Fabrication and Characterization of Carbon Nitride Fluorescent Material Using Annealed Melamine

Fluorescent carbon nitride (CN) thin films are fabricated by annealing melamine powder. Four kinds of fabrication methods are tested: (1) annealing melamine powder on glass substrate; (2) annealing spin‐coated melamine powder in acetic acid solution on glass substrate; (3) annealing melamine powder in a test tube and evaporating on a glass substrate; (4) spin‐coating annealed melamine powder in acetic acid and nitric acid solutions on glass substrates. As a result, method (1) produces fluorescent CN grains when the annealing temperature was over 400 °C. Photoluminescence (PL) peaking wavelength is redshifted with an increase of the annealing temperature. However, flat CN thin films cannot be produced. Method (2) cannot produce CN‐based thin films; only small particles are found on substrates. Method (3) can drastically improve the surface roughness and produce flat CN thin films. Finally, the method (4) demonstrates that the PL peaking wavelength is blue‐shifted by nitric acid. Fourier‐transform infrared (FT‐IR) observation suggests that the protons supplied from nitric acid connect with carbon atoms in carbonyl, generating aldehydes and changing the PL properties. To fabricate flat carbon nitride (CN)‐based blue‐color fluorescent films, four kinds of wet‐ and dry‐process methods are investigated using annealed melamine powder. As a result, fine flat CN films can be prepared by evaporating melamine powder. In addition, their photoluminescence peaking wavelengths are drastically blue‐shifted when they are dispersed in nitric acid, which is caused by protonation.