Construction of naphthalimide-based fluorescent amphiphilic aggregates and sensitive detection of persulfate and pyrophosphate anions

Detection of important anions is significant and challenging. Persulfate (S2O82-) and pyrophosphate (P2O74-) are two specific anions attracting extensive attentions as they have important effects on biological processes and environmental systems. A fluorescent amphiphilic molecule based on naphthalimide derivative was synthesized and it can form aggregates in aqueous solution. The fluorescent aggregates have shown selective fluorescence quenching responses to both S2O82- and P2O74- over a series of other anions. Moreover, the sensitivity is very high, and the detection limits of S2O82- and P2O74- are determined to be 5.2 nM and 19 nM, respectively. Time-resolved fluorescence decay measurements realized that the quenching is static in nature that could be due to the electrostatic interaction between the anions and cationic probes. Dynamic light scattering measurements revealed that the two anions have different effects on the aggregate size change, which could be further used to discriminate between the two anions with the aid of Tyndall effect test. Moreover, the probe aggregates can also detect the two anions in tap water and are used to prepare paper sensor for fast visual detection of the two anion analytes.