Intercalated graphitic carbon nitride: a fascinating two-dimensional nanomaterial for an ultra-sensitive humidity nanosensor

We develop a novel humidity nanosensor based on intercalated graphitic carbon nitride (g-C3N4) nanosheets fabricated by a facile thermal polymerization of common urea in the presence of LiCl as the intercalated guest under air and ambient pressure. The response and recovery times of an optimal nanosensor can reach ∼0.9 s and ∼1.4 s, respectively, which are superior to most of the traditional oxide ceramic-based humidity nanosensors tested under similar conditions. By combining with the theoretical calculations, it is proposed that the ultrafast response–recovery time for this nanosensor is attributed to their unique 2D intercalated nanostructure by which Li species linked with the “nitrogen pots” of g-C3N4 can make the protons conduct in the first adsorbed water layer. Meanwhile, the physically adsorbed water on the surface of LiCl-intercalated g-C3N4 nanosheets can be desorbed rapidly at a relative lower RH environment due to their high adsorption energy and the strong diffusion effect of water molecules.