为了实现金纳米粒子的高效聚集,获得高灵敏度的表面增强拉曼散射(SERS)基底,并研究激光对金纳米粒子的光热效应,搭建了一套集成像、SERS探测、光捕获为一体的光操控-显微拉曼系统,通过实验研究了光热效应对溶液中金纳米粒子的作用以及对待测物芘的SERS信号增强效应。此外,利用时域有限差分(FDTD)法从理论上计算了金纳米粒子聚集体与单个金纳米粒子的电场增强效果。结果表明:溶液中的金纳米粒子在热泳力及对流的共同作用下在石英衬底表面聚集,聚集速度受外界环境温度的影响;随着聚集时间延长,待测物芘的SERS信号强度增加,且其稳定后的SERS信号强度比金纳米溶胶基底增强了15倍;FDTD模拟结果表明金纳米粒子聚集体会产生比单个金纳米粒子更高的SERS增强因子,增强因子为1.30×10 7。本研究利用光热效应实现了大范围、高效率捕获金纳米粒子的光操控,该方法可显著提高金纳米粒子的SERS效应,在化学和生物等领域的物质检测分析方面具有较大的应用潜力。

To achieve efficient aggregation of gold nanoparticles, obtain high-sensitive surface-enhanced Raman scattering (SERS) substrates, and study the photothermal effect of laser on the gold nanoparticles, a set of optical manipulations combined with a micro Raman spectroscopy system was developed, which has the combined functions of micro imaging, SERS detection, and optical manipulation. The influence of the photothermal effect on the gold nanoparticles in a solution and the SERS signal enhancement effect of pyrene were studied. Theoretically, the electric field enhancement effects of aggregated and single gold nanoparticles are calculated using the finite difference time domain (FDTD) method. The results show that the gold nanoparticles in the solution formed aggregates on the surface of the quartz substrate due to the thermophoretic force and convection, and their aggregation speed was affected by the temperature of the environment. The intensity of the SERS signal of the analyte pyrene increased with an increase in the aggregation time, and its stable SERS signal intensity was 15 times stronger than that of the gold colloid solution. FDTD simulation shows that gold nanoparticle aggregates would yield a higher SERS enhancement factor than single gold nanoparticle, the enhancement factor of the aggregates was 1.30×10 ⁷. This study employed the photothermal effect to achieve optical manipulation of gold nanoparticles (large-scale and high-efficiency capture of gold nanoparticles). This method can significantly improve the SERS effect of gold nanoparticles and has potential in detection and analysis in fields such as chemistry and biology.