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 SnCl 2 , activation with aqueous Ag[(NH 3 ) 2 ] + , followed by immersion in an aqueous solution containing [Ag(NH 3 ) 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 SnCl 2 /DMSO. Conventional sensitization solutions based on aqueous SnCl 2 (SnCl 2 /H 2 O) required a much higher Sn(II) concentration (≥5 mM) for sensitization of the polymer surface. X-ray photoelectron spectroscopy results supported the stoichiometric formation of Ag 0 from Sn(II) in the activation step on the polymer surface sensitized with Sn(OAc) 2 /DMSO as with 50 mM SnCl 2 /H 2 O. 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.