Complexes of carbon nanotubes with selected carotenoids

As proven by the UV-VIS, micro-Raman spectroscopies, differential scanning calorimetry, beta-carotene, lycopene, retinoic acid, and retinol adsorbed on the surface of single-walled carbon nanotubes (SWCNT) form electron donor-acceptor (EDA) complexes. The rate of the adsorption of carotenoids is estimated as the rate of decrease in their concentration in solution followed the exponential curve equation. The rate of the adsorption decreased with the chain length of the guest capable sorption on the surface and steric effect of the terminals in the beta-carotene was also essential. Also, increase in the polarity of the functional groups expressed, for instance, in Taft sigma* substituent constants had its impact. The HyperChem 7 followed by Gaussian 03 computations revealed that the inclusion SWCNT-carotenoid complexes were more stable than corresponding surface complexes. In the surface complexes carotenoids acted as donors in respect to SWCNT whereas in the inclusion complexes they were acceptors.