Tailoring of Upconversion Emission in Tm3+/Yb3+-Codoped Y2Mo3O12 Submicron Particles Via Thermal Stimulation Engineering for Non-invasive Thermometry

To settle the challenges of optical thermometry with high sensitivity, a series of Tm3+/Yb3+-codoped Y2Mo3O12 (YMO:Tm3+/2xYb3+) submicron particles were developed via a sol–gel route. Excited by 980 nm, bright upconversion (UC) emissions of Tm3+ are observed, in which the optimum intensity is realized when the Yb3+ concentration is 13 mol %. Moreover, the UC mechanism of the emissions originating from the 1G4 level is a three-photon absorption process, while that of the emission from the 3F2,3 level is a two-photon absorption process. Furthermore, thermally enhanced emission intensities are realized in the studied compounds due to the negative thermal expansion effect. Notably, owing to the coexistence of improved energy transfer and cross-relaxation processes at elevated temperature, the intensities of the UC emissions from the 1G4 level increase and then decrease with raising the temperature, whereas that of the UC emission from the 3F2,3 level is enhanced monotonously as temperature increases. Via analyzing the inconsistent thermal quenching characteristics of the UC emissions, we explored the thermometric behaviors of the synthesized products and found that their sensitivities are dependent on the spectral mode. Through investigating the dependence of the emission intensity rate of the emissions from 3F2,3 → 3H6 to 1G4 → 3F4 transitions on temperature, one knows that the maximum absolute and relative sensitivities of the resultant submicron particles are 0.198 K–1 and 3.27% K–1, respectively. Additionally, the thermometric behaviors of YMO:Tm3+/2xYb3+ submicron particles can also be manipulated via altering the Yb3+ concentration.