The discovery of air-stable n-dopants for organic semiconductor materials has been hindered by the necessity of high-energy HOMOs and the air sensitivity of compounds that satisfy this requirement. One strategy for circumventing this problem is to utilize stable precursor molecules that form the active doping complex in situ during the doping process or in a postdeposition thermal- or photo-activation step. Some of us have reported on the use of 1H-benzimidazole (DMBI) and benzimidazolium (DMBI-I) salts as solution- and vacuum-processable n-type dopant precursors, respectively. It was initially suggested that DMBI dopants function as single-electron radical donors wherein the active doping species, the imidazoline radical, is generated in a postdeposition thermal annealing step. Herein we report the results of extensive mechanistic studies on DMBI-doped fullerenes, the results of which suggest a more complicated doping mechanism is operative. Specifically, a reaction between the dopant and host that begins with either hydride or hydrogen atom transfer and which ultimately leads to the formation of host radical anions is responsible for the doping effect. The results of this research will be useful for identifying applications of current organic n-doping technology and will drive the design of next-generation n-type dopants that are air stable and capable of doping low-electron-affinity host materials in organic devices.

Mesoporous C-doped TiO2 nanomaterials with an anatase phase are prepared by a one-pot green synthetic approach using sucrose as a carbon-doping source for the first time. A facile post-thermal treatment is employed to enhance visible light photocatalytic activity of the as-prepared photocatalyst. The enhancement effect of post-thermal treatment between 100 and 300 °C is proved by the photodegradation of gas-phase toluene, and the optimum temperature is 200 °C. Physicochemical properties of the samples are characterized in detail by X-ray diffraction, Raman spectroscopy, N2 adsorption–desorption isotherms, transmission electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, and photoluminescence. The results indicate that the promotive effect of the post-thermal treatment can be attributed to the changes of the catalysts’ surface and optical properties. The results also show that the recombination of electron–hole pairs is effectively inhibited after thermal treatment due to the reduction of surface defects. The facile post-thermal treatment provides a new route for potential industrial applications of C-doped TiO2 nanomaterials prepared by a green approach owing to its low cost and easy scale-up.

Air-stable dimers of sandwich compounds including rhodocene and (pentamethylcyclopentadienyl)(arene)ruthenium and iron derivatives can be used for n-doping electron-transport materials with electron affinities as small as 2.8 eV. A p-i-n homojunction diode based on copper phthalocyanine and using rhodocene dimer as n-dopant shows a rectification ratio of greater than 10(6) at 4 V.

Graphitic carbon nitride (g-C 3 N 4 ) is an intriguing metal-free photocatalyst for pollution control. This research represents an efficient visible light photocatalytic removal of gaseous NO at 600 ppb level with porous g-C 3 N 4 nanostructures synthesized by pyrolysis of thiourea. TG-DSC was employed to simulate the pyrolysis of thiourea, and the mechanistic formation process of g-C 3 N 4 was revealed. The crystallinity, morphology, surface area, pore structures, band structure, and photocatalytic activity of g-C 3 N 4 can be engineered by variation of pyrolysis temperature and time. A layer-by-layer coupled with layer-splitting process was proposed for the gradual reduction of layer thickness and size of g-C 3 N 4 obtained at elevated temperature and prolonged time. The visible light photocatalytic activity of g-C 3 N 4 nanosheets toward NO purification was significantly enhanced due to the enhanced crystallinity, nanosheet structure, large surface areas and pore volume and enlarged band gap as the pyrolysis temperature was increased and the pyrolysis time was prolonged. The optimized g-C 3 N 4 nanosheets (CN-600 °C and CN-240 min) exhibited higher photocatalytic activity of 32.7% and 32.3% than C-doped TiO 2 (21.8%) and BiOI (14.9%), which are also highly stable and can be used repeatedly without obvious deactivation under repeated irradiation, demonstrating their great potential for practical applications.

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