Bactericidal efficiency of nanostructured Al–O/Ti–O composite thin films prepared by dual magnetron reactive co-sputtering technique

Mixed oxide Al–O/Ti–O composite nanostructured thin films were prepared at Ar:O2 gas ratio of 70:30 (7:3 in sccm) by reactive magnetron co-sputtering method. The effect of Al in the films on the antibacterial efficiency has been studied. In situ optical emission spectra (OES) were recorded in order to study the plasma chemistry as well as nucleation and growth process during deposition. The films were characterised by X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), field emission scanning electron microscope (FESEM), optical contact angle (OCA) and UV–visible transmission spectra (UV–vis). The qualitative and quantitative bactericidal efficiency was studied through SEM image of the treated E. coli cells (Escherichia coli NCIM 2809) and optical density (OD) measurement using UV–vis spectrometer, respectively. The better bactericidal efficiency was observed in the film with more Al content. The crystallinity, surface chemical composition, band gap in context of Al present in the films were discussed and correlated to bactericidal efficiency in the light of in situ investigation of plasma from OES.