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Biosensors need to fulfill various requirements such as selectivity, biocompatibility, large photodynamic signal-to-noise ratios, reversibility etc. Studies to the development of biosensors, therefore, require interdisciplinary approaches based on strong backgrounds of organic chemistry, physical chemistry, molecular spectroscopy and biology as well as inorganic chemistry. Among the various classes of biosensors, photoluminescent biosensors have been useful in enhancing our understanding of the molecular-level physiopathology since they are most suitable for application in in vivo cellular studies.

In our lab, we are developing sensors for detection of biological zinc ions, which cannot be identified with conventional methods of inorganic chemistry (see figure).In particular, we have developed a novel class of phosphorescent sensors based on a cyclometalated iridium complex in order to dramatically remove the noise signals that are inherent in fluorescent sensors. Our phosphorescence zinc probes feature long luminescence lifetime (~ ㎲) and enable time-gated signal detection, removing noise signals. Further, the zinc sensor can be used in confocal laser scanning microscopy and luminescence lifetime spectroscopy. The Ir complex platform has been synthetically tailored to produce dual emission through frustrated energy transfer between the different ligands,and the multi-phosphorescence properties were employed to ratiometric detection of copper ions.
In addition to the phosphorescence, we employ various excited-state photophysics including ESIPT (excited-state intramolecular proton transfer), TICT (twisted intramolecular charge transfer), FRET (Forster energy transfer) etc. for the development of biosensors. At present, we are developing photoluminescence sensors for reactive oxygen species, such as hydrogen peroxide, by extending the superior utility of the photo-functional molecules.