Recyclable magnetic Fe3O4@SiO2/β-NaYF4:Yb3+,Tm3+/TiO2 composites with NIR enhanced photocatalytic activity

To extend the activities of TiO 2 to the near infrared (NIR) region and to separate and recycle photocatalysts easily is vital for the high harvest of solar energy for sustainable society. The magnetic NIR activated Fe 3 O 4 @SiO 2 /β-NaYF 4 :Yb 3+ ,Tm 3+ /TiO 2 (FS/UC/T) composites have been synthesized by using the solvothermal method by adding Fe 3 O 4 @SiO 2 and Degussa P25 into the mixed solution of NaOH, ethanol, oleic acid, Re(NO 3 ) 3 and NH 4 F. Moreover, the obtained composites were explored for photocatalytic applications. It was found that FS/UC/T emit UV–vis light under irradiation of 980 nm laser and efficient energy transfer from β-NaYF 4 :Yb 3+ ,Tm 3+ to TiO 2 was verified. The photodegradation experiments for treating methylene blue (MB), rhodamine B (RhB), methyl orange (MO) and colorless phenol were carried out to evaluate the photocatalytic activities of the samples. The photodegradation rates reach 76.62%, 68.48%, 30.05% and 27.16% for MB, RhB, MO and phenol under irradiation of 980 nm laser, respectively, which suggested magnetic FS/UC/T composite is an advanced NIR-driven photocatalyst. Moreover, the magnetic photocatalyst showed easy separation and good stability in the recycled tests. It suggested a promising system to utilize the NIR energy for photocatalysis based on TiO 2 and to utilize the magnetic for separation of photocatalysts, which will contribute to practical environmental remediation in the future.