Graphitic carbon nitride
Graphitic carbon nitride (g-CN) is a family of carbon nitride compounds with a general formula near to CN (albeit typically with non-zero amounts of hydrogen) and two major substructures based on heptazine and poly(triazine imide) units which, depending on reaction conditions, exhibit different degrees of condensation, properties and reactivities. Preparation. Graphitic carbon nitride can be made by polymerization of cyanamide, dicyandiamide or melamine. The firstly formed polymeric CN structure, melon, with pendant amino groups, is a highly ordered polymer. Further reaction leads to more condensed and less defective CN species, based on tri-s-triazine  (CN) units as elementary building blocks. Graphitic carbon nitride can also be prepared by electrodeposition on Si(100) substrate from a saturated acetone solution of cyanuric trichloride and melamine (ratio =1: 1.5) at room temperature. Well-crystallized graphitic carbon nitride nanocrystallites also can be have prepared via benzene-thermal reaction between CNCl and NaNH at 180–220 °C for 8–12 h. Recently, a new method of syntheses of graphitic carbon nitrides by heating at 400-600 °C of a mixture of melamine and uric acid in the presence of alumina has been reported. Alumina favored the deposition of the  graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Characterization. Characterization of crystalline g-CN can be carried out by identifying the triazine ring existing in the products by X-ray photoelectron spectroscopy (XPS) measurements, photoluminescence spectra and Fourier transform infrared spectroscopy (FTIR) spectrum (peaks at 800 cm, 1310 cm and 1610 cm). Properties. Due to the special semiconductor properties of carbon nitrides, they show unexpected catalytic activity for a variety of reactions, such as for the activation of benzene, trimerization reactions, and also the activation of carbon  dioxide (artificial photosynthesis). Uses. A commercial graphitic carbon nitride is available under the brand name Nicanite. In its micron-sized graphitic form, it can be used for tribological coatings, biocompatible medical coatings, chemically inert coatings, insulators and for energy-storage solutions. Graphitic carbon nitride is reported as one of the best hydrogen storage materials. It can also be used as a support for catalytic nanoparticles. Areas of interest. Due to their properties (primarily large, tuneable band gaps and efficient intercalation of salts) graphitic carbon nitrides are under research for a variety of applications: