Fig. 6.

Morphological evolutions of Au NPs either permanently capped with nonphotoresponsive polymers or dynamically capped with small molecules. TEM images of (A) as-prepared PS-capped Au NPs before UV light irradiation, and (B and C) PS-capped Au NPs after 365- and 254-nm UV light irradiation, respectively, for 24 h. It is notable that image (C) was obtained by irradiating the PS-capped Au NPs CH₂Cl₂ solution with 254-nm UV light for an additional 24 h after it was previously exposed to 365-nm UV light for 24 h. TEM images of (D) as-prepared DDT-capped Au NPs before UV light irradiation, and (E and F; and G–I) DDT-capped Au NPs after 365-nm (for 24 h) and 254-nm (for 60 min) UV light irradiation, respectively. Notably, images (G–I) were obtained by irradiating the DDT-capped Au NPs CH₂Cl₂ solution with 254-nm UV light for an additional 60 min after it was previously exposed to 365-nm UV light for 24 h. A close-up in Inset shows the agglomeration of Au nanocrystals with no observable, individually isolated NPs.