Computational calculation identified optimal binding sites in nano-sized magnetic-cored dendrimer

Abstract

Magnetic-cored dendrimers (MDs) with amino groups were prepared with the formation of poly(amidoamine) dendrimer on the surface of magnetite nanoparticles (MNP5). The experiment involved the binding of four different heavy metal ions including Pb (II), Cu (II), Zn (II), and Cr (VI). Density functional theory (DFT) calculation was applied to the experimental results to determine the optimal configurations between the heavy metal species and generation 1 amino (-NH2) functionalized MD (G1-NH2-MD). Different binding configurations among the possible binding positions of inner and outer Gl-NH2-MD were determined with the ionic radius and coordination number of each heavy metal ion. Although Pb2+ and Zn2+ were stable in the terminal positions, Cu2+ was the most stable in the internal position. The oxygen and hydrogen atoms of HCrO4- formed a hydrogen bond with the -NH2 groups, and thus dipole-nonpolar molecular interaction occurred with the -CH2 groups of G1-NH2-MD. Specific binding positions and energies of different heavy metal species were identified through the DFT calculation in the study. The DFT calculation results also contributed to an understanding of the binding priority of each metal ions in the mixed solution. Furthermore, Pb2+ was preferably adsorbed in the mixed solution of Pb2+, Cu2+, and Zn2+.