Ballistic Diffusion in Polyaromatic Hydrocarbons on Graphite

Calvo-Almazán, Irene; Sacchi, Marco; Tamtögl, Anton; Bahn, Emanuel; Koza, Michael Marek; Miret‐Artés, Salvador; Fouquet, Peter

doi:10.1021/acs.jpclett.6b02305

Cited by 17 publications

(18 citation statements)

References 30 publications

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“…Note that a similar diffusive motion was observed for molecular hydrogen on graphite with jump diffusion and also a very low activation energy 33,50,62 . Although the role of atomic-scale friction was not explicitly discussed in those cases, it suggests together with the results presented in our study, that friction may be partly caused by the geometry of the molecule when compared to the flat-lying polycyclic aromatic hydrocarbons which closely resemble the structure of the graphite substrate 18,20,63 . Finally, the occurrence of long jumps makes the determination of a meaningful activation energy challenging since under these circumstances jumps start to become correlated as shown in theoretical studies 57,64 .…”

Section: Resultssupporting

confidence: 48%

Ultrafast molecular transport on carbon surfaces: The diffusion of ammonia on graphite

Tamtögl

Sacchi

Calvo-Almazán

et al. 2018

Carbon

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We present a combined experimental and theoretical study of the self-diffusion of ammonia on exfoliated graphite. Using neutron time-of-flight spectroscopy we are able to resolve the ultrafast diffusion process of adsorbed ammonia, NH3, on graphite. Together with van der Waals corrected density functional theory calculations we show that the diffusion of NH3 follows a hopping motion on a weakly corrugated potential energy surface with an activation energy of about 4 meV which is particularly low for this type of diffusive motion. The hopping motion includes further a significant number of long jumps and the diffusion constant of ammonia adsorbed on graphite is determined with D = 3.9 · 10 −8 m 2 /s at 94 K.

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Section: Resultssupporting

confidence: 48%

Ultrafast molecular transport on carbon surfaces: The diffusion of ammonia on graphite

Tamtögl

Sacchi

Calvo-Almazán

et al. 2018

Carbon

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“…Diffusion mechanism of H 2 O. The atomic-scale diffusion of molecules on surfaces is typically described by molecules moving or hopping along the surface while the substrate provides the thermal energy for the motion 48,[55][56][57] . For an activated diffusion process, motion of the adsorbates is governed by the interaction of the molecule with a corrugated potential energy surface (PES).…”

Section: Resultsmentioning

confidence: 99%

Nanoscopic diffusion of water on a topological insulator

et al. 2020

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The microscopic motion of water is a central question, but gaining experimental information about the interfacial dynamics of water in fields such as catalysis, biophysics and nanotribology is challenging due to its ultrafast motion, and the complex interplay of intermolecular and molecule-surface interactions. Here we present an experimental and computational study of the nanoscale-nanosecond motion of water at the surface of a topological insulator (TI), Bi 2 Te 3. Understanding the chemistry and motion of molecules on TI surfaces, while considered a key to design and manufacturing for future applications, has hitherto been hardly addressed experimentally. By combining helium spin-echo spectroscopy and density functional theory calculations, we are able to obtain a general insight into the diffusion of water on Bi 2 Te 3. Instead of Brownian motion, we find an activated jump diffusion mechanism. Signatures of correlated motion suggest unusual repulsive interactions between the water molecules. From the lineshape broadening we determine the diffusion coefficient, the diffusion energy and the pre-exponential factor.

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“…In this study, it is used as a substitute for graphite since its high-surface area allows adsorption of sufficient adsorbent material to compensate the weak neutron scattering signal. Its adequacy as a graphite substitute has been demonstrated in several prior, comparable studies [27,39,40].…”

Section: Sample Preparation and Characterizationmentioning

confidence: 80%

Ultra-fast diffusion of hydrogen in a novel mesoporous N-doped carbon

Bahn

Giraldo

Kuznetsov

et al. 2020

Carbon

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The diffusional behaviour of H 2 adsorbed in a novel mesoporous N-doped carbon material and on exfoliated graphite has been studied with quasi-elastic neutron scattering. While the activation energies for diffusion obtained for exfoliated graphite was in line with prior results, H 2 in the mesoporous carbon showed an exceptionally low diffusion barrier and behaved qualitatively like liquid hydrogen. Complementary results from neutron and X-ray diffraction as well as from isothermal nitrogen sorption studies provide a full characterisation of this novel mesoporous carbon.

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Ballistic Diffusion in Polyaromatic Hydrocarbons on Graphite

Cited by 17 publications

References 30 publications

Ultrafast molecular transport on carbon surfaces: The diffusion of ammonia on graphite

Ultrafast molecular transport on carbon surfaces: The diffusion of ammonia on graphite

Nanoscopic diffusion of water on a topological insulator

Ultra-fast diffusion of hydrogen in a novel mesoporous N-doped carbon

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