Bilayer stabilized Ln3+-doped CaMoO4 nanocrystals with high luminescence quantum efficiency and photocatalytic properties

Abstract

In this article, we discuss the microwave synthesis of sodium dodecyl sulphate (SDS) stabilized Ln³⁺-doped CaMoO₄ nanocrystals (Ln³⁺ = Eu³⁺, Er³⁺/Yb³⁺). 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 CaMoO₄ 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 Eu³⁺ ions doped in the CaMoO₄ nanocrystals display very strong red luminescence with a quantum yield close to 40%. Under 980 nm excitation, Er³⁺/Yb³⁺-doped CaMoO₄ nanocrystals display Er³⁺ 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 CaMoO₄ 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 Ln³⁺-doped CaMoO₄ nanocrystals make them a potential material for dual applications such as bio-imaging and photocatalysis.