DFT study on the chemical sensing properties of B₂₄N₂₄ nanocage toward formaldehyde

It has been previously shown that the toxic formaldehyde gas (H₂CO) cannot be detected by pristine BC₂N, carbon, and BN nanotubes, BC₃ nanosheet and graphene. Herein, density functional theory calculations were employed to investigate the electronic and structural behavior of a pristine B₂₄N₂₄ nanocluster toward H₂CO molecules. It was found that [4,6] BN bonds of the nanocluster are the most favorable sites for the H₂CO adsorption, compared to the [4,8], and [6,8] ones. When an H₂CO molecule is adsorbed on a [4,6] BN bond, an energy of about 16.40kcal/mol is released and the HOMO-LUMO gap of the cluster is decreased from 6.45 to 2.98eV. Thus, the electrical conductivity of the cluster is significantly increased, indicating that it can produce an electronic noise at the presence of H₂CO molecules. Increasing the number of adsorbed H₂CO molecules, the electrical conductivity more increases. The recovery time for the H₂CO from the surface of B₂₄N₂₄ is calculated to be very short (∼1.02s). Also, the UV-vis spectrum shows that the λ_max of the B₂₄N₂₄ shows a large redshift upon the adsorption process and transfers from the UV to the visible region.