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141.
142.
Lei Sun Tian Du Cheng Wang Prof. Dongling Geng Dr. Lin Li Prof. Yang Han Prof. Yunfeng Deng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(69):17437-17443
Low-bandgap organic semiconductors have attracted much attention for their multiple applications in optoelectronics. However, the realization of narrow bandgap is challenging particularly for small molecules. Herein, we have synthesized four quinoidal compounds, i. e., QSN3 , QSN4 , QSN5 and QSN6 , with electron rich S,N-heteroacene as the quinoidal core and indandione as the end-groups. The optical bandgap of the quinoidal compounds is systematically decreased with the extension of quinoidal skeleton, while maintaining stable closed-shell ground state. QSN6 absorbs an intense absorption in the first and second near-infrared region in the solid state, and has extremely low optical bandgap of 0.74 eV. Cyclic voltammetry analyses reveal that the lowest unoccupied molecular orbital (LUMO) energy levels of the four quinoidal compounds all lie below −4.1 eV, resulting in good electron-transporting characteristics in organic thin-film transistors. These results demonstrated that the combination of π-extended quinoidal core and end-groups in quinoidal compounds is an effective strategy for the synthesis of low-bandgap small molecules with good stability. 相似文献
143.
Yu-Huan Geng Dr. Yuan-Zhao Hua Dr. Shi-Kun Jia Prof. Dr. Min-Can Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5130-5135
The first regio-, diastereo-, and enantioselective direct Mannich reaction of β,γ,-unsaturated ketones with benzoxazinone cyclic imines was enabled by Lewis acid/Brønsted base cooperative catalysis. The dinuclear zinc complex catalyzed the reaction of a broad range of β,γ-unsaturated ketones to proceed at the α-site exclusively, leading to corresponding adducts with two consecutive tertiary carbon stereocenters in diastereomeric ratios of up to >20:1 and enantioselectivities generally in the 90–99 % ee range. These products were used as general intermediates in the synthesis of multisubstituted cyclocanalines, tetrahydro pyridazinones, and 4H-furo[2,3-b][1,4]benzoxazine derivatives. 相似文献
144.
Y. L. Jia X. Geng H. Sun Y. Luo 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(4):451-455
We have studied the exciton effects in armchair graphene nanoribbons systematically,
using the nonorthogonal tight-binding model supplement by the long-range Coulomb
interactions. It is found from our calculations that the excitation energies, the exciton
binding energies and the exciton wave function sizes of
the E
11 and E
22 excitons all
exhibit oscillation as a function of the ribbon width. And there is a phase shift
of π between the oscillation of the E
11
and E
22 excitons. 相似文献
145.
146.
147.
Influence of reaction gas flows on the properties of SiGe:H thin film prepared by plasma assisted
reactive thermal chemical vapour deposition 总被引:1,自引:0,他引:1 下载免费PDF全文
A new preparing technology, very high frequency plasma assisted reactive thermal chemical vapour deposition (VHFPA-RTCVD), is introduced to prepare SiGe:H thin films on substrate kept at a lower temperature. In the previous work, reactive thermal chemical vapour deposition (I~TCVD) technology was successfully used to prepare SiGe:H thin films, but the temperature of the substrate needed to exceed 400℃. In this work, very high frequency plasma method is used to assist RTCVD technology in reducing the temperature of substrate by largely enhancing the temperature of reacting gases on the surface of the substrate. The growth rate, structural properties, surface morphology, photo- conductivity and dark-conductivity of SiGe:H thin films prepared by this new technology are investigated for films with different germanium concentrations, and the experimental results are discussed. 相似文献
148.
1 IntroductionIn this paper we study the blow--up of positive solutions as A - 0+ fOr thefOllowing boundary value problem of the weighted pLaplacian on the unit ballcenter at the origin B = B1(0) C Rn:where cr5 u > fi --p > --n and p* = p(n + a)/(fi +n --p) is the critical exponentof the embedding Wl"(fl, lxtpdx) - Lp*(fl, lxl"dx) (see, for example, [6]).When u is radially symmetric, y(r) = u(x), fOr r = lxl, satisfieswhere the new exponents cr, g, p and p* satisfyThe existence and non-exi… 相似文献
149.
Geng NF Goh PG Johnson BF Martin CM Shephard DS Zhou W 《Angewandte Chemie (International ed. in English)》2000,39(9):1661-1664
150.
Signal changes can be detected by proton density-weighted functional imaging in both the brain and the spinal cord. These are attributed to changes in extravascular water proton (signal enhancement by extravascular protons) density during neuronal activation. In this study, we used this technique to detect correlations between acupoint stimulation and neural activity in the spinal cord. Stimulation of acupoints associated with treatment of sensorimotor deficits (LI4 and LI11) was performed on 11 volunteers. During stimulation, 8 of the 11 subjects had consistent functional activations in C6/C7. A bilateral activation pattern was common. Our findings show that acupoint stimulation modulates activity in the spinal cord. 相似文献