纳米粒子的自由运动及与其他介质的相互作用研究已成为纳米粒子应用拓展的重要领域, 特别是动态行为的实时监测仍然是目前亟待解决的难题. 本工作基于表面增强拉曼光谱(SERS)技术及布朗运动下Au纳米粒子与Au单晶微米片碰撞过程中“热点”的形成, 以苯硫酚(TP)为探针分子, 实现了碰撞过程中Au纳米粒子自由运动行为的实时监测和动态SERS研究. 通过对检测到SERS强度轨迹的“尖峰”及所含“单峰”和“簇峰”的统计分析, 深入解析了纳米粒子的微观运动本质及影响因素. 结果表明, “尖峰”主要来源于纳米粒子与平面的可逆碰撞所形成的“热点”对SERS的贡献. “单峰”对应Au纳米粒子与平面碰撞后快速离开Au片表面, “簇峰”对应Au纳米粒子与平面碰撞后在Au片表面短暂停留然后离开或可能多个粒子连续碰撞的过程. “尖峰”内多个TP的SERS光谱谱峰的相对强度不同, 并表现出振动模式的依赖性, 伸缩振动模式出现几率更高, 主要来源于动态碰撞过程中“热点”限域空间内分子的取向不同. 该研究实现了纳米粒子动态研究, 有利于理解纳米粒子的微观运动本质, 为研究碰撞过程中“热点”限域空间内动态表界面化学反应奠定基础.

The investigation on the free motion of nanoparticles and their interaction with other media has become an attractive field for extending the practical application. However, the real-time monitoring of dynamic behaviors still exists significant challenge. In this paper, based on surface enhanced Raman spectroscopy (SERS) and the formation of “hot spots” during collision between Au nanoparticles and Au single crystal microplate under Brownian motion, the real-time monitoring of free motion behaviors of Au nanoparticles during collision and the dynamic SERS study were realized accordingly by using thiophenol (TP) as the probe molecule. The nature and influencing factors of microscopic motion of nanoparticles were investigated by statistical analysis of the “spikes” in the SERS trajectories, including “single spikes” and “cluster spikes”. The results reveal that the “spike” is mainly attributed to the “hot spots” formed by reversible collision of nanoparticle and plane. “Single spikes” correspond to the rapid departure of Au nanoparticles from the surface of the Au microplate after collision with the microplate, and “cluster spikes” correspond to the process of Au nanoparticles staying on the surface of the Au microplate for a short time after colliding with the plane and then leaving or possibly multiple nanoparticles colliding continuously. Increasing the concentration of nanoparticles is beneficial to the formation of “cluster spike”. The intensity distribution of the corresponding SERS characteristic peaks is concentrated in 5.2 cps and 8.7 cps, respectively. The relative intensities of SERS peaks of TP in the “spikes” are critically depended on the vibrational modes. It demonstrates that the probability of stretching vibrational modes is higher, and it is mainly due to the different orientations of molecules in the localized area during the dynamic collision processes. The realization of dynamic collision is beneficial to deeply understand the nature of microscopic motion of nanoparticles. It provides the basis for the investigation of dynamic interfacial chemical reactions in localized area.