Pyrene-appended imidazolium probes as 3,5-dinitrosalicylic acid sensors in 10% aqueous media

• Pyrene-appended imidazolium salts (1 and 2) are developed for 3,5-DNSA sensing in aqueous solution.
• 3,5-DNSA exhibited “switch off” green emission of probe 2.
• LOD for 3,5-DNSA is 1 μM in water using probe 2 coated onto a paper strip.
• Use of probes 1–2 over a wide pH range 4–10.

Pyrene-appended imidazolium salts (1 and 2) were synthesized for sensing of salicylic acids and they selectively and sensitively detected 3,5-dinitrosalicylic acid (3,5-DNSA) in pH 7.4 PBS–EtOH (1:9) solution. The interaction of 3,5-DNSA with 1 and 2 was examined by UV–visible, fluorescence, and 1H NMR spectroscopy and was supported by DFT calculations. The binding of 3,5-DNSA to probe 2 leads to complete quenching of its green excimer emission because of loss of π–π interactions between the pyrene rings and energy transfer from electron-rich pyrene to electron-deficient 3,5-DNSA. Binding of 3,5-DNSA to probe 1 causes its blue (monomer) fluorescence to “switch off”. The limit of detection of 3,5-DNSA in water was 1 μM using probe 2 coated onto a paper strip.

Pyrene-appended imidazolium probes 1 and 2 detected 3,5-DNSA in aqueous media over a wide pH range (4–10) with a “switch off” of the green emission of probe 2 and the blue emission of probe 1 with detection limits of 1 μM and 2 μM, respectively.Figure optionsDownload as PowerPoint slide