Synthesis, Characterization, and Antibacterial Activity Test of Geothermal Silica/AgNO3 Thin Film

Abstract

Geothermal silica waste offers convenient, economical, and environmentally friendly material with high hydrophobicity to produce thin films. Silica-thin films from geothermal waste using the sol-gel method, though, no addition of AgNO₃ was conducted for antibacterial functions. This study aims to produce silica-thin films from geothermal waste with the addition of AgNO₃ and analyze the antibacterial activity. The procedures carried out in this research were (i) an acid leaching process using HNO₃; (ii) the production of silica thin film with and without the addition of AgNO₃; (iii) thin film characterization including a water contact angle measurement (WCA), XRF, FTIR, XRD and SEM-EDX on silica thin film samples with and without the addition of AgNO₃; and (iv) antibacterial activity test. The results show the optimum HNO₃ concentration for the acid leaching process was 20%, yielding 99.08% SiO₂ by mass. The WCA of the silica thin film in the presence and absence of AgNO₃ reached a value of ±160°, indicating the addition of AgNO₃ did not decrease the contact angle of the silica thin film. This research employed smart deconvolution of IR Spectra using Fityk software which reveals a higher area ratio for Si-O-Si relative to Si-OH. Furthermore, it was observed that the silica thin films exhibited an amorphous morphology, both without and with the addition of AgNO₃, with Ag discovered to be dispersed on the thin film. However, despite the presence of Ag, both TF20 and TF20+Ag samples were found to be ineffective in inhibiting bacterial growth, as evidenced by bacteria-free zones on the samples.