Synthesis of Ag-ZnO core-shell nanoparticles with enhanced photocatalytic activity through atomic layer deposition.

Herein, Ag-ZnO core-shell nanoparticles (NPs) with enhanced photocatalytic activity were prepared by coating Ag metal cores with ZnO semiconductor shells through atomic layer deposition (ALD). Instrumental analysis revealed that the ultra-thin and conformal nature of the shell allowed the core-shell NPs to simultaneously exploit the photocatalytic properties of ZnO and the plasmonic properties of Ag. In a rhodamine B photodegradation test performed under artificial sunlight, Ag-ZnO core-shell NPs exhibited better photocatalytic performance than other prepared photocatalysts, namely ZnO NPs and ALD-ZnO coated ZnO NPs. The performance enhancement was ascribed to the effect of noble metal-semiconductor heterojunctions, which increased the efficiency of electron-hole separation, i.e., the Ag core effectively captured excited electrons at the ZnO surface, which resulted in the elevated production of hydroxyl radicals from holes remaining at ZnO. A three-dimensional finite-difference time-domain simulation of the Ag-ZnO NPs with variable shell thickness showed that ZnO shells on Ag metal cores increase the intensity of light around NPs, allowing the plasmonic cores to fully utilize incident light. Unlabelled Image • The ALD technology is applied to fabricate Ag-ZnO nanoparticles for photocatalyst. • Stable ZnO shell layers with wurtzite structure are deposited on Ag core particles. • Ag-ZnO shows ~2.5 to 4 times enhanced photodegradation compared with pure ZnO. • SPR effect of Ag increases photocatalytic performance of Ag-ZnO photocatalyst. • Ultra-thin ZnO shells on Ag cores increase photocatalytic performance in UV-region. [ABSTRACT FROM AUTHOR]