Enhanced UV emission and photocatalytic activity due to morphology evolution of ZnO thin films

Abstract

Tuning the optical properties of nanomaterials through morphology evolution has attracted extensive attention. In this study, ZnO films were deposited on substrates using sol-gel approach, and ZnO nanocolumn arrays were formed on the film surface induced by doped ions. XRD results show that the nanocolumns all have a growth orientation along the c-axis and good crystallization quality. Compared with pure ZnO film, the ones with nanocolumn arrays on the film surface exhibit higher UV emission efficiency and photocatalytic activity. The enhanced UV emission efficiency is attributed to the higher crystalline quality and fewer surface defects of the nanocolumn arrays. The improved photocatalytic activity is mostly ascribed to two factors: (1) nanocolumns are more conducive to the migration of photogenerated electrons and holes to the photocatalyst surface to participate in redox reactions; (2) the formation of nanocolumn arrays improves light absorption of the ZnO films.