Photoinduced synthesis of Ag nanoparticles on ZnO nanowires for real-time SERS systems

We developed a photoinduced synthesis method for fabricating metal nanoparticles (NPs) embedded on the surfaces of metal oxide nanowires (NWs) to form hierarchical nanostructures. The process consisted of two steps: (1) the preparation of a metal oxide NW backbone structure, and (2) the photoinduced synthesis of metal NPs on the backbone structure. ZnO NWs were first prepared and reduced to form metal oxide NWs. UV light was used to generate electron-hole pairs at the metal oxide NW surface. The excited electrons successfully reduced Ag ions in solution to form Ag NPs on the ZnO NW surfaces without introducing contamination or side-reactions. The surface-enhanced Raman spectroscopy (SERS) properties of the hierarchical materials were investigated for various Ag nanostructure morphologies. The SERS activity revealed an outstanding enhancement factor of 6.36 x 10(11). A range of glucose solution concentrations was detected using the SERS method in conjunction with the hierarchical materials. The hierarchical materials were deployed in a microfluidic system to sequentially detect distinct molecules as they flowed through the channel. The photoinduced synthesis process required only simple, low-cost, and environmentally benign fabrication conditions.