Fabrication of Ag/ZnO nanostructures for SERS applications

A novel and effective approach is suggested for fabrication of composite Ag/ZnO nanostructures for surface-enhanced Raman scattering (SERS) by combining laser and ion implantation techniques. The study explores the relation between the nanoscopic features of the prepared Ag/ZnO nanocomposites and their effectiveness as SERS active substrates. The ZnO thin films are grown by pulsed laser deposition (PLD). Ag+-ion implantation is used for surface synthesis of Ag nanoparticles (NPs) in the ZnO matrix. The implanted samples are annealed by a Nd:YAG laser at various parameters. The surface morphology, composition and optical properties of the nanocomposites are studied before and after the ion and laser modifications. The possibility to apply these structures to ammonium nitrate detection is investigated by identifying the most suitable conditions for laser annealing of the implanted Ag/ZnO structures in view of producing the strongest SERS signal. A comparative Raman study is performed at two laser excitation wavelengths. New results are obtained for different ammonium nitrate (AN) concentrations. The strongest Raman signal of ammonium nitrate is detected for the Ag/ZnO substrate annealed at 532 nm and characterized by a high surface roughness and a wide nanoparticles' size distribution, where a low surface electron density of silver was obtained.