No abstract

Luminescence thermal sensing and deep-tissue imaging using nanomaterials operating within the first biological window (ca. 700-980 nm) are of great interest, prompted by the ever-growing demands in the fields of nanotechnology and nanomedicine. Here, we show that (Gd1-xNdx)2O3 (x = 0.009, 0.024 and 0.049) nanorods exhibit one of the highest thermal sensitivity and temperature uncertainty reported so far (1.75 ± 0.04% K(-1) and 0.14 ± 0.05 K, respectively) for a nanothermometer operating in the first transparent near infrared window at temperatures in the physiological range. This sensitivity value is achieved using a common R928 photomultiplier tube that allows defining the thermometric parameter as the integrated intensity ratio between the (4)F5/2 → (4)I9/2 and (4)F3/2 → (4)I9/2 transitions (with an energy difference between the barycentres of the two transitions >1000 cm(-1)). Moreover, the measured sensitivity is one order of magnitude higher than the values reported so far for Nd(3+)-based nanothermometers enlarging, therefore, the potential of using Nd(3+) ions in luminescence thermal sensing and deep-tissue imaging.

Temperature measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnology. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu(3+) ion. The thermometer is based on the simple Eu(3+) energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K(-1). The thermometric parameter is defined as the ratio between the emission intensities of the (5)D0 → (7)F4 transition when the (5)D0 emitting level is excited through the (7)F2 (physiological range) or (7)F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu(3+) were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biological transparent window. A novel and of paramount importance aspect is that the calibration factor can be calculated from the Eu(3+) emission spectrum avoiding the need for new calibration procedures whenever the thermometer operates in different media.