Structural insights into photocatalytic performance of carbon nitrides for degradation of organic pollutants

Preparation of High-Porosity B-TiO2/C3N4 Composite Materials: Adsorption-Degradation Capacity and Photo-Regeneration Properties

Adsorption can quickly remove pollutants in water, while photocatalysis can effectively decompose organic matter. B-TiO₂/g-C₃N₄ ternary composite photocatalytic materials were prepared by molten method, and their adsorption-degradation capability under visible light conditions was discussed. The morphology of the B-TiO₂/g-C₃N₄ materials was inspected by SEM, TEM, BET, and EDS, and the results showed that close interfacial connections between TiO₂ and g-C₃N₄, which are favorable for charge transfer between these two semiconductors, formed heterojunctions with suitable band structure which was contributed by the molten B₂O₃. Meanwhile, the molten B₂O₃ effectively increased the specific surface area of TiO₂/C₃N₄ materials, thereby increasing the active sites and reducing the recombination of photogenerated electron-hole pairs and improving the photocatalytic degradation abilities of TiO₂ and g-C₃N₄. Elsewhere, the crystal structure analysis (XRD, XPS, FTIR) results indicated that the polar -B=O bond formed a new structure with TiO₂ and g-C₃N₄, which is not only beneficial for inhibiting the recombination of electron holes but also improving the photocatalytic activity. By removal experiment, the adsorption and degradation performances of B-TiO₂/g-C₃N₄ composite material were found to be 8.5 times and 3.4 times higher than that of g-C₃N₄. Above all, this study prepared a material for removing water pollutants with high efficiency and provides theoretical support and experimental basis for the research on the synergistic removal of pollutants by adsorption and photocatalysis.

g-C3N5-dots as fluorescence probes prepared by an alkali-assisted hydrothermal method for cell imaging

Carbon nitride materials have become one of the highly explored carbon-based nanomaterials due to their unique properties. Herein, the novel graphitic carbon nitride quantum dots (g-C₃N₅-dots) were synthesized using an alkali-assisted hydrothermal method. The proposed strategy was simple, time-saving and the entire synthetic process only takes 60 min. And the prepared g-C₃N₅-dots showed excellent dispersion and good stability in water. What is more, the g-C₃N₅-dots displayed bright blue fluorescence with a high quantum yield of 12%. It was found that the g-C₃N₅-dots exhibited peroxidase-like activity, good biocompatibility and low cytotoxicity and can be successfully applied in cell imaging. The proposed method opens a new and efficient way for the preparation of fluorescent g-C₃N₅-dots and facilitates g-C₃N₅-dots for bioimaging and related biological sensing applications.

Novel graphitic carbon nitride quantum dots (g-C₃N₅-dots) were synthesized by an alkali-assisted hydrothermal method, having great potential applications in bioimaging and biological sensing.

Acid-activated carbon nitrides as photocatalysts for degrading organic pollutants under visible light

Three-dimensional (3D) carbon nitride (C₃N₄) can be used as a promising platform for visible-light-active photocatalysts because of its suitable band positions. This study reports that HNO₃ activation improves the photocatalytic activity of 3D melamine-derived C₃N₄ (MCN) materials, which degrade the organic pollutant rhodamine B (RhB). HNO₃ treatment under reflux removes the carbonaceous impurities in MCN and introduces oxygen-containing functional groups on its surface. Under visible light irradiation, the nitric acid treated MCN (NT-MCN) completely degrades RhB within 30 min. Photophysical characterizations and control experiments with radical scavengers reveal that MCN and NT-MCN follow different reaction mechanisms. Because NT-MCN exhibits a longer photoluminescence lifetime, smaller electrochemical resistance, and larger photocurrent than those of MCN, it enables a better transfer of charge carriers during the catalytic reaction.