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Research Articles
Fabrication and characterization of Sb-doped MXene prepared by hydrothermal method for use as a sensing electrode for heavy metal detection.
Siranaree Phoodadsuan, Thitima Maturos Daniels, Mati Horprathum, Nichaphat Thongsai, Eakkasit Punrat. (2024). Journal of Metals, Materials and Minerals. Vol. 34, No. 2, p. 2008, June 2024.
MXene, a two-dimensional material with favorable physicochemical characteristics, has demonstrated outstanding efficiency in a wide range of applications because of their superior properties, such as higher surface area and conductivity, and facile surface modification. In this study, antimony (Sb) doped MXenes were synthesized via a simple hydrothermal method, employing various Sb concentrations ranging from 5 %w/w to 25 %w/w. The successful preparation of the Sb-doped MXene (Sb@MXene) was confirmed by an X-ray diffraction (XRD) method. Physical morphologies examined through field-emission scanning electron microscopy (FE-SEM) depict the presence of Sb nanoparticles with the size of about 80 nm on the surface and interlayer of MXenes. The Sb@MXene composites demonstrated significant potential as electrochemical sensing materials for heavy metal detection. Both 5%Sb@MXene and 25%Sb@MXene composites were prepared as the screen-printed electrode (SPE) materials via drop-casting method to sense Pb²⁺, Cd²⁺, and Zn²⁺. The 25%Sb@MXene SPE show the highest sensitivity toward Pb²⁺ (3.62 μA∙ppm⁻¹), Cd²⁺ (2.53 μA∙ppm⁻¹), and Zn²⁺ (0.90 μA∙ppm⁻¹) solution, compared with that of 5%Sb@MXene SPE. This work not only demonstrates a simple preparation of Sb@MXene, but also applies the hybrid materials in electrochemical sensing application.
Development of inexpensive device for methanol detection in hand sanitizer gel using manganese-doped zinc sulfide quantum dots modified by N-methylpolypyrrole.
Sophanat Khenthaphak, Pakorn Juleang, Wanida Wonsawat, Orawon Chailapakul, Eakkasit Punrat. (2023). Journal of Metals, Materials and Minerals. Vol. 33, No. 1, pp. 82-88, March 2023.
A method for methanol detection by an inexpensive device using a nanomaterial modified by N-methylpolypyrrole (NMPPY) has been developed. Manganese-doped zinc sulfide quantum dots (Mn/ZnS-QDs) were synthesized and then characterized by a fluorescence spectrophotometer to study their spectroscopic properties. Mn/ZnS-QDs were modified with NMPPy and studied by digital-image colorimetry to optimize conditions for methanol detection. A 2 mL of 3000 mg∙L⁻¹ Mn/ZnS-QDs modified with 300 μL of 1000 mg∙L⁻¹ of NMPPy was chosen to be a detecting reagent for methanol determination. Under the optimum conditions, the linear range was found to be 2 %v/v to 50 %v/v of methanol with R-square of 0.9434 and the sensitivity of 3.569 × 10⁻³ (%v/v)⁻¹, whilst the limit of detection (LOD) was 19.5 %v/v. The selectivity of this method was also studied with several solvents; it was proven selective for methanol. Furthermore, a prototype device with simple and inexpensive has been created. The analytical performances were studied; the linearity of methanol detection was found in the range of 20 %v/v to 80 %v/v with R-square of 0.9918 and the sensitivity of 3.38 × 10⁻³ (%v/v)⁻¹. Finally, the newly developed device was applied to analyze samples of hand sanitizer gel by digital-image colorimetry with acceptable results.
Sequential injection analysis for mercury ion with modified screen-printed carbon electrode.
Eakkasit Punrat, Naphat Piyasart, Chalinee Auanphui, Rutanachai Thaipratum, Shoji Motomizu, Wanida Wonsawat. (2022). Journal of Metals, Materials and Minerals. Vol. 32, No. 3, pp. 101-107, September 2022.
In this study, we developed a simple high-throughput and cost-effective method for monitoring toxic metal ion in an environmental aqueous sample. Mercury ion determination with Sequential Injection Analysis system (SIAs) coupled with the electrochemical detection on the modified screen-printed carbon working electrode (SPCE) is an alternative green analysis of mercury ion. The gold film was used as the modified material for improved mercury ion analysis in the automated system without memory effect on the electrode. Mercury oxidation signal was found at the potential of 0.7 V in 0.1 M HNO₃ and 1.0 M HCl with the concentration low to 0.25 ± 0.18 mg∙L⁻¹. Online sample preparation and separation will study in the further experiment.
Facile and fast detection of genistein in Derris scandens by square wave voltammetry using a cobalt(II) phthalocyanine-modified screen-printed electrochemical sensor.
Surinya Traipop, Suchada Chuanuwatanakul, Orawon Chailapakul, Eakkasit Punrat. (2020). Current Analytical Chemistry. Vol. 16, Issue 3, pp. 341-348.
Background: Recently, Derris scandens, a Thai herbal medicine with anti-inflammatory activity, is widely used as beverage and supplementary food. When the traditional medicine is a choice for health therapy, the simple and reliable equipment is required to control the suitable consuming amount of the active component.
Objective: To develop the electrochemical sensor for genistein determination in Derris scandens with high sensitivity and rapid operation.
Methods: An in-house screen-printed electrochemical sensor consisting of a three-electrode system was developed for genistein determination. A silver/silver chloride (Ag/AgCl) reference electrode, a carbon counter electrode and a carbon working electrode were prepared on a 0.3-mm-thick plastic substrate by the screen-printing technique using conductive ink. The dimensions of each sensor were 2.5×1.0 cm. Only 50 µL of sample solution was required on this device for the determination of genistein concentration by rapid response square wave voltammetry.
Results: The oxidation peak of genistein appeared with good response in acidic media at a peak potential of 0.6 V. Moreover, the signal was enhanced by modifying the conductive carbon ink with cobalt(II) phthalocyanine. Under the optimized conditions, the linear range was found to be 2.5-150 µM and the detection limit was 1.5 µM. Moreover, the small volume extraction was successfully developed without any further pre-concentration. This proposed method was applied to determine genistein in Derris scandens with satisfying results.
Conclusion: The proposed method is promising as an alternative method for genistein determination with facile and fast analysis.
Objective: To develop the electrochemical sensor for genistein determination in Derris scandens with high sensitivity and rapid operation.
Methods: An in-house screen-printed electrochemical sensor consisting of a three-electrode system was developed for genistein determination. A silver/silver chloride (Ag/AgCl) reference electrode, a carbon counter electrode and a carbon working electrode were prepared on a 0.3-mm-thick plastic substrate by the screen-printing technique using conductive ink. The dimensions of each sensor were 2.5×1.0 cm. Only 50 µL of sample solution was required on this device for the determination of genistein concentration by rapid response square wave voltammetry.
Results: The oxidation peak of genistein appeared with good response in acidic media at a peak potential of 0.6 V. Moreover, the signal was enhanced by modifying the conductive carbon ink with cobalt(II) phthalocyanine. Under the optimized conditions, the linear range was found to be 2.5-150 µM and the detection limit was 1.5 µM. Moreover, the small volume extraction was successfully developed without any further pre-concentration. This proposed method was applied to determine genistein in Derris scandens with satisfying results.
Conclusion: The proposed method is promising as an alternative method for genistein determination with facile and fast analysis.
Voltammetric detection of carbofuran determination using screen-printed carbon electrodes modified with gold nanoparticles and graphene oxide.
Apapond Jirasirichote, Eakkasit Punrat, Akkapol Suea-Ngam, Orawon Chailapakul, Suchada Chuanuwatanakul. (2017). Talanta. Vol. 175, pp. 331−337, 1 December 2017.
Carbofuran is a highly toxic pesticide that is heavily used in agriculture due to its high effectiveness and low cost. Improved methods that are simpler and lower cost are needed for carbofuran detection in food and agricultural samples. Herein, we describe the development of a unique electrochemical method for carbofuran-phenol, which is the main hydrolysis product of carbofuran. We have successfully developed a highly accurate and precise method in a portable size using a screen-printed carbon electrode (SPCE) that is modified with graphene oxide (GO) and gold nanoparticles (AuNPs). Consequently, the developed electrode is highly sensitive to and selective for carbofuran. Using the central composite design (CCD) approach, we optimized the method for analysis parameters including the electrode surface loadings of GO and AuNPs as well as the working solution pH. The method exhibited a wide linear range of 1–250 µM for analyte detection using differential pulse voltammetry (DPV) on AuNPs/GO-SPCE under the optimized conditions. The limits of detection and quantitation were 0.22 and 0.72 µM, respectively. In addition, we also report the application of the method for carbofuran determination in real cucumber and rice samples. This sensitive and selective carbofuran detection method is very promising for simple and low cost analysis in real agricultural fields.
Determination of nickel(II) by ion-transfer to hydroxide medium using sequential injection-electrochemical analysis (SIECA).
Eakkasit Punrat, Panunporn Tutiyasarn, Suchada Chuanuwatanakul, Orawon Chailapakul. (2017). Talanta. Vol. 168, pp. 286−290, 1 June 2017.
A method for the determination of Ni(II) using ion-transfer to a hydroxide medium has been developed by the sequential injection-electrochemical analysis (SIECA), a combination between an automated flow-based analysis and electrochemical techniques with a homemade screen-printed carbon electrode (SPCE). A sample/standard solution was introduced into an electrochemical flow cell where the Ni(II) in the solution was electrochemically reduced and accumulated on the SPCE. The accumulated Ni was then oxidized to Ni(II) in a hydroxide medium, which led to the formation of nickel hydroxide (Ni(OH)₂) and nickel oxyhydroxide (NiOOH) on the SPCE. The electrochemical response associated with Ni(OH)₂ and NiOOH was subsequently determined by square-wave voltammetry to account for Ni(II). Under optimal conditions, the proposed method provides a low detection limit of 0.02 mg mL⁻¹. This method was further applied to determine the Ni(II) content of standard-spiked mineral water samples with satisfactory results.
Graphene oxide-modified electrode coated with in-situ antimony film for the simultaneous determination of heavy metals by sequential injection-anodic stripping voltammetry.
Prasongporn Ruengpirasiri, Eakkasit Punrat, Orawon Chailapakul, Suchada Chuanuwatanakul. (2017). Electroanalysis. Vol. 29, Issue 4, pp. 1022−1030, 28 December 2016.
The proposed chemically modified electrode was graphene oxide that was synthesized via Hummer's method followed by reduction of antimony film by in-situ electrodeposition. The experimental process could be concluded in three main steps: preparation of antimony film, reduction of analyte ions on the electrode surface and stripping step under the conditions of square wave anodic stripping voltammetry (SWASV). A simple and rapid approach was developed for the determination of heavy metals simultaneously based on a sequential injection (SI), an automated flow-based system, coupled with voltammetric method using antimony-graphene oxide modified screen-printed carbon electrode (SbF-GO-SPCE). The effects of main parameters involved with graphene oxide, antimony and measurement parameters were also investigated. Using SI-SWASV under the optimal conditions, the proposed electrode platform has exhibited linear range from 0.1 to 1.5 M. Calculated limits of detection were 0.054, 0.026, 0.060, and 0.066 μM for Cd(II), Pb(II), Cu(II) and Hg(II), respectively. In addition, the optimized method has been successfully applied to determine heavy metals in real water samples with acceptable accuracy of 94.29 – 113.42 % recovery.
Digital-imaging colorimetry of reaction between formaldehyde and purpald reagent on paper-based analytical device.
Eakkasit Punrat, Suchapa Naranarumon, Orawon Chailapakul. (2016). Huachiew Chalermprakiet Science and Technology Journal. Vol. 2, Issue 1, pp. 7−14.
Digital-image colorimetry has been used for the determination of formaldehyde using purpald reaction on a simply fabricated paper-based analytical device (PAD). The PAD can be simply fabricated by cutting filter paper to small piece (6 mm diameter) using a puncher. The reaction between formaldehyde and purpald reagent was performed and generated the purple product on the PAD. A photograph of the resulting PAD, placed in a home-made mini-studio box, was taken by a smart phone’s camera with the fixed camera settings: ISO value, white balance and shutter speed. The photograph then was analyzed the color intensity by ImageJ computer software. Using 5.0 μL of purpald reagent and the reaction time of 720 s, the standard calibration graph was in linear-log model at the range of 1.0-20 mg L⁻¹ formaldehyde with R² of 0.9919. This method will be an alternative method which is simple and low-cost for the formaldehyde determination.
Polyaniline/graphene quantum dot-modified screen-printed carbon electrode for the rapid determination of Cr(VI) using stopped-flow analysis coupled with voltammetric technique.
Eakkasit Punrat, Chakkarin Maksuk, Suchada Chuanuwatanakul, Wanida Wonsawat, Orawon Chailapakul. (2016). Talanta. Vol. 150, pp. 198−205, 1 April 2016.
Polyaniline/graphene quantum dots (PANI/GQDs) were used to modify a screen-printed carbon electrode (SPCE) in a flow-based system. A method for rapidly determining the Cr(VI) concentrations by using stopped-flow analysis has been developed using an Auto-Pret system coupled with linear-sweep voltammetry using the PANI/GQD-modified SPCE. The GQDs, synthesized in a botton-up manner from citric acid, were mixed with aniline monomer in an optimized ratio. The mixture was injected into an electrochemical flow cell in which electro-polymerization of the aniline monomer occurred. Under conditions optimized for determining Cr(VI), wide linearity was obtained in the range of 0.1–10 mg L⁻¹, with a detection limit of 0.097 mg L⁻¹. For a sample volume of 0.5 mL, the modified SPCE can be used continuously with a sample-throughput of more than 90 samples per hour. In addition, this proposed method was successfully applied to mineral water samples with acceptable accuracy, and the quantitative agreement was accomplished in deteriorated Cr-plating solutions with a standard traditional method for Cr(VI) detection.
Graphene/polyvinylpyrrolidone/polyaniline nanocomposite-modified electrode for simultaneous determination of parabens by high performance liquid chromatography.
Suphunnee Kajornkavinkul, Eakkasit Punrat, Weena Siangproh, Nadnudda Rodthongkum, Narong Praphairaksit, Orawon Chailapakul. (2016). Talanta. Vol. 148, pp. 655−660, 1 February 2016.
A nanocomposite of graphene (G), polyvinylpyrrolidone (PVP) and polyaniline (PANI) modified onto screen-printed carbon electrode (SPCE) using an electrospraying technique was developed for simultaneous determination of five parabens in beverages and cosmetic products by high performance liquid chromatography. PVP and PANI were used as the dispersing agents of graphene, and also for the enhancement of electrochemical conductivity of the electrode. The electrochemical behavior of each paraben was investigated using the G/PVP/PANI nanocomposite-modified SPCE, compared to the unmodified SPCE. Using HPLC along with amperometric detection at a controlled potential of +1.2 V vs Ag/AgCl, the chromatogram of five parabens obtained from the modified SPCE exhibits well defined peaks and higher current response than those of its unmodified counterpart. Under the optimal conditions, the calibration curves of five parabens similarly provide a linear range between 0.1 and 30 µg mL⁻¹ with the detection limits of 0.01 µg mL⁻¹ for methyl paraben (MP), ethyl paraben (EP) and propyl paraben (PP), 0.02 and 0.03 µg mL⁻¹ for isobutyl paraben (IBP) and butyl paraben (BP), respectively. Furthermore, this proposed method was applied for the simultaneous determination of five parabens in real samples including a soft drink and a cosmetic product with satisfactory results, yielding the recovery in the range of 90.4–105.0%.
Development of electrochemical paper-based glucose sensor using cellulose-4-aminophenylboronic acid-modified screen-printed carbon electrode.
Tipawan Rungsawang, Eakkasit Punrat, Jaclyn Adkins, Charles Henry, Orawon Chailapakul. (2016). Electroanalysis. Vol. 28, pp. 462−468, 14 August 2015.
The present work describes the fabrication of paper-based analytical devices (μPADs) by immobilization of glucose oxidase onto the screen printed carbon electrodes (SPCEs) for the electrochemical glucose detection. The sensitivity towards glucose was improved by using a SPCE prepared from homemade carbon ink mixed with cellulose acetate. In addition, 4-aminophenylboronic acid (4-APBA) was used as a redox mediator giving a lower detection potential for improvement selectivity. Under optimized condition, the detection limit was 0.86 mM. The proposed device was applied in real samples. This μPAD has many advantages including low sample consumption, rapid analysis method, and low device cost.
Method development for the determination of mercury(II) by sequential injection/anodic stripping voltammetry using an in situ gold-film screen-printed carbon electrode.
Eakkasit Punrat, Suchada Chuanuwatanakul, Takashi Kaneta, Shoji Motomizu, Orawon Chailapakul. (2014). Journal of Electrocanalytical Chemistry. Vol. 727, pp. 78−83, 1 August 2014.
A computer-controlled system, included a sequential injection system and an electrochemical detector, was developed for the determination of mercury(II) ion (Hg²⁺) concentrations. The screen-printed carbon electrode (SPCE), a well-known low-cost electrode, was modified by overlaying in situ with a gold film (Au-SPCE). Square wave anodic stripping voltammetry (SWASV) using the Au-SPCE was performed with a two-step deposition potential of an initial −0.5 V vs Ag/AgCl for the preparation of the gold film and then a deposition potential of +0.2 V vs Ag/AgCl for the preconcentration of mercury. An on-line medium exchange method was included in the injection step to reduce the effect of chloride ions, whilst a solid phase extraction cartridge was used to remove interference for copper(II) ions. The flow pattern of the sequentially injected solutions with the synchronized two-step deposition potentials did not significantly affect the detection of Hg²⁺. Square wave parameters of a 4 mV step potential, 150 Hz frequency and 30 mV amplitude gave an optimal Hg²⁺ detection sensitivity with a limit of detection of 0.22 μg L⁻¹ (sample volume of 0.9 mL) without any significant interference effect. This method was successfully applied to determine Hg²⁺ concentrations in real water samples, including in the chloride-rich samples of sea water and table salt, with very good accuracy (recovery in the range of 96.0–101%).
Method development for the determination of arsenic by sequential injection/anodic stripping voltammetry using long-lasting gold-modified screen-printed carbon electrode.
Eakkasit Punrat, Suchada Chuanuwatanakul, Takashi Kaneta, Shoji Motomizu, Orawon Chailapakul. (2013). Talanta. Vol. 116, pp. 1018−1025, 15 November 2013.
An automated method has been developed for determining the concentration of inorganic arsenic. The technique uses sequential injection/anodic stripping voltammetry with a long-lasting gold-modified screen-printed carbon electrode. The long-lasting gold electrode was electrochemically deposited onto a screen-printed carbon electrode at a potential of −0.5 V vs. Ag/AgCl in a supporting electrolyte solution of 1 M hydrochloric acid. Under optimal conditions and the applied potentials, the electrode demonstrated that it can be used for a long time without a renewal process. The linear range for the determination of arsenic(III) was 1–100 μg L⁻¹, and the limit of detection (LOD) in standard solutions was as low as 0.03 μg L⁻¹ for a deposition time of 120 s and sample volume of 1 mL. This method was used to determine the concentration of arsenic(III) in water samples with satisfactory results. The LOD in real samples was found to be 0.5 μg L⁻¹. In addition, speciation between arsenic(III) and arsenic(V) has been achieved with the proposed method using deposition potentials of −0.5 V and −1.5 V for the determination of the arsenic(III) concentration and the total arsenic concentration, respectively; the results were acceptable. The proposed method is an automated system that offers a less expensive alternative for determining trace amounts of inorganic arsenic.
Graphene-carbon paste electrode for cadmium and lead ion monitoring in a flow-based system.
Wanida Wonsawat, Suchada Chuanuwatanakul, Wijitra Dungchai, Eakkasit Punrat, Shoji Motomizu, Orawon Chailapakul. (2012). Talanta. Vol. 100, pp. 282–289, 15 October 2012.
An environment friendly electrode for determining Cd²⁺ and Pb²⁺ levels in an automated flow system was successfully developed. Cyclic voltammetry and square wave anodic stripping voltammetry (SWASV) coupled with sequential injection analysis (SIA) were employed to study the electrochemical behavior of the electrode. The in situ bismuth-modified graphene-carbon paste electrode (Bi-GCPE) exhibited excellent electrooxidation of Cd²⁺ and Pb²⁺ in the automated flow system with a significantly higher peak current for both metal ions compared with the unmodified CPE. The limits of detection from this method were 0.07 and 0.04 μg L⁻¹ for Cd²⁺ and Pb²⁺, respectively, with a linear oxidation peak current response for Cd²⁺ and Pb²⁺ in the range of 0.10–50.0 μg L⁻¹ under optimum conditions. The Bi-GCPE was also applied for the determination of Cd²⁺ and Pb²⁺ in low- (tap water) and high- (sea bass fish and undulated surf clam tissues) matrix complexity samples by automated flow system. The recoveries were acceptable and ranged from 70.4% to 120% for Cd²⁺ and 65.8% to 113.5% for Pb²⁺.
Determination of arsenic(III) by sequential injection/anodic stripping voltammetry (SI/ASV) using in-situ thin film-modified screen-printed carbon electrode (SPCE).
Eakkasit Punrat, Suchada Chuanuwatanakul, Orawon Chailapakul, Toshio Takayanagi, Takashi Kaneta, Shoji Motomizu. (2012). Journal of Flow Injection Analysis. Vol. 29, pp. 11–16, 20 July 2012.
Sequential injection system (SI system) was used for the pretreatment of a carbon electrode in an anodic stripping voltammetry (ASV) for the determination of arsenic (III). In this research, a screen-printed carbon electrode (SPCE) was used; SPCE was prepared in our laboratory by us. In ASV, SPCE was chosen as a working electrode because SPCE is less expensive, easy to use for a flow cell and suitable for thin-film modification method. ASV parameters were optimized with a handy-type potentiostat. The proposed method is one of alternatives for the determination of arsenic (III), which is fast, accurate and precise method with less expensive automated system.
On-line preconcentration and determination of trace heavy metals by sequential injection-anodic stripping voltammetry using bismuth film screen-printed carbon electrode.
Suchada Chuanuwatanakul, Eakkasit Punrat, Janjira Panchompoo, Orawon Chailapakul, Shoji Motomizu. (2008). Journal of Flow Injection Analysis. Vol. 25, pp. 49–52, 6 October 2008.
An automated on-line preconcentration method was developed for simultaneous determination of Pb(II), Cd(II) and Zn(II) by square-wave anodic stripping voltammetry (SWASV) using bismuth film screen-printed carbon electrode (Bi-SPCE). The preconcentration of metal ions was performed with a mini-column of a chelating resin, which was installed on a switching valve in the automated system consisted of a syringe pump, an 8-port selection valve and a switching valve. The laboratory-assembled automated on-line pretreatment system (Auto-Pret ASV system) was controlled by the Visual Basic program written by the authors. The metal ions collected on the resin were eluted with 1 M hydrochloric acid, subsequently transported into the flow cell for on-line deposition of analytes on Bi-SPCE at -1.4 V vs. Ag/AgCl; then the flow of the solution was stopped and the voltammogram was recorded from -1.2 to 0.2 V vs. Ag/AgCl by scanning a potential in the square-wave waveform. Experimental conditions, such as pH of sample, a sample flow rate, an eluent volume and its flow rate were optimized. Under the optimum conditions, the analytical characteristics were studied. In addition, the proposed method was applied to the analysis of water samples.
Conference Presentations
Methanol detection by digital-image colorimetry using optical nanoparticles with N-methylpolypyrrole.
Sophanat Khenthaphak, Waranya Benhasan, Orawon Chailapakul, Eakkasit Punrat. (2022).
In Proceedings of The 48th International Congress on Science, Technology and Technology-based Innovation (STT48): Science and Technology for Advancing Towards SDGs. School of Science, Walailak University, 29 November–1 December 2022. pp.131–138. (Proceedings)
Almost of nanoparticles such as metal nanoparticles and quantum dots (QDs) has optical properties like a specific color or fluorescence. In this work, gold nanoparticles (AuNPs) and manganese-doped zinc sulfide quantum dots (Mn/ZnS-QDs) were synthesized and studied their optical properties by spectroscopy and digital-image colorimetry (DIC). AuNPs were studied their color intensity by DIC under a white light, while Mn/ZnS-QDs were studied their fluorescence intensity by DIC under a black light. The minimum concentration limits of AuNPs and Mn/ZnS-QDs which can be detected by DIC were found to be 25 and 50 mg L⁻¹, respectively. N-methypolypyrrole (NMPPy) with sodium dodecyl benzene sulfonate was added into the optical nanoparticles. It was found that NMPPy did not significantly affect the optical response of AuNPs, but Mn/ZnS-QDs with NMPPy has a lower fluorescent response under the black light than a without one. Finally, an addition of methanol into Mn/ZnS-QDs with NMPPy can slightly increase the fluorescent response. This result shows a potential of Mn/ZnS-QDs with NMPPy that can be used as an optical nanoparticle for the methanol detection by DIC, besides a naked eye.
Portable and inexpensive spectrometer with light emitting diode for study of stability of gold nanoparticles.
Porawach Chin-orn, Pakorn Juleang, Eakkasit Punrat. (2019). The 45th Congress on Science and Technology of Thailand (STT45): Seeding Innovation for Sustainable Development. Mae Fah Luang University, 7–9 October 2019. (Oral Presentation)
Gold nanoparticle (AuNP) is a widely used nanomaterial due to its electrical property and optical property. The synthesis of AuNP from HAuCl4 reduced by gallic acid was investigated. The solution of AuNPs with a particle size less than 50 nm is red color which has an absorption wavelength of 520-530 nm. The stability of AuNPs therefore can be investigated via spectroscopic method. In this work, a pocketable spectrometer has been invented in our laboratory using simple and inexpensive components on an open-source electronic platform. A light emitting diode (LED) with red-green-blue light was chosen as the light source. The invented spectrometer has three input-buttons for selection of LED color, zeroing value for a blank solution, and reading an absorbance of a sample solution. The absorbance value and essential information are displayed on the screen. The absorbances of AuNPs solution were carried out by the spectrometer with the green LED, which emits the spectrum wavelength equivalent to absorption wavelength of AuNPs, for several days to study the stability of the AuNPs. For a week of study, the AuNPs solution kept at room temperature (27-30 °C) was not stable resulted in the absorbance decreasing of 20.9% from one at the first day, while the AuNPs solution preserved at -8 °C had a high stability with a relative standard deviation of absorbance of 3.36%. According to results, the portable and inexpensive spectrometer persists in its performances, therefore, it will be a promising alternative spectrometer to apply for quantitative analysis.
Graphene oxide modified screen printed carbon electrodes for electrochemical determination of homocysteine using catechol as redox mediator.
Suchapa Naranarumon, Eakkasit Punrat, Orawon Chailapakul, Janjira Panchompoo. (2019).
In Proceedings of The 10th National & International Conference “Global Goals, Local Actions: Looking Back and Moving Forward”. Suan Sunandha Rajabhat University, 29 March 2019, Vol 10, No 1, pp. 1140–1149. (Proceedings)
Graphene oxide (GO) was modified on the surface of screen printed carbon electrode (SPCE),whichis portable, inexpensive, and disposable, for the electrochemical detection of homocysteine (Hcy)via 1,4-Michael addition reaction using catechol (CA) as redox mediator. Typically, CAwas first oxidized to its corresponding ortho-quinone which could subsequently undergo a 1,4-Michael addition, forming a new electrochemically active species thatcould further get oxidized and reduced.This new reduction peak could be clearly observedat ca.-0.27V vs. Ag/AgClby differential pulse voltammetry (DPV).Under the optimized conditions, this new reduction peak increased linearly with Hcy concentrationsin the range of 15-150 µM, and the limit of detection (LOD) was found to be 12 µM, literally lower than the concentration of Hcy in human plasmarelated to a high risk of cardiovascular diseases (CVDs).Therefore, the developed electrochemical method for Hcy detection could potentially be applied in medical applications.
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