ABSTRACT: Although nucleophile (Nu) is associated with many important chemical reactions, there are no fluorescence sensors for Nu detection and even for calculation of its nucleophilicity up to the present. In this study, we developed a fluorescent malononitrile-modified perylenediimide (MAPDI) which can selectively and rapidly react with nucleophiles, such as amines, amino acids, and some inorganic anions, and then change its UV-vis absorption and fluorescence emission. Detection limits of MAPDI for different nucleophiles could be calculated to compare their strength of nucleophilicity. Furthermore, it was found that MAPDI could detect reductive inorganic anions. These results suggested that MAPDI might have a great potential in organocatalytic reactions, metal ioncatalyzed reactions, reactions of amines, and other nucleophilic chemical reactions.