Hybrid nanocomposites of N-heterocyclic carbene (NHC)-functionalized conducting polymers (CPs) with gold nanoparticles (AuNPs) were prepared by concurrent disproportionation and oxidative coupling. The formation of hybrid nanocomposites, NHC-CP/AuNPs, in the simultaneous process was confirmed by transmission electron microscopy, powder X-ray diffraction, cyclic voltammetry, and 13C solid-state NMR analyses. More importantly, the NHC group played a pivotal role in the dispersion of AuNPs. Further, NHC-CP/AuNPs exhibited good catalytic activity for the reduction of 4-nitrophenol.

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 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.

Single-walled carbon nanotubes (SWCNTs) were fabricated using AC dielectrophoresis into chemocapacitive sensors, and molecular receptors were applied for the selective detection of several chemical warfare agents (CWAs). The selective responses toward nerve simulants (G and V), choking and blister agents as well as a pesticide were investigated with specific receptor molecules that were either covalently functionalized or noncovalently coated onto the surfaces of the SWCNTs. The SWCNT-based chemocapacitive sensors showed reproducibility and sensitivity to 200 ppb for several target molecules. The fabricated sensor arrays were assessed for the selective detection of six different CWAs, and the principal component analysis demonstrated their specificity. VX, a real nerve agent, was tested on the fabricated SWCNT-based chemocapacitive sensor coated with a thiourea-functionalized siloxane polymer, and the successful detection of VX at 100 ppb confirmed that our SWCNT-based sensors are suitable for practical applications.

Stimuli-responsive polymeric systems are of considerable interest due to their potential applications in environment-adaptive technologies such as smart surfaces. Traditionally, such systems can be constructed either by dynamic noncovalent (supramolecular) or dynamic covalent chemistry, but the use of both chemistries in one system may offer unique opportunities for structural diversity and various controllability. Herein, we report that hydrazone–pyridinum conjugates, which can be dynamically exchanged by transimination, assemble to form one-dimensional nanowires due to direct intermolecular interactions (without metal-ion coordination). The self-assembly process can be controlled not only by dynamic covalent chemistry but also by pH adjustment. The hydrazone–pyridinum conjugates are transformed to merocyanine-type dyes of distinctive negative solvatochromism via deprotonation, which also affects their self-assembly. Such a dual control of the dynamic molecular assembly will provide unique way to develop diverse smart nanomaterials with multistimuli-responsiveness.

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