Compósitos TiO2/ZIF-67: síntese e aplicação como antibacteriano

Abstract

Drug resistant bacteria emerged as a global health crisis, turning the antibacterial materials into a necessity. This work suggests as antibacterial materials two TiO2/ZIF-67 composites synthetized by two different microwave-assisted solvothermal routes: the one-pot synthesis by directly mixing the precursors (titanium(IV) isopropoxide, cobalt(II) nitrate and 2- methylimidazole) and the two-steps synthesis by dispersing the obtained TiO2 into the cobalt(II) nitrate and 2-methylimidazole precursor solutions. The main purpose of these composites are an effective but less cytotoxic biocide when compared to its compounds. TiO2 has been wildly studied as antimicrobial agent, on the other hand ZIF-67 has only a few recent studies. These individual phases, which constitute the composites, were also synthesized by known routes and routes closer to the ones used for obtaining the composites. The produced materials were characterized by X-ray diffraction, UV-Vis, FTIR, Raman and electron dispersion spectroscopies, thermogravimetric analysis, scanning and transmission electron microscopies. From these characterizations we can see that the synthesized TiO2 and the ZIF-67 are in the expected crystalline phase, the one pot composite has amorphous titania and crystalline ZIF67, and the two steps composite has both TiO2 and ZIF-67 crystalline. For the antimicrobial study, the Staphylococcus aureus bacteria was used in a macrodilution test in the dark. The results shown that TiO2 has no activity, ZIF-67 has activity until 2.5 mg/mL, the one pot composite present activity until 5 mg/mL and the two steps composite displayed activity until 1 mg/mL. Initial studies were also made in the solar cells and in the photocatalysis filed.