Charge transfer in conjugated oligomers encapsulated into carbon nanotubes

Abstract

International audienceThis study deals with a hybrid system consisting in quaterthiophene derivative encapsulated inside single-walled and multi-walled carbon nanotubes. Investigations of the encapsulation step are performed by transmission electron microscopy. Raman spectroscopy data point out different behaviors depending on the laser excitation energy with respect to the optical absorption of quaterthiophene. At low excitation energy (far from the oligomer resonance window) there is no significant modification of the Raman spectra before and after encapsulation. By contrast, at high excitation energy (close to the oligomer resonance window), Raman spectra exhibit a G-band shift together with an important RBM intensity loss, suggesting a significant charge transfer between the inserted molecule and the host nanotubes. Those results suggest a photo induced process leading to a significant charge transfer

Diameter-dependent single- and double-file stacking of squaraine dye molecules inside chirality-sorted single-wall carbon nanotubes

“…In the past decade, the confinement of molecules inside SWCNTs has shown great potential for the templated synthesis of unique materials, [7][8][9][10][11][12] observation of new phase transitions of water, 13,14 and for the modulation of the electronic properties of the host SWCNTs. [15][16][17][18][19][20] For example, the encapsulation of solvents can be used to tune the optical properties of the SWCNTs as electronic transitions shift with the dielectric constant of the encapsulated material. 21,22 Most interestingly, the encapsulation of dyes inside SWCNTs has not only been shown to enhance the photochemical stability of the dye molecules, 3 but has also resulted in the photosensitization of the SWCNTs through efficient energy transfer from the encapsulated dye molecules to the surrounding host SWCNTs.…”

Raman resonance tuning of quaterthiophene in filled carbon nanotubes at high pressures

“…Resonance Raman spectroscopy (RRS) is an efficient tool for probing optical and electronic properties of carbon-based hybrid systems, since the Raman spectrum of carbon nanotubes is very sensitive to charge transfer (CT) [15,16,17,18,19], structural modification [20,21,22], defects [23,24,25] and doping [26,27]. Actually, specifically for the 4T@SWCNT system, RRS has been used to show that the presence of the quaterthiophene induces a charge transfer between the guest 4T molecules and the host nanotubes.…”

“…Actually, specifically for the 4T@SWCNT system, RRS has been used to show that the presence of the quaterthiophene induces a charge transfer between the guest 4T molecules and the host nanotubes. It was shown that CT scales with tube diameter and metallicity character [28,29,18,19]. Furthermore, the supramolecular organization of the oligomer inside the CNT is deeply dependent on the CNT diameter and can favor the formation of strongly coupled J-aggregates (the molecules are stacked in pairs and aligned head-to-tail inside the nanotube) [30,9].…”

Ultrafast Charge Transfer and Relaxation Dynamics in Polymer-Encapsulating Single-Walled Carbon Nanotubes: Polythiophene and Coronene Polymer

“…To obtain a better understanding of photocarrier generation at the absorption bands for single-layer PT, the band alignment between PT and the semiconducting SWNTs is considered. Theoretical calculations 39 of the band structures of a hybrid system consisting of encapsulated PT and SWNTs with (n,0) chiralities (n = 12,13,14,22) showed that the band structure is a superposition of those for PT and SWNTs except for a downward shift (0.08−0.15 eV) of the PT band energy. From this band structure, type I band alignment is suggested.…”

“…Several attempts have been made to synthesize conjugated oligomer-encapsulating SWNTs. Encapsulation of 5,5‴-dimethyl-2,2′:5′,2″:5″,2‴-quarterthiophene (4T), − α-sexithiophene (6T), − and coronene oligomers inside SWNTs, as well as observations of EET and charge transfer, has been reported for 4T- and 6T-encapsulating SWNTs. In a more recent work, Lim et al succeeded in encapsulating and synthesizing long coronene polymers, which can be regarded as graphene nanoribbons, inside SWNTs through a polymeric reaction of coronene molecules at a high temperature of 700 °C.…”