Detection and analysis of reactive oxygen species (ROS) generated by nano-sized TiO2 powder under ultrasonic irradiation and application in sonocatalytic degradation of organic dyes

Abstract

Recently, the sonocatalytic technology using various semiconductors combined with ultrasonic irradiation has been received much attention to solve the environmental problems. In this paper, nano-sized titanium dioxide (TiO(2)) powder as a sonocatalyst was irradiated by ultrasound and the generation of reactive oxygen species (ROS) during sonocatalytic reaction process has been estimated by the method of Oxidation-Extraction Photometry (OEP). That is, the 1,5-diphenylcarbohydrazide (DPCI) can be oxidized by ROS into diphenylcarbonzone (DPCO), which can be extracted by the mixed solution of benzene and carbon tetrachloride and show the great absorbance at 563 nm wavelength. The synergistic effect of TiO(2) and ultrasonic irradiation was estimated and some influencing factors, such as ultrasonic irradiation time and TiO(2) addition amount on the generation of ROS were reviewed. The results indicate that the quantities of generated ROS increase with the increase of ultrasonic irradiation time and TiO(2) addition amount. Moreover, the relationship between quantities of generated ROS and DPCI concentration was also studied. And then, several quenchers were used to determine the kind of the generated ROS. At last, the researches on the sonocatalytic degradation of organic dyes and the corresponding reaction kinetics have also been performed, which is found to follow the pseudo first-order kinetics approximately. This paper may offer some important subjects for broadening the applications of sonocatalytic technology.

Photocatalytic Activity of Quantum Dots

“…Then the molecular oxygen (O 2 ) near the interface photocatalyst could (4)- (7)), whereas the valence band holes can directly oxidize organic pollutants adsorbed on the surface of catalyst (QDs) or mineralized them indirectly through hydroxyl radicals•) OH) generated by the reaction of holes and water molecules (H 2 O) or chemisorbed (OH − ) (Eqs. (8)- (10)) [49]. For example, in the self-photosensitization pathway for the new fuchsin dye, photodegradation in the presence of QDs under visible light irradiation as shown in Scheme 1b.…”

Application of graphene quantum dots as green homogenous nanophotocatalyst in the visible-light-driven photolytic process

“…(6) and (7)) when adsorbed/or chemisorbed hydroxyl anion or water molecules oxidize with the valence-band [51]. In this regard, the valence band holes could directly oxidize organic pollutants (i.e., the Celestine Blue dye) adsorbed on the surface of the catalyst (GQDs), or indirectly mineralize them through hydroxyl radicals·) OH) generated by the reaction of the holes and water molecules (H 2 O) or chemisorbed (OH − ), [52]. As expected, the CB molecules could be oxidized by: (i), superoxide anion radicals (O 2 −⋅ ) generated by dissolved oxygen (O 2 ) molecules and electrons accumulated on the surface of catalyst (GQDs); and/or (ii), the hydroxyl radicals (·OH) resulting from the generated holes (h + ) in GQDs (Eq.…”

Nanoparticles and Bacteria

“…A better knowledge of the interactions between TiO 2 (or ZnO), electromagnetic radiation, and water is mandatory in understanding the chemical processes and risks implied by the use of sunscreens and/or cosmetics based on oxide semiconductors [28]. Recent studies suggest that sonication can replace the electromagnetic radiation in the generation of ROS in TiO 2 [17,29].…”