Christopher P Ewels

Christopher P Ewels
French National Centre for Scientific Research | CNRS · Institut des Matériaux Jean Rouxel

Materials Science

About

236
Publications
49,775
Reads
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7,400
Citations
Citations since 2017
67 Research Items
3429 Citations
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20172018201920202021202220230100200300400500600
20172018201920202021202220230100200300400500600
Introduction
In close collaboration with experimental colleagues, I use atomic scale computer simulations to understand and design new carbon-based nanostructures with unique customised properties, either through new structural topologies or chemical and structural modification.
Additional affiliations
January 2006 - present
Institut des Materiaux Jean Rouxel
Position
  • Institut des Materiaux Jean Rouxel (CNRS)
November 2005 - September 2015
French National Centre for Scientific Research
Position
  • Senior Researcher
January 2005 - December 2009
Université Paris-Sud 11

Publications

Publications (236)
Article
Full-text available
Explosive percolation is an experimentally-elusive phenomenon where network connectivity coincides with onset of an additional modification of the system; materials with correlated localisation of percolating particles and emergent conductive paths can realise sharp transitions and high conductivities characteristic of the explosively-grown network...
Article
Full-text available
Using laser-induced vaporisation to evaporate and ionise a source of curved polyaromatic hydrocarbons (carbon nanobelts), we show collision impacts between species cause mass loss and the resultant ions are catalogued via mass-spectrometry. These data are interpreted via a series of “in-silico”-simulated systematic hydrogen-loss studies using densi...
Preprint
We explore the importance of curvature in carbonaceaous species transformation and stability, using laser-induced vaporisation to evaporate and ionise a source of curved polyaromatic hydrocarbons: carbon nanobelts. Collision impacts between species cause mass loss and the resultant ions are catalogued via mass-spectrometry. To interpret the mass sp...
Article
Full-text available
We report the intercalation of iodine chains in highly crystalline arc-discharge multiwalled carbon nanotubes (MWCNTs), not in the central cavity but instead between the concentric graphene shells. High-resolution transmission electron microscopy demonstrated that the intercalation was asymmetric with respect to the longitudinal axis of the nanotub...
Article
Dislocations are a central concept in materials science, which dictate the plastic deformation and damage evolution in materials. Layered materials such as graphite admit two general types of interlayer dislocations: basal and prismatic dislocations, of which prismatic dislocations have been relatively less studied. Using density functional theory...
Article
Full-text available
Molecular entities with robust spin-1/2 are natural two-level quantum systems for realizing qubits and are key ingredients of emerging quantum technologies such as quantum computing. Here we show that robust and abundant spin-1/2 species can be created in situ in the solid state from spin-active azafullerene C59N cages supramolecularly hosted in cr...
Article
Full-text available
Hydrogenated small fullerenes (Cn, n < 60) are of interest as potential astrochemical species, and as intermediates in hydrogen-catalysed fullerene growth. However, the computational identification of key stable species is difficult due to the vast configurationally space of structures. In this study, we explored routes to predict stable hydrogenat...
Preprint
Full-text available
Dislocations are a central concept in materials science, which dictate the plastic deformation and damage evolution in materials. Layered materials such as graphite admit two general types of interlayer dislocations: basal and prismatic dislocations, of which prismatic dislocations have been relatively less studied. Using density functional theory...
Preprint
Hydrogenated small fullerenes (Cn, n<60) are of interest as potential astrochemical species, and as intermediates in hydrogen catalysed fullerene growth. However computational identification of key stable species is difficult due to the vast combinatorial space of structures. In this study we explore routes to predict stable hydrogenated small full...
Article
Full-text available
We present a comprehensive theoretical and experimental Raman spectroscopic comparative study of bulk Phosphorus allotropes (white, black, Hittorf's, fibrous) and their monolayer equivalents, demonstrating that the application of the Placzek approximation to density functional theory calculated frequencies allows reliable and accurate reproduction...
Article
Vertically aligned multiwalled carbon nanotubes synthetized by catalytic chemical vapor deposition are irradiated with low kinetic energy oxygen ions to graft oxygen functional groups at their surface. Subsequently, the thermal stability of these functional groups is investigated by heating the sample progressively to 200, 300, 400 and 500 °C. X-Ra...
Article
We report the effect of functional groups on pyrene adsorption and associated electropolymerization mechanisms on carbon nanotube model electrodes, as well as resulting electrochemical charge‐storage properties in a Li metal supercapacitor configuration. The impact of pyrene functional groups is tested by varying the alkyl chain length as well as t...
Article
Ionogels represent a route to biphasic materials, for the use of ionic liquids (ILs) for all solid devices. Confining ILs within host networks enhances their averaged dynamics, resulting in improved charge transport. Fragility, short relaxation times, low viscosity, and good ionic conductivity, all them appear to be related to the IL / host network...
Article
Two efficient excited state intramolecular proton transfer (ESIPT) dyes based on the hydroxyphenyl-oxazole core and containing one or two triphenylamine donor groups are explored with theoretical tools. These compounds are known to show clear experimental dual emission behaviour, leading to nearly pure white-light emission for one derivative. To pr...
Article
Full-text available
Pyrene carrying an 1,2-dithiolane linker was employed to functionalize exfoliated WS2 and the resulting material was used in a proof-of-concept application as a photoresistor type sensor. The WS2–pyrene hybrid material was comprehensively characterized by spectroscopic, thermal and microscopy techniques, coupled to density functional theory modelli...
Article
Laser-deposited carbon aerogel is a low-density porous network of carbon clusters synthesized using a laser process. A one-step synthesis, involving deposition and annealing, results in the formation of a thin porous conductive film which can be applied as a chemiresistor. This material is sensitive to NO2 compared to ammonia and other volatile org...
Article
Full-text available
The structural transformations of graphene defects have been extensively researched through aberration-corrected transmission electron microscopy (AC-TEM) and theoretical calculations. For a long time, a core concept in understanding the structural evolution of graphene defects has been the Stone-Thrower-Wales (STW)–type bond rotation. In this stud...
Article
We present density functional studies of the edges of single‐layer 1H‐MoS 2 . This phase presents a rich variability of edges that can influence the morphology and properties of MoS 2 nano‐objects, play an important role in industrial chemical processes, and find future applications in energy storage, electronics and spintronics. For so‐called Mo‐1...
Article
Full-text available
Environmental degradation of transition metal disulfides (TMDs) is a key stumbling block in a range of applications. We show that a simple one-pot non-covalent pyrene coating process protects TMDs from both photoinduced oxidation and environmental aging. Pyrene is immobilized non-covalently on the basal plane of exfoliated MoS2 and WS2. The optical...
Article
Above a critical diameter, single- or few-walled carbon nanotubes spontaneously collapse as flattened carbon nanotubes. Raman spectra of isolated flattened and cylindrical carbon nanotubes have been recorded. The collapse provokes an intense and narrow D band, despite the absence of any lattice disorder. The curvature change near the edge cavities...
Article
Alkylamine-strapped chromophores based on a dithienylpyrrole core, and in which the Excited State Intramolecular Proton Transfer (ESIPT) process yields a zwitterionic structure rather than a keto tautomer have been reported recently (Suzuki et al., Angew. Chem. Int. Ed. 2014, 53, 8231), and are known to exhibit large Stokes shifts. Using Time-Depen...
Article
Full-text available
Vertically aligned multiwalled carbon nanotubes (v-CNTs) were functionalized with oxygen groups using low kinetic energy oxygen ion irradiation. X-ray photoelectron spectroscopy (XPS) analysis indicates that oxygen ion irradiation produces three different types of oxygen functional groups at the CNTs surface: epoxide, carbonyl and carboxyl groups....
Article
Full-text available
A major handicap towards exploitation of radicals is their inherently instability. In paramagnetic azafullerenyl radical C59N• the unpaired electron is strongly localized neighbouring the nitrogen and induces dimerization to diamagnetic bisazafullerene (C59N)2. Conventional stabilization employing steric hindrance around the radical is inapplicable...
Article
Using density functional theory with van der Waals (vdW) corrections, we study the collapse of free-standing single-walled carbon nanotubes (also called “dogbone” nanotubes). Their thermodynamic stability is strongly influenced by the initial stacking sequence, with lateral shear allowing registry change with turbostratic stacking predominant. The...
Article
Full-text available
Durch supramolekulare Komplexierung mit einem [10]Cycloparaphenylen([10]CPP)‐Nanogürtel kann das C59N.‐Radikal effektiv stabilisiert werden. Das charakteristische Triplett‐EPR‐Signal von C59N.⊂[10]CPP wurde auch mehrere Wochen nach seiner Generierung noch detektiert. Abstract A major handicap towards the exploitation of radicals is their inherent...
Article
Full-text available
Despite decades of study the precise behavior of bromine in graphitic carbons remains unclear. In this report, using Raman spectroscopy , we reveal two types of bromine structure in graphitic carbon materials. Between fluorinated graphene layers with a composition close to C2F, Br2 molecules are intercalated in a form similar to liquid bromine. Bro...
Preprint
Aqueous batteries, particularly those integrating organic active materials functioning in a neutral pH environment, stand out as highly promising contenders in the stationary electrochemical storage domain, owing to their unparalleled safety, sustainability and low-cost materials. Herein, a novel di-block oligomer (DNVBr), serving as the negative e...
Article
Aqueous batteries, particularly those integrating organic active materials functioning in a neutral pH environment, stand out as highly promising contenders in the stationary electrochemical storage domain, owing to their unparalleled safety, sustainability, and low‐cost materials. Herein, a novel di‐block oligomer, serving as the negative electrod...
Chapter
Full-text available
In this chapter we explore the possibilities of using MoS2 for chemical gas sensing. We first introduce monolayer MoS2 and discuss the different reconstructed phases that can be produced in terms of their atomic and electronic structure. We show how these properties can vary drastically from their bulk counterparts, and how MoS2 can be taken as a u...
Preprint
div>Herein, we report a improved method for the physical grafting of 1-nitropyrene (Pyr-NO2) onto highly graphitized carbon onion. This is achieved through a lowering of the onset potential of the pyrene polymerization via in situ reduction of the NO2 group. The additional redox activity pertaining to the reduced NO2 enables exceeding the faradaic...
Book
This book presents a blueprint for researchers in the area of nanotechnology for chemical defense, especially with regard to future research on detection and protection. It addresses the synthesis of complex nanomaterials with potential applications in a broad range of sensing systems. Above all, it discusses novel experimental and theoretical tool...
Article
Full-text available
Single-walled carbon nanotubes (SWCNTs) were functionalized by ferrocene through ethyleneglycol chains of different lengths (FcETGn) and the functionalized SWCNTs (f-SWCNTs) were characterized by different complementary analytical techniques. In particular, high-resolution scanning electron transmission microscopy (HRSTEM) and electron energy loss...
Article
Using density functional calculations, we explore π-π and π-H stacking interactions in conjugated polymer-carbon nanomaterial composites, through a detailed surface energy mapping procedure. Taking the triphenyl vinylene oligomer as a structural model for poly para-phenylene vinylene (PPV), we map intermolecular stacking configurations between PPV...
Article
Full-text available
Our trifluoromethyl functionalization method enables the dissolution and isolation of missing metallofullerenes of Gd@C74(CF3) n . After multi-stage high-performance liquid chromatography purification, Gd@C74(CF3)3 and two regioisomers of Gd@C74(CF3) are isolated. X-ray crystallographic analysis reveals that all of the isolated metallofullerenes r...
Article
Full-text available
Using density functional theory approaches, we follow the sequential addition of CF3 functional groups to the surface of the metallic endofullerene species [email protected]60. The presence of gadolinium in the interior of the cage strongly influences the addition sequence. The calculations are able to successfully identify end points in the additi...
Article
Full-text available
Endohedral metallofullerenes have been extensively studied since the first experimental observation of La@C60 in a laser-vaporized supersonic beam in 1985. However, most of these studies have focused on metallofullerenes larger than C60 such as (metal)@C82, and there are no reported purified C60-based monomeric metallofullerenes, except for [Li@C60...
Article
Hybrid systems based on graphene and semiconductor quantum dots are prospective materials for optoelectronics and photonics. In this work, electronic structure and dielectric properties of small particles of cadmium sulfide on the surface of graphene were studied using the density functional theory. The optical spectrum of this hybrid structure dep...
Article
The complex of [10]cycloparaphenylene ([10]CPP) with bisazafullerene (C59N)2 is investigated experimentally and computationally. Two [10]CPP rings are bound to the dimeric azafullerene giving [10]CPP⊃(C59N)2⊂[10]CPP. Photophysical and redox properties support an electronic interaction between the com‐ponents especially with the second [10]CPP bound...
Article
The complex of [10]cycloparaphenylene ([10]CPP) with bisazafullerene (C59N)2 is investigated experimentally and computationally. Two [10]CPP rings are bound to the dimeric azafullerene giving [10]CPP⊃(C59N)2⊂[10]CPP. Photophysical and redox properties support an electronic interaction between the com‐ponents especially with the second [10]CPP bound...
Article
In article number 1701988, Joël Gaubicher, Philippe Poizot, Fabrice Odobel and co-workers report the first ever battery material that works with simultaneous uptake and release of both cations and anions. This represents one of a new family of organic electrode materials that shows great promise, thereby promoting the design of cutting-edge, low-co...
Article
Full-text available
Endohedral metallofullerenes have been extensively studied, since the first experimental observation of La@C60 in a laser-vaporized supersonic beam in 1985. However, all of these studies have been carried out on metallofullerenes larger than C60 such as (metal)@C82, and there are no reported purified C60-based metallofullerenes except for [Li@C60]+...
Article
Aqueous batteries are an emerging candidate for low-cost and environmentally friendly grid storage systems. Designing such batteries from inexpensive, abundant, recyclable, and nontoxic organic active materials provides a logical step toward improving both the environmental and economic impact of these systems. Herein the first ever battery materia...
Article
Full-text available
The covalent functionalization of exfoliated semiconducting MoS2 by 1,2-dithiolanes bearing an ethylene glycol alkyl chain terminated to a butoxycarbonyl-protected amine and a photoactive pyrene moiety is accomplished. The MoS2-based nanohybrids were fully characterized by complementary spectroscopic, thermal, and microscopy techniques. Markedly, d...
Article
Full-text available
N-methyl-2-pyrrolidone (NMP) has been shown to be the most effective solvent for liquid phase exfoliation and dispersion of a range of 2D materials including graphene, molybdenum disulphide (MoS2) and black phosphorus. However, NMP is also known to be susceptible to sonochemical degradation during exfoliation. We report that this degradation gives...
Article
Plasma fluorination of graphene is studied using a combination of spectroscopy and microscopy techniques, giving insight into the yield and fluorination mechanism for functionalization of supported graphene with both CF4 and SF6 gas precursors. Ion acceleration during fluorination is used to probe the effect on grafting functionalities. Adatom clus...
Article
Full-text available
As potential donor materials for organic photovoltaic (OPV) devices, six conjugated small molecules with donor-acceptor configuration based on 3-hexylthiophene monomer (3HT) were designed and studied by means of density functional theory (DFT) and time-dependent DFT. Their geometric structure, electronic and optical properties were investigated at...
Article
Full-text available
Double-walled carbon nanotubes (DWCNTs) are fluorinated using (1) fluorine F2 at 200 °C, (2) gaseous BrF3 at room temperature, and (3) CF4 radio-frequency plasma functionalization. These have been comparatively studied using transmission electron microscopy and infrared, Raman, X-ray photoelectron, and near-edge X-ray absorption fine structure (NEX...
Article
AA-stacked graphite and closely related structures, where carbon atoms are located in registry in adjacent graphene layers, are a feature of graphitic systems including twisted and folded bilayer graphene, and turbostratic graphite. We present the results of ab initio density functional theory calculations performed to investigate the complexes tha...
Article
Full-text available
C60 fullerene crystals may serve as important catalysts for interstellar organic chemistry. To explore this possibility, the electronic structures of free-standing powders of C60 and (C59N)2 azafullerenes are characterized using X-ray microscopy with near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy, closely coupled with density fu...
Conference Paper
Since its creation at the end of the 1990's, the EELS and X-ray Absorption Spectroscopy (XAS) database has gathered more than 220 spectra covering 37 elements of the periodic table, becoming the largest open-access electronic repository of spectra from EELS and XAS experiments. The EELS database is now a common tool used by spectroscopists, theoret...