Fig. 1. Average Raman spectra of PS microspheres with different particle sizes treated by UV radiation after different days. (a) 1 μm, molecular structure of PS shown in inset; (b) 2 μm; (c) 3 μm; (d) 5 μm

Fig. 2. Peak signal intensities of PS microspheres with different particle sizes versus UV radiation time. (a) 620 cm^-1 peak; (b) 1001 cm^-1 peak

Fig. 3. Main component analysis of single particle Raman spectra for PS microspheres with different particle sizes after 05 d aging. (a)(b) 1 μm ; (c)(d) 2 μm; (e)(f) 3 μm; (g)(h) 5 μm

Fig. 4. PC2 and PC3 load analysis for PS microspheres with different particle sizes after 05 d aging. (a) 1 μm；(b) 2 μm; (c) 3 μm; (d) 5 μm

Fig. 5. Surface morphologies of 2 μm PS particles after UV treatment for different processing days (scale is 5 μm). (a) 0; (b) 1; (c) 2; (d) 3; (e) 4; (f) 5

Fig. 6. Surface morphologies of 3 μm PS particles after UV treatment for different processing days (scale is 5 μm). (a) 0; (b) 1; (c) 2; (d) 3; (e) 4; (f) 5

Fig. 7. Surface morphologies of 5 μm PS particles after UV treatment for different processing days (scale is 10 μm). (a) 0; (b) 1; (c) 2; (d) 3; (e) 4; (f) 5

Fig. 8. Particle size evolution of PS particles with different particle sizes after UV treatment (** indicates extremely significant difference between contrast and treatment groups. (a) 1 μm; (b) 2 μm; (c) 3 μm; (d) 5 μm