Graphite Intercalation Compounds have been the subject of intensive research. With the rise of graphene, new opportunities emerge in the field. On the one hand, adsorption and/or intercalation of hetero-atoms offer a gateway to tune graphene properties. On the other hand, investigations on a simpler system open the way towards increasing knowledge on the intercalant/host physical properties. New questions to be addressed also arise, such as, what happens when the number of layers is reduced? We have developed a setup derived from the two zone vapor transport method used to produce graphite intercalation compounds. It allows performing in situ Raman experiments during graphene doping by alkali vapor. The results obtained on the evolutions of the G and 2D bands during rubidium doping of graphene and bilayer graphene will be presented and discussed.

This 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.

A hybrid system consisting of quaterthiophene derivative inserted into carbon nanotubes is studied. Encapsulation efficiency of the conjugated oligomers in the hollow core of nanotubes is investigated by transmission electron microscopy and spatial-resolved electron energy loss spectroscopy. Infrared spectroscopy showed evidence of a significant positive charge transfer on the inserted oligothiophene. Raman spectra display different behaviors depending on the excitation energy and correlated to the quaterthiophene optical absorption energy. At high excitation wavelength (far from the oligomer resonance), radial breathing modes exhibit a significant upshift consistent with an encapsulation effect. At low excitation wavelength (close to the oligomer resonance), both the G-band shift and the low-frequency modes vanishing suggest a significant charge transfer between the quaterthiophene and the nanotubes

Single-wall carbon nanotubes non-covalently functionalized with porphyrin molecules have proven to be a very promising light harvesting system either for energy or charge transfer. In this paper we investigate the dynamics of this coupling at a sub-picosecond time-scale, by means of transient absorption spectroscopy. We show that the ground state recovery time of the porphyrin is reduced by several orders of magnitude in the compound compared to the case of pristine porphyrin. Concomitantly, a strong bleaching signal is observed on the optical resonances of the nanotubes showing an ultrafast population buildup upon excitation of the porphyrin. We conclude that the energy transfer occurs on a time-scale shorter than 100 fs. Two-color measurements show that higher excited states of the nanotubes are populated on the same time-scale raising the point of the transfer mechanism. We briefly discuss two possible mechanisms.

We carried out a complete study (magnetic, electronic, dielectric, dynamic, and elastic properties) of the nickel hydroxide [Ni(OH)2] from first-principles calculations based on density functional theory. No theoretical investigations of these physical properties have been previously reported in literature. Our work supports that Ni(OH)2 is an A-type antiferromagnetic material. In addition, it is negative uniaxial and semiconducting with a direct band gap at the Γ point around 3 eV. By contrast to its electronic dielectric tensor, its static tensor is strongly anisotropic in the plane orthogonal to its optical axis. This anisotropy is mainly governed by a highly polar phonon centered around 510 cm−1 and assigned as a rotational Eu mode. Both Raman and infrared spectra have been computed to clarify the longstanding debate on the assignment of the Ni(OH)2 phonon modes reported in literature. All these theoretical results are fruitfully compared to the experimental ones obtained on large Ni(OH)2 "pseudosingle" crystals when available.