Structural Effect of Thioureas on the Detection of
Chemical Warfare Agent Simulants
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Abstract
The ability to rapidly detect, identify,
and monitor chemical warfare
agents (CWAs) is imperative for both military and civilian defense.
Since most CWAs and their simulants have an organophosphonate group,
which is a hydrogen (H)-bond acceptor, many H-bond donors have been
developed to effectively bind to the organophosphonate group. Although
thioureas have been actively studied as an organocatalyst, they are
relatively less investigated in CWA detection. In addition, there
is a lack of studies on the structure–property relationship
for gas phase detection. In this study, we synthesized various thioureas
of different chemical structures, and tested them for sensing dimethylmethylphosphonate
(DMMP), a CWA simulant. Molecular interaction between DMMP and thiourea
was measured by <sup>1</sup>H NMR titration and supported by density
functional theory (DFT) calculations. Strong H-bond donor ability
of thiourea may cause self-aggregation, and CH−π interaction
can play an important role in the DMMP detection. Gas-phase adsorption
of DMMP was also measured using a quartz crystal microbalance (QCM)
and analyzed using the simple Langmuir isotherm, showing the importance
of structure-induced morphology of thioureas on the surface