Nd3+ and Nd3+/Yb3+-incorporated complexes as optical thermometer working in the second biological window

This work reports on ratiometric optical thermometers consisting of luminescent lanthanide complexes, namely Ln-PDC (Ln = Nd, Nd1.43Yb0.57, Gd1.45Nd0.40Yb0.15, PDC = pyridine-3,5-dicarboxylate). The fluorescence intensity ratio techniques based on emissions of Stark sublevels of 4F3/2 (Nd3+) excited state for Nd3+-single doped sample, and the intensity ratio of Stark sublevels emissions which is severally from Nd3+ and Yb3+ ions for co-doped samples are employed for the thermometric characterizations in the physiological range (298–318 K).The results show that all three complexes can be employed as luminescent thermometers with comparable temperature sensing performance and operating in biological range under 808-nm excitation. Gd1.45Nd0.40Yb0.15-PDC demonstrates to be the best one with the relative sensitivity varying from 0.482 to 0.439% K−1in the physiological range, and the minimum temperature uncertainty is less than 0.08 K. The results may provide a new approach for lanthanide organic complexes based optical thermometer working in the second biological window.