All near-infrared multiparametric luminescence thermometry using Er(3+), Yb(3+)-doped YAG nanoparticles

This paper presents four new temperature readout approaches to luminescence nanothermometry in spectral regions of biological transparency demonstrated on Yb(3+)/Er(3+)-doped yttrium aluminum garnet nanoparticles. Under the 10 638 cm(−1) excitation, down-shifting near infrared emissions (>10 000 cm(−1)) are identified as those originating from Yb(3+) ions' (2)F(5/2) → (2)F(7/2) (∼9709 cm(−1)) and Er(3+) ions' (4)I(13/2) → (4)I(15/2) (∼6494 cm(−1)) 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 Er(3+ 4)I(13/2) level; (ii) intensity ratio between emissions of Yb(3+) ((2)F(5/2) → (2)F(7/2) transition) and Er(3+) ((4)I(13/2) → (4)I(15/2) transition); (iii) band shift and bandwidth and (iv) lifetime of the Yb(3+) emission ((2)F(5/2) → (2)F(7/2) transition) with maximal sensitivities of 1% K(−1), 0.8% K(−1), 0.09 cm(−1) K(−1), 0.46% K(−1) and 0.86% K(−1), 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.