High quality graphene synthesized by atmospheric pressure CVD on copper foil

Graphene was synthesized at 1000°C by Atmospheric Pressure Chemical Vapor Deposition on copper foil from methane diluted in argon and hydrogen. The influence of the main synthesis parameters was studied on 2x2 cm2 foils in order to obtain continuous monolayer graphene without crystalline defect. The uniformity, crystal quality and number of layers of graphene were analyzed by Raman spectroscopy and Scanning Electronic Microscopy. First, an increase of the annealing pre-treatment duration induced an increase of the average size of copper grains, leading to larger graphene flakes of higher crystallinity presenting a lower number of layers. Similar evolutions of graphene characteristics were observed when decreasing the methane concentration to 20 ppm, whereas an increase of run duration led to a loss of graphene quality and to a higher number of graphene layers, confirming that graphene formation is not self-limiting on copper. An optimum hydrogen/methane ratio was found, quite different from other results of the literature, probably due to differences in the copper pre-treatment step. Finally, an optimized three steps process was developed to form monolayer continuous graphene of high quality, successfully transposed to 7x7 cm2 substrates after a reactor scale-up

Supported online self-management versus care as usual for symptoms of fatigue, pain and urgency/incontinence in adults with inflammatory bowel disease (IBD-BOOST): study protocol for a randomised controlled trial.

BACKGROUND: Despite being in clinical remission, many people with inflammatory bowel disease (IBD) live with fatigue, chronic abdominal pain and bowel urgency or incontinence that limit their quality of life. We aim to test the effectiveness of an online self-management programme (BOOST), developed using cognitive behavioural principles and a theoretically informed logic model, and delivered with facilitator support. PRIMARY RESEARCH QUESTION: In people with IBD who report symptoms of fatigue, pain or urgency and express a desire for intervention, does a facilitator-supported tailored (to patient needs) online self-management programme for fatigue, pain and faecal urgency/incontinence improve IBD-related quality of life (measured using the UK-IBDQ) and global rating of symptom relief (0-10 scale) compared with care as usual? METHODS: A pragmatic two-arm, parallel group randomised controlled trial (RCT), of a 12-session facilitator-supported online cognitive behavioural self-management programme versus care as usual to manage symptoms of fatigue, pain and faecal urgency/incontinence in IBD. Patients will be recruited through a previous large-scale survey of unselected people with inflammatory bowel disease. The UK Inflammatory Bowel Disease Questionnaire and global rating of symptom relief at 6 months are the co-primary outcomes, with multiple secondary outcomes measured also at 6 and 12 months post randomisation to assess maintenance. The RCT has an embedded pilot study, health economics evaluation and process evaluation. We will randomise 680 patients, 340 in each group. Demographic characteristics and outcome measures will be presented for both study groups at baseline. The UK-IBDQ and global rating of symptom relief at 6 and 12 months post randomisation will be compared between the study groups. DISCUSSION: The BOOST online self-management programme for people with IBD-related symptoms of fatigue, pain and urgency has been designed to be easily scalable and implemented. If it is shown to improve patients' quality of life, this trial will enable clinicians and patients to make informed management decisions. This is the first trial, to our knowledge, focused on multiple symptoms prioritised by both people with IBD and health professionals. TRIAL REGISTRATION: ISRCTN71618461 . Registered on 9 September 2019

Couches à faibles permittivités diélectriques élaborées par plasma micro-onde d'organosilicies (identification et étude des paramètres contrôlant la permittivité)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Nanomechanical mapping of graphene layers and interfaces in suspended graphene nanostructures grown via carbon diffusion

Graphene’s remarkable mechanical, electronic and thermal properties are strongly determined by both the mechanism of its growth and its interaction with the underlying substrate. Evidently, in order to explore the fundamentals of these mechanisms, efficient nanoscale methods are needed that enable observation of features hidden underneath the immediate surface. In this paper we use nanomechanical mapping via ultrasonic force microscopy that employs MHz frequency range ultrasonic vibrations and allows the observation of surface composition and subsurface interfaces with nanoscale resolution, to elucidate the morphology of few layer graphene (FLG) films produced via a recently reported method of carbon diffusion growth (CDG) on platinum-metal based substrate. CDG is known to result in FLG suspended over large areas, which could be of high importance for graphene transfer and applications where a standalone graphene film is required. This study directly reveals the detailed mechanism of CDG three-dimensional growth and FLG film detachment, directly linking the level of graphene decoupling with variations of the substrate temperature during the annealing phase of growth. We also show that graphene initially preferentially decouples at the substrate grain boundaries, likely due to its negative expansion coefficient at cooling, forming characteristic “nano-domes” at the intersections of the grain boundaries. Furthermore, quantitative nanomechanical mapping of flexural stiffness of suspended FLG “nano-domes” using kHz frequency range force modulation microscopy, uncovers the progression of “nano-domes” stiffness from single to bi-modal distribution as CDG growth progresses, suggesting growth instability at advanced CDG stages

High quality graphene synthesized by atmospheric pressure CVD on copper foil

International audienceGraphene was synthesized at 1000°C by Atmospheric Pressure Chemical Vapor Deposition on copper foil from methane diluted in argon and hydrogen. The influence of the main synthesis parameters was studied on 2x2 cm2 foils in order to obtain continuous monolayer graphene without crystalline defect. The uniformity, crystal quality and number of layers of graphene were analyzed by Raman spectroscopy and Scanning Electronic Microscopy. First, an increase of the annealing pre-treatment duration induced an increase of the average size of copper grains, leading to larger graphene flakes of higher crystallinity presenting a lower number of layers. Similar evolutions of graphene characteristics were observed when decreasing the methane concentration to 20 ppm, whereas an increase of run duration led to a loss of graphene quality and to a higher number of graphene layers, confirming that graphene formation is not self-limiting on copper. An optimum hydrogen/methane ratio was found, quite different from other results of the literature, probably due to differences in the copper pre-treatment step. Finally, an optimized three steps process was developed to form monolayer continuous graphene of high quality, successfully transposed to 7x7 cm2 substrates after a reactor scale-up

Experimental study of nucleation and growth mechanisms of graphene synthesized by Low Pressure Chemical Vapor Deposition on copper foil

During the past 40 years, the fields of micro-electronic, energy and communication devices have experienced an unbelievable evolution. To continue these progresses, the development of multifunctional materials presenting a broad range of properties such as high electronic and thermal conductivities, high transparency and good mechanical properties is needed. Graphene, a hexagonal arrangement of carbon atoms forming a one-atom thick planar sheet could match these demands. Several methods can be used for graphene synthesis, even though Chemical Vapor Deposition (CVD) on catalytic surfaces is foreseen to be the most compatible one with industrial requirements. Indeed, CVD graphene with an electronic conductivity of 7350 cm²V-1s-1, an electrical resistance of 30 Ω/sq and a transparency of 90% has already been obtained.1 However, these values are still far from the theoretical ones announced by physicists, because graphene grows as randomly oriented domains in which scattering at the boundaries leads to lower physical properties. The CVD formation of graphene on Cu substrates has long been considered to be surface-mediated and selflimiting due to the very low carbon solubility in Cu, thus leading to single layers formation. However, numerous studies in 2011 have shown that this is true only in a small window of deposition conditions, especially for methane partial pressure2. As a consequence, the control of graphene thickness and crystalline uniformity on large surface areas still remains elusive and needs a better understanding of the mechanisms of graphene nucleation and growth. In this framework, the present study consists in synthesizing graphene on copper foils (25 mm thick, 99,999% Alfa Aesar) by CVD from methane diluted in hydrogen and argon at 0.5 Torr of total pressure. The operating temperature was fixed at 1000°C. Scanning electron microscopy (SEM), optical microscopy and Raman spectroscopy measurements were carried out to investigate the quality and extend of graphene sheets

Hydrophobic mesostructured organosilica-based thin films with tunable closed mesoporosity

International audienc

Surface and interfacial interactions of multilayer graphitic structures with local environment

In order to exploit the potential of graphene in next-generation devices, such as supercapacitors, rechargeable batteries, displays and ultrathin sensors, it is crucial to understand the solvent interactions with the graphene surface and interlayers, especially where the latter may be in competition with the former, in the medium of application deployment. In this report, we combine quartz crystal microbalance (QCM) and ultrasonic force microscopy methods to investigate the changes in the film-substrate and film-environment interfaces of graphene and graphene oxide films, produced by diverse scalable routes, in both polar (deionised water) and non-polar (dodecane) liquid and vapour environments. In polar liquid environments, we observe nanobubble adsorption/desorption on the graphene film corresponding to a surface coverage of up to 20%. As no comparable behaviour is observed for non-polar environment, we conclude that nanobubble formation is directly due to the hydrophobic nature of graphene with direct consequences for electrode structures immersed in electrolyte solutions. The amount of water adsorbed by the graphene films was found to vary considerably from 0.012 monolayers of water per monolayer of reduced graphene oxide to 0.231 monolayers of water per monolayer of carbon diffusion growth graphene. This is supported by direct nanomechanical mapping of the films immersed in water where an increased variation of local stiffness suggests water propagation within the film and/or between the film and substrate. Film thickness calculations performed for QCM, atomic force microscopy topography, Raman spectroscopy and optical transmission measurements, show that due to the turbostratic structures of large area films Raman returns results an order of magnitude lower (1-2 graphene layers) than direct measurement by QCM (46 ± 1 layers)