THE EFFECT OF MORPHOLOGY ON ANTIBACTERIAL PROPERTIES OF CuO-DOPED TiO₂-SiO₂NANOCOMPOSITES

In this paper, we report the synthesis of core-shell-structured TiO2-SiO2 nanocomposites doped with Copper for disinfection of E. Coli. Two different morphologies were realized by adjusting the chronological order of synthetic procedure, i.e. copper deposition using a photo-assisted deposition (PAD) method and incorporation of SiO2 shell via a Stober method. The first morphology (M1) was produced by employing PAD before the Stober method, while the second morphology (M2) was obtained by reversing the order. Copper nanoparticles (in the form of CuO) are situated solely on TiO2 core for Morphology 1, while for Morphology 2 they are scattered both on TiO2 core and SiO2 shell. Transmission Electron Microscopy (TEM) imaging confirms the presence of copper on the nanocomposites, as well as their core-shell structure which is further corroborated by X-ray Photoelectron Spectroscopy (XPS) results. Under dark conditions, nanocomposite with Morphology 2 revealed disinfection efficiency of (60.4 ± 2.5) %, superior to its Morphology 1 counterpart which merely offered (5.0 ± 1.9) % of disinfection efficiency. Importantly, both morphologies exhibit similar antibacterial activities under UV illumination, resulting in disinfection efficiency of (90.8 ± 3.7) % and (88.1 ± 4.9) % after 120-min illumination for Morphology 1 and Morphology 2, respectively. Accordingly, we suggest that morphology dictates which disinfection mechanism is predominant, i.e. self-killing of bacteria facilitated by copper or cell membrane destruction by photo-produced Reactive Oxygen Species (ROS). Based on these results, we propose Morphology 2 as the preferable morphology as it exhibits adequately effective disinfection under dark conditions and is even more reliable under UV illumination.