Armchair (4,4)-Carbon Nanotube and Phosphate-(4,4)-Carbon Nanotube As Drug Delivery Systems

The structures of CNT(4,4) and CNT(4,4)-H2PO4 were optimized using Gaussian 98 program at B3LYP/6- 31G(d) level of theory. The binding energies of compounds were calculated using the equation Ebinding = E(molecule) - i E(i), i = atom. Also, the dipole moment value of CNT(4,4)-H2PO4 (2.1353 Debye) was greater than that of CNT(4,4) (0.0016 Debye) which was attributed to the high polar nature of phosphate group. On the other hand, CNT was nonpolar but when it was functionalized with the phosphate group, its polarity was increased so that its dipole moment equaled to 2.135 Debye after it was attached onto the phosphate group. The HOMO-LUMO band gaps measured for the CNT(4,4) and CNT(4,4)-H2PO4 were close to each other (1.611, 1.425 eV, respectively). The infrared spectra of CNT(4,4) and CNT(4,4)-H2PO4 were calculated using the the density functional theory and the characteristic sharp bands at 948.92 cm-1 in CNT(4,4)-H2PO4 were attributed to the P=O stretching frequencies