Molecular Thermometer For Non-Contact Measurements With Infrared Light

Temperature measurement also on the smallest scale / molecular ruby ​​for applications in materials science, biology and medicine

Together with researchers from the Federal Institute for Materials Research and Testing (BAM) in Berlin, chemists from the Johannes Gutenberg University of Mainz (JGU) have developed a molecular thermometer. The gemstone Rubin served as an inspiration. However, the thermometer is from the group of Prof. Dr. Katja Heinze at the Institute for Inorganic Chemistry and Analytical Chemistry is a water-soluble molecule and not an insoluble solid. This molecule, however, contains, like ruby, the element chromium, which gives it the red color, is therefore also called molecular ruby. Due to its solubility, the molecular ruby ​​can be used in various ways to measure the temperature: in liquids as well as in solids, in nanoparticles and in micelles, and thus in the field of materials science,

The process of temperature measurement with the molecular ruby ​​is conceivably simple. The relevant site is irradiated with blue light, the molecular ruby ​​absorbs this light and then emits infrared radiation in two different wavelengths. Depending on the temperature, one or the other wavelength is radiated more intensively. The temperature can then be determined from the intensity ratio of the two infrared emissions. "Anyone with a simple emission spectrometer can do this measurement," explains Sven Otto, a doctoral student from Heinze. "The molecular ruby ​​works at 100 degrees Celsius as well as at minus 63 degrees Celsius, that is, in an everyday-relevant area," adds Otto.

The principle of optical ratiometric temperature measurement was previously known. However, it has hitherto not been possible to carry out the measurement with only one kind of a photoactive center. Up to now, two dyes have always been required: a dye whose emission depends on the temperature, and another whose emission is unaffected as a reference. This makes synthesis and calibration considerably more difficult. "The molecular ruby, on the other hand, is simply constructed from inexpensive starting materials and does not need any additional reference compound for temperature measurement," says Heinze. "It is suitable whenever we want to measure a temperature without having to touch the object directly as with a conventional thermometer."