Silica Nanosprings Coated with Noble Metal Nanoparticles: Highly Active SERS Substrates

Silica nanosprings with large surface-to-volume ratios were coated with noble metal nanoparticles (NPs) using chemical vapor deposition or chemisorption of presynthesized or in situ synthesized nanoparticles. Chemisorption of presynthesized silver NPs onto amine-functionalized silica NS results in particularly interesting materials with small interparticle spacings and high surface-enhanced Raman scattering activity. SERS enhancement factors approaching ∼10 10 were observed with thiophenol. In an alternative approach, silica NS coated with core−shell nanostructures, formed by deposition of catalytically reduced silver on AuNP-coated NS, exhibit a highly uniform SERS response with enhancement factors of ∼10 8 . The advantages of these materials include (i) commercial availability of silica nanosprings, AuNPs/AgNPs, and silver enhancer solutions, (ii) simplicity and reproducibility of functionalization and deposition steps, and (iii) high SERS activity of these substrates rendering them of considerable interest for a variety of sensor applications.