Ultraviolet light-induced photochemical reaction for controlled fabrication of Ag nano-islands on ZnO nanosheets: an advanced inexpensive substrate for ultrasensitive surface-enhanced Raman scattering analysis

The fascinating nanocomposites of semiconductors coupled with noble metals have a promising potential to develop a low-cost substrate for surface-enhanced Raman scattering (SERS) applications. Herein, the controlled construction of Ag nano-islands on ZnO nanosheets (Ag@ZnO nanocomposites) was successfully achieved by a green and effective strategy based on ultraviolet light induced-photochemical reaction. It was found that the Ag content in Ag@ZnO nanocomposites linearly increases to 4.62% by simply increasing the irradiation time (0~10 min). More importantly, increasing the Ag content (0~4.62%) in the nanocomposites results in enhanced SERS activities with an enhancement factor up to 107 and a detection limit as low as 10−9 M. Compared with the complete noble metal substrate, the novel Ag@ZnO nanocomposites (