KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 10

Some of the metrics are blocked by your
consent settings
Solvent-Dependent Green Synthesis of ZnO Nanopowders Using Mitragyna speciosa Leaf Extract: Impact on Piezo-Photocatalytic and Antibacterial
(2026-07-01)
Sanyen, Thanyapa
;
Songpanit, Maneerat
;
Kansaard, Thanaphon
;
Wirunchit, Supamas
;
Chutipaijit, Sutee
ZnO nanopowders were synthesized via a solvent-mediated green route using Mitragyna speciosa Korth. leaf extract as reducing and stabilizing agents. Deionized water and methanol were employed to tailor the phytochemical composition of the extracts. The influence of extract concentration (5–20 mL) and solvent polarity on structural, morphological, and functional properties was systematically investigated. Structural analyses confirmed the formation of Zn-O bonds and a phase-pure hexagonal wurtzite ZnO without secondary phases. Surface morphology revealed solvent-dependent morphological evolution toward spherical shapes and reduced aggregation in the methanol-derived system. For antibacterial activity, green ZnO nanopowders demonstrated enhanced biocidal effects against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, comparable to that of commercial ZnO nanoparticles. Enhanced piezo-photocatalytic degradation of rhodamine B was achieved under combined light and ultrasonic irradiation, with superior performance observed for methanol-derived ZnO. This enhancement is attributed to the synergistic interplay of solvent-induced defect states, reduced particle size, and piezoelectric field-driven charge separation. Scavenger analysis confirmed that superoxide radicals ((Formula presented.)) dominate the degradation pathway by green-synthesized ZnO nanopowders prepared from different solvent extracts. Thus, a correlation between solvent-mediated phytochemical environments and piezo-photocatalytic activity provides new insights for the design of sustainable, high-performance ZnO-based catalysts.
Some of the metrics are blocked by your
consent settings
Effect of Hexamethylenetetramine on Physical, Structural, and Photocatalytic Properties of ZnO Nanostructures Synthesized via One-Step Sol-Gel Process
(2026-07-01)
Songpanit, Maneerat
;
Boonyarattanakalin, Kanokthip
;
Basu, Soumya
;
Okumura, Hideyuki
;
Ishihara, Keiichi N.
Wastewater contamination with synthetic organic dyes is a significant environmental challenge. Zinc oxide (ZnO) has attracted considerable attention as a non-toxic, multifunctional material for electronics, optics, piezoelectric devices, and photocatalysis, where its performance is strongly governed by morphology. In this work, we investigate the effect of hexamethylenetetramine (HMTA) on the formation and photocatalytic behavior of ZnO nanostructures synthesized from different zinc precursors, namely zinc acetate and zinc nitrate, via a one-step sol–gel process at low temperature without any post-treatment. All samples crystallize in the hexagonal wurtzite phase without detectable impurities, and the incorporation of HMTA leads to smaller, more uniform rod- and flake-like nanostructures. Although ZnO derived from zinc acetate without HMTA exhibits the highest specific surface area, ZnO synthesized in the presence of HMTA shows more favorable crystallinity, morphology, and pore connectivity, which together enhance charge separation and reactive oxygen species generation. As a result, ZnO samples synthesized with HMTA exhibit improved photocatalytic degradation of rhodamine B under UV irradiation.
Some of the metrics are blocked by your
consent settings
The Effect of Polyvinyl Alcohol Addition on the Optical Properties and Oxygen Detection Performance of Titanium Dioxide and Methylene Blue Nanocomposite Colorimetric Indicators
(2024-05-01)
Boonyarattanakalin, Kanokthip
;
Rattan, Praphaporn
;
Songpanit, Maneerat
;
Chutipaijit, Sutee
;
Okumura, Hideyuki
In this study, we investigated the impact of polyvinyl alcohol (PVA) incorporation on the optical properties and oxygen detection performance of a titanium dioxide/methylene blue (TiO<inf>2</inf>/MB) nanocomposite colorimetric indicator for packaging applications. The nanocomposite was synthesized via mechanical milling of TiO<inf>2</inf> nanoparticles with MB and citric acid. PVA, at varying concentrations (0, 3, 9, and 14 wt%), was introduced during the wet milling process to produce a homogeneous composite film. Spin coating was employed to fabricate TiO<inf>2</inf>/MB nanocomposite films for oxygen detection evaluation. The influence of PVA loading on the films’ chemical functionalities and surface morphologies was assessed using Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). The indicator’s activation process, involving a color change between bleached and colored states, and its recovery time were monitored via optical imaging and UV-VIS-NIR spectrophotometry. The results revealed that a PVA content of 9 wt% yielded well-defined films with enhanced stability of the TiO<inf>2</inf>/MB nanocomposite’s oxygen detection performance.
Some of the metrics are blocked by your
consent settings
Characterization and Visible Light-Driven Photocatalytic Activity of BiVO4/BiOCl/Bi2S3 Nanocomposites Prepared by Sonochemical Process
(2023-05-01)
Kansaard, Thanaphon
;
Ishihara, Keiichi N.
;
Pecharapa, Wisanu
Photodecomposition performance enhancement of BiVO<inf>4</inf> is carried out by combining it with compatible semiconductors, such as bismuth oxyhalides and sulfide-based photocatalyst materials. In this article, the synthesis of BiVO<inf>4</inf>/BiOCl/Bi<inf>2</inf>S<inf>3</inf> is carried out by a one-step sonochemical process at room temperature with various S:Bi mole ratios (1:9, 2:8, and 3:7). The crystallinity and morphological features of the synthesized powders display a BiVO<inf>4</inf> monoclinic phase accompanied by BiOCl tetragonal and Bi<inf>2</inf>S<inf>3</inf> orthorhombic phases. Field-emission electron microscopy micrographs show an irregular shape with various particle sizes and layering with the characteristic shape of BiOCl. The optical bandgap of the composites has various values in the range of 1.3–3.3 eV. The best photocatalytic performance is observed for the 2–8 composite sample, which produced complete degradation of RhB, with k = 0.17 min<sup>−1</sup>, after 20 min of visible light exposure.
Some of the metrics are blocked by your
consent settings
Structural, optical and photo-induced catalytic properties of derived-Leucoxene /BiVO4 composite prepared by sonochemical process
(2022-10-01)
Kansaard, Thanaphon
;
Ishihara, Keiichi N.
;
Pecharapa, Wisanu
In this work, the Leucoxene /BiVO<inf>4</inf> composite material was prepared by sonochemical-assisted process by using low-cost leucoxene derived material (LDM) as titanium dioxide source and BiVO<inf>4</inf> with different composition ratios. Crystallinity of composite specimens show the combining structure between monoclinic BiVO<inf>4</inf> and TiO<inf>2</inf> rutile phase with corresponding optical band gap of 2.4 eV and 2.85 eV, respectively. The 2:8-LDM:BV composite performed superior photocatalytic activity with complete decomposition of RhB dye under 20 min of light exposure due to heterojunction structure assisting the recombination retardment of photogenerated electron-hole pair. Superoxide radical (•O<inf>2</inf><sup>-</sup>) is revealed to be major active specie induced by this composite. The composite catalyst exhibits excellent repeatability and reusability with 80% decomposition of organic compound after 10 times of usage.
Some of the metrics are blocked by your
consent settings
Photocatalytic properties and plastic degradation of TiO2 nanocomposite with synthetic-rutile from natural ore
(2018-01-01)
Mekprasart, Wanichaya
;
Thongpradith, Titarat
;
Pecharapa, Wisanu
;
Ishihara, Keiichi N.
Titanium dioxide (TiO<inf>2</inf>) is considered a main material in energy and environment fields. This work focused on the production of synthetic rutile-TiO<inf>2</inf> (LA) material from natural ore by milling-ultra sonic assisted in acid treatment. Modified-TiO<inf>2</inf> nanocomposite of synthetic rutile and anatase nanopowder was synthesized by high energy milling process. After milling process, the average sizes of samples were decreased at 30% as calculated from XRD peaks. The band gap value of samples analyzed by UV-Vis spectrometer showed that the decrease of the band gap in LA composite at 3.34 eV might be associated with the presence of rutile phase in anatase matrix relating to the highest photocatalytic activity under visible light illumination. Polyethylene plastic was supplemented with different LA nanocomposite loading by thermal attachment process. Photocatalyst property of LA nanocomposite was investigated photocatalytic activity under Xe lamp illumination and investigated by FTIR and XRD technique. The optimized content of LA nanocomposite was performed at 2 wt.% in PE film. FTIR patterns did not detect the difference of plastic degradation. However, the significant change in PE crystalline monitored by XRD technique confirmed the decrease of crystallite size by peak shifted position and size decreasing at 10% by photocatalyst effect.
Some of the metrics are blocked by your
consent settings
Optical characteristics of samarium doped ZnAl2O4 nanomaterials synthesized by vibrational milling process
(2018-01-01)
Mekprasart, Wanichaya
;
Boonyarattanakalin, Kanokthip
;
Pecharapa, Wisanu
;
Ishihara, Keiichi N.
Optical and fluorescence properties of samarium (Sm) doped zinc aluminate host matrix (Sm:ZnAl<inf>2</inf>O<inf>4</inf>) was studied. Sm:ZnAl<inf>2</inf>O<inf>4</inf> nanopowder was synthesized by vibrational milling process assisted with calcination treatment. Structural and optical properties of Sm:ZnAl<inf>2</inf>O<inf>4</inf> nanopowders were investigated via the crucial parameter of different doping concentration. Structural properties of as-synthesized samples and Sm: ZnAl<inf>2</inf>O<inf>4</inf> powders were characterized by X-ray diffraction and scanning electron microscope. For optical properties, Sm: ZnAl<inf>2</inf>O<inf>4</inf> phosphor materials were analyzed via diffuse reflectance and photoluminescence spectroscopy. The preliminary results suggested that Sm: ZnAl<inf>2</inf>O<inf>4</inf> powders were identically in spinel crystalline phase as host ZnAl<inf>2</inf>O<inf>4</inf> structure affirmed by XRD result. SEM images indicated the Sm:ZnAl<inf>2</inf>O<inf>4</inf> after the synthesis distinctly obtained in ultrafine power due to the effect of several milling round and sintering process. The optical properties in reflectance mode of Sm:ZnAl<inf>2</inf>O<inf>4</inf> samples were significantly increased by the presence of Sm dopant in ZnAl<inf>2</inf>O<inf>4</inf> structure. Meanwhile, the luminescent materials showed red emissions under visible light excitation in range of 650-730 nm by PL spectra. The improvement of ZnAl<inf>2</inf>O<inf>4</inf> photoluminescence property was obviously obtained at 0.5 wt.% Sm due to photon transfer from Sm to host material.
Some of the metrics are blocked by your
consent settings
Preface/Editorial
(2018-01-01)
Nukeaw, Jiti
;
Pecharapa, Wisanu
;
Yimnirun, F. Rattikorn
;
Ishihara, Keiichi N.
Some of the metrics are blocked by your
consent settings
X-ray absorption spectroscopy analysis and magnetic properties of M-doped TiO2 nanoparticles (M=Co, Mn, Ni and Zn) prepared by co-precipitation method
(2017-08-01)
Wattanawikkam, Chakkaphan
;
Pecharapa, Wisanu
;
Ishihara, Keiichi N.
M-doped TiO<inf>2</inf> nanoparticles (M=Co, Mn, Ni and Zn) were synthesized by co-precipitation method combined with annealing at 500 °C for 2 h. X-ray diffraction (XRD) was used to identify their structural phases. X-ray absorption near edge structure (XANES) was conducted to probe the chemical state and crystal atomic structure of prepared samples. Magnetic properties of all samples were characterized by vibrating sample magnetrometer (VSM). The XRD analyses reveal that all samples crystallize in anatase tetragonal structure with no additional peaks. The XANES spectra exhibit triple pre-edge fingerprint of Ti4+ of oxidation state with six-fold octahedral coordinate structure. Co-, Ni- and Zn- K-edge results indicate that the Co, Ni and Zn ions in M-doped TiO<inf>2</inf> are in 2+ formal oxidation state. Meanwhile, Mn-doped TiO<inf>2</inf> sample contains the different oxidation states of 3+ and 4+. The amount of each oxidation state is confirmed by using linear combination fitting method. The magnetic measurement illustrates the paramagnetic behavior for Co-, Mn- and Ni- doped samples that strongly depend on the doping content and no hysteresis loop is observed in undoped and Zn-doped samples.
Some of the metrics are blocked by your
consent settings
Preface
(2017-01-01)
Nukeaw, Jiti
;
Pecharapa, Wisanu
;
Yimnirun, Rattikorn
;
Ishihara, Keiichi N.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results