Colorimetric detection of H2O2: for detection of H2O2, 10 µl of Ag-HLNP dispersion was diluted using phosphate buffer (20 mM, pH 7.4) to reach an absorbance of less than 1. Then, different amounts of dilute 20 mM H2O2 solution to measure the absorbance change in different concentrations. The final volume of solution was controlled by the addition of deionized water.