Dissolution Kinetics of Silver Metal Nandparticles in Their Reaction with Nitric Acid in an Reverse Micelle Solution of AOT

摘要

The dissolution of silver nanoparticles in their reaction with aqueous HNO_3 solubilized to an reverse micelle solution of sodium bis(2-ethylhexyl)sulfosuccinate in decane is studied spectrophotometrically. A physicochemical model is advanced for quantifying the process kinetics on the basis of the following auto-catalytic scheme: Ag~0 + H~+ + NO_3~- - > Ag~+ + products (k_1), and Ag~0 + Ag~+ + NO_3~- - > 2Ag~+ + products (k_2). The effective rate constant k_2 decreases with decreasing solubilization capacity V_S/V_O (where V_S is the volume of the solubilized dispersed aqueous phase and V_O is the volume of the micelle solution); the solubilization capacity determines the size of the micelle cavities in which the reaction between Ag~0 and HNO_3 occurs: k_2 = 74 (V_S/V_O) centre dot 100 percent = 3.8 percent), 41 (2.9), and 35 (2.0) L/(mol s). The effective constant k_1 is determined with a high uncertainty; the effect of V_S/V_O on k_1 has the opposite tendency.