Concise and Efficient Fluorescent Probe via an Intromolecular Charge Transfer for the Chemical Warfare Agent Mimic Diethylchlorophosphate Vapor Detection

Abstract

Sarin, used as chemical warfare agents (CWAs) for terrorist attacks, can induce a number of virulent effects. Therefore, countermeasures which could realize robust and convenient detection of sarin are in exigent need. A concise charge-transfer colorimetric and fluorescent probe (4-(6-(tert-butyl)pyridine-2-yl)-N,N-diphenylaniline, TBPY-TPA) that could be capable of real-time and on-site monitoring of DCP vapor was reported in this contribution. Upon contact with DCP, the emission band red-shifted from 410 to 522 nm upon exposure to DCP vapor. And the quenching rate of TBPY-TPA reached up to 98% within 25 s. Chemical substances such as acetic acid (HAc), dimethyl methylphosphonate (DMMP), pinacolyl methylphosphonate (PAMP), and triethyl phosphate (TEP) do not interfere with the detection. A detection limit for DCP down to 2.6 ppb level is remarkably achieved which is below the Immediately Dangerous to Life or Health concentration. NMR data suggested that a transformation of the pyridine group into pyridinium salt via a cascade reaction is responsible for the sensing process which induced the dramatic fluorescent red shift. All of these data suggest TBPY-TPA is a promising fluorescent sensor for a rapid, simple, and low-cost method for DCP detection, which could be easy to prepare as a portable chemosensor kit for its practical application in real-time and on-site monitoring.

Challenges in Fluorescence Detection of Chemical Warfare Agent Vapors Using Solid‐State Films

“…This means that the N‐containing materials designed for the detection of nerve agents and simulants are intrinsically sensitive to acids. Therefore, it is not surprising that acids can produce false positives for these sensing materials . Studies on the N‐based compounds 2 , 3 , and 4 show that the protonated derivatives account for the fluorescence “turn on” responses upon exposure to DCP, which further confirms that these sensing materials cannot distinguish between nerve agent simulants and acids.…”

“…Therefore, it is not surprising that acids can produce false positives for these sensing materials . Studies on the N‐based compounds 2 , 3 , and 4 show that the protonated derivatives account for the fluorescence “turn on” responses upon exposure to DCP, which further confirms that these sensing materials cannot distinguish between nerve agent simulants and acids. Although films of the N–O bifunctional material 8 , and 10 or 11a in solution show stronger PL responses to simulants than acids, the PL peak wavelengths are almost identical.…”

“…Materials with nitrogen‐based nucleophiles constitute an important class of fluorescent sensors investigated for the detection of nerve agent and simulant vapors. N‐based chemosensors ( Figure ) include quinoline (e.g., 2 ), pyridine (e.g., 3 and 4 ), Schiff bases (e.g., 5 ), amines (e.g., 6 ), or quinoxaline . Solid‐state detection of the nerve agents has been reported to be achievable in different formats including drop‐casting ( 2 ) in a poly(ethylene oxide) (PEO) matrix, having ( 6 ) and ( 4 ) sorbed onto microbeads or glass, or filter paper, respectively, or in the form of a neat thin film by spin‐coating ( 3 ) or ( 5 ) onto quartz substrates.…”

“…Two typical detection mechanisms have been used with these materials to detect the nerve agents: protonation to enhance intramolecular charge transfer (ICT), e.g., compounds 2 – 5 and illustrated with 2→2′ , and phosphorylation to inhibit the photoinduced electron transfer (PET) process ( 6 →6′ ). Both the mechanisms lead to a fluorescence “turn on” response . There are other N‐based sensing materials (not listed here) that give fluorescence “turn off” signals, but the sensing mechanisms are unclear .…”

Fluorescence Responses of the Protonation and Deprotonation Processes between Phenolate and Phenol within Rosamine

“…[1,2] In recent years, the design of fluorescent pH probes was mainly focused on the protonation and deprotonation of amino group, [3] phenol group, [4] and some typical reactions with special fluorophores. [5] In addition to pH detection, the researches of protonated and deprotonated processes give a chance to view the structure-property relationship for functional dyes deeply. [6,7] Hydrogen bond plays an important role not only in the life process [8][9][10] but also in the construction of molecular systems.…”