Fig. 1. Picture and optical path of optical manipulation micro-SERS spectroscopy system. (a) Picture;(b)optical path

Fig. 2. Sample cell. (a) Picture; (b) schematic

Fig. 3. Photothermal effect of laser on gold colloid ( ① and ② represent the thermophoretic effects and convection caused by the temperature gradient difference of the laser on the gold colloid)

Fig. 4. Aggregation of gold nanoparticles produced by laser irradiation for different time

Fig. 5. Annular area for calculating the movement speed of gold nanoparticles and relation between aggregation speed of particles and ambient temperature. (a) Annular area; (b) relation between aggregation speed and ambient temperature

Fig. 6. SERS signal intensity of pyrene (5×10^-7 mol/L) based on two different substrates

Fig. 7. Variation of SERS enhancement effect of pyrene (5×10^-7 mol/L) with time. (a) SERS spectra of pyrene at different aggregation time of gold nanoparticles; (b) variation of SERS intensity of pyrene at 586 cm^-1 and 1233 cm^-1 with the aggregation time of gold nanoparticles

Fig. 8. Finite element simulated electric field enhancement distributions of a single gold nanoparticle with radius of 25 nm and 3 μm diameter gold nanoparticle aggregate composed of single gold nanoparticles. (a) Single gold nanoparticle; (b) gold nanoparticle aggregate

Fig. 9. Absorption cross-section versus wavelength for a single gold nanoparticle with radius of 25 nm and 3 μm diameter gold nanoparticle aggregate composed of single gold nanoparticles. (a) Single gold nanoparticle; (b) gold nanoparticle aggregate