Graphitic carbon nitride (g‐C3N4) is synthesized by thermal decomposition of thiourea and subsequent in situ polymerization of the products in the oxygen‐containing ambient at 450–625 °C and studied with scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, Fourier‐transform infrared spectroscopy, and photoluminescence techniques. The synthesized material contains oxygen at a concentration increasing with the processing temperature from 4.8 to 9.8 at %. The photoluminescence peak is found to be red‐shifted with the temperature increased to 575 °C becoming then blue‐shifted at higher temperatures. The observed red‐shift of the photoluminescence peak is supposed to be caused by band‐gap narrowing in g‐C3N4 doped by oxygen while its recovery behavior is controlled by thermally induced oxygen‐assisted disruption of sp2 bonds in C‐N π‐orbital conjugated system of tri‐s‐triazine units building polymer sheets in g‐C3N4.
We developed and studied facile synthesis of graphitic carbon nitride in macroporous silica glass matrix. Melamine was used as a precursor. The synthesis was performed in a closed air ambience at 400–600∘C. It was found that the synthesized material was characterized with a broadband room-temperature photoluminescence in the range of 350–750[Formula: see text]nm with the peak shifting from to 445[Formula: see text]nm to 702[Formula: see text]nm when the temperature of the synthesis was increased from [Formula: see text]C to [Formula: see text]C while the intensity of the luminescence was decreased. The nature of the luminescent centers and possible applications of the synthesized material are discussed.
The relationships governing variation of the photoluminescence of graphitic carbon nitride synthesized by heat treatment of melamine in a closed air medium containing oxygen in the temperature range of 10-300 K were investigated. It was shown that the concentration of oxygen in the obtained material 4-5 at.% increases with increase of temperature and decreases with increase in the duration of the synthesis process. By measurements at reduced temperatures right down to 10 K it was possible to resolve bands due to radiative recombination processes in the photoluminescence spectra of the graphitic carbon nitride. It was found that increase of the synthesis temperature from 500 to 600 o C and also increase of the duration at the given temperature from 30 to 240 min shift the maximum in the photoluminescence spectrum from 2.74 eV into the region of lower energies to 2.71-2.67 eV. This is due to the bigger role of the molecular system formed by the π bonds of carbon and nitrogen atoms with sp 2 hybridization and characterized by a smaller forbidden band width in the emission of light. Transitions due to recombination through oxygen-induced levels in the forbidden band of the semiconductor lead to the appearance of a "tail" in the photoluminescence spectra in the region of low energies (2.40-2.33 eV). Increase of the carbon nitride synthesis temperature to 600 o C leads to a change in the structure of the energy bands and to increase of the energy of the radiative transitions as a result of increase in the degree of doping with oxygen atoms and thermal stratifi cation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.