3.1. Sensing mechanism of the sensor
Scheme 1 illustrates the mechanism of the colorimetric detec- tion of H2O2 with triangle AgNPs. The radical reaction mechanism has been proposed, in which the redox potential of the H2O2/H2O couple (1.763 V in acidic medium) [17] is higher than that of the Ag(I)/Ag couple (0.8 V) and H2O2 can efficiently oxidize Ag nanopar- ticles in acidic medium. In our work, the oxidation potential of triangular AgNPs is about 0.38 V. Thus, when H2O2 is added into tri- angle AgNPs, Ag triangular nanoprisms were easily etched to round nanodiscs by H2O2. Correspondingly, the conversion of AgNPs to Ag+ can induce a visible color change and hence H2O2 can be quan- titatively measured.
3.2. Optimization of experimental conditions
In order to achieve the best performance for H2O2 detection, we have scrutinized the effects of some important parameters, includ- ing the pH value of the solution, the reaction time and the reaction temperature. First, the pH of the solution played an important role in the formation of the triangular Ag nanoplates. In addition, H2O2 is also a strong oxidizer in acidic or neutral [18]. Thus, the reaction of triangular Ag nanoplates was investigated from pH 3.6 to 5.4. When the pH was fixed at 5.4, the surface plasmon resonance