Endohedral copper(II)acetylacetonate/single-walled carbon nanotube hybrids characterized by electron paramagnetic resonance
Faculty of Sciences. Physics
The journal of physical chemistry : C : nanomaterials and interfaces. - Washington, D.C., 2007, currens
, p. 13505-13514
University of Antwerp
The encapsulation of an organometallic paramagnetic molecule, copper(II) acetylacetonate (Cu(acac)2), inside single-walled carbon nanotubes (SW CNTs) is studied using continuous wave electron paramagnetic resonance (EPR). By preparing samples from fully opened as well as from closed SW CNTs, the EPR spectra of encapsulated and nonencapsulated molecules can be clearly identified. The EPR spectrum originating from the encapsulated molecules is unchanged by dispersion of the endohedral nanohybrids in a solvent or by solubilization of the nanohybrids in water using bile salt surfactants, demonstrating that the CNTs protect them from changes in their external environment. The EPR parameters obtained for the encapsulated molecules show that they experience an extremely apolar environment. From the dipolar broadening of the EPR lines of the nanohybrids, the distances between the encapsulated molecules inside the CNTs can be estimated by adapting Van Vlecks method of moments for the case of a one-dimensional array of molecules. Furthermore, a combination of orientation dependent EPR experiments and polarized Raman scattering on preferentially aligned CNT hybrids in stretched polymer film samples yields information on the orientational distribution of the encapsulated molecules inside the SW CNTs.