Self-Assembly of Tetraazamacrocyclic Compounds on Single-Walled Carbon Nanotubes: Experimental and Theoretical Studies
E.V. Basiuk, V.A. Basiuk, E.V. Rybak-Akimova, D. Acosta-Najarro, I. Puente-Lee and J.M. Saniger
Universidad Nacional Autonoma de Mexico, MX
Keywords: Carbon nanotubes, single-walled, tetraazamacrocyclic, adsorption, self-assembly, molecular mechanics
All the existing methods of chemical modification of carbon nanotubes (CNTs) can be divided in two groups, depending on whether functionalizing moieties are introduced onto the nanotube tips or sidewalls. The latter approach offers wider opportunities to change CNT properties, since it allows high coverages with modifying groups. It can rely upon either covalent bond formation, or simple adsorption on CNTs via non-covalent interactions (hydrophobic, p-stacking, etc.). To explore the possibility of reversible modification of CNT sidewalls with aromatic ligands and their metal complexes employing similar stacking phenomena, we studied (experimentally and theoretically) interaction of a series of tetraazamacrocyclic compounds tetraazaannulene, meso-tetraphenylporphine, Ni(II) and Cu(II) complexes of tetramethyltetraazaannulene with single-walled carbon nanotubes. All of them are conjugated systems with a high degree of aromaticity. Molecular mechanics modeling was used to estimate what kind of arrangements can form. In some cases HRTEM results were obtained consistent with theoretical results. Adsorption of aromatic molecules, having a bent shape and/or hydrophobic substituents, allows to reversibly attach modifying chemical species. The latter stick strongly to the nanotube walls due to p-p and hydrophobic interactions and remain stable in aqueous solutions, but can be removed by washing with non-polar solvents.
Nanotech 2004 Conference Technical Program Abstract