Growing Anisotropic Silver Nanostructures from Copper-Coated Fibrous Silica and Its Application as Plasmonic Photocatalyst

Anisotropic silver nanostructures having complex morphologies are of immense importance due to its application in plasmon-enhanced photocatalysis, transparent conducting electrodes, and surface-enhanced Raman spectroscopy (SERS). We report the generation of silver nanowires, nanobelts, and nanostructures having dendritic fibrous morphologies by galvanic replacement reaction on copper thin-film coated dendritic fibrous nanosilica (DFNS). DC magnetron sputtering was used to deposit copper thin- film on DFNS. Electron microscopy revealed that galvanically grown silver nanostructures followed the wrinkled fibrous morphology of DFNS. In addition to dendritic fibrous nanosilver (DFNAg), silver nanobelts, nanowires with high aspect ratio also grew over large areas when the silver precursor concentration and the copper film thickness were varied. The SERS performance of DFNAg substrates was evaluated using a self-assembled monolayer of p-aminothiophenol (p-ATP). The SERS and plasmon-enhanced photocatalytic performance of DFNAg were compared with a standard SERS substrate, Ag film on nanosphere (AgFON). The ensemble-averaged Raman enhancement factor for DFNAg was found to be of the order of 105, on par with AgFON. Variation in Raman peak intensities revealed that plasmon-assisted photodimerization of p-ATP to p,p′-dimercaptoazobisbenzene was higher on DFNAg than AgFON which could be attributed to a high number of hot spots on DFNAg caused by its anisotropic structure.