TiO2/Ag nanostructured coatings as recyclable platforms for surface-enhanced Raman scattering detection

The surface-enhanced Raman scattering (SERS) has become irreplaceable for the direct detection of organic chemicals and biomolecules. However, the SERS-active platforms need to meet certain requirements for routine use. Among them, the most important are low detection limit, spectra reproducibility, and the possibility of being re-used. In this study, we investigate and compare the SERS performance of Ag/TiO2 coatings with three different architectures -planar, tubular and nanoparticle-based - prepared by means of plasma-assisted techniques. In all three cases, the nanoislands, made of plasmonic Ag, enhance the SERS signal, while the TiO2 provides degra-dation of surface contaminants after UV irradiation. The latter relates to the natural photoactivity of titania, which enables the recycling of the substrates. As shown, nanopatterning of surfaces offers a good compromise between the high detection limit and re-cyclability of those nanostructured Ag/TiO2 coatings with larger active surface area; here, namely TiO2 nanoparticle films decorated with silver nanoislands behave promisingly. Such nanostructured Ag/TiO2 films allow not only the detection of methylene blue (MB) at concentrations down to 5 x 10-9 M, but also may be easily cleaned by UV radiation in a reasonable time scale.

Automated summary

In this study, Ag/TiO2 coatings with different architectures were prepared using plasma-assisted techniques, and their SERS performance was investigated and compared. Nanoislands enhance the SERS signal, TiO2 degrades surface contaminants, and the photoactivity of titania enables the recycling of substrates. Nanostructured Ag/TiO2 coatings with larger active surface area show a good compromise between high detection limit and recyclability, allowing for the detection of methylene blue at low concentrations and easy cleaning by UV radiation.