Surface-Induced Photoreduction of 4-Nitrobenzenethiol on Cu Revealed by Surface-Enhanced Raman Scattering Spectroscopy

A copper foil etched in a dilute solution of HNO 3 is free of carbon and oxygen, but the nanostructure formed thereby is highly active for surface-enhanced Raman scattering (SERS), especially when 632.8-nm radiation from a He/Ne laser is used as the excitation source. We found further that the copper foil thus prepared is also an efficient photoelectron emitter such that the SERS spectrum of 4-nitrobenzenethiol on copper is readily converted to that of 4-aminobenzenethiol under 632.8-nm radiation. This surface-induced photoreduction allowed us to prepare patterned binary monolayers on copper that showed different chemical reactivities. Using the binary monolayers as a lithographic template, we found that calcium carbonate could be grown selectively on the amine-group-terminated regions by adjusting the crystal growth conditions.