Silver particle nucleation and growth at liquid/liquid interfaces: A scanning electrochemical microscopy approach

Scanning electrochemical microscopy (SECM) has been used to induce and monitor the electrodeposition of silver particles at a liquid/liquid interface by the electron transfer reaction between aqueous Ag ⁺ ions, generated by anodic dissolution of an Ag disk ultramicroelectrode (UME), and bis(pentamethylcyclopentadienyl) iron (decamethylferrocene, DMFc) in a 1,2-dichloroethane (DCE) phase. A two-electrode system with an Ag UME as the SECM tip was used to investigate the factors affecting the deposition process, such as the tip-interface separation, potential applied to the tip, concentration of the reductant in the DCE phase, and the reaction driving force, which was controlled by the concentration ratio of a common ion (ClO ₄ ^-) in the two phases. A theoretical model was developed and rate constants for Ag particle nucleation and growth at the water/ DCE interface were obtained by thorough analysis of experimental current-time curves. It was found that Ag ⁺ ion adsorption at the interface, coupled to particle nucleation and growth, best described the experimental data. The growth of Ag particles at the liquid/liquid interface was confirmed by independent microscopy measurements.