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Chachoengsao, Thailand

Wangkawong K.,Chiang Mai University | Tantraviwat D.,Thai Microelectronics Center | Phanichphant S.,Chiang Mai University | Inceesungvorn B.,Chiang Mai University
Applied Surface Science | Year: 2015

The energy band diagram and band offsets of the novel CoTiO3/Ag3VO4 heterojunction photocatalyst are investigated by X-ray photoelectron spectroscopy for the first time. Excluding the strain effect, the valence-band and conduction-band offsets are determined to be 0.2 ± 0.3 eV and -0.6 ± 0.3 eV, respectively. The CoTiO3/Ag3VO4 composite forms a type-II heterojunction, for which the photogenerated charge carriers could be effectively separated. The results suggest that determination of the energy band structure is crucial for understanding the photogenerated charge transfer mechanism at the interfaces, hence the corresponding photocatalytic activity and would also be beneficial to the design of new and efficient heterostructure-based photocatalysts. © 2014 Elsevier B.V. All rights reserved.

Kasi J.K.,Asian Institute of Technology | Kasi A.K.,Asian Institute of Technology | Afzulpurkar N.,Asian Institute of Technology | Hasan M.,Asian Institute of Technology | And 2 more authors.
Nanoscience and Nanotechnology Letters | Year: 2012

Anodic aluminum oxide (AAO) is one of attractive materials which are used for the fabrication of micro and nanostructures. This paper describes the fabrication of three dimensional (3D) microstructures with AAO nano porous membrane. A simple procedure has been adopted to develop microstructures using the same aluminum (Al) sample without any assistance of scaffold or molding process. Various shapes including micro conical tube, micro cone, and micro bowl structures have been fabricated. Those factors have also been analyzed which are affecting the shapes of microstructures like cracks, angle, and geometry. The fabricated 3D shapes have potential applications in drug delivery system. © 2012 American Scientific Publishers.

Thongkham W.,Chulalongkorn University | Thongkham W.,Research Center in Thin Film Physics | Pankiew A.,Thai Microelectronics Center | Yoodee K.,Chulalongkorn University | And 3 more authors.
Solar Energy | Year: 2013

The fabrication of Cu(In,Ga)Se2 (CIGS) thin film solar cells on flexible stainless steel (SS) foils or Na free substrates needs the impurity blocking barrier to prevent the diffusion of undesired elements from the substrate into the CIGS as well as the addition of alkali doping especially Na in the CIGS absorber layer. The amount Na in terms of the thicknesses of NaF was varied from 30Å to 200Å in order to study its contributions to the efficiency of the CIGS solar cells. The results show that the Na content in the CIGS films has a direct influence to the open-circuit voltage leading to the energy conversion efficiency and affects the distribution of Ga in the CIGS film. The influence of Na was studied and compared, based on the results of the performance of the solar cells, by using the NaF co-evaporation in various steps during the CIGS deposition process. The optimum thickness of NaF is approximately 50Å to achieve the maximum efficiency of 15.8% without antireflection coating. In addition, the quantum efficiency (QE) indicated different absorption in the long wavelength regions depending upon the methods of Na addition. © 2013 Elsevier Ltd.

Ashraf M.W.,Asian Institute of Technology | Tayyaba S.,Asian Institute of Technology | Nisar A.,Asian Institute of Technology | Afzulpurkar N.,Asian Institute of Technology | And 4 more authors.
Cardiovascular Engineering | Year: 2010

In this paper, we present design, fabrication and coupled multifield analysis of hollow out-of-plane silicon microneedles with piezoelectrically actuated microfluidic device for transdermal drug delivery (TDD) system for treatment of cardiovascular or hemodynamic disorders such as hypertension. The mask layout design and fabrication process of silicon microneedles and reservoir involving deep reactive ion etching (DRIE) is first presented. This is followed by actual fabrication of silicon hollow microneedles by a series of combined isotropic and anisotropic etching processes using inductively coupled plasma (ICP) etching technology. Then coupled multifield analysis of a MEMS based piezoelectrically actuated device with integrated silicon microneedles is presented. The coupledfield analysis of hollow silicon microneedle array integrated with piezoelectric micropump has involved structural and fluid field couplings in a sequential structural-fluid analysis on a three-dimensional model of the microfluidic device. The effect of voltage and frequency on silicon membrane deflection and flow rate through the microneedle is investigated in the coupled field analysis using multiple code coupling method. The results of the present study provide valuable benchmark and prediction data to fabricate optimized designs of the silicon hollow microneedle based microfluidic devices for transdermal drug delivery applications. © 2010 Springer Science+Business Media, LLC.

Wangkawong K.,Chiang Mai University | Suntalelat S.,Thai Microelectronics Center | Tantraviwat D.,Thai Microelectronics Center | Inceesungvorn B.,Chiang Mai University
Materials Letters | Year: 2014

A novel CoTiO3/Ag3VO4 composite is successfully synthesized by ethylene glycol-mediated route/hydrothermal method. X-ray diffraction study suggests that the composite is formed with high purity. The presence of Ag3VO4 irregular agglomerates and CoTiO3 rods in the composite is evidenced by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Photocatalytic degradation experiment under visible light irradiation (λ>400 nm) indicates that the activity of Ag3VO4 is significantly enhanced upon coupling with CoTiO3. Based on the obtained results, such enhanced photoactivity is mainly ascribed to the increased visible-light harvesting ability and the efficient separation of electron-hole pairs of the hybrid photocatalyst. © 2014 Elsevier B.V.

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