Facile preparation of squarylium dye sensitized TiO2 nanoparticles and their enhanced visible-light photocatalytic activity

• ISQ dye sensitized TiO2 nanoparticles were prepared via a facile solution method.
• ISQ/TiO2 nanoparticles exhibited significantly enhanced visible light activity.
• ISQ/TiO2 showed high visible light photocatalytic activity over MB decomposition.
• ISQ/TiO2 nanoparticles exhibited good photocatalytic stability.

A squarylium dye, 1,3-bis[(3,3-dimethylindolin-2-ylidene)methyl]squaraine (ISQ) sensitized TiO2 nanoparticles photocatalysts with different mass ratio of ISQ to TiO2 were facilely prepared by blending ISQ and TiO2 in ethanol solution. The resulting composite photocatalysts were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR) and UV–vis diffuse reflectance spectroscope (DRS). The visible light photocatalytic activities of ISQ sensitized TiO2 nanoparticles were evaluated using the degradation of methylene blue (MB) as a photodegradation target. The results showed that photo-response of the ISQ sensitized TiO2 nanoparticles were remarkably extended to visible-light region, and the ISQ dye sensitized TiO2 exhibited significantly enhanced photocatalytic activity under visible light irradiation. The maximum photocatalytic activity of the ISQ sensitized TiO2 was found at a composite photocatalyst (mass ratio of ISQ to TiO2 was 1:3), and its degradation efficiency of MB reached approximately 98% in 2 h under visible light irradiation. Furthermore, a possible mechanism for the photocatalytic oxidative degradation was also proposed.