Noncovalent Interaction between Aniline and Carbon Nanotubes: Effect of Nanotube Diameter and the Hydrogen-Bonded Solvent Methanol on the Adsorption Energy and the Photophysics

摘要

The adsorption of aniline on SWCNTs has been investigated using three different DFT methods, PW91LYP, the hybrid m-GGA MPWB1K, and the dispersion-corrected BP86-D functional. The BSSE-corrected adsorption energies for top orientation of aniline to the nanotube surface are E_(ads) = 9.7 kcal mol~(-1) and E_(ads) = 1.4 kcal mol~(-1) with BP86-D/SVP and MPWB1K/6-311+G(d), respectively. Results validated that the adsorption energy of aniline depends on the diameter of the nanotube with a pronounced manner, especially for small diameters. The TDDFT calculations of UV/vis spectra predict two electronic transitions resulting from nanotube excitations in the visible spectra (>500 nm) and one imperceptible aniline — SWCNT excitation at ca. 1200 nm. Inclusion of solvent effects (MeOH) by explicit solvent molecules leads to a pronounced red shift of the weak longest wavelength aniline → nanotube transition, whereas the strong intratube excitations are only a little influenced. Fluorescence excitation spectra (λ_(em)= 586 nm) of SWCNTs in aniline yield a broad structured absorption in the range of 22 000-18 000 cm~(-1), which is insensitive to the addition of methanol as cosolvent.