Thermally activated upconversion luminescence and ratiometric temperature sensing under 1064 nm/808 nm excitation.

In this research, a thermally activated upconversion luminescence (UCL) probe with ratiometric temperature sensing under 1064 nm and 808 nm excitation was designed. Especially, Nd 3+ , Tm 3+ and Ce 3+ were doped in rare earth nanoparticles (RENPs) as UCL modulators. By optimizing the elements and ratios, the excitation wavelength is successfully modulated to 1064 nm excitation with UCL intensity enhanced. Additionally, the prepared RENPs have a significant temperature response at 1064 nm excitation and can be used for thermochromic coatings. The intensity ratio of three-photon UCL (1064 nm excitation) to two-photon UCL (808 nm excitation) as an exponential function of temperature can be used as a ratiometric temperature detector. Therefore, this designed thermochromic coatings may enable new applications in optoelectronic device and industrial sensor.