Charge Transfer Variability in Misfit Layer Compounds: Comparison of SnS-SnS2 and LaS-TaS2

The present paper compares and discusses two selected misfit (layer) compounds exemplarily, namely SnS-SnS₂ and LaS-TaS₂. We have employed a density-functional theory-based approach to calculate structural, energetic, and electronic properties of these structures. We have put emphasis on the difference between single layers, combined double-layer systems and periodically stacked bulk structures. Especially the varying magnitudes of charge transfer between the sublayers were studied. We demonstrate how the chemical constitution of the sublayers affects the interlayer interactions: these may be a weak non-bonding van-der-Waals dominated interlayer interaction as in SnS-SnS₂ and many other layered structures or a strong interaction related to a remarkable charge transfer between the layers as in LaS-TaS₂.     

Development of Ferromagnetic Superspins in Bare Cu Nanoparticles by Electronic Charge Redistribution

We report on the results of investigating the ferromagnetic properties of bare Cu nanoparticles. Three sets of bare Cu nanoparticle assemblies with mean particle diameters of 6.6, 8.1, and 11.1 nm were fabricated, employing the gas condensation method. Curie-Weiss paramagnetic responses to a weak driving magnetic field were detected, showing the appearance of particle superspins that overcomes the diamagnetic responses from the inner core. The isothermal magnetization displays a Langevin field profile together with magnetic hysteresis appearing even at 300 K, demonstrating the existence of ferromagnetic superspins in the Cu nanoparticles. Shifting of a noticeable amount of electronic charge from being distributed near the lattice sites in bulk form toward their neighboring ions in nanoparticles was found. The extended 3d and 4s band mixture are the main sources for the development of localized 3d holes for the development of ferromagnetic particle superspins in Cu nanoparticles.     

Excited-State Proton Transfer in Bifunctional Compounds

When the acidic and basic groups of an amphoteric compound become stronger on excitation, excited-state proton transfers (ESPT) are driven by the photoinduced synergy between the two functions. This is exemplified here by 7- and 8-hydroxyquinolines (7- and 8-HQ), whatever the initially excited form. For instance, the -OH group of the 7-hydroxyquinolinium form undergoes photoinduced deprotonation even in 8M HClO₄! This reveals its outstanding photoacidity, confirmed by the value of the deprotonation rate constant k₁ at infinite dilution, 5.5 × 10¹⁰ s⁻¹. The decrease of k₁ on increasing the ionic strength pointed out the key number of 4 water molecules as proton acceptors. In neutral medium, a very efficient photoinduced tautomerization is observed. For 7-HQ in water, a mechanism consisting of three competitive paths was established: A proton translocation via a bridge of water molecules within less than 10 ps for the cis-isomer, and two stepwise competitive reactions for the trans-isomer. Concerning the weakly fluorescent 8-HQ, the photoinduced tautomerization occurs even in organic media. In most solvents, an intrinsic ESPT takes place within intramolecularly H-bonded molecules, but preferential solvation by residual water of the solvent may lead to open structures where ESPT is impaired. In alkanes, a biprotonic ESPT is expected to occur within very stable dimers (K_dim= 7.0 × 10⁷). In all cases, the coupling between proton transfers and an intramolecular electron transfer leads to the ketonic structure of the tautomer. This might be a general feature in phototautomerization reactions.     

可逆加成-断裂链转移(RAFT)聚合的研究进展

自可逆加成-断裂链转移自由基聚合技术在1998年发明以来,就逐渐成为聚合研究者的一种非常强大的合成工具,并在研究与应用领域得到很快的发展。文章综述了可逆加成-断裂链转移聚合的RAFT试剂的分类、聚合机理及聚合中的阻滞现象,简要说明了RAFT技术应用的研究进展。     

Charge Transfer at High Excitation Power of Solids

Electron transfer between excited donor molecules followed by the back reaction is treated theoretically for a solid solution at high excitation power. An expression for the average donor cation probability P⁺(t) is derived. Calculations of the time dependence for P⁺(t) are presented. The results indicate that the maximum value of P⁺(t) in the nonlinear quenching process is less than the corresponding values of P⁺(t) for the linear quenching at a low excitation power due to the depletion of the acceptors with time t. The restriction of the reaction volume slows down the charge separation if the back charge transfer takes place.     

分子内电荷转移荧光传感器的研究进展

荧光传感器提供了方便,快捷,廉价的分析检测重金属离子的方法,并且有很高的灵敏度和选择性.它在环境科学,分析化学以及生命科学等领域有着广泛的应用前景.综述了分子内电荷转移(intramolecular charge transfer)荧光传感器的最新研究进展,并展望了该领域的发展趋势.     

荷移-紫外分光光度法测定硫酸庆大霉素含量

利用硫酸庆大霉素与四氯苯醌在水溶液中发生电荷转移反应,建立了简单快速测定硫酸庆大霉素含量的荷移紫外分光光度法。荷移络合物在波长342 nm处有最大吸收,该荷移衍生物的吸光度与硫酸庆大霉素浓度在0.1~3 mg/m 范围内吸光度和浓度呈现良好线性关系y=0.1652x+0.3054,R~2=0.9996,平均加样回收率为100.81%,RSD为2.55%。该方法简便、准确、重现性好,适用于硫酸庆大霉素的快速测定。     

氮杂开链冠醚类似物

从分类,合成及应用等方面概述了近年来氮杂冠醚及其类假物的研究进展。     

线性聚能装药切割岩石的数值模拟

运用改进的MOCL程序,数值模拟了线性聚能装药金属射流的形成以及射流侵彻岩石的全过程,得到了锥角为60°的聚能装药结构爆轰产物膨胀、药型罩变形、射流形成过程及锥角为60°和90°时的射流速度梯变分布。不同时刻射流的分布显示,在拉伸过程中,锥角为60°的聚能射流速度变小,速度梯度较大,头部速度为4500m·s-1;锥角为90°的聚能射流,头部速度为3500m·s-1速度梯度较小,与实际物理过程相一致。结果表明,模拟结果基本符合聚能射流的物理现象和规律,说明采用的物理模型和数值算法是合理的。     

可逆加成—断裂链转移自由基聚合研究

可逆加成-断裂链转移(Reversible addition-fragmentation chain transfer,RAFT)自由基聚合是最近发展起来的一种活性可控自由基聚合技术。该技术对聚合调控效果好、聚合条件相对温和、适用单体范围广等优点而备受关注,已成为一种有效的聚合物分子设计手段,文章介绍了RAFT聚合的机理、优点及应用。     

Adsorption Isotherms for Intermediates Formed in Charge Transfer Processes

The adsorption of phenol in the form of phenoxy radicals on the surface of a bright Pt electrode is discussed. Two main features of the adsorption isotherm are brought out. The fractional coverage Θ changes suddenly at a characteristic potential, in a manner reminiscent of two dimensional phase formation. This is attributed to the existence of an isotherm with strong lateral attraction interaction forces. The corresponding two-dimensional equation of state resembles qualitatively the Van der Waals equation of state at temperatures below the critical temperature. For the potential dependence of adsorption a new type of isotherm is used which combines the effects of potential on charge-transfer equilibrium and on the solvent-solute replacement equilibrium on the surface of the electrode. The resulting function, describing the variation of Θ with E fits the observed inhibition effects of phenol on the rate of oxidation of Γ, and should also be taken into consideration in deriving Tafel slopes for different mechanisms.     

Charge Transfer to Metal Nanoparticles Bouncing from Conductive Surfaces

The charging behavior of metal nanoparticles bouncing from conductive surfaces was investigated in a single-stage-low-pressure-impactor. Ag and Pt particles of a fixed particle size between 20 nm and 100 nm were impacted on targets of bulk Au and Pt, respectively, and the resulting contact charge was measured as a function of impact velocity. The influence of target hardness was revealed by the comparison to measurements with soft nanostructured layers obtained by direct current sputtering of Au and Pt on mica discs. From the dataset, regions of elastic, elastoplastic, and fully plastic particle deformation were identified, and the size-dependent effective yield stress for the respective particle materials was calculated. The influence of electron back-tunneling in the separation phase of the collision on the effective contact charge is discussed.

Copyright 2014 American Association for Aerosol Research     

Intramolecular Charge Transfer Luminescence of a donorethylsubstituted pyridinium ion

The dimethoxyphenyl-ethyl-substituted pyridinium ion 1 shows a long-wave absorption and fluorescence, which are attributed to an intramolecular electron donor-acceptor complex. In contrast to electrically neutral complexes the fluorescence quantum yield of 1 in polar solvents is comparatively high and the radiative decay time is rather small. The excited complex can also be generated by electrochemical methods.     

Reversible Charge Transfer in Liquids at High Excitation Power

We discuss the influence of high excitation power on reversible charge transfer kinetics. The kinetics depends on the excited donor concentration, on the parameters of the rate constants, and on the boundary conditions for the Smoluchowski equation in liquids. The nonlinear effects of the excitation power are determined by the geometry of molecular spectra of emission and absorption. They disappear with the acceptor concentration, with the decrease in the forward rate constant. The role of Coulomb interaction of ions increases with increase of diffusion constant. Nonlinear effects for our theory of reversible charge transfer in liquids are compared with those of Dorfman and coworkers (J. Chem. Phys. 1989 , 90, 159). The difference of the effects between the two theories vanishes when the probability of the donor's excited state approaches unity.     

Energy and Charge Transfer Dynamics in Doped Semiconductor Nanocrystals

Doping semiconductor nanocrystals with transition metal ions introduces new optical, electronic, and magnetic properties to the host semiconductor nanocrystals. The energy transfer and charge transfer between exciton and dopant ions are the key photophysical processes responsible for the unique properties of doped semiconductor nanocrystals, which are distinct from their undoped counterparts. Since the energy transfer and charge transfer processes between exciton and dopant ions compete with the usual relaxation pathways of the exciton, competition among different dynamic processes ultimately determines the photophysical properties of doped nanocrystals. In this review, we discuss the dependence of the dynamics of the energy transfer and charge transfer processes in Mn-doped II-VI semiconductor nanocrystals on the structure of the host nanocrystal, spatial distribution of the dopant ions within the nanocrystal, and charge carrier-trapping molecules near the surface of the nanocrystals.     

长钢轨整体铺换车的研制和应用

长钢轨铺换车（简称换轨车）是长钢轨更换的主要设备,我段从1984年以来,就开始采用分体式换轨车更换长钢轨,为我局铺设无缝线路发挥了重要的作用。但是,分体式换轨车上下拖车,辅助时间较长,影响换轨进度;而且轨条在穿入龙口装置时,用压机顶起轨头,容易碰伤人员;特别是随着更换轨型的逐级增大和淬火轨的出现,在小半径曲线地段上换轨,由于车体自重小,容易掉道,起复难度很大。为此,研制新型的换轨车,改进技术性能,迫切需要。笔者针对分体式换轨车存在的问题,提出了相应的对策,构思出几种新型的换轨车方案,分析各自的优缺点,进行相互的比较,从中选择了桁架式整体换轨车方案进行设计与研制,通过实际应用,取得了良好的效果。     

Charge and Mass Transfer Across the Metal/Solution Interface

Electrode reactions are characterized by charge transfer across the interface. The charge can be carried by electrons or by ions. It is shown here that when both mass and charge cross the interface, the charge must be carried by the ionic species, not by the electrons, as a result of the very large difference in the time scale for electron and ion transfer. A prime example of charge transfer by ions is metal deposition. It is proposed that ion transfer occurs by migration of the ions across the interface, under the influence of the high electrostatic field in the double layer. The rate constants observed for metal deposition are comparable to those for outer-sphere charge transfer. These unexpectedly high rate constants for metal deposition are explained by a model in which removal of the solvation shell and reduction of the effective charge on the metal ion occur in many small steps, and a make-before-break mechanism exists, which lowers the total Gibbs energy of the system as it moves along the reaction coordinate from the initial to the final state.     

分光光度法测定富马酸比索洛尔

基于药物和显色剂之间荷移反应,建立了一种对富马酸比索洛尔含量检测的分光光度法。在水介质中,富马酸比索洛尔与茜素红在室温中放置15min后形成1∶1型荷移配合物,其λmax为535nm,表观摩尔吸光系数为6.76×103L/(mol·cm),线性范围为10¹00mg/L,线性回归方程为A=0.085+0.00712c,相关系数r=0.99904,相对标准偏差RSD为0.44%(n=6)。将该方法用于富马酸比索洛尔片含量的测定,回收率为在98.3%100mg/L,线性回归方程为A=0.085+0.00712c,相关系数r=0.99904,相对标准偏差RSD为0.44%(n=6)。将该方法用于富马酸比索洛尔片含量的测定,回收率为在98.3%¹02.6%之间。