Fabrication of porous Ag hollow sphere arrays based on coated template-plasma bombardment

A facile and flexible strategy is presented to produce porous Ag hollow sphere arrays, with a micro/nanostructure and contaminant-free surface, based on a combination of the bottom-up and top-down fabrication strategies, or by plasma bombardment of Ag-coated monolayer polystyrene sphere templates. The arrays consist of periodically arranged micro-sized hollow spheres with nanoscaled pores (mostly within 100 nm) in the shell layer. These arrays are structurally tunable in spherical size (in the sub-10 μm range), spacing (from a few nanometers to several microns), shell thickness (over tens of nanometers) and porous configuration by the template and bombarding conditions. The strategy is universal for the fabrication of other porous metal hollow sphere arrays. Such nanoscaled rough and porous Ag hollow sphere arrays have potential applications in catalysis, antibacterial and photonic devices. The arrays show significant surface-enhanced Raman scattering (SERS) activity (the minimum detectable concentration of the standard molecule rhodamine 6G can be down to 10^-14 M) with good stability and reproduction, and are a good candidate for the substrate of SERS effect based devices.