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Due to the anisotropy of the conductivity in AsF5-intercalated HOPG, eddy current methods have to be used for the measurement of transport effects. The measurements yield carrier concentration, mobility and charge transfer for C8nAsF5 with n=l-4 at temperatures between 4.2K and 300K. 相似文献
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P. M. Bhujbal 《辐射效应与固体损伤》2013,168(6):428-435
The lyoluminescence (LL), thermoluminescence and mechanoluminescence (ML) of a γ -ray-irradiated powder of NaCl:Dy (0.05–0.5 mol%) phosphor are reported in this paper. The nature of intensity variation of the respective luminescence spectra with different γ -ray doses and with different concentrations of Dy3+ doped in NaCl are found to be similar. The LL and ML intensities differed from each other, but their nature is found to be similar in a sublinear form up to a high dose (5.0 kGy) of γ -rays. Thus, the prepared phosphor may be useful for accidental radiation dosimetry up to a high dose (5.0 kGy) of γ -rays using the LL and ML techniques. 相似文献
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Qianxi Dang Lanzhen Hu Jiaqiang Wang Qunhua Zhang Mengmeng Han Simeng Luo Yanbin Gong Can Wang Prof. Qianqian Li Prof. Zhen Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(28):7031-7037
Organic luminescence with different forms continues to be one of the most active research fields in science and technology. Herein, an ultra-simple organic molecule (TPA-B), which exhibits both mechanoluminescence (ML) and photo-induced room-temperature phosphorescence (RTP) in the crystalline state, provides an opportunity to reveal the internal mechanism of ML and the dynamic process of photo-induced RTP in the same molecule. Through the detailed investigation of photophysical properties together with crystal structures, the key role of molecular packing and intermolecular interactions was highlighted in the luminescence response by mechanical and light stimulus, affording efficient strategies to design potential smart functional materials with multiple luminescence properties. 相似文献
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Transient and Persistent Room‐Temperature Mechanoluminescence from a White‐Light‐Emitting AIEgen with Tricolor Emission Switching Triggered by Light 下载免费PDF全文
Jian‐An Li Jinghong Zhou Dr. Zhu Mao Dr. Zongliang Xie Dr. Zhan Yang Prof. Bingjia Xu Prof. Cong Liu Xin Chen Dingyang Ren Hui Pan Prof. Guang Shi Prof. Yi Zhang Prof. Zhenguo Chi 《Angewandte Chemie (International ed. in English)》2018,57(22):6449-6453
Persistent luminescence from purely organic materials is basically triggered by light and electricity, which largely confines its practical applications. A purely organic AIEgen exhibits not only persistent photoluminescence, but also transient and persistent room‐temperature mechanoluminescence. By simply turning on and off a UV lamp, tricolor emission switching between blue, white, and yellow was achieved. The data from single‐crystal structure analysis and theoretical calculation suggest that mechanism of the observed persistent mechanoluminescence (pML) is correlated with the strong spin–orbit coupling of the bromine atom, as well as the formation of H‐aggregates and restriction of intramolecular motions in noncentrosymmetric crystal structure. These results outline a fundamental principle for the development of new pML materials, providing an important step forward in expanding the application scope of persistent luminescence. 相似文献
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The alkaline-earth fluorohalide crystals MFX, where M=Ca, Sr, Ba, Pb and X=Cl, Br, I, form an important class of materials crystallizing in the PbFCl-type tetragonal structure which is also called the matlockite structure. These compounds have long been of interest because of the various defect species which can be detected by spin resonance and associated techniques. The crystals were prepared by slow cooling of the melt of a stoichiometric mixture of BaF 2 and the corresponding chloride or bromide under 0.2 bar of ultrapure argon (5N5), often slightly fluorinated. We have studied the mechanoluminescence (ML) of BaFBr:Sm 2+ and BaFCl:Sm 2+ crystals. It is seen that after the impact of a moving piston, initially the ML intensity increases with time, attains a maximum value and then it decreases with time up to a particular minimum value, and then it increases again, attaining a peak value and finally disappears. The first peak lies in the deformation region and the second peak lies in the post-deformation region. The ML intensity of the BaFCl:Sm 2+ crystal is much higher than the ML intensity of the BaFBr:Sm 2+ crystal. For different impact velocities, the ML intensity increases with velocity; and the total ML intensity attains a saturation value for higher impact velocities. The total ML intensity increases with the increase in the applied load. It is suggested that the moving dislocation produced during deformation of crystals captures holes from hole-trapped centers (like H centers), and the subsequent radiative recombination of the dislocation holes with electron gives rise to ML. Thermoluminescence (TL) of BaFBr:Sm 2+ and BaFCl:Sm 2+ crystals was studied after exposure to ultraviolet rays with the help of a TLD reader. The peak of TL for the BaFBr:Sm 2+ crystal is found at ~247°C and for BaFCl:Sm 2+ crystals at 283°C. The TL intensity initially increases with increase in the UV radiation and then it attains saturation for higher values of UV exposure. The absorption spectrum was recorded with the help of a UV–visible spectrophotometer (Shimadzu). The band found at 275 nm was attributed to H centers. 相似文献
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B. P. Chandra R. K. Goutam V. K. Chandra D. S. Raghuwanshi A. K. Luka R. N. Baghel 《辐射效应与固体损伤》2013,168(12):907-919
Mechanoluminescence (ML) emission from coloured alkali halide crystals takes place during their elastic and plastic deformation. The ML emission during the elastic deformation occurs due to the mechanical interaction between dislocation segments and F-centres, and the ML emission during the plastic deformation takes place due to the mechanical interaction between the moving dislocations and F-centres. In the elastic region, the ML intensity increases linearly with the strain or deformation time, and in this case, the saturation region could not be observed because of the beginning of the plastic deformation before the start of the saturation in the ML intensity. In the plastic region, initially the ML intensity also increases linearly with the strain or deformation time, and later on, it attains a saturation value for large deformation. When the deformation is stopped, initially the ML intensity decreases at a fast rate; later on, it decreases at a slow rate. The decay time for the fast decrease of the ML intensity gives the relaxation time of dislocation segments or pinning time of the dislocations, and the decay time of the slow decrease of the ML intensity gives the diffusion time of holes in the crystals. The saturation value of the ML intensity increases linearly with the strain rate and also with the density of F-centres in the crystals. Initially, the saturation value of the ML intensity increases with increasing temperature, and for higher temperatures the ML intensity decreases with increasing temperature. Therefore, the ML intensity is optimum for a particular temperature of the crystals. From the ML measurements, the relaxation time of dislocation segments, pinning time of dislocations, diffusion time of holes and the energy gap between the bottom of the acceptor dislocation band and interacting F-centre level can be determined. Expressions derived for the ML induced by elastic and plastic deformation of coloured alkali halide crystals at fixed strain rates indicates that the ML intensity depends on the strain, strain rate, density of colour centres, size of crystals, temperature, luminescence efficiency, etc. A good agreement is found between the theoretical and experimental results. 相似文献
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Jie Yang Zichun Ren Zongliang Xie Yingjie Liu Can Wang Yujun Xie Prof. Qian Peng Prof. Bin Xu Prof. Wenjing Tian Prof. Fan Zhang Prof. Zhenguo Chi Prof. Qianqian Li Prof. Zhen Li 《Angewandte Chemie (International ed. in English)》2017,56(3):880-884
We report the first example of an AIEgen (DPP-BO) with fluorescence–phosphorescence dual emission under mechanical stimulation. By carefully analyzing the crystal structure of DPP-BO, the efficient intermolecular and intramolecular interactions should account for its unique mechanoluminescence (ML) properties, especially the abnormal phosphorescence, as further confirmed by controlled experiments and theoretical calculations for the presence of ISC transitions. These results provide important information for understanding the complex ML process, possibly opening up a new way to study the inherent mechanism of ML by broadening the application of AIEgens. 相似文献
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有机光电功能材料的宏观性质是分子聚集效应的客观体现,本文以力致发光和有机室温磷光为例,探讨了分子聚集态结构的影响因素和精细调控策略,并介绍了"MUSIC"的理念,以音乐创作形象化材料设计,强调了分子聚集态科学研究的重要性。 相似文献