Biotemplated nano titania for photocatalytic antimicrobial and antitumor applications

Abstract

Semiconductor oxide photocatalysis has been one of the preferred treatment methods to remove organic pollutants from water and air, without the production of any secondary pollution. These materials possess unique electronic, optical, surface and catalytic properties. Advancements in material synthesis has led to the production of highly customized, nanostructured metal oxides and sulfides. Among the many different semiconductor photocatalysts, titania has been proved to be the most suitable for water treatment applications, because, it is less expensive, nontoxic, easily modifiable and has conducive surface properties. But poor absorption of visible radiation has limited its large scale practical and commercial applications. Recent research has focused on overcoming this limitation through suitable surface modification doping, coupling and templating. Many researchers have explored non-surfactant, bio-organic templates during the shift from synthetic chemical route to biogenic synthesis. The functional groups in the organic templates are claimed to be responsible for controlled agglomeration and grain growth through hydrogen bonding interactions. In this regard, the current work is aimed to assess the influence of three chosen biomaterials namely, i) green tea extract, ii) Zingiber extract, iii) tapioca extract as templates and chitosan as a coupling agent on the properties of mesoporous titania. The various physico-chemical characteristics of the synthesized titania samples have been verified through TGA, BET, XRD, FTIR, DRS-UV, SEM-EDX and TEM analyses. The photocatalytic ability of the catalysts was examined against a model organic pollutant, Congo red, under solar irradiation under optimized reaction parameters. All the templated titania samples were mesoporous, with increased surface area and decreased particle size, compared to control titania and commercial Degussa P25. The red shift of the absorption edge of the templated titania was the significant result effected by the templates. NTG1, the green tea template titania (1:1 w/w) was found to be the most effective photocatalyst, with the highest surface area, lowest average particle size and least agglomeration, among the different template samples prepared in this study. Thus, NTG1 was further utilized to prepare a composite sample with chitosan, derived from a fungal source. The optimal composite sample, NTGC1, was not only the most efficient photocatalyst, but also the most active against Escherichia coli, Bacillus subtilis and Candida albicans. The nanocomposite titania was also biocompatible with the lowest cytotoxicity. NTGC1 also possessed antitumour activity, as proved form its ability to prevent the growth of cancer cells in the studies with AGS cell line. newline