Achieving anti-oxygen-interference temperature sensing using phosphorescent metalloporphyrins

Abstract

A temperature-sensing method immune to oxygen interference is established based on phosphorescent metalloporphyrins on regenerated cellulose (RC). A series of metalloporphyrins (hematoporphyrin monomethyl ether coordinated to Pd, Gd, and Lu ions: Pd-, Gd-, and Lu-HMME) are designed to be embedded in RC. The phosphorescence emissions of these metalloporphyrins are effectively enhanced on RC, affording phosphorescence quantum yields of 1.8%, 3.3%, and 2.2%, respectively. The phosphorescence emissions of these metalloporphyrins on RC (metalloporphyrins/RC) are independent of oxygen concentration because RC provides an oxygen-impermeable microenvironment. Meanwhile, the phosphorescence emissions are effectively quenched with increasing temperature. The phosphorescence lifetimes also decrease with temperature, indicating an increase in non-radiative relaxation, which weakens phosphorescence emission. The oxygen-independence and temperature-dependence of these metalloporphyrins/RC reveal that they could serve as promising anti-oxygen-interference temperature indicators. Temperature-response plots are obtained in the range from −75 to 50 °C. The temperature sensitivities of Pd-, Gd-, and Lu-HMME on RC are evaluated to be 0.50, 0.28, and 0.36%/°C based on the temperature-response plots. The temperature resolution values of Pd-, Gd-, and Lu-HMME on RC are 0.5, 1.3, and 1.2 °C. These temperature indicators have high photostability under extended irradiation, making them suitable for practical use. The method offers attractive new insights into phosphorescent temperature-sensing materials and the development of oxygen sensors with temperature compensation.