Silver Linings: Electrochemical Characterization of TiO2 Sol-Gel Coating on Ti6Al4V with AgNO3 for Antibacterial Excellence

Abstract

This study aimed to synthesize TiO2 and silver-containing TiO2 layers on Ti6Al4V titanium alloy substrates, also known as titanium grade 5 (TiGr5), to provide corrosion resistance and antibacterial activity. The TiO2 layers were prepared through the sol-gel method and dip-coating technique. Silver introduction into the layers was performed in two different ways. One was the impregnation method by dipping the TiO2 layer-covered metal in aqueous AgNO3 solutions of various concentrations (TiO2/AgNO3), and the other was by direct introduction of AgNO3 into the precursor sol (Ag-TiO2). The two methods for incorporating AgNO3 into the coating matrix are novel, as they preserve silver in its ionic form rather than reducing it to metallic silver. The samples were put through electrochemical characterization, namely potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), and were tested in Hank’s solution, simulating a physiological environment. The behavior of the layers was monitored over time. Also, the thin layers’ thickness and adhesion to the substrate were determined. Microbiological evaluation of the Ag-doped coatings on glass substrates confirmed their significant bactericidal activity against Gram-negative Escherichia coli. Among the two types of coatings, the impregnated coatings demonstrated the most promising electrochemical performance, as evidenced by both EIS and potentiodynamic polarization analyses.