  Recent progress in hybrid nanomaterials composed of dissimilar constituents
permitted to improve performance and functionality of novel devices developed
for optoelectronics, catalysis, medical diagnostic and sensing. However, the
rational combination of such contrasting materials as noble metals and
semiconductors within individual hybrid nanostructures $via$ a ready-to-use and
lithography-free fabrication approach is still a standing challenge. Here, we
report on a two-step synthesis of Au-Si microspheres generated by laser
ablation of silicon in isopropanol followed by laser irradiation of the
produced Si nanoparticles in presence of HAuCl$_4$. Thermal reduction of
[AuCl$_4$]$^-$ species to metallic gold phase, along with its subsequent mixing
with silicon under laser irradiation creates a nanostructured material with a
unique composition and morphology revealed by electron microscopy, tomography
and elemental analysis. Combination of such basic plasmonic and nanophotonic
materials 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 Au-Si hybrids, as well as commonly
criticized randomness of the nanomaterials prepared by laser ablation in
liquid, were proved useful for realization of anti-counterfeiting labels based
on physically unclonable function approach.
