sensing potential of BeS monolayer has been conducted using DFT calculations. Twelve common pollutant gases: NH3, NO2, NO, CO, CO2, CH4, H2, O2, N2, H2S, H2O and SO2, have been studied. Our analysis reveals defect states in the band structure near the Fermi level and strong hybridization between gas molecule orbitals and the BeS monolayer. We observe higher adsorption energies for NH3 and CO compared to other popular gas sensing materials. The optical properties of CO2 and NO2 adsorbed on the BeS monolayer show increased reflectivity and absorption coefficient in the UV and far infrared region. Tensile strain has minimal impact on adsorption energy, while biaxial compressive strains enhance the gas sensing capability of the BeS monolayer. The application of an electric field offers control over gas adsorption and desorption. We propose the BeS monolayer as a promising candidate for future gas molecule sensing applications due to its high adsorption energy, rapid recovery time, and distinct optical properties.

Abstract: The corrosion of reinforcement possesses a huge problem for our present infrastructure both in terms of human lives and monetary ground. Understanding the corrosion of thermomechanically treated (TMT) rebar in concrete structures is essential as it represents a large segment of reinforcement materials. In this review, we have tried to scrutinize this issue from different directions. The established corrosion model for rebar, especially for TMT rebar, has been examined. The main contributing factor for rebar corrosion is how passivation occurs and its disintegration in contact with aggressive ions. The effects of composition, microstructure, concrete-rebar interface, concrete type, and corrosion media on this phenomenon have been analyzed. We have realized that the exact time of chloride ion attack determines the effectiveness of the passive layer in inhabiting the corrosion initiation. A combination of suitable alloying and controlled thermomechanical treatment ensures corrosion resistant rebar. Concrete also plays an important role in corrosion prevention as it helps passivation step and stops aggressive ions from reaching the rebars. Finally, we have discussed some recent trends in corrosion management technologies and their effectiveness.

Abstract: Bio-composites have diverse functional demands for many structural, electrical, electronic, and medical applications. An expansion of the composite functionality is achieved by manipulating the material and design scheme. Smart selection of matrix-reinforcement combinations will lead to applications that have never even been considered. Research holds a huge potential to create a wide variety of usable materials by mixing different fillers and modifying the parameters. Apart from selecting the polymer and the filler, the engineer will have to understand the compatibility of the polymer and the filler, dispersion, and bonding behavior making the design of polymer nanocomposite a rather complex system. In this chapter, we have tried to display different functional materials development pursuit.