Electrophoretic fabrication of silver nanostructure/zinc oxide nanorod heterogeneous arrays with excellent SERS performance

Abstract

A simple and green strategy is presented to fabricate Ag-decorated ZnO nanorod arrays based on electrophoretic deposition in a Ag colloidal solution prepared by laser ablation in water. The edges or corners of each nanorod's upper surface feature dendritic aggregates consisting of nanoparticles, and the other surfaces exhibit irregular particles of less than 200 nm in size. Overall, the created Ag nanostructure/ZnO nanorod is hierarchically micro/nanostructured and very rough at the nanoscale. The inter-particle spacings in the decoration layer are nanometers to tens of nanometers in scale. Further experiments have revealed that suitable electrophoretic potential and sufficient growth duration are crucial for obtaining complete coverage on every nanorod. The site-specific deposition of Ag nanoparticles on ZnO nanorods can be explained by the different distributions of the electric field and the colloidal concentration during electrophoresis. Such heterogeneous nanorod arrays are functionalized and exhibit excellent surface-enhanced Raman scattering performance. This study provides a new method for creating decorated nanorod arrays with novel nanostructures by using unstable colloidal nanoparticles as building blocks and deepens the understanding of the physical mechanisms of electrophoretic deposition.