Nonlinear temperature calibration equation for Rhodamine B in different solutions for wide-temperature-range applications

In the two-color laser-induced fluorescence (LIF) ratio thermometry approach, accurate temperature calibration is the key for quantitative temperature measurement, especially in wide-temperature-range applications. In this work, the temperature behavior of Rhodamine B in two common solutions (aqueous and ethanol) in a wide temperature range (−30°C–90°C) is studied by spectroscopy methods. According to the spectral and two-color LIF ratio results, a nonlinear fitting method based on Arrhenius equation is presented for a calibration equation. Compared with the traditional linear fitting model, improved accuracy at a temperature of 2°C–3°C can be achieved even at low sensitivity. Considering the nonlinear temperature behavior of Rhodamine B, this method can achieve a higher temperature sensitivity at a lower temperature, further demonstrating the feasibility of this method for low-temperature applications.