Pulsed Laser Synthesis of Er3+/Yb3+ Co-Doped CaMoO4 Colloidal Nanocrystal and Its Upconversion Luminescence

We report a novel synthetic route for Er3+Yb3+ co-doped calcium molybdate (CaMoO4) nanoparticles by pulsed laser ablation in ethanol. The crystalline phase, particle morphology, laser ablation mechanism and upconversion (UC) luminescent properties are investigated. Stable colloidal suspensions consisting of well-dispersed Er3+/Yb3+ co-doped CaMoO4 nanoparticles could be obtained without any surfactant. Under 980 nm excitation, Er3+/Yb3+ co-doped nanocolloidal CaMoO4 suspension had a weak red emission near 670 nm and strong green UC emissions at 530 and 550 nm, corresponding to the intra 4f transitions of Er3+ (4F(9/2), 2H(11/2), 4S(3/2)) --> Er3+ (4I(15/2)). The Er3+/Yb3+ co-doped nanocrystalline CaMoO4 suspension exhibited strong green emission visible to the naked eyes and a possible UC mechanism depending on the pump power dependence is discussed in detail.