Gold semicontinuous thin-film-coated mesoporous TiO2 for SERS substrates

Abstract

In this work, the preparation and thermal evolution of sputtered semicontinuous gold thin films obtained over ordered mesoporous TiO 2 films are presented. The controlled surface topography of the ordered mesoporous TiO 2 substrate was used as template for obtaining plasmonic hotspots for Surface Enhanced Raman Spectroscopy (SERS) applications. Plasmonic thin film was obtained by Au sputtering when film thickness was under circa 10 nm. Above this value, the porosity effects from the substrate were lost and Raman signal enhancement with it. Moreover, heat treatment was explored in order to obtain gold nanoislands that can also provide very efficient Raman enhancement. Hence, a very straightforward synthesis procedure is presented for sensing application, even for large scale production.

Optical Printing of Single Au Nanostars

“…Among the many available shapes, gold nanostars (AuNSs) stand out for their higher number of hot-spots and their stronger field enhancement near the tips . For this reason, AuNSs have been extensively applied as substrates for surface enhanced Raman spectroscopy (SERS) and biosensing. − Typically, they present LSPR close to the near-infrared window of biological tissues, making them suitable for photothermal therapies − and cellular imaging . Despite their irregular shape, they tend to present an isotropic interaction with light due to the many orientations of their tips, a property that was exploited to produce random lasing in a dye-doped gain medium .…”