LAUSR

Abstract This work describes a sunlight-active photocatalyst capable of magnetically separating prepared by depositing various amounts of N-doped carbon quantum dots (N-CQDs) on the Fe3O4/C/TiO2 (FCT) nanocomposite. The photocatalytic activity of the resulting composites was investigated in the decolorization of methylene blue (MB), under UV, visible and sunlight irradiation. In the composites, the amorphous carbon interlayer is devised to prevent photodissolution of the Fe3O4 core. To coat the TiO2 nanoparticles on the insulated carbon surface of the magnetic core, a vapor phase hydrolysis method was used while a hydrothermal method was used to deposit N-CQDs on the Fe3O4/C/TiO2 nanocomposite surface. The prepared nanocomposites were characterized by photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FT-IR) spectrometry, diffuse reflectance spectroscopy (DRS) and vibrating sample magnetometry (VSM). The results revealed that the N-CQDs content of the FCT composite has a great influence on the photocatalytic activity of the nanocomposite. So that, the photocatalyst FCT/N-CQDs−4.5 wt% resulted in 95.5% MB decolorization within 80 min sunlight irradiation while pure TiO2 and FCT provided 20.3% and 31.8% decolorization, respectively. In addition, the results showed that sunlight has a significant effect on the photocatalytic activity of the composite, compared to visible and UV light irradiation. Moreover, the composite photocatalysts possessed superparamagnetic properties due to their good saturation magnetization value, i.e. 24.9 emu g−1. As a result, the developed composite photocatalyst was recovered by applying an external magnetic field without losing its activity even after five cycles. In general, this study provides new insights into the fabrication of a new generation of TiO2-based photocatalysts to overcome the main drawbacks of conventional TiO2 photocatalysts.