Single red upconversion and near-infrared downconversion luminescence properties of cubic ZrO2:Y3+-Yb3+-Er3+ nanophosphors via microwave hydrothermal synthesis

The Yb3+-Er3+-Y3+ tri-doped cubic ZrO2 (brief as YSZ:Yb, Er) nanophosphors with different Yb3+ (Er3+) doping concentrations have been prepared by microwave hydrothermal method followed by further calcining treatment. X-ray diffraction (XRD), transmission electron microscope (TEM), and photoluminescence spectra were used to characterize the properties of YSZ:Yb, Er nanophosphors. Under the 980 nm excitation, the sample gives a set of upconversion light: very strong red emissions near 655 and 679 nm (4F9/2 → 4I15/2), very weak green (525 nm 2H11/2 → 4I15/2, 544 nm and 557 nm 4S3/2 → 4I15/2). Moreover, the sample gives near-infrared downconversion emission (1530 nm 4I13/2 → 4I15/2). Concentration dependent studies revealed that the optimal composition was realized for the 15 at% Yb3+ and 1 at% Er3+-doping concentration with a strong pure red emission. All the results indicate that YSZ:Yb, Er nanophosphors could be a promising biological labeling materials.