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

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