Browsing by Author "Cheng, Wei-Yun"

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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
;
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.
Fur-dependent MrkHI regulation of type 3 fimbriae in Klebsiella pneumoniae CG43
(2012-04-01)
Wu, Chien-Chen
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Lin, Ching-Ting
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Cheng, Wei-Yun
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Huang, Ching-Jou
;
Wang, Zhe-Chong
Type 3 fimbriae play a crucial role in Klebsiella pneumoniae biofilm formation, but the mechanism of the regulation of the type 3 fimbrial operon is largely unknown. In K. pneumoniae CG43, three regulatory genes, mrkH, mrkI and mrkJ, are located downstream of the type 3 fimbrial genes mrkABCDF. The production of the major pilin MrkA is abolished by the deletion of mrkH or mrkI but slightly increased by the deletion of mrkJ. Additionally, quantitative RT-PCR and a promoter reporter assay of mrkHI verified that the transcription of mrkHI was activated by MrkI, suggesting autoactivation of mrkHI transcription. In addition, sequence analysis of the mrkH promoter region revealed a putative ferric uptake regulator (Fur) box. Deletion of fur decreased the transcription of mrkH, mrkI and mrkA. The expression of type 3 fimbriae and bacterial biofilm formation were also reduced by the deletion of fur. Moreover, a recombinant Fur was found to be able to bind both promoters, with higher affinity for P-mrkH than P-mrkA, implying that Fur controls type 3 fimbriae expression via MrkHI. We also proved that iron availability can influence type 3 fimbriae activity.
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
;
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.
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
;
Lu, Shih-Yuan
;
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.