排序方式: 共有38条查询结果,搜索用时 15 毫秒
21.
Wenhuan Huang Dr. Biao Chen Prof. Dr. Guoqing Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12497-12501
N-Substituted naphthalimides (NNIs) have been shown to exhibit highly efficient and persistent room-temperature phosphorescence from an NNI-localized triplet excited state, when the N-substitution is a sufficiently strong donor and mediates an intramolecular charge-transfer (ICT) state upon photo-excitation. This work shows that, when the electron-donating ability of the N-substitution is further increased in the presence of a carbanion or phenoxide, spontaneous electron transfer (ET) occurs and results in radical anions, verified with electron-paramagnetic resonance (EPR) spectroscopy. However, the EPR-active anion is surprisingly persistent and impervious to nucleophilic and radical reactions under anionic conditions. The stability is thought to originate from an intramolecular spin pairing between the N-donor and the NI acceptor post ET, which is demonstrated in supramolecular chemistry. 相似文献
22.
Shen Wu Aizhi Sun Wenhuan Xu Qian Zhang Fuqiang Zhai Philip Logan Alex A. Volinsky 《Journal of magnetism and magnetic materials》2012
This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn–Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20 nm, were obtained via the sol–gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn–Zn ferrites. Mn–Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn–Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10 kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn–Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400 °C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability. 相似文献
23.
Yang Yuhao Huang Wenhuan 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(5):968-975
Russian Journal of Physical Chemistry A - TiO2-graphene (P25-GR, PG) nanocomposite was fabricated from P25 titania and graphite oxide by hydrothermal method, and then Cu nanoparticles (Cu NPs) were... 相似文献
24.
Biao Chen Wenhuan Huang Hao Su Hui Miao Xuepeng Zhang Guoqing Zhang 《Angewandte Chemie (International ed. in English)》2020,59(25):10023-10026
Organic luminogens with persistent room‐temperature phosphorescence (RTP) have found a wide range of applications. However, many RTP luminogens are prone to severe quenching in the crystalline state. Herein, we report a strategy to construct a donor‐sp3‐acceptor type luminogen that exhibits aggregation‐induced emission (AIE) while the donor‐sp2‐acceptor counterpart structure exhibits a non‐emissive solid state. Unexpectedly, it was discovered that a trace amount (0.01 %) of the structurally similar derivative, produced by a side reaction with the DMF solvent, could induce strong RTP with an absolute RTP yield up to 25.4 % and a lifetime of 48 ms, although the substance does not show RTP by itself. Single‐crystal XRD‐based calculations suggest that n–σ* orbital interactions as a result of structural similarity may be responsible for the strong RTP in the bicomponent system. This study provides a new insight into the design of multi‐component, solid‐state RTP materials from organic molecular systems. 相似文献
25.
浮选-原子吸收光谱法的研究 总被引:2,自引:0,他引:2
本文研究了浮选技术与原子吸收光谱测定相结合的新方法,灵敏度高、选择性好可连续测定多种痕量元素,操作简便快速。建立了M-SCN-RB、M-I-MB、M-I-MV、M-Br-RB萃取浮选和M-SCN-CPC泡沫浮选体系,直接用火焰原子吸收法测定。研究了金属离子在上述各体系中的浮选行为和分析特性,讨论了测定灵敏度,选择性和竞争浮选的问题。已用于测定水中ppb级Cd、Ag、Au、Pb、Cu、Bi和矿物中Au、Ag、Cd、Pb、Cu、Bi,分析结果与标准值相吻合。 相似文献
26.
锂硒电池是一种非常有潜力的下一代高能量密度电池,具有理论体积能量密度大(3253 mAh·cm-3)、电导率高(1×10-3 S·m-1)、环境友好等优良特性,已经逐渐成为电化学领域的一个研究热点。然而,目前锂硒电池仍面临活性材料利用率低、库仑效率低、容量衰减快以及多硒化物中间体穿梭等诸多问题。针对这些问题,国内外研究人员进行了大量的探索,例如,在正极处采用多种碳材料、金属化合物、硒合金等进行封装改性;在负极处采用固体电解质界面方法进行保护。本文全面综述了锂硒电池在正极、负极、电解质、隔膜、黏结剂、集流体等方面取得的最新研究进展,特别是在纳米硒的封装、固体电解质保护层的制备、新型多功能隔膜的研究、多种黏结剂和集流体的应用等方面进行了重点总结。最后,对锂硒电池的未来发展前景和商业化应用进行了展望。 相似文献
27.
Xiancheng Nie Hao Su Xiaoyu Chen Wenhuan Huang Linkun Huang Dr. Biao Chen Dr. Hui Miao Prof. Dr. Jun Jiang Dr. Tao Wang Prof. Dr. Guoqing Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(56):12743-12746
A new strategy was devised for estimating and screening pKa values among different carbon acids under ambient conditions by using the UV/Vis absorption spectrum of persistent radical pairs (PRPs), which are generated from an N-substituted naphthalimide (NNI) derivative in the presence of various carbanions in organic solutions. The electron paramagnetic resonance (EPR) spectroscopy was used to examine the presence of radicals. Unexpectedly, it was discovered that the UV/Vis spectrum of PRPs reveals a distinct linear relationship between the PRP absorption and the pKa value of a corresponding carbon acid, which is likely due to the energy difference among different RPRs. The finding may offer organic chemists an alternative reference to conduct carbanion-mediated reactions in various organic solutions. 相似文献
28.
Wenhuan Yu Fengling Zhang Weisong Xie 《Journal of Mathematical Analysis and Applications》2003,279(1):78-96
In this paper we discuss some continuous dependency between a C0-semigroup and its parameter. We first get the following results: if the infinitesimal generator of a C0-semigroup is continuous in the generalized sense, strongly (or weakly) Fréchet continuously differentiable, or strongly (or weakly) Gâteaux continuously differentiable with respect to the parameter, respectively, so is the corresponding C0-semigroup. We then obtain corresponding expressions for the differential operators. Finally, the obtained results are applied to a mixed initial-boundary value problem of a semi-linear parabolic equation, and it is proved that the solution of the equation is Fréchet continuously differentiable with respect to the leading variable coefficient of the equation. 相似文献
29.
溴金酸-罗丹明B和氯金酸-罗丹明6G超高灵敏显色反应的研究——离心光度法测定金 总被引:3,自引:0,他引:3
本文研究了一个超高灵敏的测定金的方法,离心光度法。在Au-Br-RB体系中络合物λ_(max)=559nm,表观摩尔吸光系数ε_(559)=3.39×10~(11)L·mol~(-1)·cm~(-1),Au(Ⅲ)浓度(0.20×10~(-5)~2.5×10~(-5)μg/10 ml呈线性关系;Au-Cl-R6G体系络合物λ_(max)=531 nm,表观摩尔吸光系数ε_(531)=2.52×10~8L·mol~(-1)·cm~(-1),Au(Ⅲ)浓度(0.20×10~(-2)~2.4×10μg/10ml。呈线性(Ⅲ)关系。本法已用于某些低品位矿样中金的分析,分析结果与标准值相吻合。探讨了超高灵敏的显色反应机理。 相似文献
30.
本文用具紧支集的尺度函数之张量乘积构成人工神经网络的基函数,再由这个小波神经网络辨识静态与动态的离散线性系统,并且证明了依所给的方法产生的模型是收敛的.最后,用一个仿真例子,说明如何实现算法及算法的效果. 相似文献