A colorimetric assay for H2O2 and glucose based on the morphology transformation of Au/Ag nanocages to nanoboxes

Herein, we introduced a sensitive colorimetric platform for hydrogen peroxide (H2O2) assay based on gold/silver (Au/Ag) nanocages with porous structure. In the presence of H2O2, the morphology of hollow Au/Ag nanocages was converted to closed nanoboxes, altering their localized surface plasmon resonance (LSPR) peak position and the solution color from light blue to deep blue. The morphology transformation and LSPR peak position of Au/Ag nanocages were proportional to H2O2 concentration at the range of 0.1 to 50 mu M. The limit of detection (LOD) was obtained to be 0.02 mu M, and the relative standard deviation (RSD, for 0.2, 2.0, and 20 mu M) was 2.7, 2.3, and 2.9%, respectively. Moreover, a smartphone-based colorimetric sensor was developed for H2O2 assay at the concentration range of 0.25-4.0 mu M, with LOD of 0.2 mu M and RSD of 3.2, 2.5, and 2.9% (for 0.5, 1.0, and 3.0 mu M, respectively). We exploited the established sensor for glucose assay by measuring the generated H2O2 from the enzymatic reaction between glucose and glucose oxidase. There was a linear relationship between LSPR peak wavelength variations and the amount of glucose from 1.0 to 50 mu M, with LOD of 0.4 mu M and RSD of 3.2, 3.1, and 3.8% (for 2.0, 10, and 30 mu M, respectively). The sensor was successfully applied to determine H2O2 and glucose in food and human serum samples, respectively.

Automated summary

We introduced a sensitive colorimetric platform for hydrogen peroxide (H2O2) assay using gold/silver nanocages. The platform exhibits high sensitivity and low detection limit, and can be used for measurement using a smartphone.