Résumé:

The study of hybrid systems MPA@SWNT of peapods kind involving photoactive molecules (MPA) confined in single-walled carbon nanotubes (SWNT) find its motivation in the possibility of modulating the physical properties of the nanotubes. Many experimental studies using vibrational spectroscopy in particular are interested in the physical properties of these hybrid systems. The key point of this issue is the nature of the interaction between the nanoconfinement matrix and MPAs, and the complexity of its study requires a comparison between experimental data and modelizations. In this work, we study the hybrid systems MPA@SWNT through modeling performed in different settings ranging from the use of molecular dynamics (MD) to that of the density functional theory (DFT). The limiting factor in DFT calculations is the computation time. the latter which varies in N3 (N is the number of atoms) increases drastically when N exceeds a hundred atoms for energy minimizations calculation, and even more for phonons calculations. In this context, the study of hybrid systems with organic MPAs is delicate. Indeed, the MPAs are complex molecules generally comprising side chains for the solubility of the system. For example, the smallest hybrid system studied, which consists on encapsulating a single molecule of thiophene oligomer functionalized with methyl groups at the edges inside an (11,0) nanotube contains 344 atoms. For the computation time not to be prohibitive, we tested different methods of simulation of the vibrational spectra of MPA@SWCNT: molecular dynamics, tight binding, and hybrid calculations MD/DFT. We discuss in details the results comparing models with experimental data for 1D thiophene oligomer molecules encapsulated inside nanotubes.