Bilayer stabilized Ln~(3+)-doped CaMoO_4 nanocrystals with high luminescence quantum efficiency and photocatalytic properties

摘要

In this article, we discuss the microwave synthesis of sodium dodecyl sulphate (SDS) stabilized Ln~(3+)-doped CaMoO_4 nanocrystals(Ln~(3+) = Eu~(3+), Er~(3+)/Yb~(3+)). The nanocrystals are quite monodispersed with an average size close to 100 nm. FTIR and TGA analyses suggest strong binding of the SDS molecules to the CaMoO_4 nanocrystals surface. The high dispersibility of the nanocrystals in water implies that SDS stabilizes the nanocrystals as a bilayer structure. The SDS coating also assists in the easy dispersion of the nanocrystals in toluene without any additional surface chemistry. The Eu~(3+) ions doped in the CaMoO_4 nanocrystals display very strong red luminescence with a quantum yield close to 40%. Under 980 nm excitation, Er~(3+)/Yb~(3+)-doped CaMoO_4 nanocrystals display Er~(3+) emissions at 550 and 650 nm. In addition, interestingly, a NIR peak at around 833 nm is observed, which occurred via a three photon process. Furthermore, the CaMoO_4 nanocrystals exhibit photocatalytic activity which is studied through the degradation of Rhodamine B (RhB) dye in neutral conditions. The RhB dye is significantly degraded by ～80% under UV illumination within 4 h and the rate of degradation is comparable to that observed for well known ZnO nanoparticles. The high luminescence quantum efficiency and strong photocatalytic activity of the Ln~(3+)-doped CaMoO4 nanocrystals make them a potential material for dual applications such as bio-imaging and photocatalysis.