Prompt liquid-phase visual detection and low-cost vapor-phase detection of DCP, a chemical warfare agent mimic

A new rhodamine-based probe (RTU) was prepared as a colorimetric/fluorescent probe for the selective detection of DCP (a mimic of the Soman nerve agent) with a broad pH range of 7-11.0. RTU contains two reactive sites: (i) a nucleophilic thiourea group able to undergo complexation with electrophilic phosphorous and (ii) a spirolactam carbonyl group that acts as a reactive site for phosphorous. RTU exhibits great photostability, high sensitivity, and good selectivity for DCP (in both the liquid and vapor phases) compared with other reactive species, such as metal ions and H+, under alkaline conditions. Upon mixing with DCP in 3% Et3N-DMF, the spirolactam of RTU opened, which triggered the dramatic enhancement of both fluorescence and absorbance intensity and a color change of the solution. The probe displays a linear response to DCP in the range from 2.0 x 10(-5) to 15 x 10(-5) M with a detection limit of 1.42 x 10(-7) M. The kinetics results indicate that RTU exhibits instantaneous sensing behavior within a few minutes. Its recognition behavior toward DCP was investigated by H-1 NMR, FAB-MS, and P-31 NMR. Portable kits were developed and tested to demonstrate the practical application of RTU in real-time monitoring. (C) 2016 Elsevier B.V. All rights reserved.