  Rational combination of plasmonic and all-dielectric concepts within unique
hybrid nanomaterials provides promising route toward devices with ultimate
performance and extended modalities. However, 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 unique amorphous TiO$_2$ nanospheres simultaneously decorated and
doped with Au nanoclusters via single-step nanosecond-laser ablation of
commercially available TiO$_2$ nanopowders dispersed in aqueous HAuCl$_4$. The
fabricated hybrids demonstrate remarkable light-absorbing properties (averaged
value $\approx$ 96%) in the visible and near-IR spectral range mediated by
bandgap reduction of the laser-processed amorphous TiO$_2$, as well as plasmon
resonances of the decorating Au nanoclusters, which was confirmed by combining
optical spectroscopy, advanced electron energy loss spectroscopy, transmission
electron microscopy and electromagnetic modeling. Excellent 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
one-sun irradiation conditions.
