Light Induced Processes in CsPbBr3-Au Hybrid Nanocrystals: Electron Transfer and Expulsion of Au

Semiconductor-metal heterostructures such as CsPbBr3-Au are useful in photocatalysis. When Au nanoparticles are deposited on the CsPbBr3 nanocrystal surface, they efficiently quench the photoluminescence of the semiconductor. This process has been studied by femtosecond transient absorption spectroscopy measurements, which indicate that electron transfer to the Au nanoparticles occurs from both hot and relaxed electrons in the conduction band of CsPbBr3. The electron transfer rate constant is much larger for the hot electrons compared to the relaxed electrons. Under steady state photoirradiation of CsPbBr3-Au heterostructure, the photogenerated electrons from the excited CsPbBr3 nanocrystals continue to charge the Au nanoparticles. After sufficient irradiation, the gold nanoparticles dissociate from the CsPbBr3 surface and aggregate into larger size gold nanoparticles. The expulsion of gold nanoparticles restores the original luminescence behavior of CsPbBr3 nanocrystals. The spectroscopic and morphological studies provide insight into the expulsion of gold nanoparticles in photoirradiated CsPbBr3-Au heterostructures.