Chemical deposition of silver and gold nanoaprticles on polydopamine-coated silica nanoparticle surfaces and its application for surface-enhanced Raman scattering (SERS) substrates

Abstract

Inspired by adhesive proteins secreted by marine mussels, dopamine has emerged as a versatile surface modification agent for a wide range of materials. Through oxidative self-polymerization of dopamine in an alkaline buffer solution, a thin layer of polydopamine can be spontaneously coated on material surfaces, and the modified surface can act as a metal-binding layer in a subsequent metal deposition process. Based on the metal-binding capability of the polydopamine layer, a simple one-pot method for the deposition of silver (Ag) or gold (Au) nanoparticles on polydopamine-coated silica nanoparticles is proposed, respectively. Both composite particles were fabricated by dispersing SiO2 NPs in a dopamine solution followed by a chemical reduction of Ag or Au ions to metallic Ag or Au using a reducing agent, respectively. Chemically deposited Ag or Au NP-aggregates and Ag nanosheet-assembled shells generated rough surfaces, which is responsible for the generation of strong local electromagnetic (EM) fields and the enhancement of SERS signals. Hot spots created by Ag and Au nanostructures on the surface of SiO2-polydopamine NPs have potential as a surface-enhanced Raman scattering (SERS) substrate to analyze Rhodamine 6G (R6G) as a model analyte molecule.