Degradation of tetracycline hydrochloride by near-infrared light-responsive 0D/3D GdF3:Yb3+,Er3+/MgIn2S4 upconversion photocatalysts

Abstract

Broadening the light-absorption range of photocatalysts is a long-standing challenge in photocatalysis. Combination with upconversion luminescent materials is considered an effective strategy for improving the sunlight utilization rate of a photocatalyst. In this paper, zero-dimensional/three-dimensional GdF₃:Yb³⁺,Er³⁺/MgIn₂S₄ upconversion photocatalysts with near-infrared photo-response were synthesized by a simple one-step hydrothermal method. Under visible–near light irradiation, the composite removed 72.53% of 10 mg L⁻¹ tetracycline hydrochloride (TCH) in 1 h, improving the MgIn₂S₄ removal rate by 14.16%. The results of spectral overlap and fluorescence lifetime attenuation prove that effective fluorescence resonance energy transfer (FRET) process occurs between GdF₃:Yb³⁺,Er³⁺ and MgIn₂S₄, which reduces the energy loss during the transfer process. The enhanced photocatalytic performance is attributed to efficient utilization of the upconversion emission light, the special 0D/3D structure, the tight interface contact, and the efficient FRET process. Electron paramagnetic resonance identified ˙OH and ˙O₂⁻ as the main active species during the degradation process. Finally, a reasonable TCH degradation path was derived from liquid chromatography–mass spectroscopy results. The proposed method efficiently utilizes the near-infrared light component of sunlight to remove environmental pollutants.