Among the many Hg 2+ sensors that have been reported to date, only the very recent one (MF-1) developed by Wong and Chang has successfully met both of the above two challenges. 8 In this sensor an N1S4 crown ether was utilized as the Hg 2+ receptor. The detection limit of MF-1 was found to be about 60 nM. Using MF-1, Wong and Chang have successfully measured the mercury levels in fish within the safe edible limit. Herein, we wish to report ...