Oxidative Dissolution of Silver Nanoparticles by Dioxygen: A Kinetic and Mechanistic Study

We have recently reported a kinetic and mechanistic study on oxidative dissolution of silver nanoparticles (AgNPs) by H2O2. In the present study, the parameters that govern the dissolution of AgNPs by O-2 were revealed by using UV/Vis spectrophotometry. Under the same reaction conditions (Tris-HOAc, pH 8.5, I=0.1m at 25 degrees C) the apparent dissolution rate (k(app)) of AgNPs (10 +/- 2.8 nm) by O-2 is about 100-fold slower than that of H2O2. The reaction rate is first-order with respect to [Ag-0], [O-2], and [Tris] T, and inverse first-order with respect to [Ag+] (where [Ag-0] = total concentration of Ag metal and [Tris](T) = total concentration of Tris). The rate constant is dependent on the size of AgNPs. No free superoxide (O-2(-)) and hydroxyl radical (center dot OH) were detected by trapping experiments. On the basis of kinetic and trapping experiments, an amine-activated pathway for the oxidation of AgNPs by O-2 is proposed.