Rational design of a 1,8-naphthalimide-based fluorescent probe for water detection in organic solvents

Generally, trace amounts of water in organic solvents are deadly to chemical production and laboratory chemical reactions. Thus, a novel derivative of 1,8-naphthalimide (NPP-N+) was designed and synthesized for detecting water content in water-miscible organic solvents. NPP-N+ features a donor-π-acceptor (D-π-A) structure, where strong intramolecular charge transfer (ICT) and suppressed twisted intramolecular charge transfer (TICT) in aqueous media lead to stronger fluorescence in water than in organic solvents. The experimental results show that the detection limits of NPP-N+ for water in ethanol (EtOH), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetone, and N,N-dimethylformamide (DMF) are 0.99%, 0.75%, 0.50%, 1.77%, and 0.35% respectively, indicating that NPP-N+ exhibited excellent fluorescent sensitivity to water in organic solvents. In addition, the potential of NPP-N+ for the quantitative detection of moisture content in medical alcohol samples and the natural absorbent DMSO was successfully demonstrated.