New 1,8-naphthalimide-conjugated sulfonamide probes for TNP sensing in water

- New 1,8-naphthalimide based probes 1 and 2 synthesized.
- Probes 1 and 2 exhibited AIEE with water in DMSO.
- Probe 1 exhibited excimer emission.
- Probe 1 ued forTNP detection with LOD 25.6 pM..
- Probe 1 coated filter paper strips have LOD of 3 nM for TNP.

Two 1,8-naphthalimide (NPI)-conjugated sulfonamide probes (1 and 2) were synthesized for sensitive detection of 2,4,6-trinitrophenol (TNP) in aqueous media. In a PBS buffer, probe 1 (with two NPI units) showed an emission spectrum with λmax = 484 nm while probe 2 (with only one NPI unit) gave an emission spectrum with λmax = 383 nm. Probe 1 showed aggregation-induced emission enhancement (AIEE) in a mixture of DMSO: H2O, but this emission was completely quenched in the presence of 2 equiv. of TNP. Partial de-aggregation of the nanoparticles and a conformational change of probe 1 induced by strong binding of the probe with TNP are mainly responsible for its sensitive TNP detection. Probe 1 provided sensitive detection of TNP in sea water, with observed and calculated limits of detection (LOD) of 3 nM and 5.86 ppt, respectively. In addition, filter paper strips coated with probe 1 were successfully utilized for TNP detection with high sensitivity.

TNP interaction with probe 1 lead to its conformational change from locked to unlocked and decreased its aggregation in water with quenching having LOD 25.6 pM.164