Synthesis and properties of a new green water‐soluble polymer for proton and metal‐cation sensing

A novel water‐soluble colored polymer, based on 1,8‐naphthalimide, was synthesized through a series of easy reactions with high yields. It emitted green fluorescence both in an aqueous solution and in a solid state. Fluorescence characteristics of the polymer as a function of pH were investigated in aqueous solutions. The polymer solution showed weaker fluorescence in a more acidic medium. When the pH of the solution was higher than 5, stronger fluorescence could be seen with a p K a value of 3.5. The presence of metal cations (Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ ) could quench the fluorescence intensity of an aqueous solution of this polymer to different levels. It was highly sensitive to Cu 2+ and Fe 3+ present in the studied system. The results suggest that this newly synthesized compound could work as a polymeric sensor responding to water polluted by Cu 2+ , Fe 3+ , and protons. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009