On-Demand Plasmon Nanoparticle-Embedded Laser-Induced Periodic Surface Structures (LIPSSs) on Silicon for Optical Nanosensing

Ultrashort laser pulses deliver electromagnetic energy to matter causing its localized heating that can be used for both material removal via ablation/evaporation and driving interface chemical reactions. Here, it is shown that both mentioned processes can be simultaneously combined within straightforward laser nanotexturing of Si wafer in a functionalizing solution to produce a practically relevant metal-semiconductor surface nano-morphology. Such unique hybrid morphology represents deep-subwavelength Si laser-induced periodic surface structures (LIPSSs) with an extremely short period down to 70 nm and high-aspect-ratio nano-trenches loaded with controllable amount of plasmonic nanoparticles formed via laser-induced decomposition of the precursor noble-metal salts. Moreover, heat localization driving reduction process is 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, applicability of such hybrid morphology for fluorescence-based detection of nanomolar concentrations of mercury cations in solution is demonstrated.