A high sensitivity optical thermometry on the basis of the intensity ratio between the fluorescence and phosphorescence in lutecium porphyrin

An optical thermometry was performed utilizing the intensity ratio between the fluorescence and the phosphorescence of lutecium hematoporphyrin (Lu-HMME). In spite of the large energy level difference between the singlet first excited state (S₁) and the triple first excited state (T₁), the emission intensities of the two channels were on the same order of magnitude, and the resulted luminescence intensity ratio was confirmed to follow the Boltzmann distribution law. The huge difference in population was made up by the intrinsic properties of Lu-HMME that the transition probability of the S₁ state is several orders of magnitude higher than that of T₁. Based on this, Lu-HMME is a candidate for optical high-temperature sensors with high relative sensitivity and good temperature resolution.