Laser-Induced Synthesis and Processing of Nanoparticles in the Liquid Phase for Biosensing and Catalysis.

Laser ablation (LAL) and irradiation in liquids (LIL) are becoming two of the most studied and dominant ways of synthesis and modification for nanostruc tured materials. Such rapid development is due to a fast and economic way to obtain nanoparticles of any material. Starting from solid targets submerged in water or other liquids, it is possible to obtain noble metals, metal alloys, metal oxides, and graphene nanoparticles, simply by irradiating the target with a focused laser beam. Moreover, it is also possible to modify already existing nanoparticles, generating defects in their structures or reshaping them, through laser irradiation of their colloidal disper sion using an unfocused laser beam. In this chapter, a focus on the fundaments of laser ablation and modification in liquids is reported as well as some advances in the synthesis and modification of new nanostructures with their relative application in different fields of research such as bio-sensing, catalysis, and optoelectronics. The example of the synthesis of ultra-pure silver nanoparticles by LAL and their appli cation as surface-enhanced Raman scattering (SERS) active substrate for biosensing application is provided. In such a study, it is possible to detect and characterize a protein involved in diabetes mellitus type 2 (amylin), at nanomolar concentration. LIL has been also considered to modify commercial TiO2 and graphene oxide (GO) colloids. Such unconventional treatment has shown to enhance the performances of these two materials, towards photocatalytic water splitting and water purification applications, thanks to the modification of the morphology and oxygen functionali ties of these materials. As an added value, the LIL of TiO2 and GO is a more green technique and tunable methodology concerning conventional reduction methods. Laser irradiation of GO results in conferring to the material an antimicrobial activity not shown by the untreated one. Similarly, the performance in the photocatalytic H2 production of laser-treated TiO2 samples is examined pointing out that the TiO2 structural modifications induced by the LIL process are fundamentals to strongly increase the photocatalytic performance.