Browsing by Author "Chang, I-Chun"

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Alkali metal ion assisted synthesis of faceted anatase TiO2
(2013)
Yang, Min-Han
;
Chen, Po-Chin
;
Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Chang, I-Chun
This work reports on a simple hydrothermal method for tuning the shape and exposed face of TiO2 nanocrystal by using sodium titanate as a precursor in the presence of different alkali metal ion salts. The {101}-exposed anatase TiO2 was synthesized in lithium salt solution. The formation of anatase TiO2 with exposed high-index {301} facet, obtained in the presence of sodium ions, has never before been reported upon. When the reaction proceeded in potassium salt solution, the obtained anatase TiO2 with a high aspect ratio was elongated in the < 001 > direction. Anatase TiO2 with a high aspect ratio was obtained in hydrothermal process in the presence of low charge density high atomic number alkali metal ions, which were not easily absorbed by the {001} planes of anatase, so the growth along this direction was not restrained. The photodegradation of methylene blue, assisted by anatase TiO2 with various exposed faces reveals that the photoactivity of anatase {101} planes is larger than that of {301} planes.
Anatase and brookite TiO2 with various morphologies and their proposed building block
(2014)
Yang, Min-Han
;
Chen, Po-Chin
;
Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Chang, I-Chun
In this work, brookite TiO2 has been synthesized by a simple hydrothermal approach using sodium titanate as a precursor in the presence of a sodium fluoride aqueous solution. The ratio of brookite and anatase TiO2 can be tailored by the NaF concentration. In a concentrated NaF solution, high quality brookite TiO2 was acquired. Pure anatase nanoparticles were obtained in only deionized water. Moreover, the morphology and size of brookite TiO2 can be tailored by using various acid treated titanates which influence the stability of the building blocks and nucleation points of TiO2. Micro-sized flower-like brookite, submicro-sized urchin-like brookite and brookite nanorods with anatase nanoparticles were obtained. The micro-sized flower-like brookite remains the same shape and phase even at 800 degrees C, whereas obvious grains were formed on the matrix with brookite, rutile and anatase mixture phases at 900 degrees C. On the other hand, as the submicro-sized urchin-like brookite was heated, a rutile phase appeared at 750 degrees C and 100% grain-like rutile was obtained at 900 degrees C.
Enhanced photocatalytic decomposition of methylene blue by the heterostructure of PdO nanoflakes and TiO2 nanoparticles
(2012-12-15)
Huang, Chien-Jung
;
Pan, Fu-Ming
;
Chang, I-Chun
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We prepared PdO nanoflakes by reactive sputter deposition to form a heterostructure with TiO2 nanoparticles on the SiO2 substrate for the study of photocatalytic decomposition of methylene blue (MB) molecules. Although the PdO nanoflake has little photocatalytic activity toward MB decomposition, the PdO/TiO2 heterostructure has a photocatalytic activity toward MB decomposition under UV light illumination as large as twice that of bare TiO2 nanoparticles. The enhancement in the photocatalytic activity is ascribed to the fast photogenerated carrier separation resulting from the potential barrier formed at the heterojunction between the two oxide semiconductors. Although PdO nanoflakes can be photoexcited under visible light illumination, the PdO/TiO2 heterostructure exhibits little photocatalytic activity toward the MB decomposition. (C) 2012 Elsevier B. V. All rights reserved.
Glucose sensing by electrochemically grown copper nanobelt electrode
(2009-11-15)
Huang, Ting-Kai
;
Lin, Kuan-Wen
;
Tung, Sze-Ping
;
Cheng, Ta-Ming
;
Chang, I-Chun
A simple design of growing Cu nanobelt (NB) electrode for glucose sensing is presented. Cu NBs were grown directly on carbon electrodes by using electrochemical deposition. The average width, thickness and length of the NBs were about 50 nm, 20 nm and several tens of micrometers, respectively. Cyclic voltammetric (CV) experiments showed that a Cu NB electrode grown by a reduction charge of 0.5 C on a substrate of 0,018 cm(2) enhanced glucose oxidation ability. For glucose sensing, the electrode exhibited a high sensitivity of 79.8 mu A/mM and a measurable detection limit of 10 mu M in amperometric detection. (C) 2009 Elsevier B.V. All rights reserved.
Growth of Pagoda-Topped Tetragonal Copper Nanopillar Arrays
(2009-07-01)
Chang, I-Chun
;
Huang, Ting-Kai
;
Lin, Huang-Kai
;
Tzeng, Yu-Feng
;
Peng, Chih-Wei
Growth of arrays of pagoda-topped tetragonal Cu nanopillar (length 1 - 6 mu m; width 150 +/- 25 nm) with {100) side races on Au/glass is achieved by,a simple electrochemical reduction of CuCl(2)(aq) by Al(s) in aqueous dodecyltrimethylammonium chloride. Field-emission measurement shows that the Cu nanopillars can emit electrons (10 mu A cm(-2)) at a turn-on field or 12.4 V mu m(-1) with a calculated held enhancement factor of 713.
Large-scale synthesis of uniform Cu2O nanocubes with tunable sizes by in-situ nucleation
(2013)
Chang, I-Chun
;
Chen, Po-Chin
;
Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Yang, Min-Han
Uniform Cu2O nanocubes with various sizes were synthesized by reducing Cu(OH)(2) using ascorbic acid in the presence of various amounts of sodium citrate. The monodispersed nanocubes with an edge length of approximately 80 nm used as an anode exhibit excellent lithium storage behavior.
Porous titanium oxynitride sheets as electrochemical electrodes for energy storage
(2014)
Chen, Ting-Ting
;
Liu, Hsiao-Ping
;
Wei, Yen-Ju
;
Chang, I-Chun
;
Yang, Min-Han
A flexible, porous TiOxNy sheet consisting of numerous conductive fibers was synthesized by nitridation of titanate and further used as an electrochemical electrode. The high surface area and mixed-oxidation state of titanium make TiOxNy sheets to be promising candidates for a good supercapacitor.
Scattering resonance enhanced dye absorption of dye sensitized solar cells at optimized hollow structure size
(2014-12-05)
Tsai, Min-Chiao
;
Lee, Jeng-Yi
;
Chang, Ya-Chen
;
Yang, Min-Han
;
Chen, Tin-Tin
This study elucidates the size effect on dye-sensitized solar cells (DSSCs) by synthesizing highly uniform hierarchical hollow sphere TiO2 samples, with the diameters from 220 nm to 800 nm. Experimental results indicate that the optimum conversion efficiency using N719 dye can be achieved around 5.5%, as the diameter of hierarchical hollow spheres is 450-550 nm. According to the incident photon-to-current conversion efficiency (IPCE) spectra, large-sized hierarchical hollow spheres significantly enhance the light harvesting by scattering; whereas small-sized hallow spheres (<360 nm) improve negligibly. Additionally, mesoporous and solid spheres with an identical diameter, 440 nm in this study, are also studied as a comparison. Our results demonstrate that hollow spheres perform the same conversion efficiency as that of mesoporous spheres owing to the equivalent adsorption of dye molecules in both hierarchical structures - regardless of the surface area of the interior of mesoporous structure, which shows that hollow spheres have higher conversion efficiency per unit volume than that of mesoporous spheres. (C) 2014 Elsevier B.V. All rights reserved.
Self-powered electrochemical deposition of Cu@Ni(OH)(2) nanobelts for high performance pseudocapacitors
(2014)
Chang, I-Chun
;
Chen, Ting-Ting
;
Yang, Min-Han
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
Two aluminum-driven spontaneous electrochemical reactions are developed for depositing Cu@Ni(OH)(2) nanobelts on carbon/aluminum electrodes. The Cu@Ni(OH)(2) NBs function as pseudocapacitor electrodes, which exhibit a high specific capacitance of 2426 F g(-1) and a remarkable rate performance.
Size-controlled wurtzite zinc oxide spheres with the characteristics of visible absorption and Mie scattering
(2014)
Chen, Ting-Ting
;
Chang, I-Chun
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Tsai, Min-Chiao
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Chang, Yi-Chun
;
Yang, Min-Han
The enhancement of the light harvesting efficiency over a metal oxide is crucial to optic-related applications which can convert solar energy into chemical energy. Here, we demonstrated a method to develop the characteristics of visible light absorption and visible Mie scattering over wurtzite ZnO microspheres. Size-controlled ZnO microspheres were successfully prepared in the thermal decomposition of amorphous/ layered basic zinc salt (LBZ) spheres. Firstly, trisodium citrate was employed as the chelating agent to synthesize amorphous/LBZ microspheres in a nucleation-controlled method. The sphere size was controlled by the nuclei number, which depends on the competition between hydroxyl ions and citrate to the ligand with Zn2+. Secondly, visible-active wurtzite ZnO spheres were obtained by thermal decomposition. The uniform sized microspheres exhibited Mie scattering in the visible range due to the interaction with specific incident electromagnetic radiation, and the full absorption spectrum was easily obtained by tuning the size of the spheres. Such uniform spheres exhibited superior visible absorption and scattering effects and thus are expected to be good candidates for the optic-related applications.
The exceptional photo-catalytic activity of ZnO/RGO composite via metal and oxygen vacancies
(2013-10-01)
Chen, Ting-Ting
;
Chang, I-Chun
;
Yang, Min-Han
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
ZnO/reduced graphene oxide (RGO) nanocomposite with many zinc and oxygen vacancies, synthesized in a simple solvothermal reaction exhibits significant photocatalytic activity. Photoluminescence and electron paramagnetic resonance measurements indicate that the zinc vacancies and oxygen vacancies were generated on the ZnO surface, and were crucial to that photocatalytic behavior. The photodegradation of methylene orange was significantly reduced by the addition of h(+) and (OH)-O-center dot scavengers. Both zinc and oxygen vacancies cause effective charge separation in the photodegradation of methylene orange, which markedly inhibits the recombination of charges. The advanced photocatalytic behavior of the ZnO/RGO composite is discussed in detail herein. (c) 2013 Elsevier B.V. All rights reserved.