All near-infrared multiparametric luminescence thermometry using Er, Yb-doped YAG nanoparticles.

This paper presents four new temperature readout approaches to luminescence nanothermometry in spectral regions of biological transparency demonstrated on Yb/Er-doped yttrium aluminum garnet nanoparticles. Under the 10 638 cm excitation, down-shifting near infrared emissions (>10 000 cm) are identified as those originating from Yb ions' F → F (∼9709 cm) and Er ions' I → I (∼6494 cm) electronic transitions and used for 4 conceptually different luminescence thermometry approaches. Observed variations in luminescence parameters with temperature offered an exceptional base for studying multiparametric temperature readouts. These include the temperature-dependence of: (i) intensity ratio between emissions from Stark components of ErI level; (ii) intensity ratio between emissions of Yb (F → F transition) and Er (I → I transition); (iii) band shift and bandwidth and (iv) lifetime of the Yb emission (F → F transition) with maximal sensitivities of 1% K, 0.8% K, 0.09 cm K, 0.46% K and 0.86% K, respectively. The multimodal temperature readout provided by this material enables its application in different luminescence thermometry setups as well as improved the reliability of the temperature sensing by the cross-validation between measurements.