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排序方式: 共有788条查询结果,搜索用时 31 毫秒
781.
Jisun Kim Alexander Ako Khajetoorians Wenguang Zhu Zhenyu Zhang Chih-Kang Shih 《Surface science》2012,606(3-4):450-455
Using scanning tunneling microscopy (STM), we demonstrate that oxidation on Pb films is greatly enhanced by atomic Cs catalysts. With only a minute concentration of isolated Cs substitutional atoms in the surface layer (0.004 ML coverage), surface oxidation rates are greatly enhanced. First-principles density functional theory (DFT) calculations reveal that a substitutional Cs atom strongly increases O2 binding on the surface. Then, with additional oxygen exposure this substitutional Cs-initiated oxidation process results in growth of PbO layers in an auto-catalytic manner. Furthermore, we investigate the role of temperature in the oxidation of the Pb films with and without Cs, and we explore the overall morphology of the resultant oxide layers. 相似文献
782.
Yan Wang Zhenyu You Jianfu Li Zhaojie Zhu En Ma Chaoyang Tu 《Optics Communications》2012,285(5):650-654
A series of Cr,Er:Gd3Ga5O12 crystals with high concentrations of Er3 + were grown by Czochralski method. The absorption spectra, the up-conversion, near infrared (NIR) and mid-infrared (Mid-IR) luminescence spectra as well as the luminescence decay curves of Er: 4I13/2 and 4I11/2 levels were measured at room temperature. The spectroscopic properties of Cr,Er:Gd3Ga5O12 crystals and Cr–Er energy transfer processes were investigated. The spectroscopy of the Er3 +:4I11/2 → 4I13/2 transition was centralized to discuss, and the important optical parameters including luminescence lifetimes and the Cr–Er energy transfer efficiency are presented. Based on the comprehensive spectral analyses, 0.6 at.%Cr/50 at.%Er:GGG crystal is preferred as candidate of potential xenon lamp pumped ~ 2.7 μm laser in this work. 相似文献
783.
Wavelet shrinkage is an image restoration technique based on the concept of thresholding the wavelet coefficients. The key challenge of wavelet shrinkage is to find an appropriate threshold value, which is typically controlled by the signal variance. To tackle this challenge, a new image restoration approach is proposed in this paper by using a variance field diffusion, which can provide more accurate variance estimation. Experimental results are provided to demonstrate the superior performance of the proposed approach. 相似文献
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786.
Wei Song Qinrui Ye Shuncheng Yang Lin Xie Yuanyuan Meng Zhenyu Chen Qun Gu Daobin Yang Jingyu Shi Prof. Ziyi Ge 《Angewandte Chemie (International ed. in English)》2023,62(41):e202310034
The wearable application of flexible organic solar cells (f-OSCs) necessitates high power conversion efficiency (PCE) and mechanical robustness. However, photoactive films based on efficient non-fullerene small molecule acceptors (NF-SMAs) are typically brittle, leading to poor mechanical stability in devices. In this study, we achieved a remarkable PCE of 18.06 % in f-OSCs while maintaining ultrahigh mechanical robustness (with a crack-onset strain (COS) of higher than 11 %) by incorporating a linker dimerized acceptor (DOY-TVT). Compared to binary blends, ternary systems exhibit reduced non-radiative recombination, suppressed crystallization and diffusion of NF-SMAs, and improved load distribution across the chain networks, enabling the dissipation of the load energy. Thus, the ternary f-OSCs developed in this study achieved, high PCE and stability, surpassing binary OSCs. Moreover, the developed f-OSCs retained 97 % of the initial PCE even after 3000 bending cycles, indicating excellent mechanical stability (9.1 % higher than binary systems). Furthermore, the rigid device with inverted structure based on the optimal active layer exhibited a substantial increase in efficiency retention, with 89.6 % after 865 h at 85 °C and 93 % after more than 1300 h of shelf storage at 25 °C. These findings highlight the potential of the linker oligomer acceptor for realizing high-performing f-OSCs with ultrahigh mechanical robustness. 相似文献
787.
Zhouzhou Chen Xiaoyue Zhu Yue Geng Zhenyu Huang Erwin Adams Daijie Chen Sheng Tang Yu Yin Yaozuo Yuan 《Journal of separation science》2023,46(10):2201012
A previously developed high-performance liquid chromatography method combined with pulsed amperometric detection allowed to separate many impurities of paromomycin. However, due to the presence of ion pairing agents and sodium hydroxide in the mobile phase, direct coupling to mass spectrometry for the identification of the chemical structures of the impurities was not an option. Indeed, ion suppression was encountered by trifluoroacetic acid and pentafluoroproponic acid in the mobile phase. A cation self-regenerating suppressor, which was originally designed for increasing analyte conductivity of ammonia and amines analysis in ion chromatography, was coupled between the liquid chromatography and ion trap-time of flight-mass spectrometry and almost all trifluoroacetic acid and pentafluoroproponic acid in the mobile phase was removed. The limit of detection of paromomycin in this integrated system improved significantly to 20 ng/ml (0.4 ng). The chemical structures of 19 impurities were elucidated and seven impurities were reported for the first time. 相似文献
788.
Jiawen Zhu Jiaqi Cao Guolei Cai Jing Zhang Wei Zhang Shuai Xie Jinxi Wang Dr. Hongchang Jin Junjie Xu Prof. Xianghua Kong Dr. Song Jin Prof. Zhenyu Li Prof. Hengxing Ji 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(3):e202214351
Appling an electrochemical catalyst is an efficient strategy for inhibiting the shuttle effect and enhancing the S utilization of Li-S batteries. Carbon-based materials are the most common conductive agents and catalyst supports used in Li-S batteries, but the correlation between the diversity of hybridizations and sulfur reduction reaction (SRR) catalytic activity remains unclear. Here, by establishing two forms of carbon models, i.e., graphitic carbon (GC) and amorphous carbon (AC), we observe that the nitrogen atom doped in the GC possesses a higher local charge density and a lower Gibbs free energy towards the formation of polysulfides than in the AC. And the GC-based electrode consistently inherits considerably enhanced SRR kinetics and superior cycling stability and rate capability in Li-S batteries. Therefore, the function of carbon in Li-S batteries is not only limited as conductive support but also plays an unignorable contribution to the electrocatalytic activities of SRR. 相似文献