Electron-electron interaction in multiwall carbon nanotubes

Magnetic susceptibility $\chi$ of pristine and brominated arc-produced sample of multiwall carbon nanotubes was measured from 4.2 to 400 K. An additional contribution $\Delta \chi(T)$ to diamagnetic susceptibility $\chi(T)$ of carbon nanotubes was found at T $<$ 50 K for both samples. It is shown that $\Delta \chi(T)$ are dominated by quantum correction to $\chi$ for interaction electrons (interaction effects-IE). The IE shows a crossover from two-dimensional to three-dimensional at $B$ = 5.5 T. The effective interaction between electrons for interior layers of nanotubes are repulsion and the electron-electron interaction $\lambda$$_c$ was estimated to be $\lambda_c\sim$ 0.26.Comment: 10 pages, 7 figure

Structural Characterization of Intercalated C2Fx Compounds Using XAFS Polarization Dependencies

Orientation dependencies of FeK, BrK EXAFS and XANES spectra have been measured for intercalated compounds of the composition C2Fx*yA (X≈1, A=Br2, BrF3, Fe(AA)3, FeCl3) synthesized by diffusion from solutions. An approach has been developed which allows determination of the ranges of the orientation angles of T-shaped BrF3 molecules from XANES spectra. The values of the orientation angles of BrF3 molecules were determined by simultaneously analyzing EXAFS and XANES data. It was found that heating leads to the formation in the intercalated compound of lens-like regions containing oriented BrF3 molecules. The orientation and geometry of Br2 molecules in the studied compounds were shown to be substantially different from those in graphite intercalation compounds. The intercalation was shown to lead to deformation of the Fe(AA)3 molecule while the FeCl3 molecules form dimers

Graphene nanochains and nanoislands in the layers of room-temperature fluorinated graphite

International audienceIntercalated compound of graphite fluoride with n-heptane has been synthesized at room temperature using a multi-stage process including fluorination by a gaseous BrF3 and a set of intercalant exchange reactions. It was found that composition of the compound is CF0.40(C7H16)0.04 and the guest molecules interact with the graphite fluoride layers through the van der Waals forces. Since the distance between the filled layers is 1.04 nm and the unfilled layers are separated by ∼0.60 nm, the obtained compound can be considered as a stack of the fluorinated graphenes. These fluorinated graphenes are large in area making it possible to study local destruction of the π conjugated system on the basal plane. It was shown that fluorine atoms form short chains, while non-fluorinated sp2 carbon atoms are organized in very narrow ribbons and aromatic areas with a size smaller than 3 nm. These π electron nanochains and nanoislands preserved after the fluorination process are likely responsible for the value of the energy gap of the compound of ∼2.5 eV. Variation in the size and the shape of π electron regions within the fluorinated graphene layers could be a way for tuning the electronic and optical characteristics of the graphene-based materials