The exfoliation of graphite to give graphene dispersions in nonaqueous solvents is an important area with regards to scalable production of graphene in bulk quantities and its ultimate application in ...devices. Understanding the mechanisms governing the stability of these dispersions is therefore of both scientific interest and technological importance. Herein, we have used addition of an indifferent electrolyte to perturb few-layer graphene dispersions in a nonaqueous solvent (1,2-dichloroethane) as a way to probe the importance of interparticle electrostatic repulsions toward the overall dispersion stability. At a sufficient electrolyte concentration, complete sedimentation of the dispersions occurred over 24 h, and the relationship between dispersed graphene concentration and electrolyte concentration was consistent with a dispersion stabilized by electrostatic repulsions. We also found that an increased oxygen content in the graphite starting material produced dispersions of greater stability, indicating that the extent of oxidation is an important parameter in determining the extent of electrostatic stabilization in nonaqueous graphene dispersions.
Here, we evaluate the electrochemical performance of sparsely studied natural crystals of molybdenite and graphite, which have increasingly been used for fabrication of next generation monolayer ...molybdenum disulphide and graphene energy storage devices. Heterogeneous electron transfer kinetics of several redox mediators, including Fe(CN)6(3-/4-), Ru(NH3)6(3+/2+) and IrCl6(2-/3-) are determined using voltammetry in a micro-droplet cell. The kinetics on both materials are studied as a function of surface defectiveness, surface ageing, applied potential and illumination. We find that the basal planes of both natural MoS2 and graphite show significant electroactivity, but a large decrease in electron transfer kinetics is observed on atmosphere-aged surfaces in comparison to in situ freshly cleaved surfaces of both materials. This is attributed to surface oxidation and adsorption of airborne contaminants at the surface exposed to an ambient environment. In contrast to semimetallic graphite, the electrode kinetics on semiconducting MoS2 are strongly dependent on the surface illumination and applied potential. Furthermore, while visibly present defects/cracks do not significantly affect the response of graphite, the kinetics on MoS2 systematically accelerate with small increase in disorder. These findings have direct implications for use of MoS2 and graphene/graphite as electrode materials in electrochemistry-related applications.
The interfacial adsorption of single-walled carbon nanotubes and few-layer graphene flakes, prepared by solution phase exfoliation, is compared. Strong adsorption of carbon nanotubes was observed at ...the water/1,2-dichloroethane interface, while a weaker adsorption of the graphene dispersion was seen. Addition of electrolyte to the organic phase was found to have a strong effect on the adsorption of graphene. A simple surface energy model does not fully explain these observations, rather residual charges and their distribution appears to be the key factor behind this difference in adsorptive behaviour. Carbon nanomaterials adsorbed at the liquid-liquid interface can function as bipolar electrodes: a preliminary investigation of the oxidation of the 1,2-dichlorobenzene by metal-modified graphene particles is performed.
Table 21 - Summary of fatal exposures reported to TESS in 2004 The term "long-acting" is used throughout for all sustained-release, extended-release, delayed-release, or long-acting formulations. p ...Indicates prehospital (cardiac and/or respiratory) arrest; i, reported to poison center indirectly (by coroner, medical examiner, or from other source) after the fatality occurred; m, reported by medical examiner to poison center; C, chronic exposure; A, acute exposure; A/C, acute on chronic; derm, dermal; U, unknown; Ocu, ocular; Inh, inhalation; Ing, ingestion; Adv rxn, adverse reaction; Env, environmental; Int, intentional; Occ, occupational; Paren, parenteral; Ther err, therapeutic error; Unint gen, unintentional general. Table 22A - Demographic profile of exposure cases by generic category of substances and products: nonpharmaceuticals Table 22B - Demographic profile of exposure cases by generic category of substances and products: pharmaceuticals MAO indicates monoamine oxidase; SSRI, selective serotonin reuptake inhibitors; OTC, over-the-counter; ACE, angiotensin-converting enzyme; GHB, γ-hydroxybutyrate; LSD, lysergic acid diethylamide. 1 Introduction Toxic Exposure Surveillance System (TESS) data are compiled by the American Association of Poison Control Centers (AAPCC) on behalf of the US poison centers.
Recent progress in the field of liquid–liquid electrochemistry is reviewed, with a particular focus on two notable trends that have come to the fore over the last decade, the electrochemical ...properties of particle-modified interfaces and the related topic of electrocatalysis at the liquid–liquid interface.
Diving ectothermic vertebrates are an important component of many aquatic ecosystems, but the threat of climate warming is particularly salient to this group. Dive durations typically decrease as ...water temperatures rise; yet, we lack an understanding of whether this trend is apparent in all diving ectotherms and how this group will fare under climate warming. We compiled data from 27 studies on 20 ectothermic vertebrate species to quantify the effect of temperature on dive durations. Using meta-analytic approaches, we show that, on average, dive durations decreased by 11% with every 1°C increase in water temperature. Larger increases in temperature (e.g. +3°C versus +8-9°C) exerted stronger effects on dive durations. Although species that respire bimodally are projected to be more resilient to the effects of temperature on dive durations than purely aerial breathers, we found no significant difference between these groups. Body mass had a weak impact on mean dive durations, with smaller divers being impacted by temperature more strongly. Few studies have examined thermal phenotypic plasticity (
=4) in diving ectotherms, and all report limited plasticity. Average water temperatures in marine and freshwater habitats are projected to increase between 1.5 and 4°C in the next century, and our data suggest that this magnitude of warming could translate to substantial decreases in dive durations, by approximately 16-44%. Together, these data shed light on an overlooked threat to diving ectothermic vertebrates and suggest that time available for underwater activities, such as predator avoidance and foraging, may be shortened under future warming.
The electrochemical reactivity of single-walled carbon nanotube (SWCNT) films, assembled at a polarisable organic/water interface, has been probed using model redox species. Electrons generated by ...the oxidation of organic 1,1′-dimethylferrocene (DMFc) to DMFc
+
can be transferred through the assembled SWCNT layer and reduce aqueous ferricyanide (Fe(CN)
6
3−
) to ferrocyanide (Fe(CN)
6
4−
), with a doping interaction observed. Several electrochemical techniques, including cyclic voltammetry and electrochemical impedance spectroscopy (EIS), were employed to confirm that the model redox couples dope/charge the SWCNTs.
In situ
Raman spectro-electrochemistry was also applied to verify the charge transfer processes occurring at the assembled SWCNT films and confirm that the doping effect of the carbon nanotubes is initiated by electrochemical reactions. This doping interaction indicated that the adsorbed SWCNT films can act as a pseudo-capacitor, showing a high area-normalised capacitance. The deeper understanding of the electrochemical properties of SWCNTs, gained from this study, will help determine the performance of this material for practical applications.
The interaction of single-walled carbon nanotubes (SWCNTs), assembled at a polarisable organic/water interface, with model redox species, was probed using a combination of electrochemical techniques and
in situ
Raman spectro-electrochemistry.
The reduction of oxygen and protons at the interface between two immiscible electrolyte solutions (ITIES) has received a great deal of interest over the last decade, with various materials being used ...to catalyse these reactions. Probing the mechanisms through which these reactions proceed when using interfacial catalysts is important from both from the perspective of fundamental understanding and for catalyst optimisation. Herein, we have used interfacial‐assembled graphene to probe the importance of simple electron conductivity towards the catalysis of the oxygen reduction reaction (ORR) at the ITIES, and a bipolar setup to probe the homogeneous/heterogeneous nature of the ORR proceeding through interfacial graphene. We found that interfacial graphene provides a catalytic effect towards the reduction of oxygen at the ITIES, proceeding via the heterogeneous mechanism when using a strong reducing agent.
Face to face: The reduction of oxygen and protons at the interface between two immiscible electrolyte solutions (ITIES) has received a great deal of interest over the last decade, with various materials being used to catalyze these reactions. Here, interfacial‐assembled graphene, which functions as a bipolar electrode, is used to probe the importance of simple electron conductivity towards catalysis of the oxygen reduction reaction at the ITIES.
PDF
