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Nakhon Ratchasima, Thailand

Jaikaew W.,Suranaree University of Technology | Patanakul R.,Synchrotron Light Research Institute | Schulte A.,Suranaree University of Technology
Electroanalysis | Year: 2016

We report the first utilization of copper disk electrodes as suitable cathodic transducer platforms for glucose biosensors. Simple and cheap Cu disk electrodes were fabricated from ordinary electrical cable by cementing into a glass tube with epoxy resin and subsequent polishing to expose the active area. Glucose oxidase was immobilized on the electrode tips by entrapment in dropped and dried polymeric Nafion deposits. At a H2O2 detection potential of -0.15V vs. a reference electrode, the linear response range of fabricated cable Cu glucose biosensors was 20-1500μM, with a sensitivity of about 700nAμM-1cm-2. Quantitative analysis of glucose-supplemented buffer solutions showed a recovery of 106±4% (n=3). The principal advantage of the glucose biosensors described in this study, compared to other options, is the simplicity of the cathodic H2O2 readout, which exploits cheap and readily available electrical cable, without any extra surface modification with catalytically active micro- or nanomaterials. The analytical performance of the biosensor is competitive and suggests potential applications in routine glucose testing, in particular in academic teaching and research laboratories. The work is also a starting point for transfer of the methodology from simple cable Cu electrodes to arrays of miniaturized Cu sensors, using a combination of microlithography, electroforming and molding (LIGA). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Siritapetawee J.,Ubon Ratchathani University | Pattanasiriwisawa W.,Synchrotron Light Research Institute | Sirithepthawee U.,Nakhon Ratchasima Rajanagarindra Psychiatric Hospital
Journal of Synchrotron Radiation | Year: 2010

The trace elements of scalp hair samples from ≥60-year-old dementia patients and normal persons have been studied by X-ray absorption near-edge spectroscopy (XANES) in fluorescent mode and wavelength-dispersive X-ray fluorescence spectrometry. Comparisons of hair trace element levels of age-matched dementia patients and normal persons revealed significantly elevated amounts of calcium, chlorine and phosphorus in dementia patients relative to normal persons. The results of XANES measurements identify the chemical forms of deposited calcium and phosphorus in the hair samples of both dementia patients and normal persons to be calcium chloride (CaCl2) and phosphate (PO43-), respectively. The amount of sulfur in hairs of dementia patients was found to be not significantly different from that in normal persons. The sulfur K-edge XANES spectra, however, show significantly higher accumulations of sulfur in the sulfate (SO42-) form in hairs of Alzheimers disease and Parkinsons disease dementia patients. This study presents the possible roles of calcium, chlorine, phosphorus and sulfur in the etiology of dementia in elderly patients. © 2010 International Union of Crystallography Printed in Singapore - All rights reserved. Source


Thungprasert S.,Chiang Mai University | Sarakonsri T.,Chiang Mai University | Klysubun W.,Synchrotron Light Research Institute | Vilaithong T.,Chiang Mai University
Journal of Alloys and Compounds | Year: 2011

In this research, Pt-based ternary catalysts for proton exchange membrane fuel cell (PEMFC) have been successfully prepared by the solution route method. This type of catalyst was claimed to improve the activities of oxygen reduction reaction (ORR). The ternary catalyst was prepared using 10% platinum, 5% cobalt, and 5% chromium by weight support on untreated and treated carbons by reduction with NaBH4 at room temperature. The FTIR spectra showed a new functional group as carboxyl group on treated carbon using H2O 2. The XRD patterns for both carbon samples confirmed platinum and carbon phases in the products. The EDS spectra detected platinum, cobalt, chromium, oxygen and carbon atoms in the prepared catalysts. The XAS patterns revealed that the products were mixed Pt-CoO-Cr2O3 catalysts. The SEM and TEM images showed more dispersion of catalyst on the treated carbon support surface than on the untreated carbon support. Particles size were 3.97 nm for untreated carbon and 1.93 nm for treated carbon. Finally, the electrochemical property was tested by CV technique. It indicated that Pt-CoO-Cr2O3/C catalyst supported on treated carbon exhibited the highest performance among the prepared ternary alloy catalysts. © 2011 Elsevier B.V. All rights reserved. Source


T-Thienprasert J.,Kasetsart University | Rujirawat S.,Suranaree University of Technology | Klysubun W.,Synchrotron Light Research Institute | Duenow J.N.,National Renewable Energy Laboratory | And 4 more authors.
Physical Review Letters | Year: 2013

The synchrotron x-ray absorption near edge structures (XANES) technique was used in conjunction with first-principles calculations to characterize Al-doped ZnO films. Standard characterizations revealed that the amount of carrier concentration and mobility depend on the growth conditions, i.e. H2 (or O2)/Ar gas ratio and Al concentration. First-principles calculations showed that Al energetically prefers to substitute on the Zn site, forming a donor AlZn, over being an interstitial (Ali). The measured Al K-edge XANES spectra are in good agreement with the simulated spectra of AlZn, indicating that the majority of Al atoms are substituting for Zn. The reduction in carrier concentration or mobility in some samples can be attributed to the AlZn-VZn and 2Al Zn-VZn complex formations that have similar XANES features. In addition, XANES of some samples showed additional features that are the indication of some α-Al2O3 or nAl Zn-Oi formation, explaining their poorer conductivity. © 2013 American Physical Society. Source


Sinyoung S.,King Mongkuts University of Technology Thonburi | Songsiriritthigul P.,Synchrotron Light Research Institute | Songsiriritthigul P.,Suranaree University of Technology | Asavapisit S.,King Mongkuts University of Technology Thonburi | And 2 more authors.
Journal of Hazardous Materials | Year: 2011

The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca6Al4Cr2O15, Ca5Cr3O12, Ca5Cr2SiO12, and CaCr2O7, with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca5(CrO4)3OH, CaCrO4·2H2O, and Al2(OH)4CrO4, with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr3+ from Ca6Al4Cr2O15 and Cr6+ from CaCr2O7, CaCrO4·2H2O, and Al2(OH)4CrO4, were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process. © 2011 Elsevier B.V. Source

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