A water soluble fluorescent probe for selective and sensitive detection of picric acid – a nitroexplosive

Abstract

A novel water soluble material was synthesized and employed as a sensing probe towards a common nitro-aromatic explosive, namely, picric acid (2,4,6-trinitrophenol). The probe was prepared in a four step process, including extraction of saponin, oxidation of saponin into sapal, intrusion of pyrene and dip coating on a chitosan film. The oxidation of saponin into sapal was determined by DNPH assay. The saponin (SAP), oxidized saponin (SAPAL) and SAPAL-PY were well characterized by UV–vis, fluorescence, FT-IR, AFM, SEM and NMR spectroscopy methods. The sensing studies were carried out with SAPAL-PY, which has shown a highly selective “turn off” sensing behavior towards picric acid with a good sensitivity and detection limit of 5 × 10⁻¹⁰ ML⁻¹ and was selective over other nitroaromatics. Also, the SAPAL-PY dip-coated chitosan film showed a very effective detection of picric acid within the concentration range of 0 to 10⁻⁹ M. The simplicity, selectivity and sensitivity of the proposed probe make it a potential sensor to detect nitroexplosives. Furthermore, the detection process of picric acid was reversible and repeatable for five cycles.