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.
Recent progress in hybrid optical nanomaterials composed of dissimilar constituents permitted an improvement in the performance and functionality of novel devices developed for optoelectronics, catalysis, medical diagnostics, and sensing. However, the rational combination of contrasting materials such as noble metals and semiconductors within individual hybrid nanostructures via a ready-to-use and lithography-free fabrication approach is still a challenge. Here, we report on a two-step synthesis of hybrid Au-Si microspheres generated by laser ablation of silicon in isopropanol followed by laser irradiation of the produced Si nanoparticles in the presence of HAuCl 4 . Thermal reduction of [AuCl 4 ] − species to a metallic gold phase, along with its subsequent mixing with silicon under laser irradiation, creates a nanostructured material with a unique composition and morphology, as revealed by electron microscopy, tomography, and elemental analysis. A combination of basic plasmonic and nanophotonic materials such as gold and silicon within a single microsphere allows for efficient light-to-heat conversion, as well as single-particle SERS sensing with temperature-feedback modality and expanded functionality. Moreover, the characteristic Raman signal and hot-electron-induced nonlinear photoluminescence coexisting within the novel Au-Si hybrids, as well as the commonly criticized randomness of the nanomaterials prepared by laser ablation in liquid, were proved to be useful for the realization of anticounterfeiting labels based on a physically unclonable function approach.
Combination of dissimilar materials such as noble metals and common semiconductors within unified nanomaterials holds promise for optoelectronics, catalysis and optical sensing. Meanwhile, difficulty of obtaining such hybrid nanomaterials using common lithography-based techniques stimulates an active search for advanced, inexpensive, and straightforward fabrication methods. Here, we report one-pot one-step synthesis of Ag-decorated Si microspheres via nanosecond laser ablation of monocrystalline silicon in isopropanol containing AgNO3. Laser ablation of bulk silicon creates the suspension of the Si microspheres that host further preferential growth of Ag nanoclusters on their surface upon thermal-induced decomposition of AgNO3 species by subsequently incident laser pulses. The amount of the AgNO3 in the working solution controls the density, morphology, and arrangement of the Ag nanoclusters allowing them to achieve strong and uniform decoration of the Si microsphere surface. Such unique morphology makes Ag-decorated Si microspheres promising for molecular identification based on the surface-enhanced Raman scattering (SERS) effect. In particular, the designed single-particles sensing platform was shown to offer temperature-feedback modality as well as SERS signal enhancement up to 106, allowing reliable detection of the adsorbed molecules and tracing their plasmon-driven catalytic transformations. Considering the ability to control the decoration degree of Si microspheres by Ag nanoclusters via amount of the AgNO3, the developed one-pot easy-to-implement PLAL synthesis holds promise for gram-scale production of high-quality hybrid nanomaterial for various nanophotonics and sensing applications.
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