Engineering the plasmonic activities of copper nanostructures for SERS and photocatalysis

Abstract

Nanoparticles of plasmonic metals such as gold (Au), silver (Ag) and copper (Cu) have numerous applications due to their localized surface plasmon resonance. Among these, nanoparticles of Cu remain underexplored when compared to Au and Ag, although the former is much cheaper. Here we report the surface enhanced Raman spectroscopy (SERS), interaction of molecule with a plasmonics and photocatalysis applications of Cu nanostructures. Hexagonal and cubic shaped Cu nanostructures were successfully synthesized by varying the reaction conditions in a polyol synthesis method. Rapid nucleation at an elevated temperature (140 °C) and subsequent slow growth at lower temperature (80 °C) in presence of polymeric stabilizer resulted in the formation of uniform cube shaped Cu nanoparticles (Cucube). Whereas polyol synthesis at a low temperature (80 °C) resulted in hexagonal Cu nanoparticles (Cuhex). Both the nanostructures exhibited very good surface enhanced Raman scattering (SERS) enhancement of the order 6.9 × 105 for rhodamine B (RhB). Cuhex also showed reliable SERS sensing of RhB with a very low experimental limit of detection (10−10 M). Moreover, based on emission and time-dependent measurements, strong molecular and plasmonic interactions reveal energy transfer from RhB molecules to the Cu nanostructures. Additionally, Cuhex showed very good catalytic and visible light plasmonic photocatalytic activities for the para-nitrophenol (p-NP) reduction reaction.