Latest Trends in Temperature Sensing by Molecular Probes

In this Review, we summarize the work in the last ten years on the development of fluorescent molecular probes with possible applications in microscopic thermometry. We discuss four principal types of temperature‐dependent photoluminescence features: 1) Emission intensity; 2) Ratio of emission intensities; 3) Emission peak shift; and 4) Emission lifetime. We compare the advantages, limitations, and challenges of the different probes using these types of sensing mechanisms. By focusing on molecular probes, rather than nanoparticles or polymers, the mechanisms of temperature dependence are discussed thoroughly, with the most common including twisted intramolecular charge transfer (TICT), aggregation‐induced emission (AIE), and mechanically induced change in emission (MICE). With many different confounding variables associated with each experimental method and mechanism of temperature‐dependent photoluminescence, lanthanide and transition metal complexes seem to be promising candidates for future microscopic thermometry applications. Feel the heat: The determination of temperature is vital in the characterization of any chemical or physical process in living and non‐living systems. While temperature can be easily measured in macroscopic systems, the measurement of temperatures at the micro‐ and nanoscales have their own challenges. Herein we offer an overview of molecular fluorescent sensors developed to measure temperature in microscopic environments, their uses, and current limitations.