Papers by Author: Chanchana Thanachayanont

Abstract: This study examines the effect of hydrazine hydrate levels on chemically reduced graphene oxide (GO) to synthesize reduced graphene oxide (rGO) for Pb (II) electrochemical detection. GO was prepared by the modified Hummers’ method and reduced with 1-5 mL hydrazine hydrate. FTIR analyzed changes in oxygen-containing groups. rGO samples were drop-cast onto screen-printed carbon electrodes (SPCEs) and characterized by SEM-EDX. Electrochemical behavior was evaluated by cyclic voltammetry (CV) in 5 mM [Fe (CN)₆]³⁻/⁴⁻ with 0.1 M KCl. rGO reduced with 3 mL hydrazine hydrate showed the highest current (52.45 ± 1.98 µA), a 196.6% increase over bare electrodes. This condition also gave the best detection of 1 ppm Pb (II) in 0.1 M acetate buffer (pH 5) via square wave anodic stripping voltammetry (SWASV), with a 135.0% signal enhancement. These results highlight the importance of hydrazine hydrate level on optimizing rGO for improved electrochemical properties, sensitivity, and reproducibility for Pb (II) detection.

Abstract: Perfluorooctane sulfonate (PFOS), a toxic and persistent pollutant, poses significant environmental and health risks, making its detection crucial. This study developed silver nanoparticle (AgNP)-modified screen-printed carbon electrodes (SPCEs) for on-site PFOS detection and compared them with glassy carbon electrodes (GCEs). AgNPs were electrodeposited at various concentrations (1–9 mM) using amperometry. SEM-EDS confirmed increasing silver deposition with higher AgNO₃ concentrations, and cyclic voltammetry showed enhanced current responses with increased silver content. Differential pulse voltammetry revealed that 5 mM Ag/SPCE achieved the highest PFOS detection signal (Δi = 11.218 µA), demonstrating the effectiveness of AgNP-modified SPCEs for PFOS detection.

Abstract: CuO microparticle was syntheszied by hydrothermal method. The starting precursors were used as copper (II) nitrate trihydrate (Cu (NO₃)₂·3H₂O), nitric acid (HNO₃) and sodium hydroxide (NaOH). The final pH value of the mixed solution was used 2M NaOH to adjust the pH was 8 and treated at 100-200 oC for 4-6 h in a hydrothermal vessel. The black fine powder was obtained after dried at 100 oC for 5 h. The phase and structure of CuO microparticle were characterized by X-ray diffraction (XRD). A single phase monoclinic structure synthezied by hydrothermal method at 200 oC for 4 and 6 h was obtained without calcination steps. The morphology CuO microparticle was investigated by scanning electron microscopy (SEM). It was likely grain in shape and the particle size in range of 2.94-4.06 μm. The element composition of CuO microparticle was indicated by energy dispersive X-ray spectrometry (EDX). The chemical compositions showed the characteristic X-ray energy of copper (Kα = 0.98 keV) and oxygen (Kα = 0.53 keV), respectively. The functional group of CuO microparticle was indentified by Fourier transform spectrophotometry (FTIR). The wavenumber at 690, 514 and 437 cm^-1 was corresponded to vibration of Cu-O stretching.

Abstract: In this research, CuO powder was prepared by low temperature hydrothermal method. Copper (II) nitrate trihydrate (Cu (NO₃)₂.3H₂O) and sodium hydroxide (NaOH) were used as the starting precursors. The final pH value of the mixed solution was adjusted to 9 by 4M NaOH and treated at 100 oC and 200 oC for 4 and 6 h. The black fine powder was obtained after dried at 80 oC for 4 h. The phase was characterized by X-ray diffraction (XRD). A single phase of monoclinic structure of CuO powder prepared by low temperature hydrothermal method at 200 oC for 4 and 6 h was obtained without calcination step. The morphology and particle size were investigated by scanning electron microscopy (SEM). The morphology was flower-like in shape and the average particle size in range of 0.3×0.7 μm. The element composition was indicated by energy dispersive X-ray spectrometry (EDX). The chemical compositions showed the characteristic X-ray energy of copper (Kα = 0.95 keV) and oxygen (Kα = 0.53 keV). The functional group was indentified by fourier transform spectrophotometry (FTIR). The wavenumber at 433-531 cm^-1 was corresponded to vibration of Cu-O stretching.

Abstract: Synthesis routes of CoSb₃ need a long reaction time, especially at high temperature and-/or high pressure. Although the modified polyol process assisted with microwave radiation can be used to solve these problems, it used the excess amount of Sb ion. Therefore, this study aimed to solve this drawback by retarding the rate of reduction. The different microwave times (0, 1, and 3 min) were investigated to find out the shortest heating duration for preparing CoSb₃ nanoparticles. Te-doped and Sn-doped CoSb₃ were synthesized to investigate the benefit of this synthesis method for increasing the solubility limit of Te and Sn in the CoSb₃ structure. The phase and microstructure of the synthesized products were characterized by using x-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the high crystalline phase of CoSb₃ (JCPDS: 78-0977) without any metallic impurity phases product was successfully synthesized in 3 minutes for a heating time at normal pressure, non-excessive addition of Sb ion precursor, and low temperature. The XRD results of Te-doped and Sn-doped CoSb₃ products exhibited poor crystalline phase and hard to exactly identify. In SEM and TEM results, the CoSb₃ powder consisted of very tiny spherical-like particles around 10 nanometers attaching together even at different microwave time similar to Te-doped/Sn-doped samples.

Abstract: Mesoporous silica (MPS) is a porous silica material with various pore structures. In this study, mesocellular foam silica (MCF) was synthesized and functionalized by hexamethyldisilazane (HMDS) to study effects of surface chemistry on benzene adsorption capability. Physical and chemical properties of pristine and functionalized MCFs were characterized and compared. Scanning and transmission electron microscopy showed that the complex pore structures of the MCFs were retained after the functionalization at relatively high temperature (573K). TGA and FTIR results showed that the functionalization led to a reduction of water adsorbed on the surfaces of the MCF. The functionalization improved adsorption of benzene compared to the pristine MCF and the optimum HMDS:SiO₂ molar ratio was 1.5. The amount of benzene adsorbed has a linear relationship with the concentration of benzene in the environment. This relationship enables quantitative benzene detection by using the functionalized MCF as sensing materials in resistive-type or gravimetric-type benzene gas sensors.

Abstract: To handle persistent toxic organic contaminants in water, advanced oxidation process (AOP) by titanium dioxide (TiO₂) and its composites has been extensively utilized. A smart combination of composite materials was synthesized to improve photocatalytic activity of TiO₂ via engineering effective charge transfer. In this study, synthesis of Ag/Graphite Oxide (GO)/TiO₂ was investigated. Degussa P25 TiO₂ (Rutile:Anatase of 85:15, 99.9%, 20nm) nanopowder was purchased. Graphite oxide was prepared using modified Hummer’s method. Photoreduction and ultrasonication were conducted to prepare Ag nanoparticles (AgNPs). XRD was used to confirm formation of Ag- GO- TiO₂, i.e., peaks of GO, AgNPs and phases of anatase and rutile of TiO₂ P25. Backscattered SEM was used to identify the AgNPs in different compositions of the AgNPs/GO/TiO₂ composites. TEM was used for high resolution images to observe sizes and shapes of nanomaterials involved. X-ray absorption near edge structure (XANES) spectra of the Ag L₃-edge were used to confirm zero-valence AgNPs. The best performed photocatalyst from this study was 5Ag0.5GOTiO₂ with 78.86 % degradation of RhB after 2 hours. The AgNPs were found to be spherical with sizes of around 2-10 nanometers and evenly distributed within the GO/TiO₂ matrix.

Abstract: In this study, hydrothermal carbonization of carrot juice was conducted at 180 °C for 6 hours, followed by annealing at 500 °C for 6 hours. In the absence of a catalyst, hydrothermal carbonization of carrot juice produced hollow and solid carbon microspheres (CMS) with diameters ranging from 0.3 to 4.0 µm. SEM and TEM images of the CMS showed various morphologies and sizes. X-ray diffraction and Raman spectroscopy indicated the CMS had a disordered graphitic structure. A HAADF micrograph showed that although the majority of the CMS in this study were hollow, there were also solid spheres which had not previously been reported for hydrothermal carbonization. STEM EDS mapping of a solid CMS indicated approximately 95 wt% of C with traces of N, O, Si, P, S, Cl and K. The effect of the starting precursors on the hard sphere formation mechanism is discussed.

Abstract: Charcoal consists mostly of carbon materials prepared by carbonization, i.e., traditionally by pyrolysis [1,2] of wood pieces in a kiln. At a high enough temperature and an absence of oxygen [3], high-quality charcoal with low resistance can be produced. A possible application of the low-resistivity charcoal is as an electrode material for electrochemical devices. In this research, bamboo waste was used to produce low-resistance bamboo charcoal. During heating, the temperature gradually increased up to 700°C, was kept approximately constant overnight, and was left to cool down to room temperature. Then, the charcoal bamboo pieces were obtained. A rough temperature-resistivity map was constructed. The bamboo charcoals were divided into 3 resistivity ranges, namely, 20, 100 and 1000 ohm.cm^-1. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and microEDX (energy dispersive X-ray spectroscopy), were conducted for charcoal morphology and spectroscopic characterization [4-6]. The morphological results from SEM did not show any significant differences among bamboo charcoals with different resistivity. DF-STEM and EDS-STEM mapping revealed impurities inside the bamboo charcoal. Elemental analysis of micro areas showed weight percentage of carbon and other impurities in the bamboo charcoals. The 20 ohm.cm^-1 bamboo charcoal was the best among all resistivity studied in terms of purity and main carbon structure. Decreasing the impurity content was found to be one of the essential parameters to obtain low resistivity bamboo charcoal. It was concluded that improving the stability and condition of the burning process in the conventional kiln was necessary in order to get a high yield of low resistance bamboo charcoals.

Abstract: Titanium dioxide nanotubes on titanium surface were prepared by electrolytic anodization in aqueous solution at constant voltages at room temperature for 2, 4 and 6 hours. Anodized titanium was heat treated in a furnace at 450 °C for 4 hours to convert amorphous structure to anatase and rutile crystalline structure. A scanning electron microscope was utilized for morphology investigation of the anodized titanium surfaces. For HF containing water media, porous surface on titanium was revealed after anodizing for 2 hours. Nanotubes (NT) were formed in this media at 4 and 6 hours anodizing time, the diameters of the tubes were approximately 70 to 100 nm. For HF/Na₂SO₄ aqueous solution, fine NTs, approximately 50 nm in diameter, were grown after 2 hours. However, the NTs obtained at anodizing time 4 and 6 hours were the same size, ranging from 100 to 120 nm. Anatase and rutile phases of TiO₂ were formed in the anodized samples after annealing at 450 °C for 4 hours. The anodized samples were tested for their abilities to degrade Rhodamine B, to demonstrate their application as a material for waste water treatment. The Rhodamine B was degraded up to 41% in annealed sample anodized by electrolyte contained HF.