Towards nanoprinting with metals on graphene

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a `pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections

A 3D insight on the catalytic nanostructuration of few-layer graphene

The catalytic cutting of few-layer graphene is nowadays a hot topic in materials research due to its potential applications in the catalysis field and the graphene nanoribbons fabrication. We show here a 3D analysis of the nanostructuration of few-layer graphene by iron-based nanoparticles under hydrogen flow. The nanoparticles located at the edges or attached to the steps on the FLG sheets create trenches and tunnels with orientations, lengths and morphologies defined by the crystallography and the topography of the carbon substrate. The cross-sectional analysis of the 3D volumes highlights the role of the active nanoparticle identity on the trench size and shape, with emphasis on the topographical stability of the basal planes within the resulting trenches and channels, no matter the obstacle encountered. The actual study gives a deep insight on the impact of nanoparticles morphology and support topography on the 3D character of nanostructures built up by catalytic cutting

Intracellular degradation of functionalized carbon nanotube/iron oxide hybrids is modulated by iron via Nrf2 pathway.

The in vivo fate and biodegradability of carbon nanotubes is still a matter of debate despite tremendous applications. In this paper we describe a molecular pathway by which macrophages degrade functionalized multi-walled carbon nanotubes (CNTs) designed for biomedical applications and containing, or not, iron oxide nanoparticles in their inner cavity. Electron microscopy and Raman spectroscopy show that intracellularly-induced structural damages appear more rapidly for iron-free CNTs in comparison to iron-loaded ones, suggesting a role of iron in the degradation mechanism. By comparing the molecular responses of macrophages derived from THP1 monocytes to both types of CNTs, we highlight a molecular mechanism regulated by Nrf2/Bach1 signaling pathways to induce CNT degradation via NOXjournal article2017 Jan 252017 01 25importe

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

A single-stage functionalization and exfoliation method for the production of graphene in water: stepwise construction of 2D-nanostructured composites with iron oxide nanoparticles:

A practically simple top-down process for the exfoliation of graphene (GN) and few-layer graphene (FLG) from graphite is described. We have discovered that a biocompatible amphiphilic pyrene-based hexahistidine peptide is able to exfoliate, functionalize, and dissolve few layer graphene flakes in pure water under exceptionally mild, sustainable and virtually innocuous low intensity cavitation conditions. Large area functionalized graphene flakes with the hexahistidine oligopeptide (His(6)-TagGN = His(6)@GN) have been produced efficiently at room temperature and characterized by TEM, Raman, and UV spectroscopy. Conductivity experiments carried out on His(6)-TagGN samples revealed superior electric performances as compared to reduced graphene oxide (rGO) and non-functionalized graphene, demonstrating the non-invasive features of our non-covalent functionalization process. We postulated a rational exfoliation mechanism based on the intercalation of the peptide amphiphile under cavitational chemistry. We also demonstrated the ability of His(6)-TagGN nanoassemblies to self-assemble spontaneously with inorganic iron oxide nanoparticles generating magnetic two-dimensional (2D) His(6)-TagGN/Fe3O4 nanocomposites under mild and non-hydrothermal conditions. The set of original experiments described here open novel perspectives in the facile production of water dispersible high quality GN and FLG sheets that will improve and facilitate the interfacing, processing and manipulation of graphene for promising applications in catalysis, nanocomposite construction, integrated nanoelectronic devices and bionanotechnology

High-Density Monodispersed Cobalt Nanoparticles Filled into Multiwalled Carbon Nanotubes

Magnetic cobalt-based nanoparticles (NPs) with homogeneous size were selectively cast inside the channel of multiwalled carbon nanotubes (CNTs). The proposed synthesis method allows for filling only the CNTs channel with an unprecedented high density. The CNTs act as “nanoreactors” and provide protection against oxidation

Few layer graphene decorated with homogeneous magnetic Fe3O4 nanoparticles with tunable covering densities

Magnetic iron oxide nanoparticles (NPs) with narrow size distribution (8 +/- 2 nm), well defined chemical composition and crystalline structure are synthesized and homogeneously dispersed onto the surface of few-layer graphene (FLG) via a solvothermal decomposition method. The iron oxide NPs are strongly anchored to the graphene surface and confer a magnetic character to the final composite. The metal oxide/support interaction is high enough to avoid the NPs coalescence and/or agglomeration and thus to preserve the NPs size and dispersion after thermal treatment up to 400 degrees C. The introduced iron oxide NPs on FLG also play a role of nano-spacers to prevent the re-stacking of the graphene sheets upon the drying process. It is expected that such a composite could find use in several application fields such as catalyst support for liquid-phase reactions with easy magnetic separation, in electrochemical energy storage and in waste water treatment. The ability of the synthesized iron oxide NP/FLG composite to adsorb foreign elements (organic pollutants) is demonstrated in the methylene blue (MB) adsorption and its catalytic properties are evaluated in the selective oxidation of H2S

Low Oxidation State and Enhanced Magnetic Properties Induced by Raspberry Shaped Nanostructures of Iron Oxide

Nanostructures with controlled size, morphology, and composition represent a main challenge in materials science because controlling these parameters is fundamental to optimizing the subsequent functional properties. Aggregated nanostructures, combining both individual and collective properties of nanocrystals, offer interesting perspectives to design new magnetic nanomaterials. In that context, original porous raspberry shaped nanostructures consisting of oriented aggregates of ferrite nanocrystals have been synthesized by an one-pot polyol solvothermal method. Synthesis conditions have been optimized to obtain nanostructures featured by similar sizes of about 250 nm and nanocrystal sizes modulated from 5 to 60 nm, leading to porous structures with tunable specific surface area. Structural and magnetic studies of nanostructures as a function of the nanocrystal size evidenced their low oxidation state and enhanced magnetic properties. Indeed, the oriented aggregation of nanocrystals leads to high interface between nanograins reducing significantly their surface oxidation and enhancing their saturation magnetization in comparison to individual nanoparticles of similar sizes. Magnetic moments of each grain are also consequently strongly coupled by dipolar interactions which led to superspin glass effects

Carbon nanotube channels selectively filled with monodispersed Fe3-xO4 nanoparticles

Magnetic iron oxide (Fe3-xO4) nanoparticles (NPs) with high density and narrow size distribution were selectively cast inside or at the outer surface of the channels of carbon nanotubes (CNTs) by performing thermal decomposition of an organic iron precursor in liquid-phase medium in the presence of adequately pre-treated CNTs. The size of the Fe3-xO4 NPs generated by the synthesis is around 13 +/- 3 nm and no agglomeration was observed thanks to the presence of oleic acid playing the role of surfactant in the synthesis medium. The selective filling of the Fe3-xO4 NPs inside the CNT channel was confirmed by X-ray diffraction, transmission electron microscopy (also in tomography mode) and X-ray photoelectron spectroscopy. Such NPs were found to be less sensitive towards oxidation compared to the same NPs synthesized without CNTs according to the powder X-ray diffraction and they display thus a higher saturation magnetization (65 emu g(-1)). Such a composite was found to be superparamagnetic at room temperature. Due to its new "magnetic state", it could efficiently be employed in applications, which need both magnetic and electric properties, especially in catalysis in liquid-phase medium where the catalyst-product separation is facilitated by the magnetic properties of the catalyst