Synthesis of hexagonal phase Gd2O2CO3:Yb3+, Er3+ upconversion nanoparticles via SiO2 coating and Nd3+ doping

Abstract

By SiO₂ shell coating and Nd³⁺ doping, layer-structured hexagonal phase Gd₂O₂CO₃:Yb³⁺, Er³⁺ nanoparticles were synthesized successfully through a homogeneous precipitation method. The detailed mechanism was investigated and the results indicate that the SiO₂ shell and Nd³⁺ doping ions can effectively prevent hexagonal phase Gd₂O₂CO₃ from decomposing into cubic phase Gd₂O₃ during heat treatment, because the SiO₂ shell limits the diffusion of CO₂ gas and the Nd³⁺ doping increases the decomposition temperature of Gd₂O₂CO₃. Compared with non-layer-structured GdVO₄:20%Yb³⁺, 2%Er³⁺, 4%Nd³⁺ particles with similar diameters and morphologies and lower phonon energies, layer-structured Gd₂O₂CO₃:20%Yb³⁺, 2%Er³⁺, 4%Nd³⁺/SiO₂ hexagonal phase particles show much a stronger upconversion emission, suggesting that layer-structured materials are more appropriate as upconversion hosts. Furthermore, the paramagnetic properties of Gd₂O₂CO₃:Yb³⁺, Er³⁺, Nd³⁺/SiO₂ nanoparticles were also demonstrated.