Black Au-Decorated TiO₂ Produced via Laser Ablation in Liquid

The rational combination of plasmonic and all-dielectric concepts within hybrid nanomaterials provides a promising route toward devices with ultimate performance and extended modalities. Spectral matching of plasmonic and Mie-type resonances for such nanostructures can only be achieved for their dissimilar characteristic sizes, thus making the resulting hybrid nanostructure geometry complex for practical realization and large-scale replication. Here, we produced amorphous TiO2 nanospheres decorated and doped with Au nanoclusters via single-step nanosecond-laser irradiation of commercially available TiO2 nanopowders dispersed in aqueous HAuCl4. Fabricated hybrids demonstrate remarkable light-absorbing properties (averaged value ≈96%) in the visible and near-IR spectral range mediated by bandgap reduction of the laser-processed amorphous TiO2 as well as plasmon resonances of the decorating Au nanoclusters. The findings are supported by optical spectroscopy, electron energy loss spectroscopy, transmission electron microscopy, and electromagnetic modeling. Light-absorbing and plasmonic properties of the produced hybrids were implemented to demonstrate catalytically passive SERS biosensor for identification of analytes at trace concentrations and solar steam generator that permitted to increase water evaporation rate by 2.5 times compared with that of pure water under identical 1 sun irradiation conditions.