TiO2-Embedded Ag Nanocrystals with Tunable Plasmon Resonance

The goal of this work is to investigate the potential and limitations of post-deposition annealing as a way to tune the optical and morphological properties of a paradigmatic plasmonic nanocomposite, Ag/TiO2, deposited by supersonic cluster beam synthesis (SCBD) on silica and sapphire. SCBD is a sustainable, high-throughput technique with high control over the composition of the target material. Due to the cluster-based nature of the technique, Ag/TiO2 films deposited by SCBD exhibit very small and finely dispersed Ag nanoparticles embedded in a TiO2 matrix, providing the perfect starting point for annealing treatments. Furthermore, since the nanoparticle deposition is ballistic in nature, films with the same properties can be deposited on different substrates, allowing a deeper understanding of filmsubstrate interactions. We address the role of the substrate during thermal annealing, outlining how using different substrates can steer the evolution of the film morphology and optical properties in drastically different directions. Furthermore, we show how the combination of conventional oven annealing and light-induced photothermal melting allow us to tune the size and distribution of the Ag nanoparticles inside the material over a wide range of configurations, opening new potential applications for the material. Finally, we investigate the viability of the Ag/TiO2 nanostructured material described so far in the fabrication of novel plasmon-based substrates for superresolution fluorescence microscopy, plasmonic structured illumination microscopy (LPSIM).