Fig. 5: Temperature-dependent luminescence properties of NBFYE HNPs synthesized by adding 1.5 g PAA and 5 mL H2O to the reaction system.

a Normalized emission spectra of NBFYE HNPs as a function of temperature upon NIR irradiation (P = 4.85 W cm−2). The inset in the upper right corner shows the luminescence photograph of HNPs under 980 nm NIR irradiation at room temperature. b The linear relationship between the natural logarithm of R (I525/I544) vs 1/T. c R (I525/I544) as a function of temperature. d The sensing sensitivity of NBFYE HNPs varies with temperature from 223 K to 548 K