Synthesis of Plasmonic Silver Nanoisland Films (AgNIFs) and Gold Nanoisland Films (AuNIFs) for Antibacterial Theranostics

Antibiotics have revolutionized medicine, reducing bacterial infection morbidity and mortality. However, the emergence of antibiotic-resistant microorganisms threatens their efficacy. Silver nanoisland films (AgNIFs) and gold nanoisland films (AuNIFs) which are part of plasmonic metal nanoparticles have great performance for bacterial theranostics. AgNIFs and AuNIFs were alternative solutions against gram-positive and gram-negative bacteria combined with photothermal therapy. AgNIFs and AuNIFs were synthesized by a chemical reaction in 3 steps of growing, including Au3+ creation, Ag seeding, and nanoisland growing. AFM, SEM, and UV-Vis spectroscopy were used to characterize the AgNIFs and AuNIFs. In addition, the Photothermal effect of AgNIFs and AuNIFs was carried out using stimulated solar light and was continued by fluorescence and SEM imaging after light irradiation. Finally, the Raman signal of AgNIFs and AuNIFs surface was confirmed after light exposure. SEM images showed AgNIFs and AuNIFs inhomogeneous size with nanoisland cross on the glass substrate. AgNIFs and AuNIFs are well-suited for use with solar light because their maximal absorbance occurs in the visible light spectrum of the electromagnetic spectrum. A combination of AgNIFs, AuNIFs, and photothermal therapy generated good antibacterial properties in either E. coli or S. aureus. Those materials can convert light to heat by plasmonic localized heating. Light irradiation on AgNIFs and AuNIFs surfaces revealed significant enhancement in antibacterial activity. In the end, AgNIFs and AuNIFs could be used as substrate agents for SERS bacterial detection.