Tm 3+ /Yb 3+ :BaMoO 4 phosphor for high-performance thermometry operating in the first biological window.

The development of optical thermometers operating within the first biological window (650-1000 nm) has drawn great interest lately in the biological and medical fields. Here a new type of luminescent thermometer relying on the intensity ratio between G ₄ 1-F ₄ 3 (652 nm) and F _2,3 3-H ₆ 3(691 nm) transitions in Tm ³⁺ /Yb ³⁺ :BaMoO ₄ phosphor is reported under 980 nm excitation. The thermometry is found to be independent on the excitation power, benefiting the reduction of the measurement error. Moreover, it exhibits extremely high absolute sensitivity ranging from 210.5×10 ^-4 to 1034.5×10 ^-4   K ^-1 in 298-498 K. The maximal relative sensitivity and temperature resolutions (1.36%  K ^-1 and 0.37 K, respectively) are also among the highest values of those previous thermometric materials. This Letter provides guidance in selecting the suitable emission bands to construct the ratiometric luminescent thermometers with high performance.