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Investigation of the influences of reaction temperature and time on the chemical reduction of graphene oxide by conventional method using Vitamin C as a reducing agent
(2017-01-01)
Sriwong, Chaval
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Choojun, Kittisak
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Kongtaweelert, Samart
The aim of this work is to investigate the synthesis of reduced graphene oxide (rGO) aqueous suspension by a conventional heating method using vitamin C as a reducing agent. The influences of reaction temperatures (70, 90 and 100 °C) and heating times (30, 45 and 60 min) on the chemical reduction of graphene oxide (GO) were studied. Then, the obtained rGO samples were characterized by FT-IR, Raman, UV-Vis, XRD and TEM techniques. The FT-IR and Raman results showed that the reduction degree of GO to rGO was increased with the rising of the reaction temperature and time. Moreover, the UV-Vis spectra demonstrated that the absorption band at around 230 nm (π-π*) of pristine GO had shift to the longer wavelength upon the chemical reduction, indicating that GO is reduced to rGO. The optimal condition of the chemical reduction of GO to achievable rGO was the temperature of 90 °C with the 45 min of heating time. This condition yielded the rGO black aqueous suspension with the high quality and stability. Thus, this method of synthesis has an advantage of the rGO dispersion which led to many potential applications.
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Bioactive compounds from Mesua ferrea stems
(2015-01-01)
Keawsa-Ard, Sukanya
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Liawruangrath, Boonsom
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Kongtaweelert, Samart
The chemical constituents and biological activities of Mesua ferrea Linn. were studied. The stems of M. ferrea were extracted with hexane, dichloromethane and methanol, respectively. The methanol extract exhibited the highest antibacterial activity against Escherichia coli with the MIC value of 31.25 μg/mL. The methanol extract and the dichloromethane extract exhibited the highest activity against Staphylococcus aureus with the MIC values of 31.25 μg/mL. The dichloromethane extract exhibited anticancer activities against KB-oral, MCF-7 and NCI-H187 cell lines with the IC<inf>50</inf>values of 18.01, 28.83 and 18.42 μg/mL, respectively. Friedelin, the mixture of α-amyrin and β-amyrin, lupeol and β-sitosterol were isolated from the active dichloromethane extract of the stems. Friedelin, the mixture of α-amyrin and β-amyrin, lupeol and β-sitosterol showed the antibacterial activity against E. coli with the MIC values of 250, 250, 250 and 1000 μg/mL, respectively. They also showed antibacterial activity against S. aureus with the MIC values of 250, 250, 500 and 1000 μg/mL, respectively. The mixture of α-amyrin and β-amyrin exhibited anticancer activity against MCF-7 cell line with the IC<inf>50</inf>value 28.45 μg/mL and lupeol exhibited anticancer activities against KB, MCF-7 and NCI-H187 cell lines with the IC<inf>50</inf>values of 30.12, 34.25 and 21.56 μg/mL, respectively. All the extracts and the isolated compounds were non-cytotoxic to Vero cells.
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Electrical and optical properties of p-type CuFe1-xSn xO2 (x = 0.03, 0.05) delafossite-oxide
(2013-01-14)
Ruttanapun, Chesta
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Boonchom, Banjong
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Thongkam, Montree
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Kongtaweelert, Samart
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Thanachayanont, Chanchana
The CuFe<inf>1-x</inf>Sn<inf>x</inf>O<inf>2</inf> (x = 0.03, 0.05) delafossite samples have been synthesized by a solid-state reaction to investigate electrical and optical properties of the transparent conducting oxide materials. Crystal structure was characterized by XRD. The electrical conductivity and Seebeck coefficient were measured in the high temperature range of 300 to 960 K, while the Hall coefficient, XPS, and UV-VIS-NIR spectra were analyzed at room temperature. The XRD peaks of the samples indicate the delafossite structure phase, and the XPS spectra reveal the stable Sn 2+-doping state. The Seebeck and Hall coefficient display a positive sign indicating the p-type conducting oxide. The optical allowed direct gap is 3.45 eV as a visible-transparent material. The activation energies for polaron hopping between Sn2+ sites and Fe3+ sites of 36 and 32 meV are obtained from the samples having x = 0.03 and 0.05, respectively. The CuFe<inf>1-x</inf>Sn<inf>x</inf>O<inf>2</inf> delafossite oxide compounds, of which the Fe3+ sites in the CuFeO<inf>2</inf> are substituted by the Sn2+ ions, are p-type transparent conducting oxide materials. The activation energy is found to decrease with an increased in Sn content. © 2013 American Institute of Physics.
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Antioxidant, antibacterial, anticancer activities and chemical constituents of the essential oil from Mesua ferrea leaves
(2012-01-01)
Keawsa-Ard, Sukanya
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Kongtaweelert, Samart
Essential oil from leaves of Mesua ferrea L. was isolated by hydrodistillation and analyzed by means of GC and GC-MS. The yield of obtained essential oil was at 0.064% and it was appearred as yellow liquid. Thirty-five constituents were identified, constituting 81.4% of the total volatile components. The major constituents were trans-caryophyllene (30.9%), β-caryophyllene oxide (17.9%), α-humulene (6.0%), δ-cadinene (4.1%), γ-muurolene (3.5%), γ-cadinene (2.3%), β-selinene (1.9%), germacrene D (1.8%) and β-bisabolene (1.6%). Antioxidant activity of the essential oi l was evaluated by using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals scavenging assay. The essential oil showed antioxidant activity with the IC<inf>50</inf> of 31.67 mg/mL. In addition, the essential oil exhibited significant antibacterial activity against Escherichia coli and Staphylococcus aureus with the MIC values of 250 and 125 mg/mL, respectively. This oil also exhibited anticancer activities against KB, MCF-7 and NCI-H187 cell lines with the IC<inf>50</inf> values of 24.02, 16.19, and 20.32 μg/mL, respectively, but it was non-cytotoxic to Vero cell line.
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Kinetics and thermodynamics of zinc phosphate hydrate synthesized by a simple route in aqueous and acetone media
(2010-04-21)
Boonchom, Banjong
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Baitahe, Rattanai
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Kongtaweelert, Samart
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Vittayakorn, Naratip
Zinc phosphate (Zn<inf>3</inf>(PO<inf>4</inf>)<inf>2</inf>·4H <inf>2</inf>O) was prepared by a simple route using ZnO and H<inf>3</inf>PO <inf>4</inf> in aqueous and acetone media at ambient temperature. Zn <inf>3</inf>(PO<inf>4</inf>)<inf>2</inf>·4H<inf>2</inf>O decomposes to Zn<inf>3</inf>(PO<inf>4</inf>)<inf>2</inf> by three dehydration reactions, as revealed by thermal analytical (TG/DTG/DTA) and differential scanning calorimetry (DSC) techniques. The synthesized Zn<inf>3</inf>(PO <inf>4</inf>)<inf>2</inf>·4H<inf>2</inf>O and its dehydration product Zn<inf>3</inf>(PO<inf>4</inf>)<inf>2</inf> were characterized by powder X-ray diffraction, Fourier transfer infrared, and scanning electron microscopy. Kinetic triplet parameters (activation energy, E; preexponential, A; Avrami exponent, n) and thermodynamic functions (ΔH*, ΔG*, and ΔS*) of three dehydration reactions are calculated by DSC experiments. Evaluation and control of the specific characteristics of three dehydration processes of Zn<inf>3</inf>(PO<inf>4</inf>)<inf>2</inf>· 4H<inf>2</inf>O are essentially important in the variously oriented studies, which were discussed from the viewpoints of thermal stability based on kinetics and thermodynamics. © 2010 American Chemical Society.
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Study of kinetics and thermodynamics of the dehydration reaction of AlPO4 . H2O
(2010-02-01)
Boonchom, Banjong
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Kongtaweelert, Samart
The kinetics and thermodynamics of the thermal dehydration of aluminum phosphate monohydrate, AlPO<inf>4</inf> . H<inf>2</inf>O were studied using thermogravimetry (TG-DTG-DTA) at four heating rates in dry air atmosphere. The activation energies of the dehydration step of AlPO<inf>4</inf> . H<inf>2</inf>O were calculated through the methods of Friedman (FR) and Flynn-Wall-Ozawa (FWO) and the possible conversion function has been estimated through the Achar and Li-Tang equations. The independent activation energies on extent of conversions and the better kinetic model of the dehydration reaction for AlPO<inf>4</inf> . H<inf>2</inf>O indicate single kinetic mechanism and the F<inf>2.05</inf> model as a simple n-order reaction of "chemical process or mechanism no-invoking equation", respectively. The positive values of ΔH# and ΔG# for the dehydration reaction show that it is endothermic and non-spontaneous process and it is connected with the introduction of heat. The kinetic and thermodynamic functions calculated for the dehydration reaction by different techniques and methods were found to be consistent. © Akadémiai Kiadó, Budapest, Hungary 2009.
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Flower-like microparticles and novel superparamagnetic properties of new binary Co1/2Fe1/2(H2PO4) 2·2H2 O obtained by a rapid solid state route at ambient temperature
(2009-12-01)
Boonchom, Banjong
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Thongkam, Montree
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Kongtaweelert, Samart
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Vittayakorn, Naratip
A new binary Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O was synthesized by a simple, rapid and cost-effective method using CoCO<inf>3</inf>-Fe(c)-H<inf>3</inf>PO<inf>4</inf> system at ambient temperature. Thermal treatment of the obtained Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O at 600 °C yielded as a binary cobalt iron cyclotetraphosphate CoFeP<inf>4</inf>O<inf>12</inf>. The FTIR and XRD results of the synthesized Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and its final decomposed product CoFeP<inf>4</inf>O<inf>12</inf> indicate the monoclinic phases with space group P2<inf>1</inf>/n and C2/c, respectively. The particle morphologies of both binary metal compounds appear the flower-like microparticle shapes. Room temperature magnetization results show novel superparamagnetic behaviors of the Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and its final decomposed product CoFeP<inf>4</inf>O<inf>12</inf>, having no hysteresis loops in the range of ±10,000 Oe with the specific magnetization values of 0.045 and 12.502 emu/g at 10 kOe, respectively. The dominant physical properties of the obtained binary metal compounds (Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and CoFeP<inf>4</inf>O<inf>12</inf>) are compared with the single compounds (M(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and M<inf>2</inf>P<inf>4</inf>O<inf>12</inf>; where M = Co, Fe), indicating the presence of Co ions in substitution position of Fe ions. © 2009 Elsevier Ltd. All rights reserved.
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A simple route to synthesize new binary cobalt iron cyclotetraphosphate CoFeP4O12 using aqueous and acetone media
(2009-11-03)
Boonchom, Banjong
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Thongkam, Montree
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Kongtaweelert, Samart
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Vittayakorn, Naratip
A new binary cobalt iron cyclotetraphosphate, CoFeP<inf>4</inf>O<inf>12</inf> was synthesized through solid phase reaction using cobalt carbonate, iron metal and phosphoric acid in the presence of water-acetone media with further calcinations at the temperature of 500 °C. The particle size obtained from X-ray line broadening is 65 ± 24 nm for the CoFeP<inf>4</inf>O<inf>12</inf>. FTIR spectrum of CoFeP<inf>4</inf>O<inf>12</inf> is assigned based on the P<inf>4</inf>O<inf>12</inf>4- ion in the structure. The SEM micrograph of the synthesized CoFeP<inf>4</inf>O<inf>12</inf> shows non-uniform microparticle, which is important for specific application. Room temperature magnetization result shows superparamagnetic behavior of the CoFeP<inf>4</inf>O<inf>12</inf> powder, having no hysteresis loop in the range of ±10,000 Oe with the specific magnetization value of 14.243 emu/g. The XRD and FTIR results of the synthesized CoFeP<inf>4</inf>O<inf>12</inf> appear to be very similar to that of M<inf>2</inf>P<inf>4</inf>O<inf>12</inf> (M = Co and Fe), which indicates the monoclinic phase with space group C2/c. © 2009 Elsevier B.V.

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