Browsing by Issue Date, starting with "2009-01-21"

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Hydroxynaphthyridine-Derived Group III Metal Chelates: Wide Band Gap and Deep Blue Analogues of Green Alq(3) (Tris(8-hydroxyquinolate)aluminum) and Their Versatile Applications for Organic Light-Emitting Diodes
(2009-01-21)
Liao, Szu-Hung
;
Shiu, Jin-Ruei
;
Liu, Shun-Wei
;
Yeh, Shi-Jay
;
Chen, Yu-Hung
A series of group III metal chelates have been synthesized and characterized for the versatile application of organic light-emitting diodes (OLEDs). These metal chelates are based on 4-hydroxy-1,5-naphthyridine derivates as chelating ligands, and they are the blue version analogues of well-known green fluorophore Alq(3) (tris(8-hydroxyquinolinato)aluminum). These chelating ligands and their metal chelates were easily prepared with an improved synthetic method, and they were facially purified by a sublimation process, which enables the materials to be readily available in bulk quantity and facilitates their usage in OLEDs. Unlike most currently known blue analogues of Alq(3) or other deep blue materials, metal chelates of 4-hydroxy-1,5-naphthyridine exhibit very deep blue fluorescence, wide band gap energy, high charge carrier mobility, and superior thermal stability. Using a vacuum-thermal-deposition process in the fabrication of OLEDs, we have successfully demonstrated that the application of these unusal hydroxynaphthyridine metal chelates can be very versatile and effective. First, we have solved or alleviated the problem of exciplex formation that took place between the hole-transporting layer and hydroxynaphthyridine metal chelates, of which OLED application has been prohibited to date. Second, these deep blue materials can play various roles in OILED application. They can be a highly efficient nondopant deep blue emitter: maximum external quantum efficiency (eta ext) of 4.2%; Commision Internationale de L'Eclairage x, y coordinates, CIE(x,y) = 0.15, 0.07. Compared with Alq(3), Bebqp(2) (beryllium bis(benzoquinolin-10-olate)), or TPBI (2,2',2 ''-(1,3,5-phenylene)tris(1-phenyl-1H-benzimidazole), they are a good electron-transporting material: low HOMO energy level of 6.4-6.5 eV and not so high LUMO energy level of 3.0 3.3 eV. They can be ambipolar and possess a high electron mobility of 10(-4) cm(2)/V s at an electric field of 6.4 x 10(5) V/cm. They are a qualified wide band gap host material for efficient blue perylene (CIE(x,y) = 0.14, 0.17 and maximum (eta ext) 3.8%) or deep blue 9,10-diphenylanthracene (CIE(x,y) = 0.15, 0.06 and maximum (eta ext) 2.8%). For solid state lighting application, they are desirable as a host material for yellow dopant (rubrene) in achieving high efficiency ((eta ext) 4.3% and (eta P) 8.7 lm/W at an electroluminance of 100 cd/m(2) or (eta ext) 3.9% and (eta P) 5.1 lm/W at an electroluminance of 1000 cd/m(2)) white electroluminescence (CIE(x,y) = 0.30, 0.35).
Transition States and Nonlinear Excitations in Chloroform Observed with a Sub-5 fs Pulse Laser
(2009-01-21)
Iwakura, Izumi
;
Yabushita, Atsushi
;
Kobayashi, Takayoshi
;
電子物理學系
;
Department of Electrophysics
Sub-5 fs pulse dynamics observed in neat chloroform (CHCl(3)) and the CHCl(3)center dot center dot center dot O(2) charge-transfer complex in oxygen-saturated chloroform (O(2)-CHCl(3)) were found to be dominated by wave packet motions in the excited state and the ground state, respectively. The time-resolved signal of CHCl(3) exhibits dynamics in the electronic excited state generated by a three-photon absorption process, and that Of O(2)-CHCl(3) is explained in terms of the dynamics of the electronic ground state excited by the stimulated Raman process. In addition, we found that the oxidation reaction of chloroform in the charge-transfer complex of chloroform and oxygen easily proceeds via a C-H insertion process triggered by the stimulated Raman process under the irradiation of a visible laser pulse. The spectrogram analysis enabled direct observation of the real-time dynamics of the Raman-triggered oxidation process. These results demonstrate that observation of transition states by sub-5 fs time-resolved spectroscopy is applicable to "ground-state reactions" as well as "excited-state reactions" via stimulated Raman excitation in a wide variety of chemical reactions.
Dual-mode recognition of transition metal ions by bis-triazoles chained pyrenes
(2009-01-21)
Hung, Hao-Chih
;
Cheng, Chi-Wen
;
Ho, I-Ting
;
Chung, Wen-Sheng
;
應用化學系
Fluorescent chemosensors 7-10, with variable methylene chain length as spacers between the two triazole methyl ether units, have been synthesized under 'Click' condition, where the bistriazoles are used as the metal ion binding sites and the pyrenes as the fluorophores. Compound 10, having the longest methylene chain among 7-10, shows monomer and excimer fluorescence quenching in acetonitrile toward Ni(2+), Pb(2+), Cu(2+), Hg(2+), and Cr(3+) ions, however, it shows an enhanced monomer but a decreased excimer emission when complexed with Cd(2+) and Zn(2+) ions. (C) 2008 Elsevier Ltd. All rights reserved.
新穎芳基胺衍生物及使用它之電致發光元件
(2009-01-21)
許慶豐
;
吳芳奕
;
施秉彝
本發明提供一種具高玻璃轉移溫度的新穎芳基胺衍生物、光電效能優異電洞傳輸層材料、高安定性的有機光電元件、及製程容易且便宜之製造有機光電元件之方法、以及電致發光元件。一種芳基胺化合物,具有以下述之一般式(I)所表示之構造: (式中,P係代表0~1之整數;Z係代表取代或非取代的碳原子數為1~8之烷基、芳基或雜芳基;X係代表取代或非取代的碳原子數為1~8之烷基、芳基或雜芳基;Ar1或Ar2係代表取代或非取代的芳基、或含氮之雜芳基)。
PHOSPHORS AND LIGHTING APPARATUS USING THE SAME
(2009-01-22)
Chen, Teng-Ming
;
Tai, Hsiao-Ping
A phosphor has a chemical formula of: Am(Ba1-xEux)nPyOz, wherein A is at least one of the group consisting of Li, Na and K, while 0
LIGHT-EMITTING DEVICE AND METHOD FOR MAKING THE SAME
(2009-01-22)
CHIU, Ching-Hua
;
HUANG, Hung-Wen
;
KUO, Hao-Chung
;
LU, Tien-Chang
;
WANG, Shing-Chung
A light-emitting device is capable of emitting a light having a wavelength ranging from 300 to 550 nm, and includes: a substrate; a p-type semiconductor layer disposed on the substrate; an active layer disposed on the p-type semiconductor layer; a n-type semiconductor layer disposed on the active layer and having a waveguide-disposing surface; and a waveguide structure formed on the waveguide-disposing surface of the n-type semiconductor layer and having a plurality of spaced apart nanorods extending from the waveguide-disposing surface.
Single-layer triplet white polymer light-emitting diodes incorporating polymer oxides: Effect of charge trapping at phosphorescent dopants
(2009-01-26)
Chen, Fang-Chung
;
Chien, Shang-Chieh
;
Chen, Yung-Shiuan
;
光電工程學系
;
顯示科技研究所
This paper describes the effects of charge trapping on the device performances of triplet polymer light-emitting diodes (PLEDs) after the cathode contact had been improved through the blending of poly(ethylene glycol) (PEG) into the active layer. The external quantum efficiency (EQE) was enhanced when the dopant tended to trap electrons. In contrast, we observed no EQE enhancement for the device featuring a hole-trapping dopant. Because PEG promoted electron injection, more electrons were trapped in the triplet molecules, thereby enhancing the probability of recombination. Finally, after incorporating PEG, we further achieved white PLEDs exhibiting both high EQE and high power efficiency.
Room temperature negative differential resistance in DNA-based molecular devices
(2009-01-26)
Jangjian, Peng-Chung
;
Liu, Tzeng-Feng
;
Li, Mei-Yi
;
Tsai, Ming-Shih
;
Chang, Chia-Ching
A molecular device fabricated from metallic deoxyribonucleic acid (M-DNA) exhibits a negative differential resistance (NDR) behavior. When two gold electrodes were connected by Ni(2+)-chelated DNA, which was converted from lambda-DNA, not only was the conductivity of DNA improved, but a NDR device was formed as a full cyclic voltage sweep was applied to measure its current versus voltage characteristics at room temperature and in an ambient environment. Such electronic characteristics of a M-DNA device may have been caused by the redox reactions of Ni ions. This finding provides a simple way to construct electrical nanodevices from biological molecules.
Bonding anisotropy in multiferroic TbMnO3 probed by polarization dependent x-ray absorption spectroscopy
(2009-01-26)
Chen, J. M.
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Lee, J. M.
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Chen, C. K.
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Chou, T. L.
;
Lu, K. T.
O K- and Mn L-2,L-3-edges x-ray absorption spectra of orthorhombic TbMnO3 single crystals show strong polarization dependence, in contrast with results of previous experiments on orthorhombic LaMnO3 and DyMnO3 thin films that show nearly isotropic spectral structure. First-principles calculations reveal that TbMnO3 exhibits a zigzag e(g) orbital ordering ground state. The highly distorted MnO6 octahedron and orbital ordering in TbMnO3 produce highly anisotropic Mn-O bonding within the ab plane, a frustration of the magnetic ordering, and the formation of complicated incommensurate magnetic structures.
Fabrication and characterization of three-dimensional all metallic photonic crystals for near infrared applications
(2009-01-26)
Yang, Yu-Lin
;
Hou, Fu-Ju
;
Wu, Shich-Chuan
;
Huang, Wen-Hsien
;
Lai, Ming-Chih
Three-dimensional all metallic photonic crystals with a feature size of 0.20 mu m were fabricated using electron-beam lithography with the photoresist of hydrogen silesquioxane. This process method has high compatibility with the fabrication of damascene copper interconnections and also simplifies the whole process flow. The dependence of the complete photonic band gaps on polarization was experimentally observed and compared with the simulation results. The band edge for the four-layer lattice was found at a wavelength of around 0.80 mu m in normal incidence.
Bonding anisotropy in multiferroic TbMnO(3) probed by polarization dependent x-ray absorption spectroscopy
(2009-01-26)
Chen, J. M.
;
Lee, J. M.
;
Chen, C. K.
;
Chou, T. L.
;
Lu, K. T.
O K- and Mn L(2,3)-edges x-ray absorption spectra of orthorhombic TbMnO(3) single crystals show strong polarization dependence, in contrast with results of previous experiments on orthorhombic LaMnO(3) and DyMnO(3) thin films that show nearly isotropic spectral structure. First-principles calculations reveal that TbMnO(3) exhibits a zigzag e(g) orbital ordering ground state. The highly distorted MnO(6) octahedron and orbital ordering in TbMnO(3) produce highly anisotropic Mn-O bonding within the ab plane, a frustration of the magnetic ordering, and the formation of complicated incommensurate magnetic structures.
Non-Condon vibronic coupling of coherent molecular vibration in MEH-PPV induced by a visible few-cycle pulse laser
(2009-01-26)
Kobayashi, Takayoshi
;
Zhang, Jun
;
Wang, Zhuan
;
電子物理學系
;
Department of Electrophysics
Vibrational real-time spectra of poly-[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH- PPV) were measured in a 5 fs pump-probe experiment simultaneously at 128 probe wavelengths with a multi-channel detection system. The spectral dependence of the coherent vibrational amplitudes obtained from the Fourier transform (FT) on the probe wavelength detected was found to be given by the sum of the ground-state absorption spectrum and its first and second derivatives. This indicates that the change of the transition probability caused by a wave packet motion can be explained as induced by both the non-Condon effect (non-Condon (NC) mechanism) and the time-dependent Franck-Condon factor (Frank-Condon (FC) mechanism). The FC mechanism can contribute to the first and second derivatives' dependence. On the other hand, the NC mechanism is dominant in the zeroth-order derivative. This result proves that the 1(1)B(u) exciton is strongly coupled with the excited (1)A(g) state, which is known to be essential in third-order optical nonlinearity. The amounts of shift of the absorption peaks and changes in the bandwidth due to the wave packet motions were determined for the four most prominent modes in the FT power spectra. The shift due to the FC mechanism was about 1.3-1.1% of the peak transition energy and the broadening of the vibronic transition due to the NC mechanism was about 8.0-7.6% of the bandwidth for the four modes. A novel ultrafast optical switch utilizing the modulation of electronic transition probability by molecular vibration through vibronic coupling and the interference of the wave packets is proposed.
Tunable terahertz wavelength selector device using magnetically controlled birefringence of liquid crystals
(2009-01-27)
Chao
;
Ru-Pin
;
Pan
;
Ci-Ling
;
Chen
The present invention provides a tunable terahertz (THz) wavelength selector device, which includes a fixed phase retarder, a tunable phase retarder and a pair of linear polarizers to form a unit. The fixed phase retarder and tunable phase retarder basically utilizes liquid crystals to provide phase retardation, moreover, utilizing birefringence phenomenon possessed by liquid crystals can provide adequate phase retardation. The fixed phase retarder utilizes horizontal orientation of liquid crystal cell to provide fixed phase retardation, while the tunable phase retarder however utilizes homeotropic liquid crystal cell and a rotatable magnet to provide a tunable phase retardation, wherein the tunable phase retarder can provide the positive or negative phase retardation relative to the fixed phase retarder, based on the direction of the magnet's rotating axes and totally use the entire tunable range into adjusting frequencies which can pass through. Besides, the present invention can also serially connect multiple units described above so as to achieve a narrow enough band-pass bandwidth.
Transforming an error-tolerant separable matrix to an error-tolerant disjunct matrix
(2009-01-28)
Chen, Hong-Bin
;
Cheng, Yongxi
;
He, Qian
;
Zhong, Chongchong
;
應用數學系
Recently, Chen and Hwang [H.B. Chen, F.K. Hwang, Exploring the missing link among d-separable, (d) over bar -separable and d-disjunct matrices, Discrete Applied Mathematics 133 (2007) 662-664] provided a method for transforming a separable matrix to a disjunct matrix. In [D.Z. Du, F.K. Hwang, Pooling Designs and Nonadaptive Group Testing - Important Tools for DNA Sequencing, World Scientific, 2006], Du and Hwang attempted to extend this result to its error-tolerant version; unfortunately, they gave an incorrect extension. This note gives a solution to this problem. (C) 2008 Elsevier B.V. All rights reserved.
Symbol time synchronization method for OFDM systems
(2009-01-29)
Chin, Wen-Long
;
Chen, Sau-Gee
A symbol time synchronization method for OFDM systems is disclosed. The invention presents a joint maximum-likelihood (ML) synchronization method for symbol time offset (STO) for OFDM systems. The method is developed in frequency-domain under time-variant multipath channels. By analyzing the received frequency-domain data, a mathematical model for the joint effects of symbol time offset (STO), carrier frequency offset (CFO) and sampling clock frequency offset (SCFO) is derived. The results are used to formulate a log-likelihood function of two consecutive symbols. The joint estimation's method is robust, because it exhibits high performances in high mobility and time-variant multipath fading channels.
NOVEL PHOSPHOR AND FABRICATION OF THE SAME
(2009-01-29)
CHEN, Teng-Ming
;
Chiu, Yi-Chen
;
Huang, Chien Hao
The present invention provides a novel phosphor represent by the following general formula:
NOVEL PHOSPHOR AND FABRICATION OF THE SAME
(2009-01-29)
CHEN, Teng-Ming
;
CHIU, Yi-Chen
The present invention provides a light emitting diode-converted phosphor compound having the following formula:
Tone-Interleaved Coded Modulation Scheme for MIMO OFDM Communication
(2009-01-29)
Wu, Wen-Rong
;
Shen, Shih-Chi
A MIMO OFDM system for TICM is provided. The tone-level interleaver at the transmitter uses a block of NT symbols as its basic unit. This results in different decoding architectures at the receiver. The main advantage of TICM is to merge soft-bit demapping into the Viterbi algorithm. Taking the advantage of the trellis structure inherent in the Viterbi algorithm, TICM can have lower computational complexity and potentially better performance than BICM with the LSD detector and the vector demapper. Although the tone-level interleaving may not have spatial diversity gain, the performance is not affected in 802.11n environments.
Co-evolution positions and rules for antigenic variants of human influenza A/H3N2 viruses
(2009-01-30)
Huang, Jhang-Wei
;
King, Chwan-Chuen
;
Yang, Jinn-Moon
;
生物科技學系
;
生物資訊及系統生物研究所
Background: In pandemic and epidemic forms, avian and human influenza viruses often cause significant damage to human society and economics. Gradually accumulated mutations on hemagglutinin (HA) cause immunologically distinct circulating strains, which lead to the antigenic drift (named as antigenic variants). The "antigenic variants" often requires a new vaccine to be formulated before each annual epidemic. Mapping the genetic evolution to the antigenic drift of influenza viruses is an emergent issue to public health and vaccine development Results: We developed a method for identifying antigenic critical amino acid positions, rules, and co-mutated positions for antigenic variants. The information gain (IG) and the entropy are used to measure the score of an amino acid position on hemagglutinin (HA) for discriminating between antigenic variants and similar viruses. A position with high IG and entropy implied that this position is highly correlated to an antigenic drift. Nineteen positions with high IG and high genetic diversity are identified as antigenic critical positions on the HA proteins. Most of these antigenic critical positions are located on five epitopes or on the surface based on the HA structure. Based on IG values and entropies of these 19 positions on the HA, the decision tree was applied to create a rule-based model and to identify rules for predicting antigenic variants of a given two HA sequences which are often a vaccine strain and a circulating strain. The predicting accuracies of this model on two sets, which consist of a training set (181 hemagglutination inhibition (HI) assays) and an independent test set (31,878 HI assays), are 91.2% and 96.2% respectively. Conclusion: Our method is able to identify critical positions, rules, and co-mutated positions on HA for predicting the antigenic variants. The information gains and the entropies of HA positions provide insight to the antigenic drift and co-evolution positions for influenza seasons. We believe that our method is robust and is potential useful for studying influenza virus evolution and vaccine development.
Enhancement of metal bioleaching from contaminated sediment using silver ion
(2009-01-30)
Chen, Shen-Yi
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
A silver-catalyzed bioleaching process was used to remove heavy metals from contaminated sediment in this study. The effects of silver concentration added on the performance of bioleaching process were investigated. High pH reduction rate was observed in the bioleaching process with silver ion. The silver ion added in the bioleaching process was incorporated into the lattice of the initial sulfide through a cationic interchange reaction. This resulted in the short lag phase and high metal solubilization in the bioleaching process. The maximum pH reduction rate and the ideal metal solubilization were obtained in the presence of 30 mg/L of silver ion. When the added silver ion was greater than 30 mg/L, the rates of pH reduction and metal solubilization gradually decreased. The solubilization efficiencies of heavy metals (Cu, Zn, Mn, Ni and Cr) were relatively high in the silver-enhanced bioleaching process, except Pb. No apparent effect of silver ion on the growth of sulfur-oxidizing bacteria was found in the bioleaching. These results indicate that the kinetics of metal solubilization can be enhanced by the addition of silver ion. (C) 2008 Elsevier B.V. All rights reserved