Nd3+ doped Y2O3 micro- and nanoparticles: A comparative study on temperature sensing and optical heating performance within the 1st biological window

In this work, Y2O3 phosphors doped with Nd3+ at two different concentrations (2% and 10%) were prepared by coconut water-assisted sol-gel method, at two different calcination temperatures (1000 °C and 1400 °C). Structure and morphology analyses were performed by XDR and SEM. Thermometric analyses were performed with 800 nm laser excitation, exploring the emission corresponding to the 4F3/2 – 4I9/2 transition from Nd3+ by the luminescence intensity ratio and valley-peak intensity ratio techniques. The results obtained indicate that the samples correspond to the cubic structure of Y2O3 of space group Ia3. SEM images reveal particles with an approximately spherical shape, with mean diameters of 41 ± 14 nm and 1.1 ± 0.4 μm for samples calcined at 1000 and 1400 °C, respectively. The thermometric characterization of these samples included the relative sensitivity, temperature uncertainty, repeatability, and reproducibility. Sensitivities of up to 0.46%.K−1 were obtained, with temperature uncertainties between 0.5 and 3.5 K over the entire temperature range analyzed (294–373K). Good repeatability and reproducibility were also obtained. Additional optical heating measurements indicated that the micrometric sample doped with 2% Nd3+ has a heating rate similar to the nanometric sample doped with 10% Nd3+. Among the investigated samples, the micrometric sample containing 2% Nd3+ presented the best potential for application as a multifunctional platform for heating and temperature sensing within the first biological window, as it offers high emission intensities, sensitivity, and heating rate.