Woods-Saxon限制势两电子量子点的自旋单态—三重态跃迁(英文)

使用Woods-Saxon限制势,研究了磁场对二维两电子量子点系统的影响,研究方法的优点是在模型位阱中可以通过两个参数改变限制范围。计算是在有效质量近似框架下采用矩阵对角化方法进行,发现了一个基态行为(自旋单态—三重态跃迁)作为磁场强度的函数。此外还发现Woods-Saxon限制垒的位置和斜率对二维两电子量子点系统的基态跃迁和低激发态性质是重要的。

两电子量子环的磁场效应(英文)

使用矩阵对角化方法,研究了磁场中两电子量子环自旋单态和三重态的电学和光学性质,发现磁场强度对两电子量子环的能谱和光吸收有强烈的影响.计算结果显示两电子量子环的光吸收系数可以达到107/m,这个结果要比两电子量子点高一个数量级.通过引入磁场和改变量子环半径可以获得较大的吸收系数.

准一维有机铁磁体中的电荷密度和自旋密度分布

考虑格点间的电子—电子Coulomb排斥及非最近邻电子跳跃相互作用 ,对具有链间耦合的准一维有机铁磁体系统的电荷密度和自旋密度的分布进行了研究。结果表明 ,格点间的电子—电子Coulomb排斥相互作用将导致电荷密度和自旋密度在系统的主链不同格点及侧自由基之间转移 ;两条相邻的链的对应格点间的链间耦合相互作用使电荷密度和自旋密度在主链格点以及侧自由基间发生重新分布的规律相反 ,且在主链格点以及侧自由基间转移的电子均为自旋向下的电子。

Electric-Current-Induced Heat Generation in Kondo Regime

Using the nonequilibrium Green's function technique,we investigate the current induced heat generationin Kondo regime.The Kondo effect influences the heat generation significantly.In the curve of heat generation versusthe bias,a negative differential of the heat generation is exhibited.The symmetry of the heat generation is destroyed bythe strong electron-electron interaction and the electron-phonon interaction.

Singlet-Triplet Transitions of a Poeschl-Teller Quantum Dot

We study the energy spectra of a two-dimensional two-electron quantum dot （QD） with P6schl-Tefler confining potential under the influence of perpendicular homogeneous magnetic field. Calculations are made by using the method of numerical diagonalization of Hamiltonian matrix within the effectlve-mass approximation. A ground-state behavior （spin singlet-triplet transitions） as a function of the strength of a magnetic field is found. We find that the dot radius R of a Poeschl-Teller potential is important for the ground-state transition and the feature of ground-state for a Poeschl Teller QD and a parabolic QD is similar when R is larger. The larger the well depth, the higher the magnetic field for the singlet-triplet transition of the ground-state of two interacting electrons in a Poesehl-Teller QD.

Ultrafast Electron Transfer in All-Small-Molecule Photovoltaic Blends Promoted by Intermolecular Interactions in Cyanided Donors

Cyano substitution has been established as a viable approach to optimize the performance of all-small-molecule organic solar cells.However,the effect of cyano substitution on the dynamics of photo-charge generation remains largely unexplored.Here,we report an ultrafast spectroscopic study showing that electron transfer is markedly promoted by enhanced intermolecular charge-transfer interaction in all-small-molecule blends with cyanided donors.The delocalized excitations,arising from intermolecular interaction in the moiety of cyano-substituted donor,undergo ultrafast electron transfer with a lifetime of∼3 ps in the blend.In contrast,some locally excited states,surviving in the film of donor without cyano substitution,are not actively involved in the charge separation.These findings well explain the performance improvement of devices with cyanided donors,suggesting that manipulating intermolecular interaction is an efficient strategy for device optimization.

Corona Discharge Ion Mobility Spectrometry of Ten Alcohols

Ion mobility spectra for ten alcohols have been studied in an ion mobility spectrometry apparatus equipped with a corona discharge ionization source. Using protonated water cluster ions as the reactant ions and clean air as the drift gas, the alcohols exhibit different product ion characteristic peaks in their ion mobility spectra. The detection limit for these alcohols is at low concentration pmol/L level according to the concentration calibration by exponential dilution method. Based on the measured ion mobilities, several chemical physics parameters of the ion-molecular interaction at atmosphere were obtained, including the ionic collision cross sections, diffusion coefficients, collision rate constants, and the ionic radii under the hard-sphere model approximation.

Persistent Currents and Edge States in a Quasi－One－Dimensional Mesoscopic Ring with a Screened Interaction

The effect ofthe edge state on the persistent current in quasi-1D mesoscopic rings with a screened interactionwhich exists only between nearest-neighboring particles is studied with the Hartree-Fock approximation. The theoreticalvalue of the current magnitude is greatly enhanced by both the edge state and the Coulomb interaction, and pinningthe electrons into a lattice is good for the enhancement if screening happens. In high dimensional systems the screeningeffect can make the interacting range show anisotropy, and create a tendency of gathering for particles with a repulsivepotential.

Surface Structure, Spectroscopic and Photocatalytic Activity Study of Polyaniline/TiO2 Nanocomposites

PANI （polyaniline） as a promising conducting polymer and photosensitizer has been used to prepare PANI/TiO2 （polyaniline/TiO2） nanocomposite as photocatalyst. TiO2 nanoparticles with size of 5-100 nm were encapsulated by PANI via the ＂in situ＂ polymerization of aniline on the surface of TiO2 nanoparticles. IR, SEM, EPR techniques were used to characterize the mechanism of electron interaction in PANI/TiO2 nanocomposite. The resulting PANI-modified TiO2 composites exhibit significantly higher photocatalytic activity than that of neat PANI on degradation of MB （methylen blue） aqueous solution under UV irradiation.

Direct observation of Pt nanocrystal coalescence induced by electron-excitation-enhanced van der Waals interactions

Nanocrystal coalescence has attracted paramount attention in nanostructure fabrication in the past decades. Tremendous endeavor and progress have been made in understanding its mechanisms, benefiting from the development of transmission electron microscopy. However, many mechanisms still remain unclear, especially for nanocrystals that lack a permanent dipole moment standing on a solid substrate. Here, we report an in situ coalescence of Pt nanocrystals on an amorphous carbon substrate induced by electron-excitation- enhanced van der Waals interactions studied by transmission electron microscopy and first principles calculations. It is found that the electron-beam-induced excitation can significantly enhance the van der Waals interaction between Pt nanocrystals and reduce the binding energy between Pt nanocrystals and the carbon substrate, both of which promote the coalescence. This work extends our understanding of the nanocrystal coalescence observed in a transmission electron microscope and sheds light on a potential pathway toward practical electron- beam-controlled nanofabrication.

Comparison of luminescent properties of helicene-like bibenzothiophenes with o-carborane and 5,6-dicarba-nidodecaborane

This article describes comparison of the anchoring effect on electronic properties of the helicene-like bibenzothiophene between o-carborane and 5,6-dicarba-nido-decaborane. The o-carborane and nido-decaborane-fused bibenzothiophenes were simultaneously obtained in the same reaction and successfully isolated. Initially, the X-ray single crystal analysis revealed that the helicene-like distorted structure was realized in the nido-decaborane-fused bibenzothiophene. From optical measurements in the solution state, distinct different characteristics depending on the type of anchors were observed. It was summarized that the absorption and luminescent properties originated from weak π-conjugation at the bibenzothiophene moiety in the o-carboranefused compound were obtained, whereas robust π-conjugation and significant emission from the intramolecular charge transfer state were detected from the nido-decaborane-fused compound. These data can be explained by the theoretical results that π-conjugation was restrictedly developed within the bibenzothiophene moiety in frontier orbitals of the o-carborane-fused compound. In contrast, π-conjugation can be constructed even through the distorted bibenzothiophene because of the nido-decaborane unit. Moreover, the intramolecular charge transfer state should be realized because of electronic interaction involving the nido-decaborane unit in the excited state. Furthermore, it was demonstrated that the nido-decaborane-fused compound possessed solid-state emission and mechanochromic luminescent properties. The π-conjugation on the distorted structure supported by the nido-decaborane anchor should play a significant role in suppressing aggregation-caused quenching followed by presenting solid-state emission with stimuli responsiveness.

The effect of cation size(H^+, Li^+, Na^+, and K^+) on McLafferty-type rearrangement of even-electron ions in mass spectrometry

Protonation and alkali-metal cation adduction are the most important ionization processes in soft-ionization mass spectrometry.Studies on the fragmentation mechanism of protonated and alkali-metal-cationized compounds in tandem mass spectrometry are essential and helpful for structural analysis.In some cases,it was often observed that a compound attached by different alkali-metal cations(or proton)exhibits similar fragmentation patterns but the relative abundances of product ions are different.This difference was considered to derive from the different electrostatic interactions of alkali-metal cations(or the bonded effect of proton)with the analyte.The alkali-metal cation with a smaller ionic radius shows stronger electrostatic interaction with the molecule because of its higher charge density.In addition,the bonded effect of the proton is stronger than the electrostatic interaction of the alkali-metal cation.In the present study,which used McLafferty-type rearrangements of even-electron ions([M+Cat]+,Cat=H,Li,Na,K)as model reactions,the effect of cation size in mass spectrometric fragmentation reactions is highlighted.These considerations were also successfully applied to interpret the similar but distinct fragmentation behavior of proton and alkali-metal cation adducts of a synthetic compound(2-(acetamido(phenyl)methyl)-3-oxobutanoate)and a drug(entecavir).

Optical Conductivity of Graphene Sheet Including Electron-Phonon Interaction

Using an expression of optical conductivity,based on the linear response theory,the Green's function technique and within the Holstein Hamiltonian model,the effect of electron-phonon interaction on the optical conductivity of graphene plane is studied.It is found that the electron-phonon coupling increases the optical conductivity of graphene sheet in the low frequency region due to decreasing quasiparticle weight of electron excitation while the optical conductivity reduces in the high frequency region.The latter is due to role of electrical field's frequency.