Nanocomposites of Titanium Dioxide and Peripherally Substituted Phthalocyanines for the Photocatalytic Degradation of Sulfamethoxazole

Phthalocyanines (Pcs) are often used in photosensitization of titanium(IV) oxide, a commonly employed photocatalyst, as such an approach holds the promise of obtaining highly stable and efficient visible light-harvesting materials. Herein, we report on the preparation, characterization and photoactivity of a series of composites based on TiO(2) and peripherally modified metallophthalocyanines: either tetrasulfonated or 4,4′,4′′,4′′′-tetraazaphthalocyanines, with either copper(II), nickel(II) or zinc(II) as the central metal ion. Physicochemical characterization was performed using UV-Vis diffuse reflectance spectroscopy, hydrodynamic particle-size analysis, surface-area analysis using N(2) adsorption-desorption measurements and thermogravimetry combined with differential scanning calorimetry. The band-gap energy values were lower for the composites with peripherally modified phthalocyanines than for the commercial TiO(2) P25 or the unsubstituted zinc(II) phthalocyanine-grafted TiO(2). TG–DSC results confirmed that the chemical deposition, used for the preparation of Pc/TiO(2) composites, is a simple and efficient method for TiO(2) surface modification, as all the Pc load was successfully grafted on TiO(2). The photocatalytic potential of the Pc/TiO(2) materials was assessed in the photocatalytic removal of sulfamethoxazole—a commonly used antibacterial drug of emerging ecological concern. To compare the activity of the materials in different conditions, photodegradation tests were conducted both in water and in an organic medium.