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899 results on '"Xu, Qing-Hua"'

153. Tuneable near white-emissive two-dimensional covalent organic frameworks

Author

Li, Xing, primary, Gao, Qiang, additional, Wang, Juefan, additional, Chen, Yifeng, additional, Chen, Zhi-Hui, additional, Xu, Hai-Sen, additional, Tang, Wei, additional, Leng, Kai, additional, Ning, Guo-Hong, additional, Wu, Jishan, additional, Xu, Qing-Hua, additional, Quek, Su Ying, additional, Lu, Yixin, additional, and Loh, Kian Ping, additional

Published
2018
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157. Vapour–liquid–solid growth of monolayer MoS2 nanoribbons

Author

Li, Shisheng, primary, Lin, Yung-Chang, additional, Zhao, Wen, additional, Wu, Jing, additional, Wang, Zhuo, additional, Hu, Zehua, additional, Shen, Youde, additional, Tang, Dai-Ming, additional, Wang, Junyong, additional, Zhang, Qi, additional, Zhu, Hai, additional, Chu, Leiqiang, additional, Zhao, Weijie, additional, Liu, Chang, additional, Sun, Zhipei, additional, Taniguchi, Takaaki, additional, Osada, Minoru, additional, Chen, Wei, additional, Xu, Qing-Hua, additional, Wee, Andrew Thye Shen, additional, Suenaga, Kazu, additional, Ding, Feng, additional, and Eda, Goki, additional

Published
2018
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162. Controllable deuteration of halogenated compounds by photocatalytic D2O splitting

Author

Liu, Cuibo, primary, Chen, Zhongxin, additional, Su, Chenliang, additional, Zhao, Xiaoxu, additional, Gao, Qiang, additional, Ning, Guo-Hong, additional, Zhu, Hai, additional, Tang, Wei, additional, Leng, Kai, additional, Fu, Wei, additional, Tian, Bingbing, additional, Peng, Xinwen, additional, Li, Jing, additional, Xu, Qing-Hua, additional, Zhou, Wu, additional, and Loh, Kian Ping, additional

Published
2018
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167. Temperature-dependent vibrational dephasing: Comparison of liquid and glassy solvents using frequency-selected vibrational echoes.

Author

Xu, Qing-Hua and Fayer, M. D.

Subjects
*CARBON monoxide, *VIBRATIONAL spectra
Abstract

Frequency-selected vibrational echo experiments were used to investigate the temperature dependences of vibrational dephasing associated with the 0-1 transition of the CO stretching mode of RuTPPCOPy (TPP=5,10,15,20-tetraphenylporphyrin, Py=pyridine) in two solvents: polymethylmethacrylate (PMMA) and 2-methyltetrahydrofuran (2-MTHF). In PMMA, a glass, the echo decay is exponential at all the temperatures studied, and the dephasing rate increases linearly with increasing temperature. In 2-MTHF, there is a change in the functional form of the temperature dependence when the solvent goes through the glass transition temperature (T[sub g]). Below T[sub g], the dephasing rate increases linearly with temperature, while above T[sub g], it rises very steeply in a nonlinear manner. In the liquid at higher temperatures, the vibrational echo decays are nonexponential. A model frequency-frequency correlation function (FFCF) is proposed in which the FFCF differs for a glass and a liquid because of the intrinsic differences in the nature of the dynamics. At least two motions, inertial and diffusive, contribute to the vibrational dephasing in the liquids. The different temperature dependences of inertial and diffusive motions are discussed. Comparison of the model calculations of the vibrational echo temperature dependence and the data show reasonable, but not quantitative agreement. [ABSTRACT FROM AUTHOR]

Published
2002
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168. Wavelength-dependent resonant homodyne and heterodyne transient grating spectroscopy with a diffractive optics method: Solvent effect on the third-order signal.

Author

Xu, Qing-Hua, Ma, Ying-Zhong, Stiopkin, Igor V., and Fleming, Graham R.

Subjects
*SPECTRUM analysis, *OPTICS, *OPTICAL diffraction
Abstract

We carried out a wavelength-dependent homodyne and heterodyne transient grating (TG) studies on a resonant system, rhodamine 640 in dimethylsulfoxide, with a simplified diffractive optics method. The real and imaginary components of the third-order molecular polarization at different excitation wavelengths have a similar longtime decay (>200 fs), while the amplitude of the real component is strongly wavelength dependent. The nonresonant solvent and the resonant solute contributions to the third-order polarization are found to have a similar magnitude in a dilute solution. The interference of the wavelength-dependent resonant solute contributions with the nonresonant solvent contribution is found to be crucial to properly understand the wavelength dependence of the initial dynamics in homodyne TG and other four-wave mixing techniques. Such an interference effect is further confirmed by concentration-dependent homodyne TG measurements. [ABSTRACT FROM AUTHOR]

Published
2002
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169. In Situ Synthesis of Lead-Free Halide Perovskite Cs2AgBiBr6Supported on Nitrogen-Doped Carbon for Efficient Hydrogen Evolution in Aqueous HBr Solution

Author

Jiang, Yiqun, Li, Kui, Wu, Xiao, Zhu, Menglong, Zhang, Hongwei, Zhang, Kun, Wang, Ye, Loh, Kian Ping, Shi, Yumeng, and Xu, Qing-Hua

Abstract

Lead halide perovskites have shown great potential in photovoltaic and photocatalytic fields. However, the toxicity of lead impedes their wide application. Herein composites of lead-free halide perovskite Cs2AgBiBr6supported on nitrogen-doped carbon (N-C) materials were synthesized successfully through a facile one-pot method for the first time. Without deposition of noble metals as the cocatalyst, the optimal composite Cs2AgBiBr6/N-C (Cs2AgBiBr6/N-C-140) exhibits outstanding photocatalytic performance with a high hydrogen evolution rate of 380 μmol g–1h–1under visible light irradiation (λ ≥ 420 nm), which is about 19 times faster than that of pure Cs2AgBiBr6and 4 times faster than that of physically mixed Cs2AgBiBr6/N-C-140, respectively. The Cs2AgBiBr6/N-C-140 composite also displays high stability with no significant decrease after six cycles of repeated hydrogen evolution experiments. The addition of N-C with a high surface area helps to prevent aggregation of Cs2AgBiBr6NPs and provides more pathways for the migration of photoinduced carriers. The nitrogen dopant can facilitate photoinduced electron transfer from Cs2AgBiBr6to N-C to result in spatially separated electrons and holes with prolonged electron time and greatly enhance the photocatalytic performance. This study indicates that Cs2AgBiBr6-based perovskite materials are promising candidates for photocatalytic hydrogen evolution.

Published
2021
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170. Bioinformatics Analysis on Regulating Axillary Branch Gene of Cucumber (Cucumis sativus L.)

Author

Hu Baozhong and Xu Qing-hua

Subjects
Signal peptide, Genetics, Transmembrane domain, Complementary DNA, Nucleic acid sequence, Biology, Gene, Peptide sequence, Protein secondary structure, Protein tertiary structure
Abstract

The regulating axillary branch gene was cloned and named as CsCCD7. Using a series bioinformatic computer softwares, database and online programes, CsCCD7 nucleotide sequence and CsCCD7 amino acid sequence were analyzed and CsCCD7 function was predicted. The results showed that CsCCD7 cDNA full length sequence was 2 136 bp, and included a 1 665 bp ORF which encoded a 554 AA protein; there were 32 kinds of cis-acting regulating element in 2 136 bp cDNA sequence; CsCCD7 was an unstable protein (the unstable coefficient: 40.77), including many phosphorylation sites related with CsCCD7 function; CsCCD7 had no transmembrane domain, and its subcellular localization was in chloroplast. CsCCD7 secondary structure contained four conformations including α-helix, β-sheet, β-turn and random coil. CsCCD7 protein had no signal peptide, so was non-secretory protein and hydrophilicity protein (grand average of hydropathicity: −0.401). Both CsCCD7 secondary and tertiary structure prediction results showed that it was classified as carotenoid oxygenase family. Phylogenetic tree drew by Geneious showed that CsCCD7 was more closely related to AtCCD7 than any other Arabidopsis CCD protein.

Published
2011
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183. Band Nesting Bypass in WS2Monolayers viaFörster Resonance Energy Transfer

Author

Yan, Zhiyuan, Poh, Eng Tuan, Zhang, Zheng, Chua, Sing Teng, Wang, Xinyun, Wu, Xiao, Chen, Zhihui, Yang, Jing, Xu, Qing-Hua, Goh, Kuan Eng Johnson, Zhao, Rong, and Sow, Chorng-Haur

Abstract

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have attracted intensive interest due to the direct-band-gap transition in the monolayer form, positioning them as potential next-generation materials for optoelectronic or photonic devices. However, the band-nested suppression of the recombination efficiency at higher excitation energies limits the ability to locally control and manipulate the photoluminescence of WS2for multifunctional applications. In this work, we exploit an energy transfer method to modulate the fluorescence properties of TMDs under a larger excitation range spanning from UV to visible light. Self-assembled lanthanide (Ln)/TMD hybrids have been designed based on a low-cost and highly efficient solution-processed approach. The emission energy from Ln3+sources can be effectively transferred to the TMD monolayers under low power exposure (0.13 mW) at room temperature, activating the characteristic monolayer fluorescence in place of Ln3+emission signatures. The Ln/TMDs photonics can potentially tune the excitation of TMDs to provide variable yet controllable emissions. This provides a solution to the suppression of direct exciton recombination in monolayer TMDs at the band nesting resonant energy region. Our work on such Ln/TMD systems would overcome the limited excitation energy range in TMDs and extend their functionalities for optoelectronic or photonic applications.

Published
2020
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184. New Family of Plasmonic Photocatalysts without Noble Metals.

Author

Wan, Dongyang, Yan, Bixing, Chen, Jianqiang, Wu, Shuyang, Hong, Jindui, Song, Dongsheng, Zhao, Xiaoxu, Chi, Xiao, Zeng, Shengwei, Huang, Zhen, Li, Changjian, Han, Kun, Zhou, Wenxiong, Cao, Yu, Rusydi, Andrivo, Pennycook, Stephen J., Yang, Ping, Ariando, Xu, Rong, and Xu, Qing-Hua

Published
2019
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188. Two-Photon Excitation of Gold Nanorods Interrupted by Extremely Fast Solvent-to-Metal Electron Transfer

Author

Zhu, Hai, Garai, Monalisa, Chen, Zhihui, and Xu, Qing-Hua

Abstract

Gold nanorods (Au NRs) have been widely exploited for various biomedical applications due to their strong two-photon photoluminescence (2PPL). 2PPL of Au NRs were found significantly quenched in organic solvents, which was originally ascribed to reduced luminescence yields caused by electron transfer quenching. It was recently found that excitation of 2PPL of Au NRs involved two sequential one-photon absorption steps. Here various ultrafast spectroscopic techniques have been employed to demonstrate two different solvent-to-metal electron transfer pathways: electron transfer from organic solvents to sp and d band holes of excited Au NRs, which have different influences on 2PPL of Au NRs. Electron transfer to sp band holes occurs extremely fast (∼25 fs), which blocks absorption of the second photon and reduces overall two-photon excitation efficiency, which is the dominant mechanism for the observed 2PPL quenching. In contrast, electron transfer to d band holes hinders the radiative recombination process and results in reduced luminescence yield, which plays the minor contribution for the observed 2PPL quenching. This work has proposed and demonstrated an additional brand-new quenching mechanism of 2PPL emission of Au NRs: extremely fast electron transfer to the intermediate states within the laser pulse duration interrupts sequential absorption of two photons, which results in significantly reduced two-photon excitation efficiency. This study provides new insight on fundamental understanding of two-photon excitation processes and nonlinear optical properties of these materials.

Published
2024
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190. Gold nanorings synthesized via a stress-driven collapse and etching mechanism

Author

Fang, Jixiang, primary, Li, Jiang, additional, Tian, Cuifeng, additional, Gao, Qiangqiang, additional, Wang, Xiangjie, additional, Gao, Nengyue, additional, Wen, Xinglin, additional, Ma, Chuansheng, additional, You, Hongjun, additional, Yang, Zhilin, additional, Xu, Qing-Hua, additional, Xiong, Qihua, additional, and Li, Zhiyuan, additional

Published
2016
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