Production and characterization of TixOy films by reactive magnetron sputtering deposited on substrate laminar Bamboo for the inactivation of Escherichia coli 226 in domestic wastewater

This study presents the synthesis and characterization of titanium oxide (TixOy) thin films deposited by DC reactive magnetron sputtering on biochar substrates derived from Guadua angustifolia laminated bamboo. The biochar was obtained via controlled pyrolysis at 300 °C, resulting in thermally and mechanically stable substrates suitable for oxide thin film growth. A 2² factorial design and a general factorial approach were employed to evaluate the effects of discharge power, target oxidation state, and annealing temperature on the crystallinity, morphology, and optical behaviour of the TixOy monolayers. Additionally, multilayer configurations were fabricated to improve film homogeneity and surface performance. Comprehensive physicochemical characterization using XRD, FTIR, UV–VIS DRS, SEM-EDS, and XPS revealed mixed anatase/rutile phase formation, increased surface oxygen vacancies, and tuneable optical band gaps ranging from 3.52 to 3.16 eV, with a redshift observed as the number of layers increased. The evolution of these properties was strongly correlated with the deposition parameters, demonstrating precise control over the structural and interfacial features of the films. The results demonstrate the potential of combining natural-origin carbon substrates with reactive sputtering to obtain functional oxide films with tailored optoelectronic and surface properties, supported by 37.6 ± 9.4 % E. coli inactivation under UV exposure in 30 min.