光激发作用下分子与多金属纳米粒子间的电荷转移研究

金属纳米粒子在光激发作用下的增强作用是纳米科学领域的一个研究热点. 针对分子和多个不同位形下的金属纳米粒子在光激发下的相互作用展开了理论研究. 应用密度矩阵理论描述分子和金属纳米粒子同时激发产生表面等离激元后的电荷输运过程. 研究发现, 表面等离激元增强效应与分子和各个金属纳米粒子的相对位置有密切关系. 详细分析了金属纳米粒子间的耦合强度、分子和金属纳米粒子间的耦合强度、表面等离激元能级杂化、分子激发能和外场频率对表面等离激元增强效应的影响.

Theoretical study of photoinduced charge transfer in molecule and multi-metalnanoparticles system

Photoinduced enhancement effect of the metal nanoparticle is one of the hot topics in the field of nanomaterial. Interaction between one molecule and a number of metal nanoparticles in different configurations in an applied external field is theoretically investigated in the scheme of density matrix theory, where the molecule and metal nanoparticles are excited simultaneously, and the subsequent charge transfer dynamics is simulated. Besides, the Coulomb interactions between the molecule and metal nanoparticles are calculated in the framework of dipole-dipole approximation. Parameters for metal nanoparticles with a 10 nm radius are used in the text and the polarization of the molecule has the same direction as that of external laser field. It is found that plasmon enhancement is closely related to the relative positions between the molecule and metal nanoparticles. Effects of enhancement due to the surface plasmon is discussed in detail for different configurations of the molecule and metal nanoparticles, and the surface plasmon hybridization, as well as the molecular excitation energy and the frequency of external field applied. Plasmon hybridization levels are formed when metal nanoparticles have strong enough interactions between themselves. The blue shift of the resonant frequency can be found for shorter distance of different metal nanoparticles. In the case that the centers of mass of metal nanoparticles and the molecule are on the same plane, it is found that the population in excited state of the molecule at a resonance frequency increases for a shorter distance between metal nanoparticles and the molecule. On the contrary, in the case that the centers of mass of four metal nanoparticles are located in a plane which is parallel to the x-y plane and above it by 10 nm, the population in the excited state of the molecule on resonant frequency will decrease at a shorter distance between the four metal nanoparticles.