Development of photocatalyst based on NaYF4: Yb, Tm@NaYF4: Yb, Ce/NH2-MIL-101 (Cr): Doping Ce3+ ions to promote the efficient energy transfer between core and shell

Utilization of the whole solar spectrum for the photocatalysis is still a challenge and interesting topic. A series of novel photocatalysts are fabricated by combination of core-shell upconversion nanoparticles NaYF4: Yb, Tm@NaYF4: Yb, Ce (Tm@Ce) with the NH2-MIL-101 (Cr) (NMC) (Tm@Ce/NMC). Tm@Ce/NMC displays the high stability, wide photoresponsive range from UV-Vis to NIR, and excellent photocatalytic activity for decomposition of RhB. With the optimal doping amount of Ce3+ ions and ratio between Tm@Ce and NMC, the degradation of RhB is improved by 1.13, 1.14, and 1.50 times as compared with NaYF4: Yb, Tm/NMC (Tm@NMC), under the simulated solar light, UV + Vis, and NIR, respectively. The enhanced photocatalytic activity of Tm@Ce/NMC is mainly attributed to the efficient energy transfer between core and shell by the doping Ce3+ ions along with the distinct charge separation and suppressed recombination. By the controlled synthesis, the NaYF4: Yb, Tm (YT) nanoparticle is developed with the similar size as the Tm@Ce to further testify the effect of doping Ce3+ ions and exclude the influence of the increased size. The photocatalytic activity of YT/NMC is the less than that of Tm@Ce/NMC, which is almost the same with that of Tm/NMC. It suggests that to merely increase the size of upconversion nanoparticles is not the judicious choice for enhancement of the photocatalytic activity. On the basis of the trapping experiments and other spectra properties, the possible photocatalytic mechanism is conjectured, which is helpful to refine the structure design with the ultimate aim to get the robust photocatalyst.