Photocatalysis of NaYF₄:Yb,Er/CdSe composites under 1560 nm laser excitation

The most common materials used to generate near-infrared-driven photocatalysis occur by 980 nm laser excitation of composites that are a combination of a semiconductor and upconverting luminescence particles. The challenge remains to increase the light harvesting efficiency, and thus, it is necessary to extend the absorption spectra of photocatalysts. In this work, NaYF₄:Yb,Er/CdSe composites were prepared by depositing CdSe nanocrystals onto the surface of NaYF₄:Yb,Er microcrystals. UV and visible emission of light resulted from multiphoton upconverting processes in Er³⁺ under 1560 nm laser irradiation, which, in turn, activated the CdSe catalyst. The energy transfer between NaYF₄:Yb,Er and CdSe was investigated by steady-state and dynamic fluorescence spectroscopy. The photocatalytic performance was investigated by the degradation of methylene blue in aqueous solution. These results show that Er coupled with semiconductor heterojunctions provides a photocatalyst that operates in the extended near-infrared range.