In this paper, it is first reported that gray hydrogenated TiO2 sphere photocatalysts (H-TiO2) with high reactivity to solar light are mass produced within a few minutes using an underwater discharge plasma modified sol-gel method at room temperature and atmospheric pressure. This plasma modified system is an easy one-step in-situ synthetic process and the crystallinity, hydrogenation, and spherical structure of H-TiO2 are achieved by the synergy effect between the continuous reaction of highly energetic atomic and molecular species generated from the underwater plasma and surface tension of water. The resultant H-TiO2 demonstrated high anatase/rutile bicrystallinity and extended optical absorption spectrum from the ultraviolet (UV) to visible range. Furthermore, various defects including oxygen vacancies and hydroxyl species on the TiO2 surface permitted the enhancement of the photocatalytic performance. It was demonstrated that H-TiO2 photocatalysts showed significant degradation efficiencies for reactive black 5 (RB 5), rhodamine B (Rho B), and phenol (Ph) under solar light irradiation, up to approximately 5 times higher than that of commercial anatase TiO2 (C-TiO2), which resulted in good water purification. Notably, it was also possible to cultivate HepG2 cells using such well-purified water (to degrees up to 76%), with minimal cytotoxicity. Considering all these results, we believe that this novel plasma technology is promising for important environmental applications.
Keywords: Cytotoxicity; Photocatalysts; Photocatalytic activity; Titanium dioxide (TiO(2)); Underwater discharge plasma treatment.
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