Urchin-like ZnO-nanorod arrays templated growth of ordered hierarchical Ag/ZnO hybrid arrays for surface-enhanced Raman scattering.

Here, a universal strategy for the controllable synthesis of three dimensional (3D) hierarchical Ag/ZnO hybrid arrays based on the urchin-like ZnO-nanorod array template is presented. The urchin-like ZnO-nanorod arrays are first achieved by electrodepositing a high density of ZnO-nanorods onto the surface of highly hexagonally arranged arrays of polystyrene (PS) microspheres, and then Ag-nanoparticles (Ag-NPs) are assembled onto the surface of each ZnO-nanorod via photochemical reaction, ion sputtering, galvanic cell reaction deposition and electrochemical deposition, forming the ordered hierarchical Ag/ZnO hybrid arrays. The urchin-like Ag/ZnO hybrid arrays with well-ordered hierarchical morphology and high density 'hot spots' located in the sub-10 nm gaps between neighboring Ag-NPs on both the same ZnO-nanorod and neighboring ZnO-nanorods can be directly utilized as hybrid surface-enhanced Raman scattering (SERS) substrates with high SERS activity. This work provides a strategy for the rational assembly of well-ordered hierarchical noble metal/semiconductor hybrid arrays, which may open up many opportunities in areas such as catalysis, SERS, and biosensing.