An instant, biocompatible and biodegradable high-performance graphitic carbon nitride.

Polymer graphitic carbon nitride (g-C3N4) materials have attracted growing interest owing to their impressive applicability in photocatalysis and optoelectronic devices. However, further applications of g-C3N4 materials are greatly restricted by their chemical inertness and insolubility in most solvents. Regarding the rising prospect of g-C3N4 nanosheets in the biomedicalfield, high solubility and biocompatibility are required for the further development of g-C3N4 materials. In this study, a simple one-step thermal polymerization method was designed to prepare fast-soluble mesoporous g-C3N4 nanosheets by using NH4HSO4 as the critical adjuvant. The products, especially the optimal g-C3N4 NSs-4, showed impressive solubility, biocompatibility and partial biodegradability. The enriched surface hydrophilic groups (-NH2 and -OH) may contribute to improving the solubility of g-C3N4 nanosheets, while the partial biodegradability can be ascribed to the presence of the disulfide bond in the g-C3N4 framework. In this system, the NH4HSO4 adjuvant acted not only as O and S sources, but also as a bubbling agent that endows the g-C3N4 a porous structure with greatly enlarged specific surface area and high separation efficiency of photogenerated electron-hole pairs. These integrative positive factors also greatly contributed to the photocatalytic activity of the g-C3N4 nanosheets. This facile, economic and general fabrication strategy for mesoporous, fast-soluble and biocompatible g-C3N4 with superior visible-light photocatalytic activity is promising in environmental, energy and biomedical fields.

Polymeric structure optimization of g-C3N4 by using confined argon-assisted highly-ionized ammonia plasma for improved photocatalytic activity.

The optimization of the polymeric structure and the modulation of surface amino groups in graphitic carbon nitride (g-CN) are critical but challenging in improving the photoelectric and photocatalytic performances of this polymer semiconductor. Ammonia plasma treatment may provide a fast and useful approach to optimize g-CN materials yet is seriously restricted by the low ionization ability of ammonia. Herein, a confined fast and environmental-friendly ammonia plasma method based on argon-assisted high ionization of NH3 was developed for efficient modification of raw g-CN. Compared with the weakly-ionized pure ammonia plasma which can only introduce amino group onto the surface g-CN, the argon-assisted highly-ionized ammonia plasma treatment obviously contributes to the comprehensively polymeric structure optimization of g-CN, and thus plays a key role in enhancing its light-harvesting and decelerating the recombination of the photogenerated charge carriers. As a result, the argon-assisted highly-ionized ammonia plasma-treated g-CN-Ar+NH3 outperformed the raw g-CN by a 2.5-fold higher photocatalytic reduction of hexavalent chromium and a remarkable 3.8-fold higher photocatalytic H2 evolution activity (up to 957.8 µmol·h-1·g-1) under visible light irradiation. Our findings suggest the great prospects of this novel highly-ionized ammonia plasma treatment method in the controllable modification of semiconductors and polymers.

Surface Amino Group Regulation and Structural Engineering of Graphitic Carbon Nitride with Enhanced Photocatalytic Activity by Ultrafast Ammonia Plasma Immersion Modification.

Surface amino group regulation and structural engineering of graphitic carbon nitride (g-CN) for better catalytic activity have increasingly become a focus of academia and industry. In this work, the ammonia plasma produced by a microwave surface wave plasma generator was developed as a facile source to achieve fast, controllable surface modification, and structural engineering of g-CN by ultrafast plasma treatment in minutes, thus enhancing photocatalytic performance of g-CN. The morphology, surface hydrophilicity, optical absorption properties, and states of C-N bonds were investigated to determine the effect of plasma immersion modification on the g-CN catalyst. The structure and photoelectric features of the plasma-modified samples were characterized by X-ray diffractometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. The results indicate that the ammonia plasma-treated g-CN-NH3 exhibits an ultrathin nanosheet structure, enriched amino groups, and an ideal molecular structure, a narrower band gap (2.35 eV), extended light-harvesting edges (560 nm), and enhanced electron transport ability. The remarkably enhanced photocatalytic activity demonstrated in the photoreduction and detoxification of hexavalent chromium (Cr(VI)) can be ascribed to the optimization of the structural and photoelectric properties induced by the unique ammonia plasma treatment. The effective and ultrafast approach developed in this work is promising in the surface amino group regulation and structural engineering of various functional materials.

Moderate Bacterial Etching Allows Scalable and Clean Delamination of g-C3N4 with Enriched Unpaired Electrons for Highly Improved Photocatalytic Water Disinfection.

Delamination treatment is crucial in promoting the activity of bulk graphitic carbon nitride (g-C3N4). However, most of the currently used methods of exfoliating bulk g-C3N4 to achieve g-C3N4 thin layers suffer from low yield and environmental pollution. Herein, we developed a facile bacterial etching approach for the preparation of high-quality g-C3N4 nanosheets by exfoliating bulk g-C3N4 under room temperature. Morphology and physicochemical characterizations show that the bacteria-treated g-C3N4 (BT-CN) samples, especially BT-CN-2d, have a lamina-like two-dimensional (2D) in-plane porous structure, a significantly enlarged specific surface area (82.61 m2 g-1), and a remarkable narrow band gap (2.11 eV). X-ray photoelectron spectroscopy and electron paramagnetic resonance spectra confirm the dramatic enrichment of unpaired electron in the BT-CN-2d g-C3N4 nanosheets. EIS spectra and photocurrent tests indicate the fast electron transportation. As a result, the representative BT-CN-2d g-C3N4 photocatalyst shows an optimal visible light-driven photocatalytic performance in water disinfection (fourfold higher than bulk g-C3N4), as well as good cycle stability. This moderate and clean bacterial etching process can be realized in tens of gram scale in the laboratory and should be readily extended to kilogram scale. The present work provides fundamental knowledge about the scalable production of high-quality g-C3N4 by bioengineering method, offering extendable availability for designing and fabricating other functional 2D materials.