Quaternized zinc(II) phthalocyanine-sensitized TiO<sub>2</sub>: surfactant-modified sol–gel synthesis, characterization and photocatalytic applications

<p>TiO<sub>2</sub> nanoparticles and zinc phthalocyanine-sensitized TiO<sub>2</sub> (ZnPc/TiO<sub>2</sub>) nanocomposite were synthesized in the presence and absence of Triton X100 (a nonionic surfactant) by a modified sol–gel method to improve the photocatalytic activity of TiO<sub>2</sub> under near visible light (365 nm). A novel quaternized ZnPc molecule was used as sensitizer. Prepared nanoparticles and nanocomposite were characterized by scanning electron microscopy, energy dispersive analysis, X-ray diffractometry, transmission electron microscopy (TEM), Brunauer–Emmett–Teller, thermogravimetry analysis, and UV–vis–NIR. The results demonstrated that the ZnPc was successfully loaded on the TiO<sub>2</sub> nanoparticles and the nanocomposite possesses the anatase crystalline phase with the specific surface area of 110.04 m<sup>2</sup> g<sup>−1</sup>. The TEM micrograph showed that the average grain crystal size is 5–15 nm. ZnPc in the TiO<sub>2</sub> structure shifted the absorption edge to visible region. The photocatalytic activities of prepared photocatalysts (ZnPc/TiO<sub>2</sub>, ZnPc/TiO<sub>2</sub>-TX100, TiO<sub>2</sub>, and TiO<sub>2</sub>-TX100) were evaluated for degradative removal of methyl orange and reductive removal of Cr(VI) ions as test pollutants. Results of photocatalytic removal revealed that the ZnPc/TiO<sub>2</sub>-TX100 has shown much more photocatalytic efficiencies than the ZnPc/TiO<sub>2</sub> prepared without TX100 and neat TiO<sub>2</sub> prepared with or without TX100. Therefore, this sol–gel method modified with TX100 is useful in the preparation of nanostructure ZnPc/TiO<sub>2</sub> with high photocatalytic activity and higher surface area.</p>