Photocatalytic inactivation of Escherischia coli under UV light irradiation using large surface area anatase TiO2 quantum dots

Abstract

In this study, high specific surface areas (SSAs) of anatase titanium dioxide (TiO₂) quantum dots (QDs) were successfully synthesized through a novel one-step microwave-hydrothermal method in rapid synthesis time (20 min) without further heat treatment. XRD analysis and HR-TEM images showed that the as-prepared TiO₂ QDs of approximately 2 nm size have high crystallinity with anatase phase. Optical properties showed that the energy band gap (E _g) of as-prepared TiO₂ QDs was 3.60 eV, which is higher than the standard TiO₂ band gap, which might be due to the quantum size effect. Raman studies showed shifting and broadening of the peaks of TiO₂ QDs due to the reduction of the crystallite size. The obtained Brunauer-Emmett-Teller specific surface area (381 m² g^-1) of TiO₂ QDs is greater than the surface area (181 m² g^-1) of commercial TiO₂ nanoparticles. The photocatalytic activities of TiO₂ QDs were conducted by the inactivation of Escherischia coli under ultraviolet light irradiation and compared with commercially available anatase TiO₂ nanoparticles. The photocatalytic inactivation ability of E. coli was estimated to be 91% at 60 µg ml^-1 for TiO₂ QDs, which is superior to the commercial TiO₂ nanoparticles. Hence, the present study provides new insight into the rapid synthesis of TiO₂ QDs without any annealing treatment to increase the absorbance of ultraviolet light for superior photocatalytic inactivation ability of E. coli.

Keywords: TiO2; X-ray diffraction; microwave–hydrothermal; photocatalysis; quantum dots.