High Stability Thiol-Coated Gold Nanostars Monolayers with Photo-Thermal Antibacterial Activity and Wettability Control.

The adhesion and proliferation of bacteria on abiotic surfaces pose challenges in both health care and industrial applications. Gold nanostars (GNSs) monolayers grafted on glass have demonstrated to exert antibacterial action due to their photo-thermal features. Here, these GNS layers were further functionalized using thiols monolayers, in order to impart different wettability to the surfaces and thus adding a feature that could help to fight bacterial proliferation. Thiol that has different functional groups was used and the thiol-protected surfaces were characterized by means of UV-vis spectroscopy, contact angles, SEM and surface enhanced Raman spectroscopy (SERS). We verified that (i) coating with the proper thiol allows us to impart high hydrophilicity or hydrophobicity to the surfaces (with contact angle values ranging from 10 to 120°); (ii) GNS monolayers are strongly stabilized by functionalization with thiols, with shelf stability increasing from a few weeks to more than three months and (iii) photo-thermal features and subsequent antibacterial effects caused by hyperthermia are not changed by thiols layers, allowing us to kill at least 99.99% of representative bacterial strains.