Reactivity and Lability Modulated by a Valence Electron Moving in and out of 25-Atom Gold Nanoclusters

The emergence of atomically precise metal nanoclusters with unique electronic structures provides access to currently inaccessible catalytic challenges at the single-electron level. We investigate the catalytic behavior of gold Au₂₅(SR)₁₈ nanoclusters by monitoring an incoming and outgoing free valence electron of Au 6s¹. Distinct performances are revealed: Au₂₅(SR)₁₈⁻ is generated upon donation of an electron to neutral Au₂₅(SR)₁₈⁰ and this is associated with a loss in reactivity, whereas Au₂₅(SR)₁₈⁺ is generated from dislodgment of an electron from neutral Au₂₅(SR)₁₈⁰ with a loss in stability. The reactivity diversity of the three Au₂₅(SR)₁₈ clusters stems from different affinities with reactants and the extent of intramolecular charge migration during the reactions, which are closely associated with the valence occupancies of the clusters varied by one electron. The stability difference in the three clusters is attributed to their different equilibria, which are established between the AuSR dissociation and polymerization influenced by one electron.     

一种新型平板彩色显示器件的制备和光谱分析

以MEH-PPV(聚[2-甲氧基-5-(2′-乙基己氧基-对苯乙烯)])和Alq₃作为发光层, 成功制备出ITO/SiO₂/MEH-PPV/SiO₂/Al结构和ITO/SiO₂/Alq₃ /SiO₂/Al结构的固态阴极射线器件。通过分析SSCL光谱,认为这些高速电子激发有机材料后形成Frenkel激子。当器件两个电极之间加的电压比较低时,有机薄膜层的场强也比较低,这些激子被解离的概率很小,从而产生的是激子发光的长波发射;当器件两个电极之间加的电压比较高时,有机薄膜层的场强很高, 在有机层形成的激子大部分被解离, 解离后的电子直接跃迁至LUMO(lowest unoccupancied molecular orbit),这些电子弛豫后从LUMO能级到HOMO(highest occupancied molecular orbit )能级直接辐射跃迁, 接着重新复合发光,从而产生短波发射。制作的固态阴极射线器件可以实现全色发光, 提高发光效率和加强蓝光发射。作者可以预期所研制出的这种SSCL器件必将引发平板显示领域一场新的革命性变革。     

双荧光层靶Kα线强度比诊断靶内超热电子温度

 利用双荧光层复合靶产生的Kα特征线强度比诊断了靶内超热电子的温度,即通过实验测量复合靶中两种不同材料荧光层辐射出的Kα特征线强度比,结合ITS3.0程序模拟结果,对超热电子温度进行诊断。将诊断结果与实验中利用电子磁谱仪测量的超热电子温度进行了比较,二者基本一致。结果表明,选取适当的荧光层靶厚,可以利用双荧光层复合靶产生的Kα特征线强度比对靶内的超热电子温度进行诊断。     

The location of excess electrons on H2O/TiO2(110) surface and its role in the surface reactions

Excess electrons play a key role in many of the properties of Titanium dioxide (TiO₂). Understanding their behaviour is important for improving the performance of TiO₂ in energy-related applications. Here, we describe a DFT + U study of the locations of the unpaired electron (UPE) on rutile TiO₂(110) (R-TiO₂(110)) surface and H₂O/R-TiO₂(110) surface. Our results show that the subsurface are preferred with R-TiO₂(110) surface. In contrast to previous studies, we find that the UPE tends to migrate to the surface H₂O-Ti_5c (the five-coordinated titanium (Ti_5c) at surface with H₂O adsorption) with the increasing of H₂O coverage and UPE concentration. In addition, we have shown that the UPE plays an important role in the O-H bond dissociation and other important elementary reactions in photo-catalytic H₂O dissociation on R-TiO₂(110) such as H, OH and H₂ desorption. Specifically, it enhances the O-H bond dissociation, as well as H and H₂ desorption from bridging hydroxyl and Ti_5c-OH (the Ti_5c with OH adsorption), but hinders the OH and H desorption from Ti_5c. We believe our results afford a further understanding of the adsorbent dependent UPE migration, and the role of UPE in the surface reactions.     

Dynamics of One‐Dimensional Electrons With Broken Spin–Charge Separation

Spin–charge separation is known to be broken in many physically interesting one‐dimensional (1D) and quasi‐1D systems with spin–orbit interaction because of which spin and charge degrees of freedom are mixed in collective excitations. Mixed spin–charge modes carry an electric charge and therefore can be investigated by electrical means. We explore this possibility by studying the dynamic conductance of a 1D electron system with image‐potential‐induced spin–orbit interaction. The real part of the admittance reveals an oscillatory behavior versus frequency that reflects the collective excitation resonances for both modes at their respective transit frequencies. By analyzing the frequency dependence of the conductance the mode velocities can be found and their spin–charge structure can be determined quantitatively.     

Permutation complexity via duality between values and orderings

We study the permutation complexity of finite-state stationary stochastic processes based on a duality between values and orderings between values. First, we establish a duality between the set of all words of a fixed length and the set of all permutations of the same length. Second, on this basis, we give an elementary alternative proof of the equality between the permutation entropy rate and the entropy rate for a finite-state stationary stochastic processes first proved in [J.M. Amigó, M.B. Kennel, L. Kocarev, The permutation entropy rate equals the metric entropy rate for ergodic information sources and ergodic dynamical systems, Physica D 210 (2005) 77-95]. Third, we show that further information on the relationship between the structure of values and the structure of orderings for finite-state stationary stochastic processes beyond the entropy rate can be obtained from the established duality. In particular, we prove that the permutation excess entropy is equal to the excess entropy, which is a measure of global correlation present in a stationary stochastic process, for finite-state stationary ergodic Markov processes.