Combined Experimental and DFT Study of the Chemical Binding of Copper Ions on the Surface of Nanodiamonds

DFT (density functional theory) computations of the chemical fixation of copper ions on the naturally functionalized surface of nanodiamond crystallites bound by (111) planes revealed exothermic formation of chelate Cu complexes with two appropriately located carboxylic groups on the (111) surface. The irreversible strict fixation of copper ions is achieved via removing acetic acid in low-pressure conditions yields the corresponding chelate complexes not bearing any other ligands except for the surface carboxylic groups. Optimization of positional isomers of the chelating complexes showed that complexation is more likely to take place near the edges (linear ribs) of the nanoparticle. Nearby functional groups like -F, -Cl, or -OH substituents on the surface strongly affect the structures and stabilities of the resulting chelate complexes. Some of the copper atoms may be incorporated into unusual Cu(III) complexes with Cu-C covalent bonds.