Multi-responsive self-assembled pyrene-appended β-cyclodextrin nanoaggregates: Discriminative and selective ratiometric detection of pirimicarb pesticide and trinitroaromatic explosives

Multi-responsive fluorescent aggregates have attracted growing interest for the development of high-performance sensory materials for monitoring environmental hazards. Herein, we develop a multi-responsive pyrene-appended beta-cyclodextrin probe 25, which self-assembles into nanoaggregates (150 nm-164 nm) in water driven by hydrophobic p-p interactions, evaluated by Tyndall scattering, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The formed fluorescent nanoaggregates were found to exhibit an efficient and selective ratiometric detection of pirimicarb (PC), a potent toxic carbamate pesticide with significant enhancement (85 times) in the monomer to excimer ratio (IM/IE). Further, among the trinitroaromatic explosives, the formed nanoaggregates displayed discriminative fluorogenic detection of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB) and picric acid (PA). Significant reduction in the size and morphological changes in the shape of the nanoaggregates were observed upon interaction with 50 and 100 equivalents of PC, TNT, TNB and PA. The highly ordered intermolecular packing of pyrene moieties in the nanoaggregates and their orientation specific monomer (I-M) and excimer (I-E) emissions allowed guest specific distinctive detection of PC, TNT, TNB and PA, which otherwise, have not been achieved so far.