Biodegradability of graphene is one of the fundamental parameters determining the fate of this material in vivo. Two types of aqueous dispersible graphene, corresponding to single‐layer (SLG) and ...few‐layer graphene (FLG), devoid of either chemical functionalization or stabilizing surfactants, were subjected to biodegradation by human myeloperoxidase (hMPO) mediated catalysis. Graphene biodegradation was also studied in the presence of activated, degranulating human neutrophils. The degradation of both FLG and SLG sheets was confirmed by Raman spectroscopy and electron microscopy analyses, leading to the conclusion that highly dispersed pristine graphene is not biopersistent.
Not biopersistent: Two types of aqueous dispersible graphene, corresponding to single layer (SLG) and few layer graphene (FLG), devoid of either chemical functionalization or stabilizing surfactants, were subjected to biodegradation. Graphene can be degraded by human myeloperoxidase secreted by activated neutrophils, indicating that this material is not biopersistent.
Dispersing graphite in water to obtain true (single-layer) graphene in bulk quantity in a liquid has been an unreachable goal for materials scientists in the past decade. Similarly, a diagnostic tool ...to identify solubilized graphene in situ has been long awaited. Here we show that homogeneous stable dispersions of single-layer graphene (SLG) in water can be obtained by mixing graphenide (negatively charged graphene) solutions in tetrahydrofuran with degassed water and evaporating the organic solvent. In situ Raman spectroscopy of these aqueous dispersions shows all the expected characteristics of SLG. Transmission electron and atomic force microscopies on deposits confirm the single-layer character. The resulting additive-free stable water dispersions contain 400 m
l
of developed graphene surface. Films prepared from these dispersions exhibit a conductivity of up to 32 kS m
.
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Interfaces are often crucial determinants of the physicochemical properties of a material. As a result, the rational production and engineering of heterogeneities, and the resulting ...interfaces, can enhance the functionality of a material system. This is especially true of two dimensional (2D) materials, which are only a few atoms thick and thus sensitive to small perturbations of their surroundings. As a result, 2D materials and their heterostructures have been recently modified to function as catalysts, photodetectors, chemical sensors, memory, logic devices, single photon emitters, and more. In this review, we summarize the current understanding of functional interfaces in few-layered chalcogenide 2D systems, and address the following topics: The classification of interfaces by dimensionality and electronic structure, methods of creating 2D interfaces, characterization techniques and related challenges, applications of interfacial engineering in 2D systems, and finally a perspective on the future of this rapidly advancing field of study.
Pd was supported on boron-doped hollow carbon spheres and carbon nanotubes and the Pd-supported catalyst showed activity controlled by Pd particle size. Display omitted
•Successful synthesis of ...boron-doped B-HCSs and B-CNTs by using a CVD method.•Pd was well dispersed on Pd/B-HCS and Pd/B-CNT catalysts (2–8nm) with size determined by calcination temperature.•Pd/B-HCS and Pd/B-CNT catalysts are selective, highly efficient, and reusable catalyst for the solvent-free oxidation of benzyl alcohol.•Activity was controlled by Pd size as determined by calcination temperature of catalysts.
Boron-doped hollow carbon spheres (B-HCSs) were synthesized using a CVD injection method (BCl3 in toluene; Ar; 900°C; 4h) using Stöber silica spheres as template. A Pd complex was loaded onto the B-HCSs using deposition and impregnation methods, and the materials were studied by XRD, SEM, TEM, Raman spectroscopy, TGA, ICP-OES, XPS, and 11B solid-state NMR spectroscopy. The boron-doped carbon-supported Pd catalysts (Pd/B-HCS) were compared with a Pd-loaded boron-doped carbon nanotube (Pd/B-CNT) catalyst (both have a hollow interior) in the solvent-free oxidation of alcohols using oxygen as an oxidant at 125°C under base-free conditions. The Pd particle size was varied (2.5–12nm) by changing the Pd/B-HCS calcination temperature (200–550°C), and this affected the activity but not the selectivity of the benzyl alcohol to benzaldehyde reaction. The data revealed the key role of the Pd particle size on the reaction that was influenced by the B–Pd–C interaction. The reaction rate depended on the mean size of Pd particles and showed a maximum when catalysts were calcined at 300°C, revealing that the aerobic oxidation of benzyl alcohol catalyzed by the supported PdO (dPd>2.5nm) nanoparticles was not a structure sensitive reaction.
Here, it is shown that by placing a thin film of N‐CNTs on top of the transparent ITO hole collecting electrode of a polymer solar cell, the short circuit current density and efficiency are enhanced ...by 25 and 50%, respectively, and the usual efficiency losses in polymer solar cells as a function of incident light illumination intensity are significantly reduced. Nanostructuring the anode improves the mobility and collection of holes toward the anode, and as a result reduces space‐charge accumulation in the polymer solar cell.
The findings in this article show that, modifying the ITO hole collecting electrode/active layer interface of a polymer solar cell using CNTs results in a significant enhancement of the current density and efficiency. The efficiency enhancement in polymer solar cells not only requires a broader optical absorption in the active region layers, but also, appropriately designed active layer/electrode interfaces, to increase the charge transport efficiency throughout the device.
Biodegradability of graphene is one of the fundamental parameters determining the fate of this material in vivo. Two types of aqueous dispersible graphene, corresponding to single‐layer (SLG) and ...few‐layer graphene (FLG), devoid of either chemical functionalization or stabilizing surfactants, were subjected to biodegradation by human myeloperoxidase (hMPO) mediated catalysis. Graphene biodegradation was also studied in the presence of activated, degranulating human neutrophils. The degradation of both FLG and SLG sheets was confirmed by Raman spectroscopy and electron microscopy analyses, leading to the conclusion that highly dispersed pristine graphene is not biopersistent.
Nicht übertrieben stabil: Der biologische Abbau von zwei Arten in Wasser dispergierbaren Graphens (bestehend aus einer oder einigen Schichten) ohne chemische Funktionalisierung oder stabilisierende Tenside wurden untersucht. Graphen wird durch humane Myeloperoxidase zersetzt, die von aktivierten Neutrophilen abgesondert wird. Das Material ist daher im Körper nicht persistent.
Chemical doping of graphene with small boron nitride (BN) domains has been shown to be an effective way of permanently modulating the electronic properties in graphene. Herein we show a facile method ...of growing large area graphene doped with small BN domains on copper foils using a single step CVD route with methane, boric acid powder and nitrogen gas as the carbon, boron and nitrogen sources respectively. This facile and safe process avoids the use of boranes and ammonia. Optical microscopy confirmed that continuous films were grown and Raman spectroscopy confirmed changes in the electronic structure of the grown BN doped graphene. Using XPS studies we find that both B and N can be substituted into the graphene structure in the form of small BN domains to give a BNC system. A novel structure for the BN doped graphene is proposed.
An atomic model showing the possible small BN units (a) and (b) that can be incorporated in a graphene matrix.
We report a detailed Raman study of single layer graphene dispersed in degassed water without additives (SLGiw), so-called “‘eau de graphene”’ (EdG). The most characteristic signature of SLGiw is a ...narrow (28 ± 2 cm–1) and symmetric 2D band. The intensity of the D band is dominated by the contribution of sp3 defects due to slight functionalization of the basal-planes. The density of defects is estimated in the range 200–650 ppm by studying thin films prepared from EdG. These defects can be fully and easily cured by annealing the films at 800 °C. The position of the G and 2D bands, blue-shifted with respect to pristine SLG, are assigned to moderate biaxial compressive strain (≈0.09 ± 0.02%) and likely weak n doping (<4 × 1012 electrons/cm2) of SLGiw.
Manipulation of electrical properties and hence gas sensing properties of multi-walled carbon nanotubes (MWNTs) by filling the inner wall with vanadium oxide is presented. Using a simple capillary ...technique, MWNTs are filled with vanadium metal which is later oxidized. It is observed that the methane gas detection response time at room temperature (293K), is significantly improved from 138s (in vanadium pentoxide) to 16s (in filled MWNTs) while the recovery times changes from 234s to 120s respectively. The response sensitivity of the unfilled CNTs is improved from 0.5% to 1.5% due to the metal oxide filling. Using theoretical Density Functional Theory (DFT) electronic structure calculations, we show that the enhanced response is due to the increased density of states around the Fermi level of the composite material as a result of the encapsulated metal oxide. And we propose an adsorption mechanism at three different sites of the MWNTs surface based on the Langmuir model. This work also highlights the influence of ambient oxygen in carbon nanotube based sensors, an aspect that has not been clearly addressed in many previous theoretical and experimental studies.
The main hurdle preventing the widespread use of single-walled carbon nanotubes remains the lack of methods with which to produce formulations of pristine, unshortened, unfunctionalized, ...individualized single-walled carbon nanotubes, thus preserving their extraordinary properties. In particular, sonication leads to shortening, which is detrimental to percolation properties (electrical, thermal, mechanical, etc.). Using reductive dissolution and transfer into degassed water, open-ended, water-filled nanotubes can be dispersed as individualized nanotubes in water–dimethyl sulfoxide mixtures, avoiding the use of sonication and surfactant. Closed nanotubes, however, aggregate immediately upon contact with water. Photoluminescence and absorption spectroscopy both point out a very high degree of individualization while retaining lengths of several microns. The resulting transparent conducting films are 1 order of magnitude more conductive than surfactant-based blanks at equal transmittance.
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