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Preparation of Composite Films of Rod-like Structure of ZnO and Corn Starch for Bending Sensor
(2026-01-01)
Feemuchang, Kitikamol
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Onlaor, Korakot
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Tunhoo, Benchapol
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Thiwawong, Thutiyaporn
In this work, rod-like structure zinc oxide (R-ZnO) was synthesized by a hydrothermal process with the hydrothermal times of 3, 5, and 10 h. The effect of reaction time was reflected in the physical properties of the prepared R-ZnO, such as crystalline structure, shape geometries, and optical properties. Then, a bending device was fabricated with starch composite films and the rod-like structure of zinc oxide with different R-ZnO concentrations. The fabricated device exhibited flexibility characteristics at various bending angles. The composite film of corn starch and 1%wt. R-ZnO at a hydrothermal reaction time of 10 h demonstrated a high sensitivity at 89.5% with a gauge factor of 1.58. Moreover, the device of corn starch composited with R-ZnO exhibited fast response/recovery time of 0.23/0.15 s with high stability of bending cycle of more than 1,600 cycles. Therefore, the composite films of R-ZnO and natural starch are strong potential candidates for bending devices.
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Enhancement in Sensitivity and Selectivity of Electrochemical Technique with CuO/g-C3N4 Nanocomposite Combined with Molecularly Imprinted Polymer for Melamine Detection
(2024-07-01)
Limthin, Dalawan
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Leepheng, Piyawan
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Tunhoo, Benchapol
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Klamchuen, Annop
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Suramitr, Songwut
This study focused on enhancing the sensitivity and selectivity to detect melamine by utilizing a photoelectrochemical method. This was achieved by combining a melamine-imprinted polymer with a CuO/g-C<inf>3</inf>N<inf>4</inf> nanocomposite, which was synthesized through chemical precipitation and calcination. The resulting nanocomposite exhibits improved carrier mobility and photoelectrochemical properties. A molecularly imprinted receptor for selective detection was created through bulk polymerization with methacrylic acid and a melamine template. The characterization of the nanocomposite was performed using X-ray photoelectron spectroscopy for the chemical oxidation state, X-ray diffraction patterns for the crystalline structure, and ultraviolet/visible/near-infrared spectroscopy for optical properties. The CuO/g-C<inf>3</inf>N<inf>4</inf> nanocomposite exhibits photoactivity under visible light. The modified electrode, incorporating the CuO/g-C<inf>3</inf>N<inf>4</inf> nanocomposite and melamine-imprinted polymer, demonstrates a linear detection range of 2.5 to 50 nM, a sensitivity of 4.172 nA/nM for melamine, and a low detection limit of 0.42 nM. It shows good reproducibility and high selectivity to melamine, proving effective against interferences and real samples, showcasing the benefits of the molecularly imprinted polymer.
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Preparation of calcium oxide/graphitic carbon nitrides (CaO/g-C3N4) composite for photocatalyst dye degradation
(2024-06-01)
Chaisrisongkram, Chinanun
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Thiwawong, Thutiyaporn
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Onlaor, Korakot
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Tunhoo, Benchapol
Dye degradation properties of composited calcium oxide (CaO) and graphitic carbon nitride (g-C<inf>3</inf>N<inf>4</inf>) were studied. The CaO and g-C<inf>3</inf>N<inf>4</inf>nanoparticles were derived under separate thermal calcination processes from eggshells and melamine, respectively. Physical properties of the synthesized CaO and g-C<inf>3</inf>N<inf>4</inf>were investigated by X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The synthesized CaO and g-C<inf>3</inf>N<inf>4</inf>nanoparticles were, then, composited at various concentrations, and the photocatalytic behaviors of the composited samples were investigated in an aqueous solution of methylene blue, with a irradiation source of 220 W white light-emitting diode lamp. Results showed that the optimal ratio of the composite material for dye degradation was 10% CaO:90% g-C<inf>3</inf>N<inf>4</inf>, giving 95.89% degradation efficiency with an exposure time of 15 min and degradation rate of 0.1727 min-1.
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Influence of Phase Structure of TiO2 Nanoparticles on Resistive Switching Devices
(2024-01-03)
Tunhoo, Benchapol
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Chantarawong, Direklit
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Thiwawong, Thutiyaporn
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Onlaor, Korakot
In this work, the electrical memory properties of a bi-stable device based on the structure of aluminum/poly (9-vinyl carbazole) (PVK): TiO<inf>2</inf> NPs/indium-tin-oxide (ITO) were reported. The effects of the modified phase structural of titanium dioxide nanoparticles (TiO<inf>2</inf> NPs) on the electrical memory characteristics were determined. The TiO<inf>2</inf> NPs were annealed at different annealing temperatures. The physical properties of the annealed TiO<inf>2</inf> NPs were characterized by transmission electron microscope and X-ray diffraction, which revealed the composition and structure of the anatase and rutile phases. Current-voltage measurements showed that the bi-stable characteristics were affected by the phase structure of the TiO<inf>2</inf> NPs. The ON/OFF current ratio of the fabricated device was noted to be approximately 2.06×105 in the case of TiO<inf>2</inf> NPs annealed at 500°C. A theoretical model was used to explain the charge injection mechanisms of the device. Moreover, the temperature dependence and retention-time measurements of the device were demonstrated.
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Preparation of surface-modified electrode of copper(ii) oxide mixed with the molecularly imprinted polymer for enhancement of melamine detection with photoelectrochemical technique
(2023-05-15)
Limthin, Dalawan
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Leepheng, Piyawan
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Tunhoo, Benchapol
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Onlaor, Korakot
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Klamchuen, Annop
Melamine contamination in food and beverages affects short- and long-term health. In this work, enhanced sensitivity and selectivity in photoelectrochemical determination for melamine detection was achieved using copper(ii) oxide (CuO) combined with a molecularly imprinted polymer (MIP). A CuO nanomaterial was used to achieve MIP surface modification via co-precipitation synthesis. An MIP film was deposited by polymerizing the methacrylic acid monomer and a melamine template. The properties of the CuO nanomaterials, such as the surface morphology, chemical oxidation state, and crystalline structure, were characterized using field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction patterns (XRD), respectively. The diffuse reflection spectroscopy technique was applied to evaluate the optical properties of the CuO nanoparticles. The results indicated that the synthesized CuO nanomaterials had a monoclinic structure with an optical bandgap of 1.49 eV, which corresponds to absorbance in the visible light region. CPE electrodes with surface-modified CuO/MIP were measured using the photoelectrochemical techniques of cyclic voltammetry, differential pulse voltammetry (DPV), and amperometry. The modified CuO/MIP electrode for melamine detection in 7.4 pH PBS buffer solution exhibited a high sensitivity of 0.332 nA nM−1, with a linear range of 5.0-75.0 nM and a limit of detection of 2.45 nM. Moreover, real samples of various kinds of milk were applied to evaluate the sensing response of the prepared CuO/MIP electrode. The modified CuO/MIP electrodes could be reused seven times with good reproducibility and high selectivity for melamine detection.
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Preparation of Conductive Screen-Printing Ink for High-Performance Bendable and Wearable ECG Electrodes on Fabric Substrates
(2022-12-15)
Chansaengsri, Kasidid
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Tunhoo, Benchapol
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Onlaor, Korakot
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Thiwawong, Thutiyaporn
Monitoring of vital signs is a necessary tool to diagnose the symptoms of illness. This work developed screen-printing inks for conductive nanomaterials to fabricate electrocardiogram (ECG)-compatible fabric electrodes. The contents of the polymer matrix, calcium carbonate additive filler, and conductive nanomaterials (silver nanoparticles and copper nanowires) on the resistivity of the composite inks were optimized. A facile process of screen printing was applied to fabricate the electrodes on fabric to create an efficient conductor with high stability in conduction. The fabricated electrodes exhibited flexible and bendable behavior over 0.7% bending strain for wearable components. The results showed that the fabricated electrode based on copper nanowires resistivity was 40.01 ± 1.94 k Ω/cm, and the proposed signal-to-noise ratio (SNR) was approximately 27.16 ± 9.37 dB. Therefore, these fabricated electrodes can be applied in wearable vital biosignal detection devices that perform with high sensitivity during movement, thereby providing health monitoring opportunities. Moreover, the fabricated electrodes can be used without excessive pressure or an electrolyte gel layer, thus overcoming the challenges of developing a portable device.
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Preparation of Nanofibers of Poly (methyl methacrylate) Composited with Few-Layer-Graphene for Anticorrosion Layer
(2022-12-01)
Onlaor, Korakot
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Putta, Boonthawee
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Thiwawong, Thutiyaporn
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Tunhoo, Benchapol
An anticorrosion layer is a significant component that prevents the corrosion process in materials. In this work, a nanofiber of poly (methyl methacrylate) composited with few-layer-graphene was prepared as an anticorrosion layer. An electrospinning process was applied to prepare composite nanofiber on a metal substrate at various concentrations of few-layer graphene. The physical properties of the composite nanofiber were investigated with field-emission scanning electron microscope, Raman spectroscopy, and contact angle measurement. The corrosion behavior was tested in an aqueous solution of 3.5% by weight of sodium chloride. It was found that a few-layer graphene concentration of 2 wt% in polymethacrylate showed the optimum anticorrosion on aluminum sheet, as observed on a Tafel graph. Compared with the uncoated metal, the coated aluminum sheet was protected against corrosion with a protection efficiency of 99.33%. The prepared materials prevented the infiltration of water and solution ions into the metal plate.
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Enhancing the sensitivity and selectivity of salbutamol detection using reduced graphene oxide combined with molecularly imprinted polymers (RGO/MIP)
(2022-06-01)
Limthin, Dalawan
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Leepheng, Piyawan
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Onlaor, Korakot
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Tunhoo, Benchapol
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Klamchuen, Annop
In this study, to enhance the selectivity and sensitivity of salbutamol detection performed by a carbon plate electrode, the electrode was modified using a novel molecularly imprinted polymer (MIP) combined with reduced graphene oxide (RGO). The RGO/MIP combination was prepared by the polymerization of methacrylic acid as a monomer using salbutamol as a template. The surface morphologies of the modified electrodes were studied using field-emission scanning electron microscopy (FE-SEM), and their performance was tested by an electrochemical technique that investigated both the cyclic voltammetry (CV) and amperometry (AMP) modes. The performance of the modified RGO/MIP electrode was compared with that of an MIP electrode, in which the RGO/MIP electrode was demonstrated to have 4.16 nA/ppm of sensitivity, more than the 0.91 nA/ppm of the MIP electrode. The limit of detection (LOD) of the RGO/MIP electrode, which was 0.83 ppm, was lower than that of the MIP electrode. Moreover, the RGO/MIP electrode’s dynamic range extended from 1 to 1000 ppm, and it exhibited consistency, repeatability, a fast response, and high selectivity for salbutamol detection.
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Selective electrochemical determination based on magnetic molecularly imprinted polymers for albumin detection
(2022-06-01)
Leepheng, Piyawan
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Limthin, Dalawan
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Onlaor, Korakot
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Tunhoo, Benchapol
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Thiwawong, Thutiyaporn
Egg allergy is one of the most common allergies in humans. Allergenic egg protein as ovalbumin is the most abundant protein found in egg white. A selective electrode in electrochemical analysis for albumin from egg white was developed based on magnetic molecularly imprinted polymers (albumin-MMIPs) modified on a screen-printed electrode. Surface modification was applied using methyl methacrylate polymer to create surface specificity for albumin protein. The modified surface was characterized by a field-emission scanning electron microscope (FE-SEM). The average pore size was obtained by Brunauer-Emmett-Teller (BET) analysis, and the potentiostat obtained all electrochemical analysis. The albumin-MMIP electrode was selectivity with albumin, comparison with gluten, glycine, casein, and glucose. The modified electrodes present selectivity of 1.13 × 104 μAg-1ml and a limit of detection of 0.18 mg ml-1. The electrode can be applied to albumin protein detection in solution form in food industries.
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Electrical Properties of Eggshell-Derived CaO Composited with Polyvinylpyrrolidone for Bistable Device
(2022-01-01)
Tunhoo, Benchapol
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Onlaor, Korakot
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Songkeaw, Potiyan
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Sriyapan, Jaturon
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Thiwawong, Thutiyaporn
In this work, bistable devices were fabricated from eggshell-derived calcium oxide (CaO). CaO powders can be obtained from the calcination of chicken eggshells at temperatures from 700-1000 °C. The properties of derived CaO were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy. CaO was composited with polyvinylpyrrolidone (PVP) polymer to fabricate a bistable device with the device structure of ITO/PVP:CaO/Al. The maximum ON/OFF current ratio for the device was approximately 104. In addition, the retention time operations reached higher than 104 s, which revealed the stability of the bistable device. The theoretical model and conduction mechanisms were presented to explain the behavior of the bistable device.

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