Heterogeneous catalysts play an important role in surface catalytic reactions, but selective bond breaking and control of reaction products in catalytic processes remain significant challenges. High‐vacuum tip‐enhanced Raman spectroscopy (HV‐TERS) is one of the best candidates to realize surface catalytic reactions. Herein, HV‐TERS was employed in a new method to control dissociation by using hot electrons, generated from plasmon decay, as plasmonic scissors. In this method, the N?N bond in 4,4′‐dimercaptoazobenzene was selectively dissociated by plasmonic scissors, and the reaction products formed from the radical fragment (SC6H5N) were controlled by varying the pH value. Under acidic conditions, p‐aminothiophenol was produced from the radical fragment by attachment of hydrogen ions, whereas under alkaline conditions, 4‐nitrobenzenethiol was obtained by attachment of oxygen ions to the substrate. 相似文献
We present the isolation of the first mononuclear dihalogermylene, and mono‐ and dinuclear stannylene complexes of transition metals. These exhibit exceptionally pyramidalized Group 14 centers. Additionally, removal of the halide substituents from the Ge/Sn atom was successfully performed in two ways, halide abstraction and reduction, leading to a variety of unusual structural motifs. 相似文献
Electromagnetic mechanism of deep ultraviolet tip-enhanced Raman scattering (DUV-TERS) is investigated theoretically with the finite-difference time-domain (FDTD) method, stimulated by recent DUV-TERS experimental reports. FDTD results reveal that the strongest electromagnetic enhancement factor for DUV-TERS is as high as 7 orders in the optimal geometry. 相似文献
In this study, a novel kinetic model is established to investigate the dynamic characteristic of the ball screw feed system by considering the thermal deformation of bearing joints, screw-nut joints and screw shaft. Based on the Hertz contact theory, the relationship between elastic restoring force and axial deformation of bearing joints and screw-nut joints is obtained, respectively. Then the dynamic characteristics of the kinetic equation are analyzed by Runge–Kutta method. The vibration characteristics of the feed system with and without thermal deformation are analyzed, and the results indicate that the amplitude becomes larger when thermal deformation is considered. The motion state of the feed system at different frequencies is analyzed, and the results show that with the change of frequency, the motion state of the system will appear period-doubling motion, quasi-periodic motion and chaotic motion. Finally, the influence of different parameters on the vibration characteristics of the system is discussed.
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are... 相似文献
Optical physical properties of neutral and charged quinquethiophene monomer, and neutral and cationic pi-dimeric quinquethiophenes were investigated with density functional theory as well as the two dimensional (2D) site (transition density matrix) and three dimensional (3D) cube (transition density and charge difference density) representations, stimulated by the recent experimental report [T. Sakai et al., J. Am. Chem. Soc. 127, 8082 (2005)]. Transition density shows the orientation and strength of the transition dipole moment of neutral and charged quinquethiophene monomer, and charge difference density reveals the orientation and result of the charge transfer in neutral and charged quinquethiophene monomer. To study if coupling exciton and oscillation of electron-hole pair exist in neutral and cationic pi-dimeric quinquethiophenes, the coupling constants J (coupling exciton of electron-hole pair) and K (coupling oscillation of electron-hole pair) were introduced to the exciton coordinate and momentum operators, respectively, and the 2D and 3D analysis methods were further developed by extending our previous theoretical methods [M. T. Sun, J. Chem. Phys. 124, 054903 (2006)]. With the new developed 2D and 3D analysis methods, we investigated the excited state properties of neutral and cationic pi-dimeric quinquethiophenes, especially on the coupling exciton and oscillation of electron-hole pair between monomers. The 2D results show that there is neither coupling exciton (J=0) nor oscillation (K=0) of electron-hole pair in neutral pi-dimeric quinquethiophenes. For some excited states of cationic pi-dimeric quinquethiophenes, there is no coupling exciton (J=0), but there is coupling oscillation (K not equal0); while for some excited states, there are both coupling exciton and coupling oscillator simultaneously (J not equal0 and K not equal0). The strength of transition dipole moments of pi-dimeric quinquethiophenes were interpreted with 3D transition density, which reveals the orientations of their two subtransition dipole moments. The 3D charge transition density reveals the orientation and result of intermonomer and/or intramonomer charge transfer. The calculated results reveal that excited state properties of neutral pi-dimeric quinquethiophene are significantly different from those of the cationic pi-dimeric quinquethiophenes. 相似文献