Sensitization with Stannous Acetate in Dimethyl Sulfoxide for Silver Electroless Deposition

Abstract

This paper reports the applicability of a dimethyl sulfoxide (DMSO) solution of stannous acetate (Sn(OAc)2/DMSO) for sensitization in electroless deposition (ELD). Silver ELD was examined on nanostructured surfaces derived from polystyrene-blockpoly(methylmethacrylate) via sensitization with an aqueous or DMSO solution of Sn(OAc)2 or SnCl2, activation with aqueous Ag[(NH3)2]+, followed by immersion in an aqueous solution containing [Ag(NH3)2]+ and tartrate. Sensitization with 0.5 mM Sn(OAc)2/DMSO led to the preferential deposition of silver nanoparticles (Ag-NPs) on the nanoscale ridges of the polymer film upon 10-minute ELD. In contrast, Ag-NPs were negligibly deposited on the polymer film sensitized with 0.5 mM SnCl2/DMSO. Conventional sensitization solutions based on aqueous SnCl2 (SnCl2/H2O) required a much higher Sn(II) concentration (≥5mM) for sensitization of the polymer surface. X-ray photoelectron spectroscopy results supported the stoichiometric formation of Ag0 from Sn(II) in the activation step on the polymer surface sensitized with Sn(OAc)2/DMSO as with 50 mM SnCl2/H2O. Sn(OAc)2/DMSObased sensitization was inefficient on thiolate self-assembled monolayers. The efficient sensitization of the polymer surface with Sn(OAc)2/DMSO was explained by the reduction of hydroxide formation by the use of the organic solution and efficient partitioning of Sn(OAc)2 into the solvent-swollen surface region of the polymer film.