Temperature-dependent emission color and temperature sensing behavior in Tm3+/Yb3+:Y2O3 nanoparticles

Tm3+/Yb3+:Y2O3 nanoparticles (NPs) were prepared by solution combustion method. The prepared NPs are confirmed to be pure cubic Y2O3 phase with the mean size of about 45 nm by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observation. Under 980 nm excitation, the temperature dependent upconversion (UC) emission spectra of the NPs are obtained. It is found that the NPs show color tunability with a variation in temperature (from blue to almost white) and also a relatively good suppression of temperature quenching (i.e. ∼70.4% of the initial intensity at 473 K). By using the fluorescent intensity ratio (FIR) technique, the temperature sensing behaviors are investigated based on the thermal coupled 1G4(a) (477 nm) and 1G4(b) (490 nm) levels and non-thermal coupled 3F2,3 (684 nm) and 1G4(b) (490 nm) levels from Tm3+ ions, respectively. The results demonstrate that both the absolute sensitivity (Sa) and relative sensitivity (Sr) values based on non-thermal coupled levels of 3F2,3 and 1G4(b) is larger in the experimental temperature range. The maximum Sa and Sr values are obtained to be ∼1170 × 10−4 K−1 at 573 K and ∼1.51%K−1 at 445 K, respectively. Therefore, the studied material is a potential multifunctional composite for optical thermometry and temperature safety sign.