Selective cleavage of C−C bonds can be a valuable tool for various applications including polymer degradation and biomass utilization. Performing chemical transformations involving C−C bond cleavage steps under mild conditions and ambient temperature remains challenging due to the high dissociation energies of the C−C bond. This fundamental challenge can be solved by coupling a dye-sensitized photoelectrochemical cell (DSPEC) system, that generally targets the water splitting reaction, with a hydrogen atom transfer (HAT) mediator (HAT-DSPEC). Here, we report the solar-driven selective cleavage of the C(aryl)− C(alkyl) σ-bond in lignin at ambient temperature using an HAT-DSPEC under redox-neutral conditions. The photocatalyst (bis-2,2′-bipyridine)(2,2′-bipyridine-4,4′-dicarboxylic acid)Ru(II) (RuC) adsorbed onto a TiO 2 nanorod array with the length of ∼1.6 μm and a rod diameter of 100 nm atop fluorine-doped tin oxide (FTO|TiO 2 NRAs|RuC) film was prepared and investigated with an HAT mediator, 4-acetamido 2,2,6,6tetramethylpiperidine-1-oxyl (ACT), in solution. Photophysical and electrochemical studies of RuC and ACT with a lignin model compound, 1-(4-hydroxy-3,5-dimethoxyphenyl)-2-(2-methoxyphenoxy) propane-1,3-diol (LMC) reveal that the metal-toligand charge transfer (MLCT) excited states from the RuC are efficiently quenched in the presence of ACT with LMC. The HAT-DSPEC photoanode, containing the surface-bound photocatalyst RuC at the photoanode with ACT and LMC in solution, sustained an excellent photocurrent density, significantly outperforming that with the photocatalyst RuC alone. Moreover, the chemoselective cleavage of the C(aryl)−C(alkyl) bond in the LMC at the ambient temperature was demonstrated in the HAT-DSPEC system with a remarkable photocatalytic turnover number (>3000) leading to excellent selectivity (>90%) of C−C bond cleavage under AM1.5G irradiation (1 sun, 100 mW cm −2 ). These results were obtained over short reaction times and mild, redox-neutral reaction conditions without the need for extended reaction time (e.g., >24 h) or high temperature that is typical of homogeneous catalytic systems. This is the first report to demonstrate that an HAT-DSPEC can serve as a viable method for performing visible-light-driven selective C−C bond cleavage at ambient temperature.

Organophosphates are powerful inhibitors of acetylcholinesterase, which is critical to nerve function. Despite continuous research for detecting the highly toxic organophosphates, a new and improved methodology is still needed. Herein we demonstrate simple-to-fabricate chemiresistive gas sensors using conducting-polymer polypyrrole (PPy) nanotube transducers, which are chemically specific and capable of recognizing sub-ppb concentrations (ca. 0.5 ppb) of dimethyl methylphosphonate (DMMP), a simulant of nerve agent sarin. Interestingly, the introduction of carboxylic groups on the surface of PPy nanotube transistors resulted in enhanced sensitivity to DMMP via intermolecular hydrogen bonding. Furthermore, it was found that the sensitivity of the nanotube transducer depended on the degree of the carboxylic group introduced. Finally, a sensor array composed of 5 different transducers including the carboxylated nanotubes exhibited excellent selectivity to DMMP in 16 vapor species.

A facile route to graphene/polymer hydrogel nanofibers was developed. An aqueous dispersion of graphene (containing >40% bilayer graphene flakes) stabilized by a functionalized water-soluble polymer with phenyl side chains was successfully electrospun to yield nanofibers. Subsequent vapor-phase cross-linking of the nanofibers produced graphene-embedded hydrogel nanofibers (GHNFs). Interestingly, the GHNFs showed chemical sensitivity to the cationic dyes methylene blue (MB) and crystal violet (CV) in the aqueous phase. The adsorption capacities were as high as 0.43 and 0.33 mmol g s for MB and CV, respectively, even in a 1.5 mL s flow system. A density functional theory calculation revealed that aqueous-phase MB and CV dyes were oriented parallel to the graphene surface and that the graphene/dye ensembles were stabilized by secondary physical bonding mechanisms such as the π-π stacking interaction in an aqueous medium. The GHNFs exhibited electrochemical properties arising mainly from the electric double-layer capacitance, which were applied in a demonstration of GHNF-based membrane electrodes (5 cm in diameter) for detecting the dyes in the flow system. It is believed that the GHNF membrane can be a successful model candidate for commercialization of graphene due to its easy-to-fabricate process and remarkable properties.