Upconversion fluorescence modulation of CaTiO₃: Yb³⁺/Er³⁺ nanocubes via Zn²⁺ introduction

Abstract

To investigate the effect of Zn²⁺ ions on the luminescence properties of rare earth (RE) doped calcium titanate materials, CaTiO₃: Yb³⁺/Er³⁺/Zn²⁺ nanocubes with uniform size were prepared by solvothermal method in this paper. They were respectively characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectroscopy and their fluorescence lifetimes. The results show that the average size of the nanocubes is about 550 nm×650 nm×850 nm with good upconversion luminescence (UCL) properties. Under 980 nm laser excitation, the effects of the ratio between activator Er³⁺ and sensitizer Yb³⁺ and Zn²⁺ doping on the upconversion fluorescence properties were investigated, and the optimal ion ratio was obtained. The results of steady-state spectra show that the strongest fluorescence intensity of CaTiO₃: Yb³⁺/Er³⁺ was obtained with the addition of 10 mol% Zn²⁺ at a Yb³⁺/Er³⁺ molar doping ratio of 3:0.3, which was attributed to the crystal field asymmetry generated by the introduction of Zn²⁺ ions. The energy transfer and upconversion mechanism between Yb³⁺ and Er³⁺ ions in CaTiO₃ nanocubes were investigated by analyzing the upconversion fluorescence kinetics.