Enhancement of the Ln3+ ratiometric nanothermometers by sensitization with transition metal ions

Abstract

• The transition metal ions were used for sensitization of lanthanide ions. • This strategy enables the enhancement of the thermal LIR changes. • An increase of relative sensitivity by 300% was observed after co-doping. One of the most important parameters that affect the thermal resolution in the luminescent thermometry is the relative sensitivity of phosphor to temperature changes. Therefore various approaches to enhance its value are intensively investigated. The strategy of the relative sensitivity enhancement of the ratiometric lanthanide ions based luminescent thermometer by the sensitization with the transition metal ions is proposed in this work. It was found that by taking advantage of the temperature dependent energy transfer from transition metal ion (Mn 4+ -, Cr 3+ - and Ti 3+/4+ -) to the Tb 3+ and Eu 3+ ions in the YAG powder, the thermal variation of the Tb 3+ to Eu 3+ luminescence intensity ratio increases leading to the improvement of its thermometric properties even by 300%. Therefore, the maximal relative sensitivity increases from S R = 0.09%/°C for unco-doped powder up to S R = 0.15, 0.28, 0.30%/°C, for powders co-doped with Cr 3+ , Mn 4+ and Ti 3+/4+ , respectively. The beneficial influence of the transition metal to lanthanides energy transfer was investigated in a function of the transition metal ion concentration.