Step by step designing of sensitive luminescent nanothermometers based on Cr3+,Nd3+ co-doped La3−xLuxAl5−yGayO12 nanocrystals

Abstract

In this work we present step by step designing of sensitive luminescent thermometers utilizing Cr³⁺,Nd³⁺ co-doped La_3−xLu_xAl_5−yGa_yO₁₂ garnets. In order to achieve this purpose, modification of the local ion environment by the adjustment of the La³⁺ to Lu³⁺ and the Al³⁺ to Ga³⁺ ion ratios was performed. Additionally, the influence of the Cr³⁺ and Nd³⁺ ion concentration on the thermal quenching of Cr³⁺ luminescence was investigated. All of the abovementioned steps of the host stoichiometry optimization enabled us to obtain a relative sensitivity of luminescent thermometers based on the luminescence intensity ratio of Nd³⁺(⁴F_5/2 → ⁴I_9/2)/Cr³⁺(²E → ⁴A₂) electronic transitions as high as S = 1.47% °C⁻¹ at −150 °C and S = 1.23% °C⁻¹ at 260 °C for La₂LuGa₅O₁₂:1%Cr³⁺,5%Nd³⁺ nanocrystals. The presented studies provide the verification how stoichiometry of host material affect the relative sensitivity of transition metal/lanthanide ion based luminescent thermometers, enabling knowledgeable designing of highly sensitive luminescent thermometers.