Peculiar covalent bonding of C 60 /6 H -SiC(0 0 0 1)-(3 × 3) probed by photoelectron spectroscopy

High resolution photoemission with synchrotron radiation was used to study the interfaceformation of a thin layer of C60 on 6H-SiC(0 0 0 1)-(3 × 3), characterized by protrudingSi-tetramers. The results show that C60 is chemisorbed by orbital hybridization between thehighest-occupied molecular orbital (HOMO) and the pz orbital of Si adatom at the apex ofthe tetramers. The covalent nature of the bonding was inferred from core level as well asvalence band spectra. The Si 2p spectra reveal that a large fraction (at least 45%) of the Siadatoms remain unbound despite the reactive character of the associated dangling bonds.This is consistent with a model in which each C60 is attached to the substrate through a singlecovalent C60–Si bond. A binding energy shift of the core levels associated with sub-surface Sior C atoms indicates a decrease of the SiC band bending caused by a charge transfer from theC60 molecules to the substrate via the formation of donor-like interface states

Peculiar covalent bonding of C 60 / 6H-SiC(0001)-(3 × 3) probed by photoelectron spectroscopy

International audienceHigh resolution photoemission with synchrotron radiation was used to study the interface formation of a thin layer of C60 on 6H−SiC(0001)-(3 × 3), characterized by protruding Si-tetramers. The results show that C60 is chemisorbed by orbital hybridization between the highest-occupied molecular orbital (HOMO) and the pz orbital of Si adatom at the apex of the tetramers. The covalent nature of the bonding was inferred from core level as well as valence band spectra. The Si 2p spectra reveal that a large fraction (at least 45%) of the Si adatoms remain unbound despite the reactive character of the associated dangling bonds. This is consistent with a model in which each C60 is attached to the substrate through a single covalent C60-Si bond. A binding energy shift of the core levels associated with sub-surface Si or C atoms indicates a decrease of the SiC band bending caused by a charge transfer from the C60 molecules to the substrate via the formation of donor-like interface states

Peculiar covalent bonding of C 60 / 6H-SiC(0001)-(3 × 3) probed by photoelectron spectroscopy

International audienceHigh resolution photoemission with synchrotron radiation was used to study the interface formation of a thin layer of C60 on 6H−SiC(0001)-(3 × 3), characterized by protruding Si-tetramers. The results show that C60 is chemisorbed by orbital hybridization between the highest-occupied molecular orbital (HOMO) and the pz orbital of Si adatom at the apex of the tetramers. The covalent nature of the bonding was inferred from core level as well as valence band spectra. The Si 2p spectra reveal that a large fraction (at least 45%) of the Si adatoms remain unbound despite the reactive character of the associated dangling bonds. This is consistent with a model in which each C60 is attached to the substrate through a single covalent C60-Si bond. A binding energy shift of the core levels associated with sub-surface Si or C atoms indicates a decrease of the SiC band bending caused by a charge transfer from the C60 molecules to the substrate via the formation of donor-like interface states

Discerning Inter- and Intramolecular Vibrations of Sulfur Polyaromatic Compounds

Thiophenes are an important class of molecules in fields as diverse as petrochemistry, molecular electronics, and optoelectronics. Thiophenic submolecular motifs are thought to play a role in molecular association and nanoaggregation phenomena in both pure materials and natural and synthetic mixtures. Vibrational (infrared and Raman) spectroscopy provides the means to characterize these species. In this work far-infrared photoacoustic and low-frequency Raman spectra of a series of polycyclic aromatic hydrocarbons containing sulfur have been measured and interpreted using DFT calculations based on a perturbational-variational method coupled with potential truncation. The approach and outcomes illustrate how inter- and intramolecular vibrations for thiophenic systems in single and multicomponent mixtures can be discriminated. This work offers the perspective to search the inter- and intramolecular signatures of the main submolecular motifs and heteroelements postulated as being present in the asphaltenes

Image calculations with a numerical frequency-modulation atomic force microscope

cited By 6International audienceWe investigated the implementation of a numerical tool able to mimic an experimental noncontact atomic force microscope (nc-AFM). Main parts of an experimental setup are modeled and are implemented inside a computer code. The goal was to build a numerical AFM (n-AFM) as versatile, efficient, and powerful as possible. In particular, the n-AFM can be used in the two working regimes, that is, in attractive and repulsive regimes, with settings for a standard AFM cantilever oscillating with a large amplitude (typically, 10 nm) or for a tuning-fork probe with ultrasmall amplitudes (∼0.01 nm). We present various tests to show the reliability of the n-AFM used as a frequency-modulation AFM (FM-AFM). As an example, we calculated FM-AFM images of adsorbed molecular systems, which range from two-dimensional planar molecules to corrugated systems with a three-dimensional molecule. The submolecular resolution of the FM-AFM is confirmed to originate from repulsive Pauli-like interactions between the tip and the sample. The versatility of the n-AFM is finally discussed in the perspective of new functionalities that will be included in the future

Irritable bowel syndrome and functional dyspepsia in patients with eating disorders ‐ a systematic review

Objectives: The prevalence of eating disorders is rising worldwide. The low body weight in anorexia nervosa as well as the increase in body mass index due to binge eating disorder are contributing to a strikingly high morbidity and mortality. In a similar pattern, the prevalence and burden of the disease of functional gastrointestinal disorders such as functional dyspepsia and irritable bowel syndrome is increasing. As gastrointestinal complaints are commonly reported by patients with eating disorders, the question arose whether there is a relationship between eating disorders and functional gastrointestinal disorders. Methods: To address the need to better understand the interplay between eating disorders and functional gastrointestinal disorders as well as factors that might influence this connection, the data bases Medline, Web of Science and Embase were systematically searched. Results: After removal of duplicates the search yielded 388 studies which were screened manually. As a result, 36 publications were selected for inclusion in this systematic review. Conclusion: The occurrence of functional gastrointestinal disorders like irritable bowel syndrome and functional dyspepsia in patients with eating disorders is considerably high and often associated with psychological, hormonal and functional alterations. In the future, further research addressing the underlying mechanisms accounting for this relationship is required