Synthesis of Carbon Dots on Fe3O4 Nanoparticles as Recyclable Visible-Light Photocatalysts

Carbon dots (C-dots)/Fe3O4 nanocomposite powders were synthesized by bottom-up procedures at 140 °C with different reaction times ( $t = 0$ –18 h), to study the photocatalytic activity under visible light and recyclable ability in wastewater treatment. The results from vibrating sample magnetometer, X-ray diffraction, and Fourier transform infrared spectra indicated that C-dots were gradually attached on Fe3O4 nanoparticles with the increase of t, and C-dots/Fe3O4 nanocomposite powders were obtained. The microstructure images confirmed that magnetic Fe3O4 nanoparticles were surrounded by C-dots. The C-dots/Fe3O4 nanocomposite powders presented photocatalytic ability in visible light ( $\lambda > 420$ nm). In this paper, higher extent of degradation was addressed in a larger amount of C-dots on Fe3O4 nanoparticles surface. Methylene blue (MB) concentration can be decreased by 83% within 30 min exposing time. The C-dots/Fe3O4 nanocomposite powders exhibited good degradation ability for MB under visible light and could be easily recycled by applied magnetic field after photodegradation.