A selective and stepwise aggregation of a new fluorescent probe for dinitrate explosive differentiation by self-adaptive host-guest interaction

Abstract

Nitrate explosive is hard to detect due to lack of aromatic ring and weak interaction with fluorescence probe. More challenging is even to differentiate the dinitrates with multiple nitrate explosives based on photo induced electron transfer or aggregation caused fluorescence change mechanism. A highly selective dinitrate explosive probe was designed based on a new strategy ¾ stepwise aggregation of multiple anchored fluorene dimer 8Py-2F . Compared with its monomer counterpart 2Py-F , 8Py-2F showed a selective and stepwise fluorescence quenching to dinitrate explosives—ethylene glycol (EGDN) and triethylene glycol dinitrate (TEGDN). The limits of detection (LODs) are 2.72 μM for TEGDN and 0.46 μM for EGDN, which is three orders of magnitude lower than those of 2Py-F . The stepwise quenching process is well matched with the stepwise aggregation process as evidence by scanning electron microscopy (SEM). Nuclear magnetic resonance (NMR) and quantum chemical calculation proved the interaction force between the dinitrate and 8Py-2F is hydron bonding interaction, and interaction distance is far less than that of the multiple nitrates coming from the flexibility of the chain and steric hinderance, which resulted in a self-adaptive interaction and higher selectivity. The new strategy is beneficial for the differentiation of the chemicals with similar energy level which is difficult to realize via other method, and the new method provides fluorometric probe for dinitrate explosive detection and makes it an ideal candidate for chemical detection and analysis in public safety and environmental monitoring.