Two-dimensional ion–molecule chelation reaction (2D-IMCRs) to form a two-dimensional dual optical sensor (2D-DOS): synthesis and application of Phen-SnO2 nanosheets for the fluorometric and colorimetric sensing of nitroaromatic explosives

Abstract

For the first time, we introduce a novel type of two-dimensional ion–molecule chelation reaction (2D-IMCR) to produce a dual optical sensor (DOS) method for the fast, sensitive, selective, and precise detection of the nitroexplosive picric acid (PA) with a limit of detection (LOD) of 0.011 μM (11 nM) in aqueous solution. The new type of 2D-IMCR utilized 1,10-phenanthroline as a precursor (molecule) to react with the Sn metal via the probe ultrasonication process to produce a 2D dual optical sensor (2D-DOS) as a fluorescent and colorimetric sensor. In contrast to the frequently reported ground-state charge-transfer- or fluorescence resonance energy transfer (FRET)-based probes for nitroaromatics detection, the signal response specifically for PA was accomplished via a significant inner filter effect (IFE). According to fluorometric investigations with nitroexplosive chemicals, the compound's emission was red-shifted after the addition of picric acid (PA), and it displayed a shift of fluorescence from blue to green. Our experimental results demonstrated that the complexation of the picrate anion with the protonated fluorophore was the mechanism by which the 2D-DOS, produced by the 2D-IMCR, achieved successful sensing.