P-thiocresol 吸附在银纳米粒子表面系统的表面增强拉曼散射和表面增强共振拉曼散射的增强研究

文中从实验和计算两方面报道了在514.5 nm激发光下P-Thiocresol吸附在银胶表面系统的表面增强拉曼散射(SERS).文中分析了它的增强机制,发现增强主要来自于电磁场增强.如果考虑距离为2nm的两个银纳米粒子的耦舍效应,两粒子之间的SERS的电磁场增强为7.16 × 107.静态化学增强亦起到部分增强作用,它的增强倍数为6.所以,总的SERS增强,包括静态化学增强和电磁场增强,是Gtotal=Gsc ×GEM=4.4×108.我们也理论地研究了此系统的表面增强共振拉曼散射(SERRS).当激发光与P-Thiocresol-Ag3系统的激发态共振时,电荷转移机制(化学增强)也将起到重要作用,最强的增强可迭106.我们使用电荷密度将激发光下p-Thlocresol和Ag团簇问的电荷转移结果可视化,这是电荷转移的直接理论证据.对于SERRS增强,包括电荷转移和电磁场增强机制,能达到1013.

Enhancement for Surface Enhanced Raman Scattering and Surface Enhanced Resonance Raman Scattering of P-thiocresol Adsorbed on Silver Nanoparticle

The surface-enhanced Raman scattering (SERS) of p-thiocresol adsorbed on colloidal silver at the incident light of 514.5 nm is reported experimentally and theoretically. The enhancement mechanisms of them are analyzed. The enhancement is mostly contributed from the electromagnetic enhancement. If the coupling effect of two Ag nanoparticles (diameter of 100 nm) with a distance of 2 nm is considered, in the center between two particles, electromagnetic enhancement of SERS is . The static chemical enhancement also plays a role and the enhancement is 6. So, the total enhancement of SERS, including the static chemical enhancement and the electromagnetic enhancement, is . The surface-enhanced resonance Raman scattering (SERRS) of the system is also studied theoretically. When the incident light resonates with the excited state of p-thiocresol-Ag3 complex, the charge transfer mechanism (chemical enhancement) also plays an important role and the strongest charge transfer enhancement can reach up to 106. We visualize the orientation and result of charge transfer between p-thiocresol and Ag cluster on the excitation with charge difference density, which is the directly theoretical evidence for charge transfer. The enhancement of SERRS, including the charge transfer and electromagnetic mechanisms, can reach up to 1013.