Upconversion and luminescence temperature sensitivity of Er3+ ions in yttrium oxysulfate nanophosphor

Near infrared-to-green upconverted emissions of Er3+-doped Y2O2SO4 yttrium oxysulfate nanophosphor have been studied exciting the sample with a 975 nm laser radiation. Temporal dynamics of the green emission indicates that the main mechanism responsible for the upconversion processes is energy transfer between Er3+ ions. The relative intensities of the near infrared-to-green upconverted emissions from the H-2(11/2) and S-4(3/2) thermalized levels to the I-4(15/2) ground state have been calibrated as a function of temperature in order to develop an optical temperature sensor both in the biological range, from 295 up to 330 K, and in the industrial application range up to 475 K. The temperature scale obtained shows a relative sensitivity with temperature of 1.1 %K-1 at 300 K, and an absolute temperature sensitivity of 73 x 10(-4) K-1 at 467 K. These results suggest that the Er3+-doped yttrium oxysulfate can be used as an optical temperature sensor by exciting in the infrared range for biomedicine and industrial applications.