Browsing by Author "Chang, Chung-Kai"

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Breath figure method for construction of high-aspect-ratio pores using diacetylene-labeled polystyrene
(2018-08-19)
Wang, Cheng-Heng
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Chang, Chung-Kai
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Li, Ming-Chia
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交大名義發表
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生物科技學系
Combination of electrophoresis and electro-flocculation for the formation of adhering IrO2 pH sensing films
(2019-07-20)
Wang, Han-Yi
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Hsieh, Yi-Chieh
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Tso, Kuang-Chih
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Chang, Chung-Kai
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Cheng, Yu-Ting
We demonstrate a simple scheme to produce dense and adhering IrO2 thin films on ITO substrates via a bipolar pulsing process combining both electrophoresis and electro-flocculation. Our fabrication steps entail the synthesis of negatively-charged IrO2 nanoparticles in size of 3.5 nm using NaClO as an oxidizer in conjunction with Na3IrCl6, citric acid, and NaOH. Subsequently, multiple bipolar potentiostatic pulses are imposed in which alternating positive and negative potentials engender the electrophoresis of IrO2 nanoparticles, followed by their immediate coalescence facilitated by proton-catalyzed electro-floccu-lation. The resulting IrO2 thin films reveal impressive physical properties in surface uniformity, robust structural integrity, and strong adhesion to the substrate. The as-synthesized IrO2 thin film exhibits an amorphous nature with a pH sensing slope between -73.6 and -71.5 mV/pH, characteristic of super-Nernstian behavior. In contrast, the annealed IrO(2 )sample demonstrates a crystalline rutile phase with a pH sensing slope between -49.5 and -54.7 mV/pH, consistent with typical Nernstian response. Our approach provides a new route for the formation of strong and adhering oxide films from their colloidal constituents. (C) 2019 Elsevier Ltd. All rights reserved.
Development of IrO2 bio-ink for ink-jet printing application
(2019-09-01)
Hsieh, Yi-Chieh
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Wang, Han-Yi
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Tso, Kuang-Chih
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Chang, Chung-Kai
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Chen, Chi-Shih
We develop a chemical formulation to synthesize stable IrO2 colloidal solution as a bio-ink for ink-jet printing purpose. This wet chemical process entails Na3IrCl6 and NaClO as the Ir precursor and oxidizer, respectively. In addition, citric acid and sodium hydroxide are employed as the complex agent and pH adjuster. The pH value of the IrO2 colloidal solution could be readily adjusted over a broad range without incurring undesirable precipitation. Their respective zeta potential decreases from positive to negative with increasing pH values. The IrO2 colloidal solution demonstrates impressive chemical stability over extended storage at 5 and 65 degrees C. Images from transmission electron microscope indicate the average size for the IrO2 nanoparticles to be 3.5 nm. The X-ray diffraction pattern from the heat-treated IrO2 sample shows a polycrystalline rutile phase. The IrO2 colloidal solution undergoes repeated filtering and washing to retrieve the IrO2 nanoparticles. After an annealing at 450 degrees C for 2 h in air, the crystalline IrO2 nanoparticles are resuspended in a 0.5 wt% aqueous medium as the bio-ink for ink-jet printing on an ITO substrate. Our method enables the synthesis of stable IrO2 nanoparticles in a neutral solution at 25 degrees C, which provides a facile and effective approach over conventional ones that require alkaline environment at elevated temperature.
Multi-scale mapping for collagen-regulated mineralization in bone remodeling of additive manufacturing porous implants
(2019-05-15)
Tsai, Pei-I.
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Lam, Tu-Ngoc
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Wu, Meng-Huang
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Tseng, Kuan-Ying
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Chang, Yuan-Wei
Long term success of metallic fusion cages depends on mechanobiological processes through the bone incorporation and rich osseointegration. An optimal configuration of porous titanium-aluminum-vanadium (Ti-6Al-4V) implant fabricated via the additive manufacturing was evaluated in complimentary structure examinations to investigate the growth of autologous osseous at multi-length scales. X-ray microcomputed tomography (micro-CT) and transmission X-ray microscopy (TXM) using newly-built analysis method indicate the porous Ti-6Al-4V is much better for bone ingrowth compared to commercially non-porous titanium (Ti) and porous tantalum (Ta) implants at the ultramicrostructural level. The evolution of bone formation and remodeling acquired by nano X-ray Laue diffraction mapping exhibits the isotropic orientation and low crystallinity of all newly formed bone whereas mature bone in Ti-6Al-4V discloses the preferential alignment and higher crystallinity volumes of constituent hydroxyapatite (HA) crystallites. The high degree in mineral crystallinity of the fully mature bone suggests additive manufactured Ti-6Al-4V pores enhance the collagen-regulated mineralization.
Structure-Dependent Photoluminescence in Low-Dimensional Ethylammonium, Propylammonium, and Butylammonium Lead Iodide Perovskites
(2020-01-29)
Lin, Chang-Wei
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Liu, Fangzhou
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Chen, Ting-Yang
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Lee, Kuan-Hua
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Chang, Chung-Kai
Hybrid organic-inorganic perovskites have attracted great attention as the next generation materials for photovoltaic and light-emitting devices. However, their environment instability issue remains as the largest challenge for practical applications. Recently emerging two-dimensional (2D) perovskites with Ruddlesden-Popper structures are found to greatly improve the stability and aging problems. Furthermore, strong confinement of excitons in these natural quantum-well structures results in the distinct and narrow light emission in the visible spectral range, enabling the development of spectrally tunable light sources. Besides the strong quasi-monochromatic emission, some 2D perovskites composed of the specific organic cations and inorganic layer structures emit a pronounced broadband emission. Herein, we report the light-emitting properties and the degradation of low-dimensional perovskites consisting of the three shortest alkylammonium spacers, mono-ethylammonium (EA), n-propylammonium (PA), and n-butylammonium (BA). While (BA)(2)PbI4 is known to form well-oriented 2D thin films consisting of layers of corner-sharing PbI6 octahedra separated by a bilayer of BA cations, EA with shorter alkyl chains tends to form other types of lower-dimensional structures. Nevertheless, optical absorption edges of asprepared fresh EAPbI(3), (PA)(2)PbI4, and (BA)(2)PbI4 are obviously blue-shifted to 2.4-2.5 eV compared to their 3D counterpart, methylammonium lead iodide (MAPbI(3)) perovskite, and they all emit narrow excitonic photoluminescence. Furthermore, by carefully optimizing deposition conditions, we have achieved a predominantly 2D structure for (PA)(2)PbI4. However, unlike (BA)(2)PbI4, upon exposure to ambient environment, (PA)(2)PbI4 readily transforms to a different crystal structure, exhibiting a prominently broadband light from similar to 500 to 800 nm and a gradual increase in intensity as structural transformation proceeds.
The synergistic effect of a well-defined Au@Pt core-shell nanostructure toward photocatalytic hydrogen generation: interface engineering to improve the Schottky barrier and hydrogen-evolved kinetics
(2016)
Hung, Sung-Fu
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Yu, Ya-Chu
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Suen, Nian-Tzu
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Tzeng, Guan-Quan
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Tung, Ching-Wei
A well-defined co-catalyst system TiO2 nanotube-Au (core)-Pt (shell) was demonstrated to be the combination of the localized surface plasmon effect of gold and excellent proton reduction nature of platinum. Furthermore, surface engineering by the descending Fermi energies of gold and platinum was beneficial to electron transfer.
Using in-situ synchrotron x-ray diffraction to investigate phase transformation and lattice relaxation of a three-way piezo-phototronic soft material
(2017-07-01)
Ko, Wen-Ching
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Hsu, Yu-Hsiang
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Weng, Shih-Chang
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Chang, Chung-Kai
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Lee, Ming-Tao
A poly(vinylidene fluoride-co-trifluoro-ethylene) piezoelectric polymer is blended with nano particles of titanium oxide phthalocyanine to bridge photoconductive and piezoelectric effects. In this study, a system is examined by in situ synchrotron x-ray to test a three-way piezo-phototronic soft-material design. The sample is heated for in situ phase transformation characterization. The semi-crystalline poly (vinylidene fluoride-co-trifluoro-ethylene) polymer gradually transforms to an amorphous structure. A complementary piezoelectric experiment before and after the heating experiment shows that the piezoelectric performance is proportional to the phase ratio. Secondly, the system is examined to test its phototronic effect. Piezoelectric responses are measured by controlling the light illumination. The positive and negative controls of light illumination which validate this newly-designed system can be modulated by a three-way piezo-phototronic effect. In-situ synchrotron x-ray diffraction experiments are employed to measure the microstructure evolution as a function of applied voltage up to 800 V. We then turned off both the light and the applied voltage to examine the kinetic behavior of the system. There is orientation-dependent anisotropic relaxation. We compared the lattice-strain evolutions. Piezo-phototronic creep is found in the (110), but not the (310) planes.
Visible-Light Modulation on Lattice Dielectric Responses of a Piezo-Phototronic Soft Material
(2015-12-16)
Huang, E-Wen
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Hsu, Yu-Hsiang
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Chuang, Wei-Tsung
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Ko, Wen-Ching
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Chang, Chung-Kai