Exploiting the Yb3+ and Er3+ Codoped β-NaYF4 Nanoparticles as Luminescent Thermometers for White-LED-Free Thermal Sensing at the Nanoscale

Luminescent ratiometric technology has been regarded as one of the most promising methods for temperature measurement, as it enables noncontact thermal sensing with minimal disturbance to the object of interest. Particularly, it, as expected, is free from the influences of many surrounding factors. However, we demonstrate here that, in some cases, this technology is under the influence of white LED that are commonly used in our daily life and industrial processes, considering the fact that these involved emitting lines used for thermal sensing are overlapped severely with the emitting spectrum of white LED. It is found that using the traditional green upconversion (UC) luminescence emanating from Er3+, namely, the 2H11/2/4S3/2–4I15/2 transitions, for thermal sensing leads to a very large temperature error, up to 17 at 303 K in the case where there is the influence of white LED. While the two violet UC luminescence bands, separately originating from the 4G11/2/2H9/2–4I15/2 transitions of Er3+ embedded in t...