Negative thermal expansion triggered anti-thermal quenching luminescence in Tm3+/Yb3+/Sc3+-tridoped Lu2W3O12 upconverting microparticles for dual-mode optical thermometry

Abstract

To settle the thermal quenching and dissatisfied sensitivity of luminescent materials, a series of Tm³⁺/Yb³⁺/Sc³⁺-tridoped Lu₂W₃O₁₂ upconverting microparticles was synthesized through sol–gel method. In-situ X-ray diffraction results reveal that the resultant samples have good negative thermal expansion (NTE) properties, which can be improved by Sc³⁺ doping. Upon 980 nm excitation, the final products can emit brightness upconverison (UC) emissions and their intensities are able to be enhanced by Yb³⁺ and Sc³⁺ doping. Moreover, the temperature-dependent UC emission spectra suggest that the designed compounds possess anti-thermal quenching luminescence. Specially, these UC emissions from ¹G₄, ³F_2,3 and ³H₄ levels show different responses to temperature, allowing their feasibilities in optical thermometry. Via utilizing the fluorescence intensity ratio technique to analyze the temperature-associated UC emissions from non-thermally coupled levels (non-TCLs), one knows that maximum absolute and relative sensitivities of developed upconverting microparticles are 0.124 K^–1 and 3.105%/K, respectively, while those of the resultant upconverting microparticles are 4.895 × 10⁻⁵ K⁻¹ and 1.774%/K, respectively, when the TCLs are used. Our findings verify that the utilization of NTE effect is an efficient route to induce the anti-thermal quenching UC luminescence, and the thermometric properties of luminescent materials can also be regulated by selecting proper sensing strategy, spatial mode and doping content.