Construction and photocatalysis of carbon quantum dots/layered mesoporous titanium dioxide (CQDs/LM-TiO2) composites

Carbon quantum dots (CQDs) were prepared by a one-step hydrothermal method using citric acid as a carbon source. Layered mesoporous titanium dioxide (LM-TiO2) was synthesized by the inorganic precipitation-peptization method using titanium sulfate as the titanium source, ammonia as the precipitant and cetyltrimethylammonium bromide (CTAB) as the template. Subsequently, CQDs and LM-TiO2 were compounded to obtain carbon quantum dots/layered mesoporous titanium dioxide composites (CQDs/LM-TiO2). The photocatalytic performance of the samples was studied by using methyl orange as the target organic pollutant. The results indicated that the addition of CTAB led to a layered mesoporous structure, reduced crystallinity and inhibited the crystal growth of TiO2. Carbonaceous groups were detected on the surface of LM-TiO2, thus confirming the formation of CQDs/LM-TiO2 composites. The light absorption intensity of LM-TiO2 was greatly enhanced in the ultraviolet range compared with simple TiO2 and that of CQDs/LM-TiO2 was improved in the visible light region. The threshold wavelength of CQDs/LM-TiO2 also shows a certain redshift compared with that of LM-TiO2. The degradation rate of methyl orange by 0.2 wt% CQDs/LM-TiO2 was 91.04% after irradiation for 24 min, which was significantly higher than that of simple TiO2 and LM-TiO2.