Water-soluble Cu2+-fluorescent sensor based on core-substituted naphthalene diimide and its application in drinking water analysis and live cell imaging

Water-soluble naphthalene diimide based fluorescent chemosensor, N1, was designed for Cu2+ recognition. The sensor exhibited significant fluorescence modulation and chromogenic change with high Cu2+ sensitivity and selectivity over interfering metal ions. The sensor was able to efficiently monitor Cu2+ in 100% aqueous buffer solution with a low detection limit of 0.7 ppb which is much lower than the recommended value in drinking water by the United States Environmental Protection Agency (U.S. EPA) and the World Health Organization (WHO). The complex formation of N1 with Cu2+ was found to be 1:1 N1-Cu2+ by Job's plot analysis. Furthermore, the sensor was highly tolerant to interference from a matrix of real samples such as drinking water and human liver carcinoma cell line.