We report on an easy-to-use, successful, and reproducible route to synthesize functionalized graphite oxide (GO) and its conversion to graphene-like materials through chemical or thermal reduction of GO. Graphite oxide containing hydroxyl, epoxy, carbonyl, and carboxyl groups loses mainly hydroxyl and epoxy groups during reduction, whereas carboxyl species remain untouched. The interaction of functionalized graphene with fluorescent methylene blue (MB) is investigated and compared to graphite, fully oxidized GO, as well as thermally and chemically reduced GO. Optical absorption and emission spectra of the composites indicate a clear preference for MB interaction with the GO derivatives containing a large number of functional groups (GO and chemically reduced GO), whereas graphite and thermally reduced GO only incorporate a few MB molecules. These findings are consistent with thermogravimetric, X-ray photoelectron spectroscopic, and Raman data recorded at every stage of preparation. The optical data also indicate concentration-dependent aggregation of MB on the GO surface leading to stable MB dimers and trimers. The MB dimers are responsible for fluorescence quenching, which can be controlled by varying the pH value.

The role of dimers in the charge stabilisation of 5,5 000 -dicyano-3,3 00 -dibutyl 2,2 0 :5 0 ,2 00 :5 00 ,2 000quaterthiophene (DCNDBQT) via an electrochemical reaction is studied in detail by in situ NMR spectroelectrochemistry. Among the two oxidation steps the first was found to be reversible while the second is completely irreversible. By in situ NMR spectroelectrochemistry we are able to demonstrate the formation of a p-dimer via the cation generated in the first electron transfer as well as the formation of a s-dimer by a follow-up reaction of the dication generated in the second oxidation step. As the thiophene oligomer is blocked in the 2-and 5-positions by the cyanide group the monomer undergoes a dimerisation in the 4 0 -position. In situ NMR spectroelectrochemistry delivers proof of the coupling reaction of the thiophene rings in the electrochemistry of a,u-endcapped oligothiophenes although such endcapped structures are expected to be prevented from chemical follow-up reactions. Furthermore, substitution by cyano groups opens the route to a cathodic reduction of the structure. The dicyanodibutylquaterthiophene gives a single reduction step which turns out to be quasi-reversible but the anionic structure formed in the reduction was not detectable by in situ NMR spectroelectrochemistry. This and the follow-up reactions are discussed in detail.

The stabilization of carbon nanotubes via the filling with inner tubes is demonstrated by probing the optical transitions in double-walled carbon nanotube bundles under hydrostatic pressure with optical spectroscopy. Double-walled carbon nanotube films were prepared from fullerene peapods and characterized by HRTEM and optical spectroscopy. In comparison to single-walled carbon nanotubes, the pressure-induced redshifts of the optical transitions in the outer tubes are significantly smaller below ∼10 GPa, demonstrating the enhanced mechanical stability due to the inner tube already at low pressures. Anomalies at the critical pressure P d ≈12 GPa signal the onset of the pressure-induced deformation of the tubular cross-sections. The value of P d is in very good agreement with theoretical predictions of the pressure-induced structural transitions in double-walled carbon nanotube bundles with similar average diameters.

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