Fig. 1. Diagram of optical manipulation microscopic Raman system

Fig. 2. SEM images of experimental materials. (a) PS nanoparticles; (b) gold nanoparticles; (c) gold nanoparticle aggregates

Fig. 3. Photographs of PS nanoparticles and gold nanoparticles. (a)(b) Morphologies of PS nanoparticles in field of view plane and out of field of view plane; (c)(d) morphologies of gold nanoparticles in field of view plane and out of field of view plane

Fig. 4. Photographs of PS nanoparticles under different environmental conditions. (a)-(d) Photos of PS nanoparticles at different time points when there are only PS nanoparticles in solution; (e)-(h) photos of PS nanoparticles at different time points in mixed fluid of gold nanoparticles and PS nanoparticles

Fig. 5. Distributions of motion velocity of PS nanoparticles. (a) Boxplot of relationship between moving speed of PS nanoparticles and gold particle size distribution; (b) boxplot of relationship between moving speed of PS nanoparticles and gold particle concentration distribution

Fig. 6. Curves of SERS signal of PS nanoparticles. (a) Waterfall plot of PS nanoparticle SERS signal with time; (b) curve of Raman peak intensity at 1000 cm^-1 with time; (c) SERS spectrum of PS nanoparticles with mass concentration of 10 μg/mL

Fig. 7. Raman map of polystyrene nanoparticles. (a) SEM image of stabilized Au-PS aggregates; (b) SERS signal intensity at points i, ii, iii, and iv with Raman shift of 1000 cm^-1

Table 1. Distance from nanoparticles 1, 2, 3, and 4 to focus position of particles