Browsing by Author "Chen, Yi-Chin"

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alpha-(Y,Gd)FS:Ce(3+): a novel red-emitting fluorosulfide phosphor for solid-state lighting
(2011-01-01)
Wu, Yun-Chen
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Chen, Yi-Chin
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Wang, De-Yin
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Lee, Chi-Shen
;
Sun, Ching-Cherng
A novel Ce(3+)-doped fluorosulfide phosphor, alpha-(Y,Gd)FS:Ce(3+), was first investigated as a new candidate for application in phosphor-converted light emitting diodes (LEDs) and thin-film electroluminescence (TFEL) devices. The detailed crystal structure was investigated based on X-ray diffraction profiles using Rietveld refinement methods. This phosphor shows good absorption ranging from ultraviolet to visible region and broad saturated red emission, which can be tuned from 660 to 672 nm, and the photoluminescence (PL) intensity was demonstrated to be effectively enhanced by Gd(3+) substitution.
alpha-(Y,Gd)FS:Ce3+: a novel red-emitting fluorosulfide phosphor for solid-state lighting
(2011-01-01)
Wu, Yun-Chen
;
Chen, Yi-Chin
;
Wang, De-Yin
;
Lee, Chi-Shen
;
Sun, Ching-Cherng
A novel Ce3+-doped fluorosulfide phosphor, alpha-(Y,Gd)FS:Ce3+, was first investigated as a new candidate for application in phosphor-converted light emitting diodes (LEDs) and thin-film electroluminescence (TFEL) devices. The detailed crystal structure was investigated based on X-ray diffraction profiles using Rietveld refinement methods. This phosphor shows good absorption ranging from ultraviolet to visible region and broad saturated red emission, which can be tuned from 660 to 672 nm, and the photoluminescence (PL) intensity was demonstrated to be effectively enhanced by Gd3+ substitution.
Color-Tunable Fluorosulfide Phosphors for Solid-State Lighting: Structure and Luminescence Investigations
(2011)
Wu, Yun-Chen
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Chen, Yi-Chin
;
Lee, Chi-Shen
;
Chen, Teng-Ming
;
應用化學系
A novel Y-2(Ca,Sr)F4S2:Ce3+ fluorosuffide phosphor, was synthesized and its crystal structure was refined with Rietveld method. Y-2(Ca,Sr)F4S2:Ce3+ can be efficiently excited by blue light and shows yellow-to-orange broadband emission at 553-590 nm. Possible mechanism of the tunable luminescence properties was explained on the basis of the band structure calculations.
Controlled synthesis and luminescent properties of monodispersed PEI-modified YVO4:Bi3+,Eu3+ nanocrystals by a facile hydrothermal process
(2012)
Chen, Yi-Chin
;
Wu, Yun-Chen
;
Wang, De-Yin
;
Chen, Teng-Ming
;
應用化學系
A series of water-soluble YVO4:Bi3+, Eu3+ nanocrystals, with surfaces functionalized by a branch polyethylenimine (BPEI) polymer, have been synthesized via a one-pot hydrothermal method. It was found that the particle size and crystal morphology could be efficiently controlled by different reaction temperatures, pH values and molecular weights of the BPEI polymer. The surface modification of the nanocrystals was characterized using Fourier transform infrared spectroscopy (FT-IR). The highly crystalline YVO4:Bi3+, Eu3+ nanoparticles, with an average diameter of 20 nm, can be dispersed in water due to the presence of amino ligands. When conjugated with biomolecules, the YVO4:Bi3+, Eu3+ nanocrystals retain their strong red emission, peaking at 619 nm under near-ultraviolet (n-UV) excitation. The results indicate that YVO4:Bi3+, Eu3+ nanocrystals can serve as a promising candidate for biological imaging, and immunoassay applications.
Crystal Structure and Mutational Analysis of Aminoacylhistidine Dipeptidase from Vibrio alginolyticus Reveal a New Architecture of M20 Metallopeptidases
(2010-12-01)
Chang, Chin-Yuan
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Hsieh, Yin-Cheng
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Wang, Ting-Yi
;
Chen, Yi-Chin
;
Wang, Yu-Kuo
Aminoacylhistidine dipeptidases (PepD, EC 3.4.13.3) belong to the family of M20 metallopeptidases from the metallopeptidase H clan that catalyze a broad range of dipeptide and tripeptide substrates, including L-carnosine and L-homocarnosine. Homocarnosine has been suggested as a precursor for the neurotransmitter gamma-aminobutyric acid (GABA) and may mediate the antiseizure effects of GABAergic therapies. Here, we report the crystal structure of PepD from Vibrio alginolyticus and the results of mutational analysis of substrate-binding residues in the C-terminal as well as substrate specificity of the PepD catalytic domain-alone truncated protein PepD(CAT). The structure of PepD was found to exist as a homodimer, in which each monomer comprises a catalytic domain containing two zinc ions at the active site center for its hydrolytic function and a lid domain utilizing hydrogen bonds between helices to form the dimer interface. Although the PepD is structurally similar to PepV, which exists as a monomer, putative substrate-binding residues reside in different topological regions of the polypeptide chain. In addition, the lid domain of the PepD contains an "extra" domain not observed in related M20 family metallopeptidases with a dimeric structure. Mutational assays confirmed both the putative di-zinc allocations and the architecture of substrate recognition. In addition, the catalytic domain-alone truncated PepD(CAT) exhibited substrate specificity to L-homocarnosine compared with that of the wild-type PepD, indicating a potential value in applications of PepD(CAT) for GABAergic therapies or neuroprotection.
Crystal Structure and Mutational Analysis of Aminoacylhistidine Dipeptidase from Vibrio alginolyticus Reveal a New Architecture of M20 Metallopeptidases
(2010-12-01)
Chang, Chin-Yuan
;
Hsieh, Yin-Cheng
;
Wang, Ting-Yi
;
Chen, Yi-Chin
;
Wang, Yu-Kuo
Aminoacylhistidine dipeptidases (PepD, EC 3.4.13.3) belong to the family of M20 metallopeptidases from the metallopeptidase H clan that catalyze a broad range of dipeptide and tripeptide substrates, including L-carnosine and L-homocarnosine. Homocarnosine has been suggested as a precursor for the neurotransmitter gamma-aminobutyric acid (GABA) and may mediate the antiseizure effects of GABAergic therapies. Here, we report the crystal structure of PepD from Vibrio alginolyticus and the results of mutational analysis of substrate-binding residues in the C-terminal as well as substrate specificity of the PepD catalytic domain-alone truncated protein PepD(CAT). The structure of PepD was found to exist as a homodimer, in which each monomer comprises a catalytic domain containing two zinc ions at the active site center for its hydrolytic function and a lid domain utilizing hydrogen bonds between helices to form the dimer interface. Although the PepD is structurally similar to PepV, which exists as a monomer, putative substrate-binding residues reside in different topological regions of the polypeptide chain. In addition, the lid domain of the PepD contains an "extra" domain not observed in related M20 family metallopeptidases with a dimeric structure. Mutational assays confirmed both the putative di-zinc allocations and the architecture of substrate recognition. In addition, the catalytic domain-alone truncated PepD(CAT) exhibited substrate specificity to L-homocarnosine compared with that of the wild-type PepD, indicating a potential value in applications of PepD(CAT) for GABAergic therapies or neuroprotection.
Crystal structure characterization, optical and photoluminescent properties of tunable yellow- to orange-emitting Y-2(Ca,Sr)F4S2:Ce3+ phosphors for solid-state lighting
(2012)
Wu, Yun-Chen
;
Chen, Yi-Chin
;
Chen, Teng-Ming
;
Lee, Chi-Shen
;
Chen, Kuo-Ju
In this study, a new efficient Ce3+-doped fluorosulfide phosphor, Y-2(Ca,Sr)F4S2:Ce3+, was obtained by using solid-state methods in a sealed silica ampoule. The synthesized Y-2(Ca,Sr)F4S2:Ce3+ was characterized by powder X-ray diffraction and refined with Rietveld methods. Y-2(Ca,Sr)F4S2:Ce3+ can be excited by blue light (440-470 nm) and shows yellow-to-orange broadband emission peaking at 553-590 nm with a quantum efficiency of 16-31%. Non-radiative transitions between Ce3+ ions in Y2CaF4S2:Ce3+ and Y2SrF4S2:Ce3+ hosts have also been demonstrated to be attributable to dipole-dipole interactions, and the critical distances were calculated to be 18.9 and 19.3 angstrom. The possible mechanism of the tunable luminescence properties was described on the basis of band structure calculations. In addition, a white LED device was fabricated by using Y-2(Ca,Sr)F4S2:Ce3+ phosphor pumped with a 460 nm blue chip. The CRI value and CCT were measured to be 74-85 and 3500-8700 K, respectively, showing promising potential for solid-state lighting.
Expression and characterization of the biofilm-related and carnosine-hydrolyzing aminoacylhistidine dipeptidase from Vibrio alginolyticus
(2008-10-01)
Wang, Ting-Yi
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Chen, Yi-Chin
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Kao, Liang-Wei
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Chang, Chin-Yuan
;
Wang, Yu-Kuo
The biofilm-related and carnosine-hydrolyzing aminoacylhistidine dipeptidase (pepD) gene from Vibrio alginolyticus was cloned and sequenced. The recombinant PepD protein was produced and biochemically characterized and the putative active-site residues responsible for metal binding and catalysis were identified. The recombinant enzyme, which was identified as a homodimeric dipeptidase in solution, exhibited broad substrate specificity for Xaa-His and His-Xaa dipeptides, with the highest activity for the His-His dipeptide. Sequence and structural homologies suggest that the enzyme is a member of the metal-dependent metallopeptidase family. Indeed, the purified enzyme contains two zinc ions per monomer. Reconstitution of His.Tag-cleaved native apo-PepD with various metal ions indicated that enzymatic activity could be optimally restored when Zn(2+) was replaced with other divalent metal ions, including Mn(2+), Co(2+), Ni(2+), Cu(2+) and Cd(2+), and partially restored when Zn(2+) was replaced with Mg(2+). Structural homology modeling of PepD also revealed a 'catalytic domain' and a 'lid domain' similar to those of the Lactobacillus delbrueckii PepV protein. Mutational analysis of the putative active-site residues supported the involvement of His80, Asp119, Glu150, Asp173 and His461 in metal binding and Asp82 and Glu149 in catalysis. In addition, individual substitution of Glu149 and Glu150 with aspartic acid resulted in the partial retention of enzymatic activity, indicating a functional role for these residues on the catalysis and zinc ions, respectively. These effects may be necessary either for the activation of the catalytic water molecule or for the stabilization of the substrate-enzyme tetrahedral intermediate. Taken together, these results may facilitate the design of PepD inhibitors for application in antimicrobial treatment and antibody-directed enzyme prodrug therapy.
Identification of a Vibtio furnissii oligopeptide permease and characterization of its in vitro hemolytic activity
(2007-11-01)
Wu, Tung-Kung
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Wang, Yu-Kuo
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Chen, Yi-Chin
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Feng, Jen-Min
;
Liu, Yen-Hsi
We describe purification and characterization of an oligopeptide permease protein (Hly-OppA) from Vibrio furnissii that has multifaceted functions in solute binding, in in vitro hemolysis, in antibiotic resistance, and as a virulence factor in bacterial pathogenesis. The solute-binding function was revealed by N-terminal and internal peptide sequences of the purified protein and was confirmed by discernible effects on oligopeptide binding, by accumulation of fluorescent substrates, and by fluorescent substrate-antibiotic competition assay experiments. The purified protein exhibited host-specific in vitro hemolytic activity against various mammalian erythrocytes and apparent cytotoxicity in CHO-K1 cells. Recombinant Hly-OppA protein and an anti-Hly-OppA monoclonal antibody exhibited and neutralized the in vitro hemolytic activity, respectively, which further confirmed the hemolytic activity of the gene product. In addition, a V. furnissii hly-oppA knockout mutant caused less mortality than the wild-type strain when it was inoculated into BALB/c mice, indicating the virulence function of this protein. Finally, the in vitro hemolytic activity was also confirmed with homologous ATP-binding cassette-type transporter proteins from other Vibrio species.
Ligand-Functionalization of BPEI-Coated YVO4:Bi3+,Eu3+ Nanophosphors for Tumor-Cell-Targeted Imaging Applications
(2013-11-01)
Chen, Yi-Chin
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Huang, Sheng-Cih
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Wang, Yu-Kuo
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Liu, Yuan-Ting
;
Wu, Tung-Kung
In this study, surface-functionalized, branched polyethylenimine (BPEI)-modified YVO4:Bi3+,Eu3+ nanocrystals (NCs) were successfully synthesized by a simple, rapid, solvent-free hydrothermal method. The BPEI-coated YVO4:Bi3+,Eu3+ NCs with high crystallinity show broad-band excitation in the =250 to 400nm near-ultraviolet (NUV) region and exhibit a sharp-line emission band centered at =619nm under excitation at =350nm. The surface amino groups contributed by the capping agent, BPEI, not only improve the dispersibility and water/buffer stability of the BPEI-coated YVO4:Bi3+,Eu3+ NCs, but also provide a capability for specifically targeted biomolecule conjugation. Folic acid (FA) and epidermal growth factor (EGF) were further attached to the BPEI-coated YVO4:Bi3+,Eu3+ NCs and exhibited effective positioning of fluorescent NCs toward the targeted folate receptor overexpressed in HeLa cells or EGFR overexpressed in A431 cells with low cytotoxicity. These results demonstrate that the ligand-functionalized, BPEI-coated YVO4:Bi3+, Eu3+ NCs show great potential as a new-generation biological luminescent bioprobe for bioimaging applications. Moreover, the unique luminescence properties of BPEI-coated YVO4:Bi3+,Eu3+ NCs show potential to combine with a UVA photosensitizing drug to produce both detective and therapeutic effects for human skin cancer therapy.
Photoluminescence investigations on a novel green-emitting phosphor Ba3Sc(BO3)(3):Tb3+ using synchrotron vacuum ultraviolet radiation
(2012)
Wang, De-Yin
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Chen, Yi-Chin
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Huang, Chien-Hao
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Cheng, Bing-Ming
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Chen, Teng-Ming
Vacuum ultraviolet (VUV) spectroscopic properties of undoped and Tb3+-doped Ba3Sc(BO3)(3) were investigated by using synchrotron radiation. The Tb3+-doped Ba3Sc(BO3)(3) sample crystallized in a flower-like shape even was synthesized at 1100 degrees C. Upon VUV excitation, Ba3Sc(BO3)(3) exhibited an intrinsic broad UV emission centered at 336 nm, which results from radiative annihilation of self-trapped exciton (STE) that may presumably be associated with band-gap excitations or molecular transitions within the BO33- group. The maximum host absorption for Ba3Sc(BO3)(3) was found at about 180 nm. Upon doping of Tb3+ ions into Ba3Sc(BO3)(3), an efficient energy transfer from the host excitations to Tb3+ via STE emission was observed, showing host sensitization of Tb3+ occurs. The energy transfer from host to Tb3+ via STE emission in Ba3Sc(BO3)(3):Tb3+ was studied as a function of temperature and Tb3+ doping concentration. It has been demonstrated that the energy transfer efficiency was increased with either increasing temperature or Tb3+ doping concentration. In the case of temperature dependent energy transfer, the energy transfer from the STE to Tb3+ is thermally activated, probably due to exciton mobility, while in the case of concentration dependent energy transfer, the energy transfer from the STE to Tb3+ is promoted due to a closer distance between the STE and Tb3+ at high Tb3+ concentration.
Wide-converter lens design for a pico projector
(2014-12-20)
Pan, Jui-Wen
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Chen, Yi-Chin
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光電系統研究所
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照明與能源光電研究所
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生醫電子轉譯研究中心
In this paper, we propose a concept for the design of a 0.702x wide-converter lens for a 0.3 in. digital micromirror device. This 0.702x wide-converter lens is capable of enlarging the size of the original projected image at the same projection distance. This 0.702x wide-converter lens is attached in front of the projection lens of a pico projector (PP). Compared with the projection lens of a PP without the 0.702x wide-converter lens, there is an increase in the size of the original projected image of 42.4% at the same projection distance. In other words, there is a saving of projection distance of 29.78% to obtain a projected image of the same size. (C) 2014 Optical Society of America