Au-decorated black TiO$_2$ produced via laser ablation in liquid

TL;DR

This paper reports a novel single-step laser ablation method to produce Au-decorated amorphous TiO$_2$ nanospheres with enhanced light absorption and plasmonic properties, enabling applications in biosensing and solar steam generation.

Contribution

The study introduces a simple, scalable laser ablation technique to create hybrid Au-TiO$_2$ nanostructures with combined plasmonic and dielectric properties for energy and sensing applications.

Findings

Achieved ~96% light absorption in visible and near-IR range.

Demonstrated effective SERS biosensing at trace levels.

Increased water evaporation rate by 2.5 times under solar irradiation.

Abstract

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.