  Ultrashort laser pulses allows to deliver electromagnetic energy to matter
causing its localized heating that can be used for both material removal via
ablation/evaporation and drive interface chemical reactions. Here, we showed
that both mentioned processes can be simultaneously combined within
straightforward laser nanotexturing of Si wafer in functionalizing solution to
produce a practically relevant metal-semiconductor surface nano-morphology.
Such unique hybrid morphology represent deep-subwavelength Si LIPSSs with a
extremely short period down to 70 nm with their high-aspect-ratio nanotrenches
loaded with controllable amount of plasmonic nanoparticles formed $via$
laser-induced decomposition of the precursor noble-metal salts. Moreover, heat
localization driving reduction process was utilized to produce surface
morphology locally decorated with dissimilar plasmon-active nanoparticles.
Light-absorbing deep-subwavelength Si LIPSSs loaded with controllable amount of
noble-metal nanoparticles represent an attractive architecture for
plasmon-related applications such as optical nanosensing where efficient
coupling of the propagating optical waves to highly localized electromagnetic
``hot spots`` is a mandatory requirement. To support this statement we
demonstrated applicability of such hybrid morphology for fluorescence-based
detection of nanomolar concentrations of mercury cations in solution.
