Chromo-Fluorogenic Detection of Soman and Its Simulant by Thiourea-Based Rhodamine Probe

Abstract

Here, we introduced a novel thiourea-based rhodamine compound as a chromo-fluorogenic indicator of nerve agent Soman and its simulant diethyl chlorophosphate (DCP). The synthesized probe N-(rhodamine B)-lactam-2-(4-cyanophenyl) thiourea (RB-CT), which has a rhodamine core linked by a cyanophenyl thiosemicarbazide group, enabled a rapidly and highly sensitive response to DCP with clear fluorescence and color changes. The detection limit was as low as 2 × 10−6 M. The sensing mechanism showed that opening of the spirolactam ring following the phosphorylation of thiosemicarbazides group formed a seven-membered heterocycle adduct, according to MS analysis and TD-DFT calculations. RB-CT exhibited high detecting selectivity for DCP, among other organophosphorus compounds. Moreover, two test kits were employed and successfully used to detect real nerve agent Soman in liquid and gas phase.

Fluorescent probes for the detection of chemical warfare agents

“…In 2019, Li and co-workers reported RB-CT ( 42 ), a thiourea-functionalized rhodamine fluorescent probe, for the detection of nerve agents. 77 RB-CT readily reacted with DCP to induce the ring opening of the spirolactam of rhodamine and form a seven-membered heterocycle adduct. This reaction affords a substantial change in colour (colourless to pink) and a fluorescence increase at 583 nm.…”

“…Fluorescent probes (22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(38)(39)(40)(41)(42) that are designed to undergo a phosphorylation-intramolecular cyclization reaction display high selectivity for nerve agents; the major limitation to this strategy is the long reaction times. The use of oximes as a recognition unit proved superior to hydroxyl units (64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76)(77)(78)(79)(80)(81), leading to shortened reaction times. Probes PTS (73), 80, and SO-BOD (81) developed based on this strategy exhibited good sensing performances.…”

Advances in Noble-Metal Nanoparticle-Based Fluorescence Detection of Organophosphorus Chemical Warfare Agents

“…(b) Proposed mechanism of RB-CT with DCP. Reproduced with permission from ref ( 79 ). Copyright 2019 The Authors under Creative Commons International CC BY 4.0 License, published by MDPI.…”

“…The probe showed significant fluorescence and color change. As shown in Figure b, the detection limit is as low as 2 × 10 –6 M …”

“…The probe showed significant fluorescence and color change. As shown in Figure 5b, the detection limit is as low as 2 × 10 −6 M. 79 A semiquantitative visual detection method for organophosphate pesticides was described by Wu et al It is based on the property of AuNRs that their absorbance is proportional to their aspect ratio. This is due to the presence of gold nanorods that exhibit localized surface plasmon resonance (SPR).…”