| Summary: | The effect of type (AgInS<sub>2</sub>, SnS, CuS<sub>2</sub>, Bi<sub>2</sub>S<sub>3</sub>) and amount (5, 10, 15 wt%) of quantum dots (QDs) on the surface properties and photocatalytic activity of QDs-sensitized TiO<sub>2</sub> composite, was investigated. AgInS<sub>2</sub>, SnS, CuS<sub>2</sub>, Bi<sub>2</sub>S<sub>3</sub> QDs were obtained by hot-injection, sonochemical, microwave, and hot-injection method, respectively. To characterize of as-prepared samples high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectroscopy and photoluminescence (PL) emission spectroscopy were applied. The size of AgInS<sub>2</sub>, SnS, CuS<sub>2</sub>, Bi<sub>2</sub>S<sub>3</sub> QDs were 12; 2–6; 2–3, and 1–2 nm, respectively. The QDs and QDs-sensitized TiO<sub>2</sub> composites obtained have been tested in toluene degradation under LEDs light irradiation (λ<sub>max</sub> = 415 nm and λ<sub>max</sub> = 375 nm). For pristine QDs the efficiency of toluene degradation increased in the order of AgInS<sub>2</sub> < Bi<sub>2</sub>S<sub>3</sub> < CuS < SnS under 375 nm and AgInS<sub>2</sub> < CuS < Bi<sub>2</sub>S<sub>3</sub> < SnS under 415 nm. In the presence of TiO<sub>2</sub>/SnS QDs_15% composite, 91% of toluene was degraded after 1 h of irradiation, and this efficiency was about 12 higher than that for pristine QDs under 375 nm. Generally, building the TiO<sub>2</sub>/AgInS<sub>2</sub> and TiO<sub>2</sub>/SnS exhibited higher photoactivity under 375 nm than the pristine TiO<sub>2</sub> and QDs which suggests a synergistic effect between QDs and TiO<sub>2</sub> matrix.
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