Annealing effect: Controlled modification of the structure, composition and plasmon resonance of hybrid Au–Ag/C nanostructures

Abstract

Here we present a novel approach to the synthesis of hybrid Au–Ag/C nanoparticles (NPs) which were found to be carbon nanospheres containing dispersed Au–Ag bimetallic nanoparticles (1–5nm). The Au–Ag/C NPs were obtained by laser-induced liquid phase deposition from solutions of supramolecular complex. It was revealed that subsequent annealing procedure of Au–Ag/C NPs at various temperatures over the range 100–600°C allows variation and directed control of NPs’ morphology and composition (relative contents of principal components). For nanoscale carbon material the critical evaporation temperature was found to be about 300°C, while for Ag and Au components – 500°C and 600°C accordingly. The morphology and composition variation makes possible tuning of the surface plasmon resonance characteristics that opens an efficient way of the NPs’ functional properties control, like for example Surface-Enhanced Raman Scattering (SERS). It was found that the obtained hybrid Au–Ag/C NPs display pronounced SERS activity with the enhancement factor (EF) ca. 105.