Implementing luminescence thermometry at 1.3 μm using (GdNd)2O3 nanoparticles

Nd3+-doped nanoparticles have recently emerged as very attractive multifunctional systems with potential for simultaneous bio-imaging and thermal sensing, due to near-infrared excitation and emission within the first (700-980 nm)and second (1000-1400 nm)biological windows. However, while these nanoparticles have been already used for thermal sensing in the first biological window very few studies concern the second biological window. Here, we show that upon 808 nm excitation a thermometer consisting of (Gd1−xNdx)2O3(x=0.020, 0.028and 0.064)nanospheres exhibits a thermal sensitivity of 0.23±0.03% K−1 at 303 K, operating in the second transparent near infrared biological window. This sensitivity value is achieved by defining the thermometric parameter as the ratio between the integrated intensity of all the transitions originated from the 4F3/2highest-energy Stark component and all the transitions from the 4F3/2lowest-energy.