Preparation of a SERS substrate and its sample-loading method for point-of-useapplication

Abstract

A simple approach was demonstrated to prepare a silver (Ag) nanoparticle(NP) assembly as a SERS substrate. Just by dipping a flat silicon (Si)wafer into an aqueous deposition solution of hydrogen fluoride (HF) + silvernitrate (AgNO3), a monolayer of Ag NPs was uniformly deposited onto the Si wafer surface. In order toload the to-be-detected sample onto the as-prepared SERS substrate, three methodshave been individually tested, (i) by incubating the SERS substrate in the samplesolution, (ii) by dropping and drying a small volume of the sample solution (1–2 µl) onto the SERS substrate surface, or (iii) by directly introducing the sample into thedeposition solution. The last approach was also employed to metalize a Si nanowire(NW). Due to the NW’s highly curved surface, the Ag NPs self-assembled andaggregated along the NW with a close interdistance. The aggregated Ag NPs on theNW surface can also be used as a SERS substrate. The demonstrated approachholds the promise to prepare a fresh SERS substrate at the point-of-use with thesample already loaded to promptly collect the SERS signal for the field application.