基于石墨烯/石墨烯卷轴复合薄膜高灵敏度柔性压力传感器

一维导电材料例如纳米线，大量应用于柔性压力传感器中. 但是一维材料和基底之间接触时相互作用力较弱，使得传感器灵敏度、响应时间、和循环寿命等性能指标有待进一步提高. 针对这些问题，设计了石墨烯/石墨烯卷轴多分子层复合薄膜作为传感器导电层. 石墨烯卷轴具有一维结构，而石墨烯的二维结构可以牢固地固定卷轴，以确保高导电性复合薄膜与基底之间的粘附性，同时整体结构的导电通道得到了增加. 由于一维和二维结构的协同效应，实现了应变灵敏度系数3.5 kPa^-1、 响应时间小于50 ms、能够稳定工作1000次以上的压阻传感器.     

Vacancy‐Rich Ni(OH)2 Drives the Electrooxidation of Amino C−N Bonds to Nitrile C≡N Bonds

Electrochemical synthesis based on electrons as reagents provides a broad prospect for commodity chemical manufacturing. A direct one‐step route for the electrooxidation of amino C?N bonds to nitrile C≡N bonds offers an alternative pathway for nitrile production. However, this route has not been fully explored with respect to either the chemical bond reforming process or the performance optimization. Proposed here is a model of vacancy‐rich Ni(OH)₂ atomic layers for studying the performance relationship with respect to structure. Theoretical calculations show the vacancy‐induced local electropositive sites chemisorb the N atom with a lone pair of electrons and then attack the corresponding N(sp³)?H, thus accelerating amino C?N bond activation for dehydrogenation directly into the C≡N bond. Vacancy‐rich nanosheets exhibit up to 96.5 % propionitrile selectivity at a moderate potential of 1.38 V. These findings can lead to a new pathway for facilitating catalytic reactions in the chemicals industry.     

高温超导无绝缘线圈励磁电压特性研究

本文通过实验研究了焊锡浸渍、励磁电流PI控制、励磁速率以及励磁幅值对高温超导无绝缘线圈励磁电压特性的影响。实验结果表明:高温超导无绝缘线圈励磁电压具有时延特性,焊锡浸渍、励磁电流PI控制分别会增大和减小时延特性,而励磁速率和励磁幅值不会影响时延特性;励磁电压幅值随励磁速率增大而增大;焊锡浸渍可降低励磁电压幅值,而励磁电流控制对励磁电压幅值影响不明显。     

1.3 GHz超导腔磁通排出效应研究

设计并搭建了一套高精度的磁场测量和补偿系统,并结合中国科学院高能物理研究所(IHEP)的2K超导腔垂直测试平台对1.3 GHz单加速间隙超导腔的磁通排出效应开展了实验研究:利用研制的磁场测量和补偿系统能够精密地测量超导腔赤道位置磁场,并能够将磁场补偿至小于5.0×10-8 T;并对超导腔不同表面温度梯度下的磁通排出效应进行了测量分析;对钉扎了磁场的超导腔进行了射频性能测试,研究了超导腔电阻对磁通钉扎的敏感度,以及在不同电场梯度下超导腔的表面电阻变化情况。结果表明,研制的高精度磁场测量和补偿系统能够满足超导腔磁通排出研究的需求;高的超导腔表面温度梯度有利于磁通的排出;磁通钉扎电阻的敏感度随着加速电场梯度的增加而增大,导致超导腔的性能下降。此实验研究也为后续超导腔的研制奠定了一定基础。     

On limiting behavior of stationary measures for stochastic evolution systems with small noise intensity

The limiting behavior of stochastic evolution processes with small noise intensity ε is investigated in distribution-based approaches.Let μ~ε be a stationary measure for stochastic process X~ε with small ε and X~0 be a semiflow on a Polish space.Assume that {μ~ε:0 ε≤ε_0} is tight.Then all their limits in the weak sense are X~0-invariant and their supports are contained in the Birkhoff center of X~0.Applications are made to various stochastic evolution systems,including stochastic ordinary differential equations,stochastic partial differential equations,and stochastic functional differential equations driven by Brownian motion or Levy processes.     

Sensitive and selective determination of 4-nitrophenol in water and food using modified polyethyleneimine-capped carbon dots

Hazardous 4-nitrophenol (4-NP) has created serious threats to humans and the environment; therefore, it is highly desirable to develop a facile and practical method for the monitoring of 4-NP in environment and food. Here, a fluorescence method based on modified polyethyleneimine-capped carbon dots (mPEI-CDs) was developed for sensitive and selective determination of 4-NP in water, fruit, and vegetable samples. First, highly fluorescent mPEI-CDs (quantum yield about 40.3%) were easily synthesized via a one-step hydrothermal method by using novel acetic anhydride modified polyethyleneimine (mPEI) and citric acid as precursors. Compared to the unmodified PEI-CDs, the acetic anhydride mPEI-CDs exhibited excellent fluorescent stability in a wider pH range of 4.0–9.0. Under pH 8.0, a selective determination of 4-NP was achieved based on the inner filter effect (IFE) mechanism. After optimization, good linear relationships between fluorescence intensity function (F₀-F)/F₀ and the concentration of 4-NP were obtained in ranges of 0.5–10 and 10–100 μM, respectively, while efficiently avoiding the interferences from two other nitrophenol isomers, possible coexisting metal cations and anions in samples. Finally, the proposed approach was successfully applied for the determination of 4-NP in water, honey, strawberry, and tomato samples.     

Sulfonated poly(ether ether ketone) composite membranes based on amino-modified halloysite nanotubes that effectively immobilize phosphotungstic acid

In this work, we prepared amino-modified halloysite nanotubes (PEI-DHNTs) via the co-deposition of self-polymerized dopamine and polyethylenimine (PEI) on the surface of nanotubes, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). A series of composite proton exchange membranes (PEMs) were prepared by incorporating PEI-DHNTs and phosphotungstic acid (HPW) into sulfonated poly(ether ether ketone) (SPEEK). It was found that both PEI-DHNTs and HPW were well dispersed in the polymer matrix, exhibiting excellent filler-matrix compatibility. The composite membranes demonstrated enhanced proton conductivity, reaching as high as 0.078 S cm⁻¹ with 33.3 wt.% HPW loading, which was ~90% higher than that of SPEEK control membrane. Such improvement was mainly attributed to the strong acid–base pairs formed by PEI-DHNT with both SPEEK and HPW, which shortened proton hopping distance and created more continuous proton conduction pathways. Furthermore, the membrane conductivity remained almost constant after 1 year's immersion in liquid water, indicating the successful immobilization of HPW in the composite membranes.     

Electron-donating methoxy group enhances the stability and efficiency of indole-based fluorescent probe for detecting Cu2+

Research on Chemical Intermediates - Two novel Schiff-base fluorescent probes bearing different substituents were synthesized by the reaction of indole derivatives with 4-aminoantipyrine. The...     

Bromine-Functionalized Covalent Organic Frameworks for Efficient Triboelectric Nanogenerator

Covalent organic frameworks (COFs) enable precise integration of various organic building blocks into porous skeletons through topology predesign. Here, we report the first example of COFs by integrating electron withdrawing bromine group onto the skeletons for triboelectric nanogenerators (TENG). The resulting framework exhibits high surface area and good crystallinity. Thus, the bromine functionalized COF has more regular aligned π columns and arrays over the skeleton than bare COFs, which in turn significantly enhances charge transport ability. As a result, bromine functionalized COFs showed higher electrical output performance at 5 Hz with a peak value of short circuit current density of 43.6 μA and output voltage of 416 V, which is 2 and 1.3 times higher than those of bare COFs (21.6 μA and 318 V), respectively. These results demonstrated that this strategy for engineering electron withdrawing groups on the skeleton could open a new aspect of COFs for developing TENG devices.