Browsing by Issue Date, starting with "2017-09-15"

Now showing 1 - 20 of 13162

Eco-friendly luminescent solar concentrators with low reabsorption losses and resistance to concentration quenching based on aqueous-solution-processed thiolate-gold nanoclusters
(2017-09-15)
Huang, H. Y.
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Cai, K. B.
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Chang, L. Y.
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Chen, P. W.
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Lin, T. N.
Heavy-metal-containing quantum dots (QDs) with engineered electronic states have been served as luminophores in luminescent solar concentrators (LSCs) with impressive optical efficiency. Unfortunately, those QDs involve toxic elements and need to be synthesized in a hazardous solvent. Recently, biocompatible, eco-friendly gold nanoclusters (AuNCs), which can be directly synthesized in an aqueous solution, have gained much attention for promising applications in 'green photonics'. Here, we explored the solid-state photophysical properties of aqueoussolution- processed, glutathione-stabilized gold nanoclusters (GSH-AuNCs) with a ligand-tometal charge-transfer (LMCT) state for developing 'green' LSCs. We found that such GSH-AuNCs exhibit a large Stokes shift with almost no spectral overlap between the optical absorption and PL emission due to the LMCT states, thus, suppressing reabsorption losses. Compared with GSH-AuNCs in solution, the photoluminescence quantum yields (PL-QYs) of the LSCs can be enhanced, accompanied with a lengthened PL lifetime owing to the suppression of non-radiative recombination rates. In addition, the LSCs do not suffer from severe concentration-induced PL quenching, which is a common weakness for conventional luminophores. As a result, a common trade-off between light-harvesting efficiency and solid-state PL-QYs can be bypassed due to nearly-zero spectral overlap integral between the optical absorption and PL emission. We expect that GSH-AuNCs hold great promise for serving as luminophores for 'green' LSCs by further enhancing solid-state PL-QYs.
Electrocatalytic performance of Pt nanoparticles sputter-deposited on indium tin oxide toward methanol oxidation reaction: The particle size effect
(2017-09-15)
Ting, Chao-Cheng
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Chao, Chih-Hsuan
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Tsai, Cheng Yu
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Cheng, I-Kai
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Pan, Fu-Ming
We sputter-deposited Pt nanoparticles with an average size ranging from 2.0 nm to 8.5 nm on the indium tin oxide (ITO) glass substrate, and studied the effect of the size of Pt nanoparticles on electrocatalytic activity of the Pt/ITO electrode toward methanol oxidation reaction (MOR) in acidic solution. X-ray photoelectron spectroscopy (XPS) reveals an interfacial oxidized Pt layer present between Pt nanoparticles and the ITO substrate, which may modify the surface electronic structure of Pt nanoparticles and thus influences the electrocatalytic properties of the Pt catalyst toward MOR. According to electrochemical analyses, smaller Pt nanoparticles exhibit slower kinetics for CO electrooxidation and MOR. However, a smaller particle size enables better CO tolerance because the bifunctional mechanism is more effective on smaller Pt nanoparticles. The electrocatalytic activity decays rapidly for Pt nanoparticles with a size smaller than 3 nm and larger than 8 nm. The rapid activity decay is attributed to Pt dissolution for smaller nanoparticles and to CO poisoning for larger ones. Pt nanoparticles of 5-6 nm in size loaded on ITO demonstrate a greatly improved electrocatalytic activity and stability compared with those deposited on different substrates in our previous studies. (C) 2017 Elsevier B.V. All rights reserved.
Change in the structure and function of lectin by photodissociation of NO
(2017-09-16)
Kurota, T.
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Sato, I.
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Kuroi, K.
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Hiramatsu, H.
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Nakabayashi, T.
We have shown here that the structure and sugar-binding activity of lectin can be changed by the photodissociation of NO. Intramolecular S-S bonds are photogenerated from SNO in the protein, which can be used to photo-control the structure and function of proteins.
Exploring the self-mode locking and vortex structures of nonplanar elliptical modes in selectively end-pumped Nd: YVO4 lasers: manifestation of large fractional orbital angular momentum
(2017-09-18)
Tung, J. C.
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Omatsu, T.
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Liang, H. C.
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Huang, K. F.
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Chen, Y. F.
An end-pumped Nd: YVO4 laser under selective pumping is used to excite lasing modes with transverse patterns performed to exhibit the characteristics of multiple spots arranged on elliptical features near degenerate cavities. The spatial distribution of elliptical lasing modes is clearly revealed to be localized on the nonplanar ray orbits, so-called nonplanar elliptical modes, which possess large fractional orbital angular momentum. Moreover, temporal dynamics for the output emission of nonplanar elliptical modes are verified to obtain self-mode-locked operation. We further numerically manifest not only the influence of radial-asymmetry distributions on the vortex structures of nonplanar elliptical modes, but also the vector field of transverse lasing modes altered with twisting phase structures in the propagation direction. (C) 2017 Optical Society of America
Forward bias operation of silicon photonic Mach Zehnder modulators for RF applications
(2017-09-18)
Chao, Rui Lin
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Shi, Jin Wei
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Jain, Aditya
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Hirokawa, Takako
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Khope, Akhilesh S. P.
In this paper, we demonstrate that forward bias (+ 0.9V) of a high-speed silicon (Si) optical Mach-Zehnder Modulator (MZM) increases the radio-frequency (RF) link gain by 30 dB when compared to reverse bias operation (-8V). RF applications require tunable, narrowband electro-optic conversion with high gain to mitigate noise of the optical receiver and realize high RF spur-free dynamic range. Compared to reverse bias, the forward bias gain rolls off more rapidly but offers higher RF link gain improvement of more than 13.2 dB at 20 GHz. Furthermore, forward bias is shown to result in comparable spurious-free dynamic range (SFDR: 104.5 dB. Hz(2/3)). We demonstrate through an analytical dc transfer curve the existence of simultaneous high gain and OIP3 and verify the theoretical results with measurement under forward bias at a bias point of around + 0.9 V. (C)2017 Optical Society of America
Analysis of a lens-array modulated coaxial holographic data storage system with considering recording dynamics of material
(2017-09-18)
Yu, Yeh-Wei
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Yang, Chi-Hsiang
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Yang, Tsung-Hsun
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Lin, Shiuan-Huei
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Sun, Ching-Cherng
In the first time, a simulation model with considering the recording dynamics of material is built and is used to simulate evolution of the grating strength of the recorded hologram in a coaxial volume holographic memory system. In addition, phase modulation by lens array in the reference is introduced and observed to perform better diffracted signal quality and higher shifting selectivity, in both simulation and experiment. The use of lens array is found to provide multiple advantages in volume holographic memory system. The new simulation model potentially can be used to precisely design the system to obtain higher diffracted signal quality, higher shifting selectivity, and reduction of M# consumption and increase of storage capacity. (C) 2017 Optical Society of America
Competitive profit maximization in social networks
(2017-09-19)
Li, Weian
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Liu, Wenjing
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Chen, Tiantian
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Qu, Xiaoying
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Fang, Qizhi
We study the competitive profit maximization problem in a social network, which can be viewed as the profit maximization problem in a game-theoretic setting. We formulate two models called the profit maximization-agent (PM-A) game and the profit maximization-society (PM-S) game. By reducing them to be valid utility systems, we show that any Nash equilibrium provides an excepted social utility within a factor 1/2 (subject to a function-dependent additive term) of the optimum in the PM-A game and a factor of 1/2 of the optimum in the PM-S game. Furthermore, for the PM-S game, a polynomial-time algorithm is given for each player that can approximate the best response within a factor (1 - 1/e). (C) 2017 Elsevier B.V. All rights reserved.
In Situ TEM Investigation of the Electrochemical Behavior in CNTs/MnO2-Based Energy Storage Devices
(2017-09-19)
Tsai, Tsung-Chun
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Huang, Guan-Min
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Huang, Chun-Wei
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Chen, Jui-Yuan
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Yang, Chih-Chieh
Transition metal oxides have attracted much interest owing to their ability to provide high power density in lithium batteries; therefore, it is important to understand the electrochemical behavior and mechanism of lithiation-delithiation processes. In this study, we successfully and directly observed the structural evolution of CNTs/MnO2 during the lithiation process using transmission electron microscopy (TEM). CNTs/MnO2 were selected due to their high surface area and capacitance effect, and the lithiation mechanism of the CNT wall expansion was systematically analyzed. Interestingly, the wall spacings of CNTs/MnO2 and CNTs were obviously expanded by 10.92% and 2.59%, respectively. The MnO2 layer caused structural defects on the CNTs surface that could allow penetration of Li+ and Mn4+ through the tube wall and hence improve the ionic transportation speed. This study provided direct evidence for understanding the role of CNTs/MnO2 in the lithiation process used in lithium ion batteries and also offers potential benefits for applications and development of supercapacitors.
Vascular anatomy is a determining factor of successful submental flap raising: a retrospective study of 70 clinical cases
(2017-09-19)
Lin, Hung-Che
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Huan, Yuahn-Sieh
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Chu, Yueng-Hsiang
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Liu, Shao-Cheng
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Shangkuan, Wei-Chuan
The vascular anatomy of submental flaps (SFs) represents a determining factor in successful SF raising. However, little attention has been focused on the venous return of SFs. Thus, the present study aimed to investigate SF venous return. This study enrolled patients who underwent SF reconstructive surgery in a tertiary referral center between November 2009 and October 2016. The drainage pathway of the SF venous return was routinely identified during the course of our operations to prevent damage during head and neck surgery. The venous return data of 70 patients were reviewed. The size of the flaps ranged from 15 to 84 cm(2), and total flap loss was not observed in the case series. All of the submental arteries originated from the facial artery; however, the submental veins of 70 patients returned to either the internal jugular vein (IJV, 72.9%) or the external jugular vein (EJV, 27.1%). Our data suggest that drainage of the submental vein into the EJV, which has been previously overlooked, should receive greater attention during SF surgeries. The results support mandatory preservation of the EJV and IJV and indicate that vascular anatomy is a determining factor for successful SF raising.
Light energy transformation over a few nanometers
(2017-09-20)
Huang, Hung Ji
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Liu, Bo-Heng
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Su, James
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Chen, Po-Jui
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Lin, Chun-Ting
Continuous platinum (Pt) thin film was fabricated via the plasma-enhanced atomic layer deposition method for a study of light energy transformation over a few nanometers. Light-to-heat experiments were used to determine the oscillating size effects on electromagnetic energy transformation in quantum wells of smooth and condensed Pt thin films. For Pt-film thicknesses of around 4 nm, 7 nm and 12 nm, electromagnetic heating presented unexpectedly high energy conversion efficiency. An empirical equation acquired from the fitting of the experimental data from various thicknesses of Pt thin films was suggested to describe the oscillating electromagnetic heating and quantized energy transformation. The experimental results show that size control of the nanostructures is extremely important for future applications involving quantum effects in nano devices.
Peroxide induced volatile and non-volatile switching behavior in ZnO-based electrochemical metallization memory cell
(2017-09-20)
Simanjuntak, Firman Mangasa
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Chandrasekaran, Sridhar
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Pattanayak, Bhaskar
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Lin, Chun-Chieh
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Tseng, Tseung-Yuen
We explore the use of cubic-zinc peroxide (ZnO2) as a switching material for electrochemical metallization memory (ECM) cell. The ZnO2 was synthesized with a simple peroxide surface treatment. Devices made without surface treatment exhibits a high leakage current due to the self-doped nature of the hexagonal-ZnO material. Thus, its switching behavior can only be observed when a very high current compliance is employed. The synthetic ZnO2 layer provides a sufficient resistivity to the Cu/ZnO2/ZnO/ITO devices. The high resistivity of ZnO2 encourages the formation of a conducting bridge to activate the switching behavior at a lower operation current. Volatile and non-volatile switching behaviors with sufficient endurance and an adequate memory window are observed in the surface-treated devices. The room temperature retention of more than 10(4) s confirms the non-volatility behavior of the devices. In addition, our proposed device structure is able to work at a lower operation current among other reported ZnO-based ECM cells.
交大e-News第240期-交大CGI圍棋程式與台灣頂尖棋士之合作計畫
(2017-09-20)
國立交通大學秘書室
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Secretariat
Intramolecular Locked Dithioalkylbithiophene-Based Semiconductors for High-Performance Organic Field-Effect Transistors
(2017-09-20)
Vegiraju, Sureshraju
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Chang, Bo-Chin
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Priyanka, Pragya
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Huang, Deng-Yi
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Wu, Kuan-Yi
New 3,3-dithioalkyl-2,2-bithiophene (SBT)-based small molecular and polymeric semiconductors are synthesized by end-capping or copolymerization with dithienothiophen-2-yl units. Single-crystal, molecular orbital computations, and optical/electrochemical data indicate that the SBT core is completely planar, likely via S(alkyl)S(thiophene) intramolecular locks. Therefore, compared to semiconductors based on the conventional 3,3-dialkyl-2,2-bithiophene, the resulting SBT systems are planar (torsional angle <1 degrees) and highly -conjugated. Charge transport is investigated for solution-sheared films in field-effect transistors demonstrating that SBT can enable good semiconducting materials with hole mobilities ranging from approximate to 0.03 to 1.7 cm(2) V-1 s(-1). Transport difference within this family is rationalized by film morphology, as accessed by grazing incidence X-ray diffraction experiments.
Photostriction of CH3NH3PbBr3 Perovskite Crystals
(2017-09-20)
Wei, Tzu-Chiao
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Wang, Hsin-Ping
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Li, Ting-You
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Lin, Chun-Ho
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Hsieh, Ying-Hui
Organic-inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light-matter interactions. The photoinduced strain of CH3NH3PbBr3 is investigated using high-resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH3NH3PbBr3 is calculated as 2.08 x 10(-8) m(2) W-1 at room temperature under visible light illumination. The significant photostriction of CH3NH3PbBr3 is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation-rotation coupling. Unlike CH3NH3PbI3, it is noted that the photostriction of CH3NH3PbBr3 is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH3NH3PbBr3 for applications in next-generation optical micro-electromechanical devices.
Oxasmaragdyrins as New and Efficient Hole-Transporting Materials for High-Performance Perovskite Solar Cells
(2017-09-20)
Mane, Sandeep B.
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Sutanto, Albertus Adrian
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Cheng, Chih-Fu
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Xie, Meng-Yu
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Chen, Chieh-I
The high performance of the perovskite solar cells (PSCs) cannot be achieved without a layer of efficient hole-transporting materials (HTMs) to retard the charge recombination and transport the photogenerated hole to the counterelectrode. Herein, we report the use of boryl oxasmaragdyrins (SM01, SM09, and SM13), a family of aromatic core-modified expanded porphyrins, as efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs). These oxasmaragdyrins demonstrated complementary absorption spectra in the low-energy region, good redox reversibility, good thermal stability, suitable energy levels with CH3NH3PbI3 perovskite, and high hole mobility. A remarkable power conversion efficiency of 16.5% (V-oc= 1.09 V, J(sc) = 20.9 mA cm(-2), fill factor (FF) = 72%) is achieved using SM09 on the optimized PSCs device employing a planar structure, which is close to that of the state-of-the-art hole-transporting materials (HTMs), spiro-OMeTAD of 18.2% (V-oc = 1.07 V, J(sc) = 22.9 mA cm(-2), FF = 74%). In contrast, a poor photovoltaic performance of PSCs using SM01 is observed due to the interactions of terminal carboxylic acid functional group with CH3NH3PbI3.
Diammonium and Monoammonium Mixed-Organic-Cation Perovskites for High Performance Solar Cells with Improved Stability
(2017-09-20)
Lu, Jianfeng
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Jiang, Liangcong
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Li, Wei
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Li, Feng
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Pai, Narendra K.
Remarkable power conversion efficiencies (PCE) of metal-halide perovskite solar cells (PSCs) are overshadowed by concerns about their ultimate stability, which is arguably the prime obstacle to commercialization of this promising technology. Herein, the problem is addressed by introducing ethane-1,2-diammonium (+NH3(CH2)(2)NH3+, EDA(2+)) cations into the methyl ammonium (CH3NH3+, MA(+)) lead iodide perovskite, which enables, inter alia, systematic tuning of the morphology, electronic structure, light absorption, and photoluminescence properties of the perovskite films. Incorporation of < 5 mol% EDA(2+) induces strain in the perovskite crystal structure with no new phase formed. With 0.8 mol% EDA(2+), PCE of the MAPbI(3)-based PSCs (aperture of 0.16 cm(2)) improves from 16.7% +/- 0.6% to 17.9% +/- 0.4% under 1 sun irradiation, and fabrication of larger area devices (aperture 1.04 cm(2)) with a certified PCE of 15.2% +/- 0.5% is demonstrated. Most importantly, EDA(2+)/MA(+)-based solar cells retain 75% of the initial performance after 72 h of continuous operation at 50% relative humidity and 50 degrees C under 1 sun illumination, whereas the MAPbI(3) devices degrade by approximately 90% within only 15 h. This substantial improvement in stability is attributed to the steric and coulombic interactions of embedded EDA(2+) in the perovskite structure.
Direct infrared observation of hydrogen chloride anions in solid argon
(2017-09-21)
Huang, Tzu-Ping
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Chen, Hui-Fen
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Liu, Meng-Chen
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Chin, Chih-Hao
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Durrant, Marcus C.
To facilitate direct spectroscopic observation of hydrogen chloride anions (HCl-), electron bombardment of CH3Cl diluted in excess Ar during matrix deposition was used to generate this anion. Subsequent characterization were performed by IR spectroscopy and quantum chemical calculations. Moreover the band intensity of HCl fi decays slowly when the matrix sample is maintained in the dark for a prolonged time. High-level ab inito calculation suggested that HCl fi is only weakly bound. Atom-in-molecule charge analysis indicated that both atoms of HCl fi are negatively charged and the Cl atom is hypervalent. Published by AIP Publishing.
Remarkable nonlinear optical response of excess electron compounds: theoretically designed alkali-doped aziridine M-(C2NH5)(n)
(2017-09-21)
Li, Bo
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Xu, Chao
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Xu, Xuan
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Zhu, Chaoyuan
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Gu, Feng Long
Theoretically designed alkali-doped aziridine M-(C2NH5)(n) (M = Li, Na and K; n = 1, 2, 3, and 4) are investigated by density functional theory (DFT) and time-dependent TD-DFT. The interaction energies at optimized electronic structures indicate that alkali-doped aziridine are quite stable. The natural population analysis of charges on alkali atoms show that all positive and electronic transitions to LUMO orbitals are large, so that the designed compounds not only have electride features, but also have large flexible ligands. This leads to a high-performance nonlinear optical response (NLO) and this remarkable NLO response mainly comes from alkali atoms. By calculating the first hyperpolarizabilities for M-(C2NH5)(4) with M@ Calix[4] pyrrole for comparison, we demonstrate that enhancements of the NLO response of M-(C2NH5)(4) are 10 to 100 times larger than those of M@ Calix[ 4] pyrrole, and in particular, the largest first hyperpolarizability values of Na-(C2NH5)(4) is up to 3.4 x 10(6) (a. u.).
Spin filtering of a termination-controlled LSMO/Alq(3) heterojunction for an organic spin valve
(2017-09-21)
Lam, Tu-Ngoc
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Huang, Yen-Lin
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Weng, Ke-Chuan
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Lai, Yu-Ling
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Lin, Ming-Wei
La1-xSrxMnO3 (LSMO) is weLL known as an efficient spin-injection electrode in ferromagnetic organic hybrid-based organic spin valves (OSV). Herein, we examine the influence of three terminating Layers of LSMO fiLms (mixed-, MnO2-, and LaSrO- (LSO-) terminated) on the spin filter at the bottom interface of tri (8-hydroxyquinoLine) aluminum (ALq(3)) deposited on these substrates. Angle-dependent X-ray photoelectron spectra (XPS) demonstrated the presence of SrO segregation at the outermost Layer for three types of LSMO fiLms but in different amounts that might contribute to their magnetic properties. A weak surface coupling between LSMO and Alq(3) was obtained through a small increase of Mn L-edge X-ray magnetic circular dichroism (XMCD) but it does not vary the bulk magnetic properties of LSMO fiLms upon Alq(3) adsorption (LSMO/Alq(3)). The surface dipoles due to the interaction between LSMO fiLms and Alq(3) were found to be 0.5, 0.5, and 0.7 eV for the mixed-ter/Alq(3), MnO2-ter/Alq(3), and LSO-ter/Alq(3) interfaces, respectively. Our results indicate that the segregated SrO Layer Ways an important role in the surface electronic and magnetic properties at LSMO/Alq(3) interfaces, which contributes to a fundamental understanding of the spin injection and transport in LSMO-Alq(3) hybrid-based OSV devices.
SEMICONDUCTOR DEVICE FOR ULTRA-HIGH VOLTAGE OPERATION AND METHOD FOR FORMING THE SAME
(2017-09-21)
Chun-Yen CHANG
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Chun-Hu CHENG
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Yu-Pin LAN
A semiconductor device for ultra-high voltage (UHV) operation disclosed in the present invention includes a substrate having a normally-on channel, a negative capacitance material layer, an electrode, a source and a drain. The negative capacitance material layer is disposed over the substrate and capable of adjusting the threshold voltage of the semiconductor device so as to transform the normally-on channel into a normally-off channel and change the transistor characteristics of the semiconductor device from a depletion mode to an enhance mode. In addition, the semiconductor device also includes a gate dielectric layer made of high-k material between the negative capacitance material layer, a gate layer between the gate dielectric layer and the negative capacitance material layer and an ion implantation layer in the substrate under the gate. Furthermore, the aforementioned technical features or structures can be formed in a semiconductor device having a gate-recessed structure.