Fabrication of Fe3O4@Ti-PDA nanoparticles with enhanced photocatalytic activities for degradation of organic dye

In this paper, we synthesized a core-shell structured Fe3O4@Ti-PDA nanoparticles as photocatalyst by a facile method in environmental friend mild reaction conditions without organic solvent. Firstly, Fe3O4 was synthesized by solvothermal method, and Fe3O4@PDA was formed by dopamine (DA) self-polymerization to encapsulate Fe3O4 to form polydopamine (PDA) lager. Then, the surface of Fe3O4@PDA was wrapped by coordinating bis(2-hydroxypropionic acid) diammonium dihydroxide(Ti-BALDH) with DA combined DA self-polymerizing to obtain Fe3O4@Ti-PDA. As control, we synthesized another photocatalyst Fe3O4@PDA@TiO2. Compared with Fe3O4@PDA@TiO2 (band gap 3.0 eV), Fe3O4@Ti-PDA had a narrower band gap (2.5 eV) and a wider light absorption range (from ultraviolet to visible light to near-infrared light), as a photocatalyst, which can make full use of sunlight to improve photocatalytic efficiency. Meanwhile, magnetic core of Fe3O4@Ti-PDA made it was easy to separate from aqueous solution for convenient recovery. Using methylene blue (MB) as model pollutant, the degradation efficiency of Fe3O4@Ti-PDA on MB reached to 92.4% under visible light irradiation for 120 min without cocatalyst, while for Fe3O4@PDA@TiO2 only to 32.5%. The result indicated Fe3O4@Ti-PDA enabled photocatalytic oxidation and rapid separation when photogenerated electron-hole pairs were generated. After three recycles, the degradation efficiency of Fe3O4@Ti-PDA on MB still remained at 86.47%, showing good recycle stability.