Surface-Enhanced Raman Scattering from Self-Assembled Film of Thiolated Peg-Modified Gold Nanoparticles

Abstract

Self-assembly of thiolated polyethylene glycol (PEG)-modifi ed Au nanoparticles (NPs) into a closely packed particle film at a water–air interface for the production of reproducible, highly active surface-enhanced Raman scattering (SERS) was developed. Upon modifi cation with thiolated PEG, the Au NPs can sustain severe conditions (e.g., 3 M NaCl solution), and after separation from colloids and drying, they can be redispersed into water, forming colloids again. We found that the thiolated PEG-modifi ed Au NPs, from their concentrated colloids, can spontaneously selfassemble into a two-dimensional (2D) closely packed particle film at the water–air interface. With abundant hot spots created and exposed, the 2D particle film produces large, reproducible SERS signal for 4-mercaptobenzoic acid (probe molecule), reaching a detection limit of 1 × 10–11 M. These results offer a useful way for the storage of Au NPs and the fabrication of highly reproducible and active SERS substrate.