Eigenschaften neuer Fullerenmaterialien

Eigenschaften neuer Fullerenmaterialien wurden unter Ultra-Hoch-Vakuum-Bedingungen untersucht

C58 on Au(111): a scanning tunneling microscopy study

C58 fullerenes were adsorbed onto room temperature Au(111) surface by low-energy (~6 eV) cluster ion beam deposition under ultrahigh vacuum conditions. The topographic and electronic properties of the deposits were monitored by means of scanning tunnelling microscopy (STM at 4.2 K). Topographic images reveal that at low coverages fullerene cages are pinned by point dislocation defects on the herringbone reconstructed gold terraces (as well as by step edges). At intermediate coverages, pinned monomers, act as nucleation centres for the formation of oligomeric C58 chains and 2D islands. At the largest coverages studied, the surface becomes covered by 3D interlinked C58 cages. STM topographic images of pinned single adsorbates are essentially featureless. The corresponding local densities of states are consistent with strong cage-substrate interactions. Topographic images of [C58]n oligomers show a stripe-like intensity pattern oriented perpendicular to the axis connecting the cage centers. This striped pattern becomes even more pronounced in maps of the local density of states. As supported by density functional theory, DFT calculations, and also by analogous STM images previously obtained for C60 polymers (M. Nakaya et al., J. Nanosci. Nanotechnol. 11, 2829 (2011)), we conclude that these striped orbital patterns are a fingerprint of covalent intercage bonds. For thick C58 films we have derived a band gap of 1.2 eV from scanning tunnelling spectroscopy data, STS, confirming that the outermost C58 layer behaves as a wide band semiconductor

Thermally Activated D₂ Emission upon Decomposition of Thin Deuterofullerene Films on Au(111)

We have studied the formation and thermal properties of thin, deuterofullerene-containing films on Au(111) under ultrahigh vacuum conditions. The films were prepared in situ by exposure of predeposited C₆₀ layers to a flux of atomic deuterium. With increasing deuterium dose, a D + C₆₀ → C₆₀D_<i>x</i> reaction front propagates through the fullerene film toward the gold surface. Heating the resulting deuterofullerene-containing films to >600 K leads to desorption of predominantly C₆₀ and C₆₀D_<i>x</i>. Interestingly, some D₂ is also evolved while a significant fraction of the carbon initially deposited is left on the surface as nondesorbable residue. This is in contrast to analogous deuterofullerene-containing films prepared on graphite, which sublime completely but do not measurably evolve D₂, suggesting that the gold surface can act as a catalyst for D₂ formation. To explore this further, we have systematically studied (i) the thermal properties of C₆₀/Au­(111) reference films, (ii) the reaction of C₆₀/Au­(111) films with D atoms, and (iii) the heating-induced degradation of deuterofullerene-containing films on Au(111). In particular, we have recorded temperature-resolved mass spectra of the desorbing species (sublimation maps) as well as performed ultraviolet photoionization spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and scanning tunneling microscopy measurements of the surfaces at various stages of study. We infer that heating deuterofullerene-containing films generates mobile deuterium atoms which can recombine to form molecular deuterium either at the gold surface or on fullerene oligomers in direct contact with it

Oxidative Stress in Endometrial Flushing Fluid of Patients with Polycystic Ovary Syndrome, Endometrioma and Uterine Leiomyoma: Comparison with Healthy Controls

OBJECTIVE: Polycystic ovary syndrome, myoma uteri and endometrioma are frequently seen gynecologic problems and all three diseases may cause infertility. Aim of this cross-sectional study was to compare total antioxidant status, ceruloplasmin, total sulfhydryl , total oxidant status, lipid hydroperoxide and oxidative stress index levels in endometrial flushing fluid of patients with Polycystic ovary syndrome (n=20), uterine leiomyoma (n=20), endometrioma (n=19), and healthy women (n=20). STUDY DESIGN: We compare endometrial flushing fluid of patients with polycystic ovary syndrome (n=20), uterine leiomyoma (n=20), endometrioma (n=19) and healthy women (n=20). Endometrial flushing fluid samples were collected during the implantation window of all women. RESULTS: Mean age of groups was 28.90±5.45, 37.25±2.73, 32.84±6.62 and 32.15±5.18 in Polycystic ovary syndrome, myoma uteri, endometrioma and control groups, respectively (p<0.05). Mean total antioxidant status, ceruloplasmin and total sulfhydryl levels indicating antioxidant state were comparable between Polycystic ovary syndrome, myoma uteri, endometrioma and control groups (p=0.806, p=0.156, p=0.328 respectively for markers). Similarly, oxidant state-related markers didn’t differ significantly between 4 groups (p=0.090 for total oxidant status, p=0.087 for lipid hydroperoxide, p=0.312 for oxidative stress index). CONCLUSION: Endometrial flushing fluid total antioxidant status, total oxidant status, lipid hydroperoxide, ceruloplasmin, and total sulfhydryl levels during implantation window didn’t differ between women with Polycystic ovary syndrome, uterine leiomyoma, endometrioma, and healthy controls

Thermal Decomposition of the Fullerene Precursor C₆₀H₂₁F₉ Deposited on Graphite

Specially fluorinated polycyclic aromatic hydrocarbons (F-PAHs) are of interest as precursors for transition metal catalyzed CVD growth of chiral-index pure single-walled carbon nanotubes as well as for the rational synthesis of fullerenes. Laser desorption/ionization of a prototypical F-PAH has recently been shown to lead to C₆₀ via a sequence of regioselective intramolecular cyclodehydrofluorination steps: C₆₀H₂₁F₉ → C₆₀H₂₀F₈ + HF → C₆₀H₁₉F₇ + HF ... → C₆₀ (Kabdulov et al. <i>Chem.–Eur. J.</i> <b>2013</b>, <i>19</i>, 17262). We have studied the thermal stability of solid C₆₀H₂₁F₉ films on graphite under UHV conditions toward exploring the extent to which such intramolecular dehydrofluorination can also occur on a hot chemically inert surface and to what extent intermolecular interactions influence such transformation processes. C₆₀H₂₁F₉ films were probed in situ by ultraviolet photoionization, X-ray ionization, Raman spectroscopy, and thermal desorption mass spectrometry, as well as by ex situ atomic force microscopy. Heating multilayer films results first in C₆₀H₂₁F₉ emission from the bulk (peaked at ∼630 K) followed at higher temperatures by desorption from the interface region (in the range 750–850 K). Sublimation from the interface region is also associated with some on-surface cyclo-dehydrofluorination as indicated by C₆₀H_{21–<i>n</i>}F_9–<i>n</i>, <i>n</i> = 1, 2, 3 emission. C₆₀ was not observed in the desorbed material suggesting that complete cage closure cannot be achieved on HOPG. Furthermore, C₆₀H₂₁F₉ deposits cannot be fully removed from HOPG. Instead, competing on-surface polycondensation of reactive intermediates yields a fluorinated carbon phase, which remains stable up to at least ∼1000 K. To complement these studies we have also used mass selective ion beam soft-landing to probe the desorption properties of monodispersed films consisting of mass-selected C₆₀H_{21–<i>n</i>}F_9–<i>n</i> fragments, <i>n</i> = 1, 2