Integration of 980/808 nm double sensitizers to fabricate the upconversion nanoparticles/NH2-MIL-101(Fe) hybrid photocatalyst toward ofloxacin, tetracycline, and Cr(VI)

Abstract

Photocatalysis is a promising pathway to treat the water pollution with lots of distinct advantages, therefore, numerous attentions have been focused on developing the robust photocatalyst to achieve the satisfied activity. Unfortunately, the degradation of antibiotics is still not an easy task by photocatalytic technology due to their stability. A novel composite photocatalyst NaYF4:Yb, Tm, Er, 0.5%Nd@NaYF4:20%Nd/NH2-MIL-101(Fe) (TmErNd@Nd(20%)/NMF) is fabricated by doping Nd3+ ions in both core and shell with the confined amount along with Yb3+ ions in the core. The Yb3+ ions and Nd3+ ions absorb the 980 nm and 808 nm NIR light, respectively. The involvement of Nd3+ ions enlarges the NIR light absorbent region, which facilitates the upconversion process resulting in the improved photocatalytic activity. More important, the 808 nm excitation for Nd3+ ions minimizes the overlap with water absorption at 980 nm. The TmErNd@Nd(20%)/NMF exhibits the excellent photoactivity for ofloxacin (OFL), tetracycline (TC), and Cr(VI) ions as compared with other ones in previous literature. Even in the aqueous environment with the mixed OFL and TC, the TmErNd@Nd(20%)/NMF still keeps the original activity. TmErNd@Nd(20%)/NMF presents the excellent stability with almost no variation of crystal phase and morphology after four cycles. The possible photocatalytic mechanism is conjectured according to the photoelectrochemical measurements, active species trapping experiments, and pump power dependence of upconversion emission intensities. The excellent activity of TmErNd@Nd(20%)/NMF is attributed to its strong near-infrared (NIR) light absorption, less overlap with water absorption, and its special core-shell structure.