Recent Developments in Accelerated Antibacterial Inactivation on 2D Cu-Titania Surfaces under Indoor Visible Light

Abstract

This review focuses on Cu/TiO 2 sequentially sputtered and Cu-TiO 2 co-sputtered catalytic/photocatalytic surfaces that lead to bacterial inactivation, discussing their stability, synthesis, adhesion, and antibacterial kinetics. The intervention of TiO 2 , Cu, and the synergic effect of Cu and TiO 2 on films prepared by a colloidal sol-gel method leading to bacterial inactivation is reviewed. Processes in aerobic and anaerobic media leading to bacterial loss of viability in multidrug resistant (MDR) pathogens, Gram-negative, and Gram-positive bacteria are described. Insight is provided for the interfacial charge transfer mechanism under solar irradiation occurring between TiO 2 and Cu. Surface properties of 2D TiO 2 /Cu and TiO 2 -Cu films are correlated with the bacterial inactivation kinetics in dark and under light conditions. The intervention of these antibacterial sputtered surfaces in health-care facilities, leading to Methicillin-resistant Staphylococcus Aureus (MRSA)-isolates inactivation, is described in dark and under actinic light conditions. The synergic intervention of the Cu and TiO 2 films leading to bacterial inactivation prepared by direct current magnetron sputtering (DCMS), pulsed direct current magnetron sputtering (DCMSP), and high power impulse magnetron sputtering (HIPIMS) is reported in a detailed manner.

Photocatalytic Antibacterial Effectiveness of Cu-Doped TiO2 Thin Film Prepared via the Peroxo Sol-Gel Method

“…Among several transition metals, copper has gained considerable attention, both as dispersions and, in the case of elemental copper and as alloys [10,17,18]. For use as antibacterial agents, copper and its compounds achieve antibacterial activity by the accumulation of copper ions within cells, eventually causing degradation of cell membranes [19][20][21]. Using titanium tetrachloride (TiCl4) as a precursor and H2O2 as a peptizing agent, previous studies have proposed a peroxo sol-gel method for the synthesis of neutral TiO2 sol [22][23][24][25].…”

“…The results are listed in Table 1. The presence of copper slightly decreased the crystallite size of TiO2, which was attributed to the inhibition of titania condensation and the crystallization in the Cu-doped system [21]. Morphology of the as-prepared samples was investigated using TEM and HRTEM.…”

“…In addition, magnified view clearly identified some small copper nanoparticles (≤4nm) deposited on the surface of the TiO 2 nanoparticles (see Figure 2c). Therefore, elliptical anatase TiO 2 nanoparticles can be synthesised via the peroxo sol-gel method without a subsequent annealing process, and the presence of copper could decrease the particles size and crystallite size of TiO 2 , attributed to phase deterioration of the TiO 2 anatase [21]. Morphology of the as-prepared samples was investigated using TEM and HRTEM.…”

“…Antibacterial activities of Cu-doped TiO2 could be attributed to the production of ROS species (e.g., O2 − , OH • , and H2O2) using TiO2, as well as CuO nanoparticles that trigger oxidative stress and cell damage in bacteria [36]. In addition, released Cu ions (Cu 2+ ) increased intracellular ROS in bacteria using the following pathway [17,21]:…”

“…Among several transition metals, copper has gained considerable attention, both as dispersions and, in the case of elemental copper and as alloys [10,17,18]. For use as antibacterial agents, copper and its compounds achieve antibacterial activity by the accumulation of copper ions within cells, eventually causing degradation of cell membranes [19][20][21].…”