Seed-mediated growth of bimetallic nanoparticles as an effective strategy for sensitive detection of vitamin C

In this work, we have demonstrated that seed-mediated growth of bimetallic nanoparticles via heterogeneous nucleation can be used as a powerful means to improve the sensitivity of an analytical method for antioxidants that involved in a redox reaction. Taking vitamin C (Vc) as a typical example, a simple and sensitive method for the detection of antioxidants has been developed. Specifically, with the aid of Vc, Ag atoms that generated from the reduction of Ag + ions tend to deposit on the surfaces of Au nanocages (the seeds) to form Au@Ag nanoboxes rather than self-nucleation. As a result, the localized surface plasmon resonance (LSPR) of Au nanocages shifts from near-infrared region to a shorter wavelength owing to the transformations in both morphology and component. The detection toward Vc can be achieved through a linear relationship between the wavelength changes of LSPR peak and the corresponding concentration of Vc in the range of 0.05–7.5   μM, with a limit of detection as low as 24   nM. Moreover, this method shows high selectivity for the detection of Vc when potential species coexisted in the system, and has been successfully applied for the determination of Vc in pharmaceutical products.