Oxygen Incorporation-Induced SERS Enhancement in Silver Nanoparticle-Decorated ZnO Nanowires

Surface-enhanced Raman spectroscopy (SERS) is a sensitive and nondestructive technique used for the detection of molecules, traditionally applied on noble-metal or semiconductor substrates. Point defect introduction has been applied to increase the enhancement of semiconductor templates due to more efficient charge transfer; however, they are still limited by low detection sensitivity and inferior SERS enhancement. Here we propose a universal approach of oxygen incorporation into metal oxide nanowire/metal nanoparticle templates that allows for greater SERS enhancement due to localized surface plasmon resonance excitation, point defect-induced optical gap shrinking, and wettability change of the substrate. We report up to 5-fold Raman relative peak intensity enhancement after annealing-induced oxygen introduction. This approach is applied to defect formation in metal oxide semiconductor nanowires such as ZnO, WO3, TiO2, and NiO and is applicable for a wide variety of probe molecules, making the method suitable for medical, security, and environmental applications.