Physical image of amino acid interaction on graphene surface: Scientific fundamental for biological identification and detection from first-principles

Revealing the interaction rules and regulatory mechanisms is very important to the identification and detection of bioactive molecules such as amino acids on low-dimensional carbon-based materials. Physical image of amino acid non-covalent interacted with graphene surface from first-principles views is highly desired to monitor the effect of acid-base regulation on the adsorption of amino acids on graphene. However, the interaction between graphene and essential amino acids in human body has not been well revealed systematically at present. In this paper, the adsorption of various acid-base structures of eight essential amino acids on graphene is investigated based on density functional theory calculations. The binding energy, adsorption distance, deformation energy of two components and the nature of non-covalent interaction of the adsorption systems are studied in details. The physical nature and image of amino acid interaction on graphene surface is studied via the combined methods with radial distribution function, energy decomposition, reduced density gradient, charge density and density of states. The contribution from electrostatic, orbital interaction and dispersion forces is various. The adsorption force of amino acids at the isoelectric point on graphene is mainly composed of dispersion force, and the image by reduced density gradient method further confirms this result.