Graphitic Carbon Nitride: Synthesis and Characterization, Monolayer at the Air–Water Interface, Langmuir–Blodgett Films, and Its Photocatalytic Performance

Langmuir-Blodgett technique (LB) is a powerful tool for ultrathin film fabrication. LB film production has attracted much attention since film thickness and architecture can be controlled at the molecular and atomic levels. However, a lack of studies still exists regarding LB films of nanomaterials, especially 2D materials. In this context, the present work aims to produce and characterize LB films of g-C₃N₄, a layered nonmetallic photocatalyst. For this purpose, g-C₃N₄ was synthesized, exfoliated, and characterized by vibrational spectroscopy, X-ray diffraction, morphological analysis, surface area determination, hydrodynamic radius, and zeta potential. Before LB film preparation, experiments of g-C₃N₄ Langmuir films at the air-liquid interface were performed. Surface pressure, Brewster angle microscopy, and surface potential experiments of Langmuir films reveal their properties and an ideal condition for monolayer transfer for solid substrates. LB films were transferred to silicon and FTO-coated glass with the latter showing excellent coverage, making it the substrate of choice for photocatalytic assays. The g-C₃N₄, in both powder form and as an LB film, achieved degradation rates of 96.3% and 73%, respectively, of the rhodamine B present in the medium after 8 h of reaction. After 24 h, the reused LB film maintained its photocatalytic activity, continuing to degrade 73% of the probe molecule, demonstrating that the transferred material adheres well to the substrate surface. These results present promising opportunities for applying g-C₃N₄ LB films in photocatalytic, photovoltaic, and other chemical conversion devices.