Enhanced Antibacterial Property of Facet-Engineered TiO₂ Nanosheet in Presence and Absence of Ultraviolet Irradiation

• Main Authors: Kenichiro Hayashi, Kosuke Nozaki, Zhenquan Tan, Kazuhisa Fujita, Reina Nemoto, Kimihiro Yamashita, Hiroyuki Miura, Keiji Itaka, Satoshi Ohara
• Format: Article
• Language: English
• Published: MDPI AG 2019-12-01
• Series: Materials
• Subjects: tio₂; facet engineering; photocatalytic activity; antibacterial activity
• Online Access: https://www.mdpi.com/1996-1944/13/1/78

Titania (TiO₂) has attracted much attention recently for reducing bacterial diseases by the generation of reactive oxygen species (ROS) under UV irradiation. However, demand for higher photocatalytic activity due to higher recombination of electron and hole remains. The aims of this study were to make titania with higher antibacterial property and show the mechanisms of the bactericidal effect. In this study, we hydrothermally synthesized TiO₂ nanosheets (NS) with highly-oriented structures. Samples were divided into five groups, depending on the fluorine/titanium ratio in the raw material, namely NS1.0, NS1.2, NS1.5, NS1.8, and NS2.0. Facet ratio and nanosheet size increased with an increase of fluorine/titanium ratio. The photocatalytic activity of TiO₂ nanosheet was assessed by the generation of ROS. Hydroxyl radicals and superoxides were generated efficiently by ultraviolet light irradiation on NS1.5 and NS1.0, respectively. Antibacterial activity against <i>Streptococcus mutans</i> was assessed in the presence and absence of UV irradiation; NS1.0 showed superior antibacterial properties compared to commercially available TiO₂ nanoparticles, under both conditions, due to the oxidation of intracellular components and cell membrane. These results together suggested TiO₂ nanosheet induced bacterial cell death by oxidation, and TiO₂ facet engineering resulted in enhancement of both photocatalytic and antibacterial activities of TiO₂.