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73. Ligand‐dependent aggregation‐enhanced photoacoustic of atomically precise metal nanocluster.

Author

Zhou, Changlin, Wang, Meng, Yao, Qiaofeng, Zhou, Yu, Hou, Chuantao, Xia, Jianfei, Wang, Zonghua, Chen, Jishi, and Xie, Jianping

Subjects
EXCITED state energies, GOLD clusters, PHOTOACOUSTIC spectroscopy, POLAR solvents, ENERGY dissipation, CONTRAST media, ENERGY transfer
Abstract

Atomically precise metal nanoclusters (MNCs), as a potential type of photoacoustic (PA) contrast agent, are limited in application due to their low PA conversion efficiency (PACE). Here, with hydrophilic Au25SR18 (SR = thiolate) as model NCs, we present a result that weakly polar solvent induces aggregation, which effectively enhances PA intensity and PACE. The PA intensity and PACE are highly dependent on the degree of aggregation, while the aggregation‐enhanced PA intensity (AEPA) positively correlates to the protected ligands. Such an AEPA phenomenon indicates that aggregation actually accelerates the intramolecular motion of Au NCs, and enlarges the proportion of excited state energy dissipated through vibrational relaxation. This result conflicts with the restriction of intramolecular motion mechanism of aggregation‐induced emission. Further experiments show that the increased energy of AEPA originates from the aggregation inhibiting the intermolecular energy transfer from excited Au NCs to their surrounding medium molecules, including solvent molecule and dissolved oxygen, rather than restricting radiative relaxations. This study develops a new strategy for enhancing the PA intensity of Au NCs, and contributes to a deeper understanding of the origin of the PA signal and the excited state energy dissipation processes for MNCs. [ABSTRACT FROM AUTHOR]

Published
2024
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95. Synthesis and characterization of permanently antistatic polyurethanes containing ionic liquids

Author

Wu, Bo, Hu, Zeyu, Zhang, Yanyan, Xiao, Yao, Lei, Jingxin, and Zhou, Changlin

Subjects
Polyurethanes -- Chemical properties, Ionic liquids -- Chemical properties, Chemical synthesis -- Methods, Engineering and manufacturing industries, Science and technology
Abstract

An in situ embed ionic liquid method is designed and employed in thermoplastic polyurethanes (PUs). Unlike the traditional physically incorporated antistatic polymers where conductive fillers do not firmly combined with the matrix. This permanently antistatic PUs are successfully synthesized by using a novel polyester diol bonded with ionic liquids (ILs), which are obtained by an esterification. The ILs and novel polyester polyol are successfully synthesized and subsequently characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectrum (¹H NMR), respectively. The effects of ILs content, temperature, and relative humidity (RH) on the surface resistivity of PUs are studied by surface resistivity tests. It is found that the surface resistivity of PUs dramatically decreases with the increment of ILs and are insensitive to surrounding environment. The surface resistivity of PUs with 5.96 wt% ILs reaches [10.sup.10] Ω [cm.sup.-2] order of magnitude. The crystalline properties, thermal decomposition behaviors and mechanical properties of synthesized PUs are investigated by X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and tensile test respectively. The crystallinity of PUs with ILs is lower than that of pure PUs. Moreover, we also investigate the effect of ILs on the surface morphology of the PUs., INTRODUCTION As a linear segmented copolymer that consists of hard segments and soft segments, thermoplastic polyurethanes (PUs) have been widely used as an important material for automobile, electrical as well [...]

Published
2016
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98. Analysis of Cantor Multistage Frequency Offset FDA-MIMO Beampattern Performance

Author

Liu, Mingjie, Wang, Chunyang, Gong, Jian, Tan, Ming, Bao, Lei, and Zhou, Changlin

Abstract

Compared with fractal array and frequency diverse array (FDA), the Cantor FDA combines both features. In this article, we analyzed the features of Cantor FDA-multiple-input multiple-output (MIMO) beampattern, it has the properties of multifrequencies; nevertheless, it also has a grating lobe and high sidelobe levels. Then, we proposed a Cantor multistage frequency offset FDA-MIMO to improve the performance. We jointly designed the transmit-receive elements spacing, the multistage frequency offset of the array, and combined sparse constraint. We got the beampattern of no grating lobe and low sidelobe. We also analyzed the ability of interference suppression of it. The simulation results and analysis show that the Cantor multistage frequency offset FDA-MIMO has frequency and frequency offset insensitivity, excellent range-angle beampattern, and antiinterference ability.

Published
2023
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