Browsing by Author "Lu, Shih-Yuan"

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Composition-balanced trimetallic MOFs as ultra-efficient electrocatalysts for oxygen evolution reaction at high current densities
(2020-12-15)
Raja, Duraisamy Senthil
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Huang, Chun-Lung
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Chen, Yu-An
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Choi, YongMan
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Lu, Shih-Yuan
Engineering synergistic effects of multi-component catalysts is the key for breakthrough catalyst design. Here, a maximized-entropy approach was proposed to maximize the synergistic effects for maximum enhancements in electrocatalytic efficiencies of multi-component catalysts. Accordingly, composition-balanced iron, cobalt, and nickel based trimetallic MOFs was developed and demonstrated outstanding oxygen evolution reaction (OER) performances with ultra-low overpotentials of 196 and 284 mV achieved at current densities of 10 and 1000 mA cm(-2), respectively, as well as an ultra-low Tafel slope of 29.5 mV dec(-1) in alkaline aqueous media. The catalyst was ultra-stable even when operated at ultra-high current densities, experiencing only 5% loss in current densities, when chronoamperometrically tested at an industrially relevant current density of 1000 mA cm(-2) for over 50 h. in situ Raman spectroscopy study and density functional theory simulations were conducted to explore the OER mechanism and to illustrate the validity of the proposed maximized-entropy approach.
Differential Sensing of Serine and Tyrosine with Aligned CdS Nanowire Arrays Based on pH-Dependent Photoluminescence Behavior
(2009-03-09)
Lin, Yi-Feng
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Hsu, Yung-Jung
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Cheng, Wei-Yun
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Lu, Shih-Yuan
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材料科學與工程學系
The differential sensing of tyrosine and serine is achieved with well-aligned CdS nanowire arrays by exploring the pH-dependent photoluminescence behavior of the nanowire arrays toward exposure to the two amino acid solutions. The contrasting trend in photoluminescence (PL) intensity with respect to variations in analyte concentration observed at pH 11 served as the check point for the present differential sensing. The application format of the nanowire array is better suited for further sensing device assembly than that of nanocrystal suspensions.
Dopant-induced formation of branched CdS nanocrystals
(2008-07-01)
Hsu, Yung-Jung
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Lu, Shih-Yuan
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材料科學與工程學系
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Department of Materials Science and Engineering
Growth of zirconia and yttria-stabilized zirconia nanorod arrays assisted by phase transition
(2010)
Chen, Chih-Chiang
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Cheng, Wei-Yun
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Lu, Shih-Yuan
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Lin, Yi-Feng
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Hsu, Yung-Jung
Well-aligned, densely distributed ZrO(2) nanorod arrays were fabricated using a non-catalytic, template-free metal-organic chemical vapour deposition process at a reaction temperature of 1000 degrees C. The reaction temperature was found to play a key role in product morphology, with particle thin films obtained at 550 degrees C and nanorod arrays produced at 1000 degrees C. Increasing the reaction temperature led to the emergence of the medium-temperature tetragonal phase from the dominant low-temperature monoclinic phase, which is advantageous for anisotropic growth necessary for the nanorod formation. With the same deposition process, yttria-stabilized zirconia nanorod arrays of polycrystalline cubic phase were fabricated by co-feeding the dopant precursor, YCl(3), with the zirconia precursor, Zr(C(5)H(7)O(2))(4). The present work demonstrated the first example of monoclinic to tetragonal phase-transition assisted one-dimensional (1D) growth, and the concept can be extended to the formation of 1D nanostructures of materials possessing the monoclinic-tetragonal polymorphism.
Growth of ZnO Nanostructures with Controllable Morphology Using a Facile Green Antisolvent Method
(2010-05-20)
Dong, Ji-Yao
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Hsu, Yung-Jung
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Wong, David Shan-Hill
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Lu, Shih-Yuan
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材料科學與工程學系
An environmentally friendly antisolvent approach, which involves only biocompatible chemicals and mild processing conditions, was developed to prepare various ZnO nanostructures including twin-cones and nanorods with controllable dimensions, The method was based on the dissolution of ZnO powders in a deep eutectic solvent (DES), followed by precipitation of ZnO nanostructures from the DES upon introduction of an antisolvent. It is the first example of the room temperature ionic liquid based antisolvent process for preparation of nanomaterials. Through suitably modulating the processing conditions, such as the ethanol content of the antisolvent and the injection time of the ZnO-containing DES, the morphology of the resulting ZnO nanostructures can be readily controlled. Anisotropic crystal growth was achieved without severe reaction conditions, such as high temperatures and high vacuums, or use of environmentally harmful chemicals, such as long carbon chain surfactants and capping reagents. The present method can be readily extended to produce versatile nanostructures of other functional materials.
Hydrothermal synthesis, characterizations and photoluminescence study of single crystalline hexagonal ZnO nanorods with three dimensional flowerlike microstructures
(2014-05-01)
Kale, Rohidas B.
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Hsu, Yung-Jung
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Lin, Yi-Feng
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Lu, Shih-Yuan
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材料科學與工程學系
A simple, low-cost, and environmentally benign hydrothermal approach has been successfully developed to synthesize uniform, large-scale well-crystallized ZnO nanorods with different aspect ratios that were united together to form three dimensional (3D) flowerlike structures. The method involved direct growth of ZnO 3D microstructures using aqueous solution of Zn(CH3COO)(2) as the precursor and NaOH to adjust the pH of resultant solution. Surfactants or templates were not used during the entire synthetic process. Moreover, the morphology evolution of the ZnO nanorods with reaction time suggests a recrystallization dissolution growth mechanism that continuously takes place for prolonged interval of time. The XRD pattern of the as-grown ZnO nanorods and relevant analyses confirm the well crystallized hexagonal structure of the ZnO microstructures and no evidence of any other impurity phases. SEM observations reveal that the ZnO product grew in the form of nanorods that were united together to form 3D flowerlike morphology. The high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) shows that the ZnO nanorods were single crystalline and grew along the c-axis of the crystal plane. PL measurements of the as-synthesized nanorods exhibit excellent excitation features and strong band-edge UV luminescence even at room temperature. The uniform single crystalline, defect free, and high aspect ratio nanorods may find promising applications in optoelectronics and photo-catalysts. The growth habit of ZnO crystal is also illustrated. This method is suitable for large-scale production of ZnO microstructures and could be extended for syntheses of other metal oxides. (C) 2014 Elsevier Ltd. All rights reserved.
Modulation and Improvement on Separation of Photoinduced Charge Carriers in CdS-Metal Nanoheterostructures
(2009-10-08)
Cheng, Wei-Yun
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Chen, Wei-Ta
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Hsu, Yung-Jung
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Lu, Shih-Yuan
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材料科學與工程學系
We demonstrate the feasibility of modulating and improving the separation of photoinduced charge carriers of CdS-M nanoheterostructures through partial replacement of S with two group 16 elements of larger atomic size, Se and Te. With the incorporation of Se or Te into the US nanowires (NWs), the defect states of the US NWs were effectively passivated, enabling a fuller extent of participation of the photoinduced electrons in the charge separation process, thus resulting in a more pronounced photoluminescence quenching and photocurrent depression for the CdS(1-x)Se(x) and CdS(1-x)Te(x) NWs. The present study provides a facile way of improving the photocatalytic efficiency of US through the improvement in retarding the recombination of photoinduced charge carriers.
Single-crystalline mesoporous ZnO nanosheets prepared with a green antisolvent method exhibiting excellent photocatalytic efficiencies
(2012)
Dong, Ji-Yao
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Lin, Cheng-Hsien
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Hsu, Yung-Jung
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Lu, Shih-Yuan
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Wong, David Shan-Hill
Single-crystalline mesoporous ZnO nanosheets were prepared with a green, deep eutectic solvent based antisolvent process followed by calcination at 300 degrees C. The antisolvent procedure led to formation of nanosheets of a mixed composition of zinc carbonate hydroxide and ZnO, calcination of which generated the product. The product nanosheets were ultrathin with a thickness of around 10 nm and pore sizes increasing from less than 10 nm to several tens nanometers with increasing calcination time and temperature. These nanosheets exhibited excellent photocatalytic efficiencies as good as that of a commercial photocatalyst, P-25 TiO2 in terms of photocatalytic degradation of a model pollutant, methylene blue. The success is attributable to the structural advantages of the nanosheets of being ultrathin, mesoporous, and single-crystalline.
Spontaneous reduction of metal ions initiated by ethylenediamine-capped CdS nanowires: A sensing mechanism revealed
(2008-05-13)
Hsu, Yung-Jun
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Lu, Shih-Yuan
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Lin, Yi-Feng
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材料科學與工程學系
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Department of Materials Science and Engineering
Superparamagnetism Found in Diluted Magnetic Semiconductor Nanowires: Mn-Doped CdSe
(2008-11-20)
Chen, Chih-Chang
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Hsu, Yung-Jung
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Lin, Yi-Feng
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Lu, Shih-Yuan
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材料科學與工程學系
Diluted magnetic semiconductor (DMS) nanowires (NWs), Mn-doped CdSe, were successfully prepared in a gold-catalyzed vapor-transport deposition process. It was demonstrated for the first time that upon incorporation of Mn of very limited concentrations, the CdSe NWs exhibited enhanced ferromagnetism at T < 40 K and turned superparamagnetic at relatively high temperatures. This finding would extend the application range of DMS NWs into the biolabeling and bioimaging fields.
Ultrafast formation of ZnO mesocrystals with excellent photocatalytic activities by a facile Tris-assisted antisolvent process
(2011)
Dong, Ji-Yao
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Lin, Wei-Hao
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Hsu, Yung-Jung
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Wong, David Shan-Hill
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Lu, Shih-Yuan
Ultrafast formation of ZnO mesocrystals was achieved with a facile, green, Tris-assisted, room temperature ionic liquid based antisolvent process. A deep eutectic solvent, formed by simply mixing and heating urea and choline chloride at 70 degrees C, served as the solvent for ZnO, whereas Tris-containing de-ionized water acted as the anti-solvent to trigger the ultrafast formation of ZnO mesocrystals at 70 degrees C. The product mesocrystals were mesoporous and near-single-crystalline with high specific surface areas, showing excellent photocatalytic activities toward photodegradation of methylene blue, comparable to that of a commercial photocatalyst, P-25 TiO(2), which is rarely achieved for pristine ZnO. The present approach is a general one and can be readily extended to production of mesocrystals of other functional metal oxides.
Wafer Scale Phase-Engineered 1T-and 2H-MoSe2/Mo Core-Shell 3D-Hierarchical Nanostructures toward Efficient Electrocatalytic Hydrogen Evolution Reaction
(2016-11-23)
Qu, Yindong
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Medina, Henry
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Wang, Sheng-Wen
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Wang, Yi-Chung
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Chen, Chia-Wei
The necessity for new sources for greener and cleaner energy production to replace the existing ones has been increasingly growing in recent years. Of those new sources, the hydrogen evolution reaction has a large potential. In this work, for the first time, MoSe2/Mo core-shell 3D-hierarchical nanostructures are created, which are derived from the Mo 3D-hierarchical nanostructures through a low-temperature plasma-assisted selenization process with controlled shapes grown by a glancing angle deposition system.
Well-aligned ternary Cd1-xZnxS nanowire Arrays and their composition-dependent field emission properties
(2007-09-13)
Lin, Yi-Feng
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Hsu, Yung-Jung
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Lu, Shih-Yuan
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Chen, Kuan-Tsung
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Tseng, Tseung-Yuen
Well-aligned plain CdS and ternary Cd1-xZnxS nanowire arrays were successfully fabricated via a noncatalytic and template-free metal-organic chemical vapor deposition process. The nanowires were grown on a 1 mu m thick buffer layer formed in situ on the surface of silicon substrates. These nanowires were 20-40 nm in diameter and 500-900 nm in length. High-resolution transmission electron microscopy analyses revealed that the nanowires were single-cry stalline and grew along the [0001] direction of the hexagonal crystalline phase. The photoluminescence characterizations showed near band edge emissions at 535, 498, and 473 nm for the US nanowire arrays and Cd1-xZnxS nanowire arrays with x values of 0.21 and 0.44, respectively, demonstrating clear color tunability achieved with the composition adjustment of the alloy nanowires. The same morphology. and single-crystallinity of these three nanowire arrays enabled investigation of the composition-dependent field emission characteristics of the nanowire arrays for the first time, excluding interferences originating from morphology and crystallinity related factors. The plain CdS nanowire arrays exhibited better field emission properties, a lower turn-on field, and a higher field enhancement factor than the ternary Cd1-xZnxS nanowire arrays, for which the lower resistivity of the CdS nanowires may have played an important role. An important parameter, the absolute field enhancement factor (beta(0)), to more intrinsically quantify the field emission performance of the plain US and ternary Cd1-xZnxS nanowires arrays was also studied. The values of beta(0) decreased with increasing Zn content in the ternary products. The high beta(0) values of the US based nanowire arrays, comparable to that of carbon nanotubes grown on silicon wafers, made these nanowire arrays a promising candidate material for high-performance field emitting devices.