咖啡酸分子表面增强拉曼光谱的理论与实验研究

咖啡酸（CA）是一种具有很高的医学价值的药物成分,在抗菌抗病毒方面应用广泛,尤其是咖啡酸及其衍生物在抗肿瘤方面有着巨大作用,现在对咖啡酸的相关研究越来越多,但大部分都是关于咖啡酸医学性质的研究,所以对咖啡酸分子的微观结构研究是非常有必要的。目前关于CA在Ag表面上的表面增强拉曼散射（SERS）光谱的理论与实验结合的研究尚未见报道,而对其振动光谱及表面增强机理的研究可以为咖啡酸的各种药学机理的研究提供一种科学的物理解释,所以有必要将密度泛函理论（DFT）方法与表面增强拉曼散射技术相结合,对咖啡酸在Ag纳米颗粒上的吸附性质及表面增强机理进行全面的研究,这对推进它们在医药学等领域的相关研究有着重要的参考价值。采用SERS与DFT技术对CA分子在Ag纳米颗粒表面上的表面增强拉曼光谱进行了研究。在实验方面,利用热还原反应原理,使用柠檬酸三钠和硝酸银在加热搅拌情况下制备Ag纳米颗粒,并使用激光共聚焦显微拉曼光谱仪测量了CA分子的常规拉曼散射（NRS）光谱及其表面增强拉曼散射（SERS）光谱。在理论计算方面,采用DFT的B3LYP方法,以6-31+G**和LANL2DZ分别作为C,H,O和Ag的计算基组来优化咖啡酸的分子构型,羟基与Ag₄的吸附构型,羧基与Ag₄的吸附构型,羟基与羧基共同与Ag₄吸附的构型,并以此为基础分析计算了CA分子的NRS光谱以及三种可能吸附模型的SERS光谱,并结合实验结果进行比较。同时对CA分子的振动模式进行了详细指认。根据实验数据和理论结果分析,在452 cm-1处的谱峰归属为环面外弯曲振动和O-H面外弯曲振动的耦合,这说明CA分子上的酚羟基是与Ag纳米颗粒表面作用的,不过相互作用较弱,推测CA分子平面可能与Ag基底表面不垂直;出现在1 338 cm-1处的谱峰归属于COO-伸缩振动,则可以说明CA分子上的羧基可能与Ag纳米颗粒垂直吸附。结果表明,CA分子是以羧基和酚羟基为吸附位吸附在Ag纳米颗粒表面上的。同时对CA分子的振动模式进行了详细指认。该工作对推进咖啡酸在生物医药等领域进一步的应用将起到重要作用。     

脱氢枞酸基D-A型分子的合成、空间构型及光谱性能

对三苯胺进行溴代和C-N偶联反应合成4-萘基三苯胺(a),对脱氢枞酸进行酯化、溴代、硝化、还原和C-N偶联反应合成13-[N,N-(4-萘基苯基)-苯基]胺基-脱异丙基脱氢枞酸甲酯(b)及13-[N,N-双(4-萘基苯基)]胺基-脱异丙基脱氢枞酸甲酯(c)两个化合物,通过1H MNR,13C MNR及MS对化合物的结构进行表征。为了研究化合物结构与光谱性能之间的关系,首先利用Gaussian 09程序采用密度泛函DFT/B3LYP方法,对三个化合物的空间构型进行全优化,得到它们的键长、键角和二面角,对比发现脱氢枞酸骨架和萘环的引入会影响化合物的共平面性,而萘环的引入会增大化合物的共轭程度。光谱性能方面,研究了三种化合物在甲醇、二氧六环、四氢呋喃、二氯甲烷和环己烷这5种极性逐渐减小的溶剂中的荧光发射光谱和紫外吸收光谱。结果表明,在荧光光谱中,化合物a,b和c在不同极性溶剂中最大荧光发射波长均有不同程度位移,在甲醇中最大,在环己烷中最小,但是位移并非随着极性的增大而只发生红移,在二氯甲烷、四氢呋喃和二氧六环3种极性依次增大的溶剂中,a,b,c的荧光发射波长均随着溶剂极性的增大而发生较大程度的蓝移;在同一溶剂中,化合物b和c相对于a的荧光发射波长依次发生红移,c的红移程度与b差距不大。紫外吸收光谱中,三个化合物在不同极性溶剂中的最大吸收波长也有差异,在200～250 nm区间,三个化合物均在二氯甲烷中有较大位移,在300～350 nm区间,在甲醇中位移较大,而在250～300 nm区间,最大吸收波长差别不大;在同一溶剂中,它们在300～350 nm区间的最大吸收波长差别较大,化合物c较a红移26 nm。结合结构优化所得数据可以证明,化合物的共轭程度对荧光发射光谱和紫外吸收光谱均有影响,而共平面性对荧光发射光谱影响较大。化合物a,b和c在不同极性溶剂中荧光发射光谱和紫外吸收光谱的较大变化,表明它们有明显的溶致变色行为,具有作为分子探针探测外部环境极性大小的潜能。     

Iterative submatrix diagonalisation for large configuration interaction problems

The Davidson method has been highly successful for solving for eigenpairs of the large matrices that are common in quantum chemical simulations. Electronic structure simulations, however, can still easily generate matrices that are too large for current computational resources to handle. Therefore, many strategies have arisen to obtain eigenpairs of sufficient accuracy without considering the full Hamiltonian matrix. This article introduces one such strategy by creating a systematic series of submatrix approximations to the full matrix using natural orbitals. By solving for eigenpairs in this series, the eigenvalue accuracy can be gradually increased until a convergence threshold is reached. Importantly, this allows the series to terminate without ever reaching the full matrix, resulting in lower computational costs and reduced memory demands. Application of the method to the full configuration interaction problem for ground states, excited states and potential energy scans of various systems shows that the iterative submatrix diagonalisation method can systematically control eigenvalue errors and provide substantial cost-savings. This method is therefore expected to be highly useful for large-scale diagonalisation problems in electronic structure theory.     

Investigation of the multiplet features of SrTiO3 in X‐ray absorption spectra based on configuration interaction calculations

Synchrotron‐based L_2,3‐edge absorption spectra show strong sensitivities to the local electronic structure and chemical environment. However, detailed physical information cannot be extracted easily without computational aids. Here, using the experimental Ti L_2,3‐edges absorption spectrum of SrTiO₃ as a fingerprint and considering full multiplet effects, calculations yield different energy parameters characterizing local ground state properties. The peak splitting and intensity ratios of the L₃ and L₂ set of peaks are carefully analyzed quantitatively, giving rise to a small hybridization energy around 1.2 eV, and the different hybridization energy values reported in the literature are further addressed. Finally, absorption spectra with different linearly polarized photons under various tetragonal crystal fields are investigated, revealing a non‐linear orbital–lattice interaction, and a theoretical guidance for material engineering of SrTiO₃‐based thin films and heterostructures is offered. Detailed analysis of spectrum shifts with different tetragonal crystal fields suggests that the e_g crystal field splitting is a necessary parameter for a thorough analysis of the spectra, even though it is not relevant for the ground state properties.     

电极位置和截面尺寸对分子器件输运性质的调控

研究表明分子器件的性能受器件结构搭建精度影响,分子与电极接触构型的微弱变化可能引起电输运特性较大差异.本文运用密度泛函理论和非平衡格林函数相结合的方法,研究了由金纳米线与benzene-1,4-dithiol（BDT）形成的分子结的电输运性质.通过对不同的Au-BDT接触构型输运性质的研究,发现当两电极处于对位构型时,有较好的电荷输运行为,而且比较符合制备工艺要求;当电极偏离轴线的角度不大于5°,且电极散射截面尺寸不小于4×4时,该分子结体系的电导和透射谱均比较稳定.电极截面尺寸小于4×4或者电极偏离轴线的夹角大于5°时,透射谱在费米能级附近出现不连续现象,导致体系电导降低.较小电极截面尺寸或者电极以较大角度偏离轴线将导致该分子结体系电导降低和透射谱连续性降低,主要是组成电极的金原子轨道与苯基分子轨道耦合缺失造成的.该研究为Au-BDT-Au体系设计和制备过程中电极的位置及电极截面尺寸做了科学的界定.     

Numerical study of coarse coal particle breakage in pneumatic conveying

Pneumatic conveying of coarse coal particles with various pipeline configurations and swirling intensities was investigated using a coupled computational fluid dynamics and discrete element method. A particle cluster agglomerated by the parallel-bond method was modeled to analyze the breakage of coarse coal particles. The numerical parameters, simulation conditions, and simulation results were experimentally validated. On analyzing total energy variation in the agglomerate during the breakage process, the results showed that downward fluctuation of the total particle energy was correlated with particle and wall collisions, and particle breakage showed a positive correlation with the energy difference. The correlation between the total energy variation of a particle cluster and particle breakage was also analyzed. Particle integrity presented a fluctuating upward trend with pipe bend radius and increased with swirling number for most bend radii. The degree of particle breakage differed with pipeline bending direction and swirling intensity: in a horizontal bend, the bend radius and swirling intensity dominated the total energy variations; these effects were not observed in a vertical bend. The total energy of the particle cluster exiting a bend was generally positively correlated with the bend radius for all conditions and was independent of bending direction.     

BH~+离子基态及激发态的势能曲线和跃迁性质的研究

利用高精度的多组态相互作用及Davidson修正方法 (MRCI+Q),采用ACV5Z-DK全电子基组计算了BH~+离子的前4个离解通道B~+(~1S_g)+H(~2S_g),B~+(~3Pu)+H(~2S_g),B(~2P_u)+H~+(~1Sg)和B~+(~1Pu)+H(~2Sg)的9个Λ—S态的势能曲线.X~2Σ~+,A~2Π和B~2Σ~+态的光谱常数和已有实验值符合得很好,其中b~4Σ~+,3~2Σ~+,3~2Π和4~2Σ~+态的光谱常数为首次报道,3~2Π和4~2Σ~+态具有双势阱结构.预测了A~2Π和B~2Σ~+态的辐射寿命:τ(A~2Π)=239.2 ns和τ(B~2Σ~+)=431.2 ns.最后在考虑自旋轨道耦合效应下讨论了B~2Σ~+与A~2Π态的势能曲线的相交对激光冷却BH~+离子的影响.     

非零色散位移光纤的改进设计及制造

介绍了一种新颖的非零色散位移光纤结构设计方法及其MCVD+OVD制造工艺,所制备的光纤有效面积达到71 μm2以上.采用关键结构区域精确微扰方法,改进了光纤的色散特性.1550 nm处色散斜率由0.0715 ps/(nm2·km),分别减小至0.0605 ps/(nm2·km),0.0466 ps/(nm2·km),零色散波长由1500 nm附近移至1450 nm以下.测量表明,所得光纤具有优越的光学传输特性、抗弯曲性能和熔接性能,适用于C+L和S+C+L工作波长的大容量高速率长距离密集波分复用系统.光纤关键结构区域精确微扰是改进光纤性能的一种有效方法,该方法不限于MCVD工艺和非零色散位移光纤,对新型光纤的设计和生产具有积极的指导意义.     

Study of the νi13/2－1 band in 189Pt

High-spin levels of ^189Pt have been studied with the in-beam T-spectroscopy method via the ^176Yb（^18O,5n） reaction at the beam energies of 88 and 95 MeV. The previously known ＂vi-1 13/2 band has been confirmed, and its unfavored signature branch extended up to the 31/2^＋ state. Within the framework of the triaxial particle-rotor model, the vi-1 13/2 band is suggested to be associated with the 11/2[615] configuration, and to have triaxial deformation.