Scientists develop molecular thermometer for contactless measurement using infrared light

Measuring the temperature with the molecular ruby is very straightforward. The relevant site is irradiated with blue light, which is absorbed by the molecular ruby that then emits infrared radiation at two different wavelengths. Depending on the temperature, there is more intense emission of infrared at one of the two wavelengths. The temperature is then determined on the basis of the corresponding ratio of intensity of the two wavelengths. "Anyone with a simple emission spectrometer can undertake this kind of measurement," explained Sven Otto, a doctoral candidate in Heinze's team. "The molecular ruby works at 100 degrees Celsius just as well as at minus 63 degrees Celsius, that is in a range relevant to everyday practice," added Otto.

The principle of optical ratiometric temperature measurement is not new. However, it was previously impossible to take measurements using only a single type of photoactive agent. To date, scientists always needed two dyes, i.e., one that produced emission dependent on temperature and another reference dye with emission independent of temperature. That made synthesis and calibration a lot more difficult. "Our molecular ruby, on the other hand, is simply made from inexpensive raw materials and no additional reference substances are required to measure temperature," said Professor Katja Heinze. "It can be employed whenever we want to measure temperature without having to contact the object directly as with a conventional thermometer."