Anukorn Phuruangrat

Synthesis of hexagonal WO3 nanowires by microwave-assisted hydrothermal method and their electrocatalytic activities for hydrogen evolution reaction

Hexagonal WO3 (hex-WO3) nanowires with high aspect ratio and crystallinity have been prepared for the first time by a microwave-assisted hydrothermal method. By using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy, the phase and morphology of the products were identified, which were controlled by reaction temperature, holding time and added salts. Uniform hex-WO3 nanowires with a diameter of 5–10 nm and lengths of up to several micrometres were synthesized by a microwave-assisted hydrothermal process at 150 °C for 3 h in a solution containing (NH4)2SO4 as a capping reagent and Na2WO4 as a starting material. The aspect ratio and specific surface area of hex-WO3 nanowires were 625 and 139 m2 g−1, respectively, which represented one of the highest values reported for WO3. The electrocatalytic activity for hydrogen evolution reaction of hex-WO3 nanowires was also investigated by cyclic voltammetry and linear sweep voltammetry. The results demonstrated that hex-WO3 nanowires were a promising electrocatalyst for the hydrogen evolution reaction (HER) from water.

Hydrothermal synthesis, characterization, and optical properties of wolframite ZnWO4 nanorods

In this research, the effects of pH, reaction temperature and holding reaction time on the synthesis of one-dimensional ZnWO4 nanostructures by a hydrothermal method were studied. Phase, morphology and atomic vibration were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and Fourier transform infrared (FTIR) and Raman spectroscopy. The pure monoclinic ZnWO4 structure was synthesized at the pH solutions of 7 and 8. By varying the pH values, the mixtures of monoclinic ZnWO4 and hexagonal ZnO as major and minor phases were detected at the pH 9 and 10 solutions, and the pure hexagonal ZnO phase at the pH 11 and 12. SEM and TEM images proved that ZnWO4 nanorods grew along the [021] direction, with the reaction temperature and time to control their morphologies. The Zn–O, Zn–O–W, and W–O stretching vibrations were detected at 474, 888, and 726 cm−1, and their corresponding bending vibrations at 430, 826, and 582 cm−1, respectively. The optical properties of ZnWO4 nanorods were also investigated by UV-visible (UV-vis) and photoluminescence (PL) spectroscopy. The above analyses proved that the appropriate condition for synthesizing of ZnWO4 nanorods is at pH 8 by the 200 °C and 24 h hydrothermal treatment.

Synthesis and Characterization of Europium-Doped Zinc Oxide Photocatalyst

Single crystalline flower-like ZnO and Eu-doped ZnO structures were successfully synthesized via a sonochemical method. Structures, morphologies, and photocatalytic activities of the as-synthesized samples were determined using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible absorption spectroscopy. The photocatalytic activities of the as-synthesized samples were evaluated by the degradation of methylene blue in aqueous solutions under UV light. The photocatalytic results indicate that the as-synthesized Eu-doped ZnO shows good photocatalytic activity and could be considered as a promising photocatalyst for dye waste water treatment.

Characterisation of one-dimensional CdS nanorods synthesised by solvothermal method

One-dimensional (1D) cadmium sulfide nanorods were successfully synthesised using cadmium nitrate and sulfur powder as starting materials and polyvinyl alcohol (PVA, MW = 1 25,000) as a capping agent in ethylenediamine as a solvent by solvothermal method at 200°C for 24 and 72 h. X-ray diffraction patterns (XRD) indicated a single phase of hexagonal wurtzite CdS structure, of which the results are in accordance with those of selected area electron diffraction (SAED). The morphologies of CdS were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which showed 1D nanorods. The length and diameter of CdS nanorods were increased when PVA was added and the reaction times were prolonged. High resolution transmission electron microscopy (HRTEM) showed that growth direction of wurtzite CdS nanorods is along [001] direction or c-axis. Raman spectra presented the 1LO and 2LO at 299.36 and 600.72 cm−1, respectively. The 2LO/1LO intensity ratios were increased when the length of CdS nanorods became longer.

Studies the effects of ultrasonic irradiation and dielectric constants of solvents on formation of lead(II) supramolecular polymer; new precursors for synthesis of lead(II) oxide nanoparticles

In order to evaluation the effects of ultrasonic irradiations and dielectric constants of solvents on formation [Pb2(5-Clq-8-ol)2(OAc)2]n (1), [H5-Clq-8-ol=5-chloroquinolin-8-ol and OAc-=acetate], we designed some experiments and synthesized six samples of 1 under different conditions. Microrods of a lead(II) supramolecular polymer, were synthesized under these conditions. These microstructures were characterized by IR spectroscopy, X-ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM). The results indicated that compound 1 with the best crystallinity can be obtained in the presence of MeCN and H2O (as the bulk sample) and in the presence of MeCN and EtOH (by sonochemical process). The least agglomeration of microrods was observed in H2O which is due to high dielectric constant of it. By considering all of the factors consist of crystallinity and agglomeration of the products and their corresponding histograms, it seems that MeCN is the best solvent for synthesis of 1. The samples which were synthesized in the presence of MeCN, had been used as new precursors for fabricating lead(II) oxide nanoparticles via thermal decomposition in oleic acid (OA).

A survey on the effects of ultrasonic irradiation, reaction time and concentration of initial reagents on formation of kinetically or thermodynamically stable copper(I) metal-organic nanomaterials

In order to evaluation the effects of ultrasonic irradiations, concentration of initial reagents and reaction time on formation [Cu4(MBT)4] or [Cu6(MBT)6] copper(I) metal-organic nanomaterials, [HMBT=2-Mercaptobenzothiazole], we designed some experiments and synthesized six samples under different conditions. These nanostructures were characterized by IR spectroscopy, X-ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM). It seems that the tetranuclear cluster of [Cu4(MBT)4] (2) is the kinetically stable product which is formed at the initial time of the reaction and as the time went, it converts to thermodynamically stable product of [Cu6(MBT)6] (1) with hexanuclear cluster unit. In the samples which synthesized with low concentration of initial reagents, against to those synthesized with high concentration of initial reagents, the ultrasonic irradiation does not have any effect on formation of any special morphology.

Hydrothermal synthesis and characterization of Bi 2 MoO 6 nanoplates and their photocatalytic activities

The pH effect of the precursor solutions on the phase, morphologies, and photocatalytic activity of Bi2MoO6 synthesized by a hydrothermal reaction at 180°C for 20 h was investigated. X-ray powder diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed the presence of pure orthorhombic well-crystallized γ-Bi2MoO6 nanoplates, including the symmetric (A1g) and asymmetric (A2u) stretching vibrations of the MoO6 octahedrons involving the motion of apical oxygen atoms. The photocatalytic activity of Bi2MoO6 nanoplates at the pH 6 determined via the decomposition of rhodamine-B (RhB) organic dye was the highest at 98.66% decolorization under Xe light irradiation.

Microwave-assisted synthesis and characterisation of uniform LaPO4 nanorods

Lanthanum phosphate (LaPO4) phosphor materials with one-dimensional (1D) nanorods and nanoparticles were successfully synthesised from LaCl3 · 7H2O and Na3PO4 · 12H2O with pH adjusted at the range 1–6 using 37% HNO3 by the microwave radiation at 180 W for 60 min. X-ray diffraction patterns indicated that the as-synthesised products were hexagonal LaPO4 nanostructures. Scanning electron microscopy and transmission electron microscopy analyses showed that these products were nanoparticles, short and long nanorods, controlled by pH of the precursor solutions. Asymmetric stretching and bending vibrations of the groups were detected using Fourier transform-infrared spectroscopy. A possible formation mechanism of LaPO4 phosphor materials with 1D nanorods and nanoparticles was also proposed according to the experimental results.

Synthesis, characterisation and photoluminescence of nanocrystalline calcium tungstate

Calcium tungstate nanocrystalline was successfully synthesised via a microwave irradiation method using Ca(NO3)2 and Na2WO4 in ethylene glycol, without the requirement of any calcination. The product was analysed by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and photoluminescence spectrometry. XRD, SAED and TEM revealed that the product was body-centred tetragonal CaWO4 with an average particle size of 12 nm. Different oscillation modes were detected by Raman spectroscopy and FTIR. They showed the strong W–O stretching in [WO4]2− tetrahedrons at 711–933 cm−1. Photoluminescence (PL) of CaWO4 nanocrystalline showed the maximum emission peak at 422 nm.

Synthesis and characterization of CeVO 4 by microwave radiation method and its photocatalytic activity

A general microwave synthesis method was developed to synthesize cerium orthovanadate (CeVO4) nanostructures without the use of any catalysts or templates. This method is able to control the shape and size of the products by adjusting the pH of precursor solutions to be 1-10. Phase, purity, and different morphologies of the products were characterized by XRD, FTIR, SEM, and TEM. They showed that the as-synthesized products exhibited pure single crystalline CeVO4 with tetragonal structure. Their morphologies developed in sequence as nanoparticles (pH = 4-10), nanorods (pH = 2, 3), and microflowers (pH = 1). UVvisible spectra were used to estimate the direct energy gaps of CeVO4 nanorods and microflowers: 3.77 and 3.65 eV, respectively. Photoluminescence (PL) of CeVO4 microflowers showed strong emission intensities at 578 nm. These results were in the range of possible application for photocatalysis, investigated by studying the degradation of methylene blue.