Temperature is a critical variable that influences countless biological processes at the cellular level. However, precisely measuring temperatures within living cells remains challenging. Conventional temperature measurement techniques often lack the spatial resolution needed to detect subtle temperature variations in complex microscopic environments. Additionally, many existing molecular thermometers have significant limitations in terms of their sensitivity, resolution, and applicable targets, highlighting the need for innovative approaches and versatile tools.

Against this backdrop, a research team led by Associate Professor Gen-ichi Konishi from the Institute of Science Tokyo, Japan, has developed a molecular thermometer using a novel solvatochromic fluorescent dye. Their findings, published online in the Journal of the American Chemical Society on March 5, 2025, demonstrate that this new compound enables high-precision temperature measurements through changes in fluorescence properties.

The researchers designed a series of donor−π–acceptor (D−π–A) fluorophores based on a π-extended fluorene structure. These molecules are specially engineered to change their fluorescence properties in response to their surrounding environment’s polarity. When the temperature increases, the polarity of the solvent slightly decreases, which causes these dyes to emit light at different wavelengths and intensities.