Functionalization of TiO₂ inverse opal structure with atomic layer deposition grown Cu for photocatalytic and antibacterial applications

Abstract

<p>TiO<sub>2</sub> inverse opal (IO) structure surfaces were functionalized with a sub-monolayer amount of Cu by atomic layer deposition (ALD) and tested for photocatalytic and antimicrobial applications. Decomposition of acetylene (C<sub>2</sub>H<sub>2</sub>) into CO<sub>2</sub> and reduction of CO<sub>2</sub> into CH<sub>4</sub> were tested in the gas phase and photodegradation of methylene blue (MB) was tested in the liquid phase. Antimicrobial activity was tested against Gram-positive Staphylococcus aureus (S. aureus) bacteria. ALD Cu without any post-deposition heat treatment (HT) decreased the photo degradation rate of both C<sub>2</sub>H<sub>2</sub> and MB but improved the activity towards CO<sub>2</sub> reduction. ALD Cu increased MB photodegradation rate and antimicrobial activity only after HT at 550 °C, which was linked to the improved chemical stability Cu after the HT. The same HT decreased the activity towards CO<sub>2</sub> reduction and decomposition of C<sub>2</sub>H<sub>2</sub>. The HT induced desorption of loosely bound ALD Cu<sup>+/2+</sup> from the TiO<sub>2</sub> IO surface and the remaining Cu<sup>+/2+</sup> was reduced to Cu<sup>+</sup>. The photocatalytic and antimicrobial activity of TiO<sub>2</sub> IO can be tailored by the addition of a sub-monolayer amounts of Cu with performance depending on the targeted reaction.</p>