Plasmonic Nanostars with Hot Spots for Efficient Generation of Hot Electrons under Solar Illumination

Abstract

Nanostars (NSTs) are spiky nanocrystals with plasmonic hot spots. In this study, we show that strong electromagnetic fields localized in the nanostar tips are able to generate large numbers of energetic (hot) electrons, which can be used for photochemistry. To compute plasmonic nanocrystals with complex shapes, we develop a quantum approach based on the effect of surface generation of hot electrons. We then apply this approach to nanostars, nanorods and nanospheres. We found that that the plasmonic nanostars with multiple hot spots have the best characteristics for optical generation of hot electrons compared to the cases of nanorods and nanospheres. Generation of hot electrons is a quantum effect and appears due to the optical transitions near the surfaces of nanocrystals. The quantum properties of nanocrystals are strongly size- and material-dependent. In particular, the silver nanocrystals significantly overcome the case of gold for the quantum rates of hot-electron generation. Another important factor is the size of a nanocrystal. Small nanocrystals are more efficient for the hot-electron generation since they exhibit stronger quantum surface effects. The results of this study can useful for designing novel material systems for solar photocatalytic applications.