Formaldehyde adsorption on the interior and exterior surfaces of CN nanotubes

Using density functional theory, we have investigated the adsorption of formaldehyde (H2CO) on the interior and exterior walls of a carbon nitride nanotube (CNNT) in terms of energetic, geometric, and electronic properties. It was found that the adsorption is more preferential on the exterior surface of the tube with maximum adsorption energy of -7.4 kcal/mol. It has also been found that the adsorption energy per molecule is increased by increasing the number of adsorbed molecules. The results reveal that the electronic properties of CNNT are very sensitive to the presence of formaldehyde so that the HOMO/LUMO gap is reduced from 4.02 eV in the free tube to 2.44 eV in the most stable configuration of 3H(2)CO/CNNT complex. Also, we have showed that the response of the tube may depend on concentration of the H2CO molecules, suggesting that the CNNT might produce an electrical signal in the presence of H2CO molecules.