Water-soluble Au nanocages for enzyme-free H2O2 sensor and 4-nitrophenol reduction

In this paper, water-soluble, high yield and quality, quasi-spherical Au nanocages have been successfully prepared via a galvanic replacement reaction with HAuCl4 in water at room temperature, where monodisperse, quasi-spherical Ag nanocrystals are used as sacrificial templates. Quasi-spherical Au nanocages were employed as both an enzyme-free electrochemical sensor and in catalytic application, which showed superior performance compared to solid and nanocrystals with other structures. In the enzyme-free H2O2 detection, the quasi-spherical Au nanocages based biosensor exhibited long linearity, a low detection limit, high stability and good selectivity. The enzyme-free H2O2 sensor also exhibited excellent selectivity for H2O2 in comparison to other normally co-existing electroactive species, such as ascorbic acid, uric acid and glucose. Furthermore, Au nanocages were also found to serve as a more effective catalyst for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4 than Au nanocrystals with other structures. The reduction has an activity parameter of 4000 s(-1) g(-1), which is also significantly higher than other Au or Ag based nanomaterials in previous research.