Browsing by Author "Lin, Yin-Kai"

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Au Nanostructure-Decorated TiO2 Nanowires Exhibiting Photoactivity Across Entire UV-visible Region for Photoelectrochemical Water Splitting
(2013-08-01)
Pu, Ying-Chih
;
Wang, Gongming
;
Chang, Kao-Der
;
Ling, Yichuan
;
Lin, Yin-Kai
Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV visible light for solar fuel production.
Au/ZnS core/shell nanocrystals as an efficient anode photocatalyst in direct methanol fuel cells
(2013)
Chen, Wei-Ta
;
Lin, Yin-Kai
;
Yang, Ting-Ting
;
Pu, Ying-Chih
;
Hsu, Yung-Jung
Au/ZnS core/shell nanocrystals with controllable shell thicknesses were synthesized using a cysteine-assisted hydrothermal method. Incorporating Au/ZnS nanocrystals into the traditional Pt-catalyzed half-cell reaction led to a 43.3% increase in methanol oxidation current under light illumination, demonstrating their promising potential for metal/semiconductor hybrid nanocrystals as the anode photocatalyst in direct methanol fuel cells.
Enhancement of adhesion between copper foil and polyimide film containing thermally decomposable polystyrene particles
(2012-11-25)
Tsai, Mei-Hui
;
Huang, Yi-Chia
;
Tseng, I-Hsiang
;
Yu, Hsin-Pei
;
Lin, Yin-Kai
A facile method was developed to synthesize porous polyimide (PI) films with enhanced adhesion to Cu foil. Various amounts (0.14 wt %) of polystyrene (PS) spheres with the diameter of 250 nm were mixed with the PI precursor synthesized from pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline in N,N'-dimethylacetamide. PS was decomposed during thermal imidization process to create the porous PI structure. The increase in surface area and surface roughness was observed from the obtained porous PI films and was a function of the PS content up to 4 wt %. A significant improvement in the adhesion strength between porous PI film and Cu foil, which was determined by 90 degrees peel test, was achieved. The adhesion strength of PI containing 4 wt % PS to Cu was 1.53 kgf/cm compared with pure PI of 1.08 kgf/cm. Meanwhile, the synthesized porous PI films exhibit sufficient mechanical strength and thermal stability for practical applications. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Metal-Cu2O core-shell nanocrystals for gas sensing applications: Effect of metal composition
(2014-12-01)
Lin, Yin-Kai
;
Chiang, Yu-Ju
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A fast, versatile citrate-binding approach has been developed to prepare metal-Cu2O core-shell nanocrystals with different metal compositions, such as Au, Ag and Pd. Because of the electron trapping of the metal core, metal-Cu2O nanocrystals exhibited enhanced CO sensing performance in comparison with pure Cu2O. Steady-state photoluminescence and photocurrent measurements were conducted to investigate the electron trapping effect of the metal and its significance in the CO sensing mechanism. Among the three metal-Cu2O nanocrystals tested, Au-Cu2O displayed the highest CO response, attributable to the largest electron trapping capability of Au which enlarged the extent of resistance change for CO detection. The ability to improve the gas sensing performance of Cu2O by means of metal introduction has significant implications in the development of gas sensor technology, especially the strategies of materials combination and heterostructure engineering. (C) 2014 Elsevier B.V. All rights reserved.
Thermal and mechanical properties of polyimide/nano-silica hybrid films
(2011-05-31)
Tsai, Mei-Hui
;
Huang, Yi-Chia
;
Tseng, I-Hsiang
;
Yu, Hsin-Pei
;
Lin, Yin-Kai
A novel route to synthesize polyimide (PI)/silica hybrid films with improved thermal and mechanical properties was developed. Low-molecular-weight poly(amic acid) (PAA), which is the precursor of PI, was successfully synthesized by controlling the molar ratio of monomers, [4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic anhydride)] (IDPA) and 2,2'-bis(4-(4-aminophenoxy)phenyl)propane (BAPP). The PM with its low-molecule-weight feature showed good compatibility with silica-sol and dispersed well within the network of silica-sol. Silica nanoparticles with an average size of 20 nm were obtained without adding coupling agents and dispersed homogenously within the resulting PI/silica hybrid films due to the hydrogen bonding between Si-OH groups and C=O in imide rings of polyimide. The improvement in the storage modulus and the coefficient of thermal expansion (CTE) by hybrid films was revealed. With the presence of 50 wt.% silica in hybrid films, the storage modulus was 5857 MPa and the CTE was 18.1 ppm/degrees C. compared with 1620 MPa and 76.5 ppm/degrees C for pure PI. Most importantly, the transmission at 550 nm was 81.4% for the hybrid film with 50 wt.% silica, which is close to 87.5% for pure PI. The CTE of the hybrid film dropped to the level comparable with that of copper without sacrificing its transparency, which was associated with the well-dispersed silica nanoparticles and the semi-interpenetrating polymer network (semi-IPN) structure within the PI matrix. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.