{101}–{001} Surface Heterojunction-Enhanced Antibacterial Activity of Titanium Dioxide Nanocrystals Under Sunlight Irradiation

Abstract

The {101}-{001} surface heterojunction constructed on polyhedral titanium dioxide (TiO) nanocrystals has recently been proposed to be favorable for the efficient electron-hole spatial separation due to the preferential accumulation of electron and hole on {101} and {001} facets, respectively. The formed free electron and hole can promote reactive oxygen species (ROS) production, which potentially can be used for inactivation of bacteria. In the present study, a series of truncated octahedral bipyramid TiO nanocrystals (T1, T2, T3, and T4) coexposed with {101} and {001} facets were prepared to form various ratios of {101} to {001} facet for optimization of electron-hole spatial separation efficiency. All these polyhedral TiO nanocrystals could more significantly produce ROS than spherical TiO nanocrystals (Ts), exhibiting the higher antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria under simulated sunlight irradiation. Among these polyhedral TiO nanocrystals, T3 with a {101}/{001} ratio of 1.78 was found to be the best one showing the highest ROS and the most potent antibacterial performance. Scanning electron microscope images of bacteria displayed that the surface membrane structure of both E. coli and S. aureus bacteria was influenced to different extents by these TiO nanocrystals, where T3 caused the most severe membrane damage. The molecular mechanism underlying the high antibacterial activity of TiO nanocrystals was ascribed to activation of oxidative stress as evidenced by intracellular ROS production, glutathione depletion, and membrane lipid peroxidation in bacteria. The surface heterojunction as a completely new strategy holds great promise to develop effective antibacterial nanomaterials.

Enhanced Antibacterial Activity of Silver Doped Titanium Dioxide-Chitosan Composites under Visible Light

“…For example, titania-chitosan composites showed a photocatalytic effect on its antibacterial performance [15]. The hydroxyl radicals produced by titania under UV light hindered the growth of bacteria [16]. However, TiO 2 with a wide band-gap can only exert its antibacterial properties under UV light [17,18,19].…”

Recent Progress in Two‐Dimensional Antimicrobial Nanomaterials

“…Due to the favorable photocatalytic activities, 2D metallic compounds, such as ZnO nanorods, MgO, and TiO 2 , have shown outstanding antibacterial performances and attracted intense attention. The reasons for this activity can be attributed to large specific surface areas, rich surface‐active sites, and short migration distances for photogenerated charges from the bulk to material surface .…”

“…It is speculated that the high concentration of Ag NPs around the bacteria and the polyvalent effect result in strong interactions between nanocomposites and bacteria, which is responsible for effectiveinactivation of bacteria. Due to the favorable photocatalytic activities, [70] 2D metallic compounds, such as ZnO nanorods, [71] MgO, [72] andT iO 2 , [73] have shown outstanding antibacterial performances and attracted intense attention.T he reasons for this activity can be attributedt ol arge specific surfacea reas, rich surface-active sites, and short migration distances for photogenerated charges from the bulk to material surface. [74] Among 2D metallic nanocompounds, ultrathin TiO 2 nanosheets (TNS) are the most accessible antibacterial materials because of their low cost, promisings tability,h igh disinfection efficiency, nontoxicity,a nd robust oxidizing capability.…”

Theoretical Studies of Titanium Dioxide for Dye-Sensitized Solar Cell and Photocatalytic Reaction

“…All of these polyhedral TiO 2 nanocrystals can produce ROS more prominently than spherical TiO 2 nanocrystals, exhibiting more bacteria against gram-negative (E. coli) and Gram-positive (Staphylococcus aureus) bacteria under simulated sunlight high antibacterial activity. Surface heterojunction as a new strategy is expected to develop effective antimicrobial nanomaterials [52].…”