▎ 摘　　要

Molecular simulations were performed to investigate the structural and electronic properties of graphene (G) nanosheet interacting with the monomer of chitosan (MCh) (C6H13O5N). The G nanosheet with the C54H18 chemical composition is modeled according to the armchair edge and is functionalized with boron atoms. The interaction between the nanosheet and the MCh is investigated to search for better bio-sensing characteristics. Simulations are done within the density functional theory, the generalized gradient approximation is applied to deal with the exchange-correlation energies, and the all-electron basis set with double polarization is used. To determine the structure stability, the minimum energy criterion is applied for the G + MCh system in seven different geometries; in addition, it is checked with the non-complex vibration frequency. Results show chemical interactions between the G nanosheets and the MCh in the ground-state geometry. In this geometry, the monomer is oriented perpendicular to the G nanosheet at a distance of 3.9 angstrom with the nanosheet remaining unchanged. The nanosheet functionalization with boron (to form an epoxy group) and interaction with the monomer yield improved adsorption conditions with a bond length of C-mesh-B-N-Amine = 3.19 angstrom and the formation of B-N (boron attached to graphene-amine of the monomer) bond of length 1.57 angstrom The polarity of the G + B and G + B + MCh systems displays ionic characteristics contrary to G behavior. The (HOMO-LUMO) energy difference is 1.30 eV for the G + B system and 0.75 eV for the G + B + MCh. Finally, the G + B + MCh system is investigated when D-(+)-glucose and cholesterol are adsorbed. Results show chemisorptions, which suggest the system to be used in biosensor devices.