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The theory developed in 1922 by Wolfgang Ostwald and Ramón de Izaguirre for adsorption from solution is revisited one hundred years later, with a main focus on its impact and repercussions. A concise historical account is initiated with an examination of the circumstances under which that work was generated. After providing some biographic data about the authors' backgrounds at the time they developed it, a concise description of the so-called Ostwald-de Izaguirre theory is presented. This is followed by an assessment of its impact as a whole in the first decades after it was produced. Starting from about 1960, interest was focused on two separate outcomes from the theory: (i) the first classification of adsorption isotherms ever proposed, and (ii) an equation (Ostwald-de Izaguirre equation) that describes adsorption by solids of binary mixtures of miscible liquids and allows separating the contributions from both components of the solution. Although still in occasional use today, the isotherm classification made by Ostwald and de Izaguirre is of almost exclusively historical interest, having been displaced by Giles' classification. Unlike this, the Ostwald-de Izaguirre equation is still used and, since it derives from a simple mass balance, there is general agreement that no assumptions were made that limit its use. Thus, it seems that there is nothing to prevent the applicability of this equation in the future., Competing Interests: Declaration of Competing Interest I, Juan M. D. Tascón, corresponding (and only) author of manuscript “Impact and repercussions of the Ostwald-de Izaguirre theory for adsorption from liquid mixtures: A 100-year perspective”, that I am submitting for posible publication in Advances in Colloid and Interface Science, declare that I have no financial of personal relationships with other people or organizations that could bias this work. I have no conflicts of interest to declare., (Copyright © 2023. Published by Elsevier B.V.)

Phosphate-functionalized carbon-based nanomaterials have attracted significant attention in recent years owing to their outstanding behavior in electrochemical energy-storage devices. In this work, we report a simple approach to obtain phosphate-functionalized graphene (PFG) via anodic exfoliation of graphite at room temperature with a high yield. The graphene nanosheets were obtained via anodic exfoliation of graphite foil using aqueous solutions of H 3 PO 4 or Na 3 PO 4 in the dual role of phosphate sources and electrolytes, and the underlying exfoliation/functionalization mechanisms are proposed. The effect of electrolyte concentration was studied, as low concentrations do not lead to a favorable graphite exfoliation and high concentrations produce fast graphite expansion but poor layer-by-layer delamination. The optimal concentrations are 0.25 M H 3 PO 4 and 0.05 M Na 3 PO 4 , which also exhibited the highest phosphorus contents of 2.2 and 1.4 at. %, respectively. Furthermore, when PFG-acid at 0.25 M and PFG-salt at 0.05 M were tested as an electrode material for capacitive energy storage in a three-electrode cell, they achieved a competitive performance of ∼375 F/g (540 F/cm 3 ) and 356 F/g (500 F/cm 3 ), respectively. Finally, devices made up of symmetric electrode cells obtained using PFG-acid at 0.25 M possess energy and power densities up to 17.6 Wh·kg -1 (25.3 Wh·L -1 ) and 10,200 W/kg; meanwhile, PFG-salt at 0.05 M achieved values of 14.9 Wh·kg -1 (21.3 Wh·L -1 ) and 9400 W/kg, with 98 and 99% of capacitance retention after 10,000 cycles, respectively. The methodology proposed here also promotes a circular-synthesis process to successfully achieve a more sustainable and greener energy-storage device.

The molecular functionalization of two-dimensional MoS 2 is of practical relevance with a view to, for example, facilitating its liquid-phase processing or enhancing its performance in target applications. While derivatization of metallic 1T-phase MoS 2 nanosheets has been relatively well studied, progress involving their thermodynamically stable, 2H-phase counterpart has been more limited due to the lower chemical reactivity of the latter. Here, we report a simple electrolytic strategy to functionalize 2H-phase MoS 2 nanosheets with molecular groups derived from organoiodides. Upon cathodic treatment of a pre-expanded MoS 2 crystal in an electrolyte containing the organoiodide, water-dispersible nanosheets derivatized with acetic acid or aniline moieties (∼0.10 molecular groups inserted per surface sulfur atom) were obtained. Analysis of the functionalization process indicated it to be enabled by the external supply of electrons from the cathodic potential, although they could also be sourced from a proper reducing agent, as well as by the presence of intrinsic defects in the 2H-phase MoS 2 lattice (e.g., sulfur vacancies), where the molecular groups can bind. The acetic acid-functionalized nanosheets were tested as a non-noble metal-based catalyst for nitroarene and organic dye reduction, which is of practical utility in environmental remediation and chemical synthesis, and exhibited a markedly enhanced activity, surpassing that of other (1T- or 2H-phase) MoS 2 materials and most non-noble metal catalysts previously reported for this application. The reduction kinetics (reaction order) was seen to correlate with the net electric charge of the nitroarene/dye molecules, which was ascribed to the distinct abilities of the latter to diffuse to the catalyst surface. The functionalized MoS 2 catalyst also worked efficiently at realistic (i.e., high) reactant concentrations, as well as with binary and ternary mixtures of the reactants, and could be immobilized on a polymeric scaffold to expedite its manipulation and reuse.

It has been shown in previous works that the interfacial adhesion in PPTA- and PBO-epoxy composites can be improved by modifying the surface properties of these high-performance fibres upon exposure to non-oxidative plasma treatments. In this work, the effects developed on both types of polymer surface were examined as a function of treatment gas nature (He or N 2 ) and exposure time (one or four minutes) using inverse gas chromatography at infinite dilution (IGC). From the adsorption of n-alkanes, it has been proved that non-oxidative plasma treatments led to energetically heterogeneous surfaces in the case of PPTA, and to low-energy surfaces in the case of PBO. Nevertheless, it was proved with the 1-min plasma treatments (either under helium or under nitrogen) that chemical reactivity was enhanced on the PBO surface. Such a behaviour was ascribed to the presence of low-molecular weight oxidized materials. The mechanisms involved in surface activation of PPTA were not equivalent under He or N 2 exposure. Nitrogen plasma exposure led to a PPTA surface that is chemically reactive as a result of polarity enhancement. Helium plasma-treated PPTA surface was characterized by the presence of branched arrangements that intensified the number of chemical contacts onto reactive sites. Finally, for both fibre sets, if the purpose is to enhance the chemical surface reactivity, it makes no sense to increase the plasma exposure time from 1 to 4 min., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Integrated approaches that expedite the production and processing of graphene into useful structures and devices, particularly through simple and environmentally friendly strategies, are highly desirable in the efforts to implement this two-dimensional material in state-of-the-art electrochemical energy storage technologies. Here, we introduce natural nucleotides (e.g., adenosine monophosphate) as bifunctional agents for the electrochemical exfoliation and dispersion of graphene nanosheets in water. Acting both as exfoliating electrolytes and colloidal stabilizers, these biomolecules facilitated access to aqueous graphene bio-inks that could be readily processed into aerogels and inkjet-printed interdigitated patterns. Na-O 2 batteries assembled with the graphene-derived aerogels as the cathode and a glyme-based electrolyte exhibited a full discharge capacity of ∼3.8 mAh cm -2 at a current density of 0.2 mA cm -2 . Moreover, shallow cycling experiments (0.5 mAh cm -2 ) boasted a capacity retention of 94% after 50 cycles, which outperformed the cycle life of prior graphene-based cathodes for this type of battery. The positive effect of the nucleotide-adsorbed nanosheets on the battery performance is discussed and related to the presence of the phosphate group in these biomolecules. Microsupercapacitors made from the interdigitated graphene patterns as the electrodes also displayed a competitive performance, affording areal and volumetric energy densities of 0.03 μWh cm -2 and 1.2 mWh cm -3 at power densities of 0.003 mW cm -2 and 0.1 W cm -3 , respectively. Taken together, by offering a green and straightforward route to different types of functional graphene-based materials, the present results are expected to ease the development of novel energy storage technologies that exploit the attractions of graphene.

The production of MoS 2 nanosheets by electrochemical exfoliation routes holds great promise as a means to access this two-dimensional material in large quantities for different practical applications. However, the use of electrolytes based on synthetic organic salts and solvents, as well as issues related to the unwanted oxidation and/or phase transformation of the exfoliated nanosheets, constitute significant obstacles that hinder the industrial adoption of the electrochemical approach. Here, we introduce a safe and sustainable method for the cathodic delamination of MoS 2 that makes use of aqueous solutions of very simple and widely available salts, mainly KCl, as the electrolyte. Combined with an appropriate biomolecule-based solvent transfer protocol, such an electrolytic exfoliation route is shown to afford colloidally dispersed, oxide-free, and phase-preserved MoS 2 nanosheets of high structural quality in considerable yields. The mechanisms behind the efficient aqueous delamination of the bulk MoS 2 cathode are also discussed and rationalized on the basis of the penetration of hydrated cations from the electrolyte between its layers and the immediate reduction of the accompanying water molecules. An asymmetric supercapacitor assembled with a cathodic MoS 2 nanosheet-single walled carbon nanotube hybrid as the positive electrode and activated carbon as the negative electrode delivered energy densities (e.g., 26 W h kg -1 at 750 W kg -1 in 6 M KOH) that were competitive with those of other MoS 2 -based asymmetric devices. When used as a catalyst for the reduction of nitroarenes, the present cathodically exfoliated nanosheets exhibited one of the highest activities reported so far with MoS 2 nanostructures, the origin of which is accounted for as well. Overall, by facilitating access to this two-dimensional material through a particularly simple, efficient, and cost-effective technique, these results should expedite the practical implementation of MoS 2 nanosheets in energy storage, catalysis, and beyond.

Two-dimensional Co 3 O 4 nanosheets have emerged as attractive materials for use in a number of relevant technological applications. To exhibit a competitive performance in such uses, however, their structure needs to be activated, which is frequently accomplished via post-synthesis reduction strategies that introduce oxygen vacancies and increase the number of active Co(II) sites. Here, we investigate a direct route for the synthesis of activated Co 3 O 4 nanosheets that avoids reduction post-treatments, yielding materials with a high potential towards energy- and environment-related applications. The synthesis relied on an interim amorphous cobalt oxide material with nanosheet morphology, which upon calcination afforded Co 3 O 4 nanosheets having Co(II) sites in quantities similar to those usually found for Co 3 O 4 nanostructures activated by reduction post-treatments. When tested as electrodes for charge storage, the nanosheets demonstrated a competitive behavior in terms of both capacity and rate capability, e.g., a gravimetric capacity of ∼293 mAh g -1 at 1 A g -1 with 57% retention at 60 A g -1 was measured for nanosheets calcined at 350 °C. The materials were shown to be efficient catalysts for the reduction of nitroarenes (4-nitrophenol and 4-nitroaniline), outperforming other Co 3 O 4 nanostructures, as well as effective adsorbents for the removal of organic dyes (methyl orange, methylene blue) from water., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Porous carbons derived from metal-organic frameworks (MOFs) are promising materials for a number of energy- and environment-related applications, but their almost exclusively microporous texture can be an obstacle to their performance in practical uses. Here, we introduce a novel strategy for the generation of very uniform mesoporosity in a prototypical MOF, namely, zeolitic imidazolate framework-8 (ZIF-8). The process, referred to as "nanopore lithography", makes use of graphene oxide (GO) nanosheets enclosing ZIF-8 particles as masks or templates for the transfer of mesoporous texture to the latter. Upon controlled carbonization and activation, nanopores created in the GO envelope serve as selective entry points for localized etching of carbonized ZIF-8, so that such nanopores are replicated in the MOF-derived carbonaceous structure. The resulting porous carbons are dominated by uniform mesopores ∼3-4 nm in width and possess specific surface areas of ∼1300-1400 m 2 g -1 . Furthermore, we investigate and discuss the specific experimental conditions that afford the mesopore-templating action of the GO nanosheets. Electrochemical characterization revealed an improved capacitance as well as a faster, more reversible charge/discharge kinetics for the ZIF-8-derived porous carbons obtained through nanopore lithography, relative to those for their counterparts with standard activation (no GO templating), thus indicating the potential practical advantage of the present approach in capacitive energy storage applications.

Graphene and graphene-based materials have shown great promise in many technological applications, but their large-scale production and processing by simple and cost-effective means still constitute significant issues in the path of their widespread implementation. Here, we investigate a straightforward method for the preparation of a ready-to-use and low oxygen content graphene material that is based on electrochemical (anodic) delamination of graphite in aqueous medium with sodium halides as the electrolyte. Contrary to previous conflicting reports on the ability of halide anions to act as efficient exfoliating electrolytes in electrochemical graphene exfoliation, we show that proper choice of both graphite electrode (e.g., graphite foil) and sodium halide concentration readily leads to the generation of large quantities of single-/few-layer graphene nanosheets possessing a degree of oxidation (O/C ratio down to ∼0.06) lower than that typical of anodically exfoliated graphenes obtained with commonly used electrolytes. The halide anions are thought to play a role in mitigating the oxidation of the graphene lattice during exfoliation, which is also discussed and rationalized. The as-exfoliated graphene materials exhibited a three-dimensional morphology that was suitable for their practical use without the need to resort to any kind of postproduction processing. When tested as dye adsorbents, they outperformed many previously reported graphene-based materials (e.g., they adsorbed ∼920 mg g -1 for methyl orange) and were useful sorbents for oils and nonpolar organic solvents. Supercapacitor cells assembled directly from the as-exfoliated products delivered energy and power density values (up to 15.3 Wh kg -1 and 3220 W kg -1 , respectively) competitive with those of many other graphene-based devices but with the additional advantage of extreme simplicity of preparation.

Chemically exfoliated MoS 2 (ce-MoS 2 ) has emerged in recent years as an attractive two-dimensional material for use in relevant technological applications, but fully exploiting its potential and versatility will most probably require the deployment of appropriate chemical modification strategies. Here, we demonstrate that extensive covalent functionalization of ce-MoS 2 nanosheets with acetic acid groups (∼0.4 groups grafted per MoS 2 unit) based on the organoiodide chemistry brings a number of benefits in terms of their processability and functionality. Specifically, the acetic acid-functionalized nanosheets were furnished with long-term (>6 months) colloidal stability in aqueous medium at relatively high concentrations, exhibited a markedly improved temporal retention of catalytic activity toward the reduction of nitroarenes, and could be more effectively coupled with silver nanoparticles to form hybrid nanostructures. Furthermore, in vitro cell proliferation tests carried out with murine fibroblasts suggested that the chemical derivatization had a positive effect on the biocompatibility of ce-MoS 2 . A hydrothermal annealing procedure was also implemented to promote the structural conversion of the functionalized nanosheets from the 1T phase that was induced during the chemical exfoliation step to the original 2H phase of the starting bulk material, while retaining at the same time the aqueous colloidal stability afforded by the presence of the acetic acid groups. Overall, by highlighting the benefits of this type of chemical derivatization, the present work should contribute to strengthen the position of ce-MoS 2 as a two-dimensional material of significant practical utility.

Nitrogen-doped ordered mesoporous carbons were synthesized by chemical vapor deposition, using acetonitrile as carbon and nitrogen source and SBA-15 as mesoporous silica template. Their porous texture, structural order and surface chemistry were studied as a function of the experimental conditions (acetonitrile stream concentration and deposition time). A non-doped ordered mesoporous carbon was also prepared by the same procedure using propylene as carbon source. Methylene blue, methyl orange and fuchsin acid were selected as probe molecules to investigate the dye adsorption behavior on the ordered mesoporous carbons. Both N-doped and non-doped ordered mesoporous carbons adsorbed large amounts of these three dyes demonstrating the importance of mesoporosity, especially for the adsorption of larger dyes (e.g. fuchsin acid). The presence of nitrogen functional groups was detrimental for the adsorption of the basic dye (methylene blue). On the other hand, the nitrogen functionalities improved the adsorption kinetics for both acid and basic dyes, and the N-doped samples achieved 100% of their maximum adsorption capacities in less than 15 min., (Copyright © 2015 Elsevier Inc. All rights reserved.)