An Aza-12-crown-4 Ether-Substituted Naphthalene Diimide Chemosensor for the Detection of Lithium Ion

We synthesised aza-12-crown-4 ether-substituted naphthalene diimide (NDI-12-C-4) and demonstrated its properties as an fluorescent and colorimetric sensor. The NDI-12-C-4 uses the aza-12-crown-4 moiety to bind Li+ ion selectively over larger monovalent cation such as Cs+, Na+ and K+. The sensor is chemically stable due to the crown-ether, and the appended NDI fluorophore allows leads to optical changes exclusively for the monovalent Li+ ion. UV-vis absorption, fluorescence, cyclic voltammetry (CV), 1HNMR and naked eye-detection clearly demonstrate selective, sensitive binding of Li+ ion with a detection limit of 5.0 mu M. Importantly, reversible binding of Li+ by NDI-12-C-4 was also observed upon addition of EDTA, after which the sensor could be recovered via simple centrifugation, indicating suitability for use in a biological sensor device.