Photocatalytic activity of phthalocyanine-sensitized TiO2–SiO2 microparticles irradiated by visible light

Zinc phthalocyanine (ZnPc) modified by cyanuric chloride was supported on TiO2–SiO2 microparticles (ZnPc–SiO2–TiO2) by covalent bonds to produce a novel photosensitizer, ZnPc–SiO2–TiO2. ZnPc sensitized TiO2 to light in the visible range, while the TiO2 acted as an acceptor of electrons generated by the photon irradiation; thus, this material can absorb low-energy photons to emit photons of higher energy. The as-prepared ZnPc–SiO2–TiO2 was characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and UV–vis diffuse reflectance spectroscopy (DRS). The results of photodecomposing methylene blue (MB) revealed that ZnPc–SiO2–TiO2 had great photocatalytic activity under visible-light irradiation (λ>400 nm). By analyzing electron paramagnetic resonance (EPR) spectra, we proposed a possible mechanism for the photodecomposition of MB by ZnPc–SiO2–TiO2.