Credit: © 2009 Wiley

Temperature sensors have many applications in the aircraft industry and in medicine, particularly in photodynamic cancer therapy. Many methods exist for determining temperature, but luminescence-based measurements are attractive because they are non-invasive, accurate and can function even under strong electromagnetic fields. So far, only a few sensors exist for measuring temperatures inside a cell. Now, researchers at the University of Regensburg and Beijing Jiaotong University report that europium nanoparticles can detect temperatures within the physiological range with good resolution.

For better photostability, Otto Wolfbeis and colleagues1 embedded the temperature sensitive europium(III) probe into a poly(methyl methacrylate) polymer matrix and coated the outer layer with silica to form nanoparticles that were between 20 and 30 nm in diameter. The nanoparticles decreased in fluorescence intensity as the temperature increased up to 50 °C, and achieved a resolution of about ±0.3 °C. Using fluorescence lifetime imaging, large-area sensor films containing the nanoparticles showed homogenous temperature-dependent intensity changes in the images and the sensing was not affected by air pressure.

These nanoparticles, which can sense within the physiological range (25–45 °C), may potentially be used for measuring the temperature inside cells.