Theoretical study of the adsorption of aromatic amino acids on a single-wall boron nitride nanotube with empirical dispersion correction

In the present study, the adsorption and properties of three popularly studied aromatic amino acids, namely phenylalanine, tyrosine, and tryptophan, on the surface of the single-wall boron nitride nanotubes (BNNTs) have been explored with an empirical dispersion corrected density functional tight-binding method. A serials of armchair BNNTs (n = 4-12) and zigzag BNNTs (n = 8-18) with the aromatic amino acid adsorbed on the surface are investigated. With the dispersion correction explicitly considered in the density functional tight-binding method, the adsorption properties between amino acids and BNNTs are described by including long-range van der Waals interactions. It is found that the pi-pi and H-pi stacking interactions are the main forces stabilizing the system. Based on the evidence of adsorption energy, charge density plots, and density of states analysis, the study concludes that the BNNT adsorbs the amino acids with no bonded interactions between the two parts. The interactions of amino with the BNNT were further studied by analyzing molecular orbitals and excited state absorption spectrum of the stable complexes.