Ref HAL: hal-01844602_v1
Ref Arxiv: 1712.01055
DOI: 10.1103/PhysRevE.98.012605
WoS: 000439065200005
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6 Citations
Résumé:

The number of precise conductance measurements in nanopores is quickly growing. To clarify the dominant mechanisms at play and facilitate the characterization of such systems for which there is still no clear consensus, we propose an analytical approach to the ionic conductance in nanopores that takes into account (i) electro-osmotic effects, (ii) flow slip at the pore surface for hydrophobic nanopores, (iii) a component of the surface charge density that is modulated by the reservoir pH and salt concentration cs using a simple charge regulation model, and (iv) a fixed surface charge density that is unaffected by pH and cs . Limiting cases are explored for various ranges of salt concentration and our formula is used to fit conductance experiments found in the literature for carbon nanotubes. This approach permits us to catalog the different possible transport regimes and propose an explanation for the wide variety of currently known experimental behavior for the conductance versus cs .

Ref HAL: hal-01829525_v1
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Résumé:

Les nanotubes de carbone monofeuilltes (SWCNT) sont fonctionnalisés avec des nanoparticules d'hexacyanoferrate de cuivre (CuHCF) pour préparer des substrats solides pour la sorption des ions de césium (Cs +) des écoulements de liquide. La haute résistance mécanique et la grande conductivité électrique des SWCNT sont associées à la capacité des nanoparticules de CuHCF à complexer sélectivement les ions Cs + afin de réaliser des buckypapers de type membrane présentant une capacité de charge élevée du césium. Les matériaux sont soigneusement caractérisés en utilisant la microscopie électronique, la diffusion Raman, la spectroscopie de photoélectrons X et les analyses thermogravimétriques. Les isothermes de sorption de Cs sont portées après avoir mesuré la concentration en Cs + par chromatographie ionique en phase liquide dans la solution avant et après l'exposition aux matériaux. On trouve que la capacité totale de sorption du matériau atteint 230 mg.g-1, et qu'environ un tiers du Cs sorbé (80 mg.g-1) est sélectivement complexé dans les nanoparticules de CuHCF greffées sur SWCNTs. Les valeurs ouvrent des perspectives intéressantes dans l'intégration de tels matériaux dans des dispositifs de sorption et de désorption contrôlée de ces ions.

Ref HAL: hal-01829522_v1
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Single-walled carbon nanotubes (SWCNTs) are functionalized with copper hexacyanoferrate (CuHCF) nanoparticles to prepare solid substrates for the sorption of cesium ions (Cs+) from liquid outflows. The high mechanical resistance and large electrical conductivity of SWCNTs are associated to the ability of CuHCF nanoparticles to selectively complex Cs+ ions in order to achieve membrane-like buckypapers presenting high loading capacity of cesium. The materials are thoroughly characterized using electron microscopy, Raman scattering, X-ray photoelectron spectroscopy and thermogravimetric analyses. Cs sorption isotherms are plotted after having measured the Cs+ concentration by liquid phase ionic chromatography in the solution before and after exposure to the materials. It is found that the total sorption capacity of the material reaches 230 mg.g-1, and that about one third of the sorbed Cs (80 mg.g-1) is selectively complexed in the CuHCF nanoparticles grafted on SWCNTs.1 These high values open interesting outlooks in the integration of such materials in devices for the controlled sorption and desorption of these ions.

Ref HAL: hal-01828151_v1
DOI: 10.1103/PhysRevB.97.165417
WoS: WOS:000429774800005
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2 Citations
Résumé:

The interactions between the layers of double-walled carbon nanotubes induce a measurable shift of the G bands relative to the isolated layers. While experimental data on this shift in freestanding double-walled carbon nanotubes has been reported in the past several years, a comprehensive theoretical description of the observed shift is still lacking. The prediction of this shift is important for supporting the assignment of the measureddouble-walled nanotubes to particular nanotube types. Here, we report a computational study of the G-band shift as a function of the semiconducting inner layer radius and interlayer separation. We find that with increasing interlayer separation, the G band shift decreases, passes through zero and becomes negative, and further increases in absolute value for the wide range of considered inner layer radii. The theoretical predictions are shown to agree with the available experimental data within the experimental uncertainty.

Ref HAL: hal-01806472_v1
DOI: 10.1016/j.jallcom.2018.05.280
WoS: 000436600000107
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3 Citations

Ref HAL: hal-01793669_v1
DOI: 10.1038/s41467-018-03479-3
WoS: WOS:000428165400020
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29 Citations
Résumé:

The understanding of interactions between electrons and phonons in atomically thin heterostructures is crucial for the engineering of novel two-dimensional devices. Electron–phonon (el–ph) interactions in layered materials can occur involving electrons in the same layer or in different layers. Here we report on the possibility of distinguishing intralayer and interlayer el–ph interactions in samples of twisted bilayer graphene and of probing the intralayer process in graphene/h-BN by using Raman spectroscopy. In the intralayer process, the el–ph scattering occurs in a single graphene layer and the other layer (graphene or h-BN) imposes a periodic potential that backscatters the excited electron, whereas for the interlayer process the el–ph scattering occurs between states in the Dirac cones of adjacent graphene layers. Our methodology of using Raman spectroscopy to probe different types of el–ph interactions can be extended to study any kind of graphene-based heterostructure.

Ref HAL: hal-01724372_v1
DOI: 10.1002/jrs.5295
WoS: WOS:000425938800001
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26 Citations
Résumé:

A After a brief overview of the discovery and the Raman study of new forms of carbons (intercalated graphite, carbon fiber, fullerenes, carbon nanotubes), the invaluable contribution of late Professor M. Dresselhaus is noted and the 10 reviews and 10 contributions collected to present a picture of the present Raman investigations of graphene and related 2D materials (such as black phosphorus, MoS2) are presented. Methods for numbering the graphene layers, the effects of external perturbations (temperature, pressure, doping and magnetic field) on the phonons of graphene, characterization of the chemical and structural properties of graphene at the nanoscale level by tip-enhanced Raman spectroscopy (TERS), surface enhanced Raman spectroscopy (SERS) and hyperspectral imaging, and applications combining graphene and Raman spectroscopy are addressed.