Nanopartículas de TiO2 funcionalizadas com monocamada de APTES e porfirinas: degradação potencializada de acetaminofeno sob luz visível

Abstract

Titanium dioxide (TiO2) is an inorganic semiconductor whose application as a photocatalyst has been studied since the 20th century. However, its activity is limited to the use of ultraviolet radiation, which corresponds to 3% of the incident solar energy on Earth. Aiming to harness solar radiation, studies propose the modification of TiO2, resulting in materials capable of absorbing energy in the visible region of the spectrum. This work aimed to obtain hybrid materials based on commercial nanoparticulate TiO2 (P25 – Degussa), utilizing the porphyrins 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H2T4CPP) and its zinc complex ([Zn(T4CPP)]), and their application as photocatalysts under white light. To obtain these materials, (3-aminopropyl)triethoxysilane (APTES) was used as a molecular bridge between the TiO2 and the porphyrins. The experimental steps of the work consisted of: (I) obtaining and characterization of the H2T4CPP and [Zn(T4CPP)] porphyrins; (II) activation of the surface of TiO2 P25 with NaOH; (III) functionalization of the activated TiO2 with APTES (TiO2-APTES); (IV) immobilization of the H2T4CPP and [Zn(T4CPP)] porphyrins onto the functionalized material (producing TiO2-APTES-H2P and TiO2-APTES-ZnP, respectively); (V) evaluation of the photocatalytic activity of the TiO2-APTES-H2P and TiO2-APTES-ZnP materials under visible light. After activation, the TiO2 presented 6.94 OH groups/nm2, indicating an increase in surface hydroxyl groups. Infrared spectroscopy and XPS identified the formation of an APTES monolayer on the material's surface. It was possible to verify the way APTES bonded to the surface. Diffuse reflectance spectroscopy confirmed the immobilization of the porphyrins onto the material. Stability tests of the materials in an aqueous solution indicated that the APTES-containing materials are unstable in water. Acetaminophen degradation experiments under white light irradiation, using the materials as photocatalysts, were performed under acetonitrile. The systems utilizing the TiO2-APTES-H2P and TiO2-APTES-ZnP materials showed approximately 40% of acetaminophen degradation when irradiated, a result 3.3 times greater than that obtained using the starting material (commercial TiO2).