A facile SERS strategy to detect glucose utilizing tandem enzyme activities of Au@Ag nanoparticles.

Surface-Enhanced Raman Scattering (SERS) is a powerful analysis technology, attracting more and more attention due to its high sensitivity and selectivity. Herein, we report a simple seed-mediated method to synthesize Au@Ag nanoparticles (NPs) as a multifunctional biosensor for the label-free detection of hydrogen peroxide (H2O2) and glucose by SERS. Au@Ag NPs, as an ultrasensitive SERS substrate, show the dual activities (peroxidase-like and GOx-like activities). Under the condition of pH 4.0 NaAc buffer solution, the glucose and H2O can be catalyzed by Au@Ag NPs to produce glucose acid and H2O2, and then H2O2 can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to form a blue oxidation product oxidic TMB (oxTMB) which exhibits strong SERS signals at 1188, 1330, 1605 cm-1. Thus, we have developed a new SERS strategy for analysis of glucose with a detection limit of 5 × 10-10molL-1, suggesting that Au@Ag NPs have the potential for biosensor, immunoassay and medical treatment.