Search

High-performance energy-storage devices are receiving great interest in sustainable terms as a required complement to renewable energy sources to level out the imbalances between supply and demand. Besides electrode optimization, a primary objective is also the judicious design of high-performance electrolytes combining novel ionic liquids (ILs) and mixtures of aqueous solvents capable of offering “à la carte” properties. Herein, it is described the stoichiometric addition of a zwitterion such as betaine (BET) to protic ILs (PILs) such as those formed between methane sulfonic acid (MSAH) or p-toluenesulfonic acid (PTSAH) with ethanolamine (EOA). This addition resulted in the formation of zwitterionic-based PILs (ZPILs) containing the original anion and cation as well as the zwitterion. The ZPILs prepared in this work ([EOAH]+[BET][MSA]− and [EOAH]+[BET][PTSA]−) were liquid at room temperature even though the original PILs ([EOAH]+[MSA]− and [EOAH]+[PTSA]−) were not. Moreover, ZPILs exhibited a wide electrochemical stability window, up to 3.7 V vs. Ag wire for [EOAH]+[BET][MSA]− and 4.0 V vs. Ag wire for [EOAH]+[BET][PTSA]− at room temperature, and a high miscibility with both water and aqueous co-solvent (WcS) mixtures. In particular, “WcS-in-ZPIL” mixtures of [EOAH]+[BET][MSA]− in 2 H2O/ACN/DMSO provided specific capacitances of approximately 83 F g−1 at current densities of 1 A g−1, and capacity retentions of approximately 90 % after 6000 cycles when operating at a voltage of 2.0 V and a current density of 4 A g−1.

For many years, the performance of Li-ion batteries (LIBs) and supercapacitors (SCs) has relied mainly on two factors, (1) the optimization of electrodes composition and/or structure and (2) the selection of salts or ionic liquids (ILs) matching well with the compositional and/or structural features of electrodes. Solvents included in electrolyte composition have been typically seen as a mere medium where the electrochemically active salts or ILs are dissolved or mixed. More recently, attention has also been paid to specific issues, such as flammability, toxicity, electrical conductivity and/or electrochemical stability window (ESW). Recent reports describing water-in-salt (WIS), solvent-in-salt (SIS) and bi-solvent-in-salt (BSIS) electrolytes demonstrated that solvent molecules may indeed play a more active role in the achievement of high-performance LIBs and SCs. This work accomplished the design of a tri-solvent-in-salt (TSIS) electrolyte where every solvent contributed (with an IL such as EMIMBF4) to the formation of an electrochemically active hydrogen bond (HB) complex structure. Raman and NMR spectroscopies, as well as molecular dynamic (MD) simulations helped elucidate the ratio among all compounds (e.g., solvents and IL) in the HB complex structure that best works as an electrolyte. For instance, one could start from the eutectic mixture of H2O and dimethylsulfoxide (DMSO) in a 2 to 1 molar ratio and then add acetonitrile (CH3CN) in different molar ratios. Thus, the 2H2O:DMSO mixture offers low melting point and low flammability, and CH3CN provides an improvement of the rate capability to the resulting electrolyte. As compared to other electrolytes, the TSIS electrolyte composed of 1.5EMIMBF4:2H2O:DMSO:3.5CH3CN (5.8 m, TSIS-5.8) was cost efficient and exhibited self-extinction rates as low as 40 s g-1. Moreover, SCs operating with TSIS-5.8, at -70 °C and up to 2.7 V provided energy densities of ca. 49 and 18 Wh kg-1 at, respectively, power densities of 10,000 and 17,000 W kg-1, a capacitance retention of ca. 82% after 15,000 cycles at 4 A g-1 and a self-discharge as low as 22%.

[EN] Knitted iron phthalocyanine-based porous polymer networks (K-FePcs) were prepared in a single step using solvent-knitting strategies with commercial iron phthalocyanine as a building monomer. The incorporation of different aryl comonomers (biphenyl and 1,2,4,5-tetraphenylbenzene) to FePc allowed quantitative yields, high porosities, and excellent ORR activity. The reversible Fe(III)/Fe(II) redox potential of FeN4 centers of the knitted polymer networks in N2-saturated electrolyte solution (i.e., ∼0.8 V vs RHE) were shown as good descriptors of their ORR activity. K-FePc2Ph presented the highest amount of FeN4 active sites and an adequate degree of steric hindrance to maintain the isolation between catalytically active sites. Moreover, it displayed comparable current density limits and superior mass activity and half-wave potential (i.e., 0.88 V vs RHE) than those of 20% Pt/C benchmark catalyst, while keeping higher stability toward methanol oxidation. K-FePc2Ph can be an interesting alternative to Pt-based ORR electrocatalysts., The authors acknowledge MINECO of Spain MAT2017-82288-C2-2-P and RTI2018-097728-B-I00 projects for financial support. A.V.-G. thanks Ministerio de Educación y Formación Profesional for FPU17/03463. L.Z.G. also acknowledges the Chinese Scholarship Council for a PhD research fellowship (CSC no. 201608330266).

Deep eutectic solvents (DESs) resulting from the right combination between a hydrogen-bond donor (HBD) and a hydrogen-bond acceptor (HBA) are becoming quite popular in number of applications. More recently, natural DESs (NADESs) containing sugars, natural organic acids, and amino acids as HBDs and ChCl as HBA have received great attention because of their further environmental sustainability as compared to regular DESs. Within this context, mixing water in controlled amounts has been widely accepted as a simple and practical way of altering DES chemical and thermodynamic properties, with viscosity and conductivity experiencing the most significant changes. However, the number of papers describing eutectic mixtures with water as the only HBD is scarce and basically none has been done in fundamental terms. Herein, we investigated mixtures composed of water as the only HBD and ChCl as the HBA using differential scanning calorimetry (DSC) as well as

Neural tissue engineering approaches show increasing promise for the treatment of neural diseases including spinal cord injury, for which an efficient therapy is still missing. Encouraged by both positive findings on the interaction of carbon nanomaterials such as graphene with neural components and the necessity of more efficient guidance structures for neural repair, we herein study the potential of reduced graphene oxide (rGO) microfibers as substrates for neural growth in the injured central neural tissue. Compact, bendable, and conductive fibers are obtained. When coated with neural adhesive molecules (poly-L-lysine and N-cadherin), these microfibers behave as supportive substrates of highly interconnected cultures composed of neurons and glial cells for up to 21 days. Synaptic contacts close to rGO are identified. Interestingly, the colonization by meningeal fibroblasts is dramatically hindered by N-cadherin coating. Finally, in vivo studies reveal the feasible implantation of these rGO microfibers as a guidance platform in the injured rat spinal cord, without evident signs of subacute local toxicity. These positive findings boost further investigation at longer implantation times to prove the utility of these substrates as components of advanced therapies for enhancing repair in the damaged central neural tissue including the injured spinal cord., This work was supported by the Instituto de Salud Carlos III-MINECO-FEDER (CP13/00060), the Ministerio de Economía y Competitividad, and the Fondo Europeo de Desarrollo Regional (MAT2016-78857-R and MAT2015-68639-R, MINECO/FEDER, UE). It was also partially funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 737116.

The elimination of small amounts of water from alcohols is by no means a trivial issue in many practical applications like, for instance, the dehumidification of biocombustibles. The use of carbonaceous materials as sorbents has been far less explored than that of other materials because their hydrophobic character has typically limited their water uptake. Herein, we designed a synthetic process based on the use of eutectic mixtures that allowed the homogeneous dispersion of graphene oxide (GO) in the liquid containing the carbon precursor, e.g., furfuryl alcohol. Thus, after polymerization and a subsequent carbonization process, we were able to obtain porous carbon–GO composites where the combination of pore diameter and surface hydrophilicity provided a remarkable capacity for water uptake but extremely low methanol and ethanol uptake along the entire range of relative pressures evaluated in this work. Both the neat water uptake and the uptake difference between water and either methanol or ethanol of our carbon–GO composites were similar or eventually better than the uptake previously reported for other materials, also exhibiting preferential water-to-alcohol adsorption, e.g., porous coordination polymers, metal–organic frameworks, polyoxometalates, and covalent two-dimensional nanosheets embedded in a polymer matrix. Moreover, water versus alcohol uptake was particularly remarkable at low partial pressures in our carbon–GO composites. This work was supported by MINECO/FEDER (Project Numbers MAT2015-68639-R, MAT2016-80285-P, and RTI2018-097728-B-I00). L.Z.G. acknowledges the Chinese Scholarship Council for a PhD research fellowship (CSC No. 201608330266). C.C.-C. acknowledges UA for a research contract.

Deep eutectic solvents (DESs) and dilutions thereof (mainly in H2O but also in many other non-aqueous solvents and co-solvent mixtures) have recently attracted great attention. It is well known that DES dilutions exhibit deviations from ideality. Interestingly, the treatment of DES as a mixture of two components or a pseudo-component is by no means trivial when determining deviations in density and, mainly, in viscosity. Herein, we studied aqueous dilutions of one of the most widely studied DES, this is, that composed of choline chloride and urea in a 1:2 molar ratio (e.g., ChCl2U). Using density and viscosity data reported in previous works, we calculated the excess molar volumes (VE) and excess viscosities (ln ηE) considering ChCl2U as either a mixture of two components or a pseudo-component, that is, taking the DES molecular weight as MChCl2U = fChClMChCl + fUMU = 86.58 g mol−1 (with fChCl = 1/3 and fU = 2/3) or as M*ChCl2U = MChCl + 2 MU = 259.74 g mol−1. We found that neither the sign of VE and VE* nor their evolution with temperature was influenced by the use of either MChCl2U or M*ChCl2U, and only the absolute magnitude of the deviation and the DES content (in wt. %) at which the minimum appears exhibited some differences. However, ln ηE and ln ηE* exhibited opposite signs, negative and positive, respectively. The odd achievement of negative ln ηE in aqueous dilutions of ChCl2U characterized by the formation of HB networks suggest the treatment of ChCl2U as a pseudo-component as more appropriate. Moreover, the role played by the presence of U in the evolution of ln ηE* with temperature was also discussed.

Deep eutectic solvents (DESs) and dilutions thereof are currently gaining increased interest in sustainable processes. DES dilutions are particularly interesting in the so-called “solvent-in-DES” regime where the intriguing features of DESs remain (coming from hydrogen bonding among the components) and some typical drawbacks (e.g., high viscosity, low electrical conductivity, etc.) are mitigated. Actually, DES dilutions may exhibit excellent performances (more so than the original neat DESs) in certain applications. Knowing about the tools that allow predicting (and eventually extending) the dilution range of the “solvent-in-DES” regime is obviously of interest. With this aim, we herein studied two sets of DES dilutions. In the first set, we used the DES composed of choline chloride (ChCl) and urea (U) and its dilutions in H2O, methanol (MeOH) and ethanol (EtOH). In the second set, we studied two DESs composed of ethylene glycol (EG) and either tetraethylammonium bromide (TEABr) or tetrabutylammonium bromide (TBABr), and their dilutions in H2O. Data coming from DSC, 1H NMR spectroscopy, and Brillouin spectroscopy revealed how the dilution range of the “solvent-in-DES” regime in ChClU dilutions in H2O, MeOH and EtOH increased in the order H2O

[EN] In the present contribution, we report how through the use of metal-organic frameworks (MOFs) composed of addressable combinations of up to four different metal elements it is possible to program the composition of multimetal oxides, which are not attainable by other synthetic methodologies. Thus, due to the ability to distribute multiple metal cations at specific locations in the MOF secondary building units it is possible to code and transfer selected metal ratios to multimetal oxides with novel, desired compositions through a simple calcination process. The demonstration of an enhancement in the electrocatalytic activity of new oxides by preadjusting the metal ratios is here reported for the oxygen reduction reaction, for which activity values comparable to commercial Pt/C catalysts are reached, while showing long stability and methanol tolerance., We acknowledge Institut Laue-Langevin and Spanish Initiatives on Neutron Scattering (ILL-SpINS) for beamtime at instrument D1B and G. Cuello for assistance during data acquisition. The Paul Scherrer Institute is also acknowledged for beamtime at instrument HRPT and V. Pomjakhusin for assistance during data acquisition. We thank E. Rodríguez-Cañas and Isidoro Poveda from the Servicio Interdepartamental de Investigación at Universidad Autónoma de Madrid for valuable support with SEM images and EDS analyses and FE-SEM image acquisition, respectively. We acknowledge E. Urones for the TEM images and TEM-EDS analysis acquisition at Centro Nacional de Microscopía Electrónica. Funding: Work at Instituto de Ciencia de Materiales de Madrid−Consejo Superior de Investigaciones Cientifícas (CSIC) has been supported by the Spanish Ministry for Science, Innovation and Universities (MINECO), and FEDER funds: Projects MAT2016-78465-R, MAT2015-68639-R, and CTQ2017-87262-R. F.G. and N.L.-S. acknowledge financial support from MINECO (Ramón y Cajal program and FPI research contract, respectively).

We have investigated the ring-opening polymerization (ROP) of ε-caprolactone using mixtures of methanesulfonic acid and the guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene as the catalyst. Our interest in these mixtures is based on the capability of both acids and bases to behave as bifunctional catalysts; the former by the combined action of acidic hydrogens and basic oxygens, and the latter by the hydrogen-bond acceptor and donor features of, respectively, a basic nitrogen center and an ortho-hydrogen atom. We found that these compounds are capable of forming eutectic mixtures at a certain molar ratio. Upon the use of these mixtures – e.g. with molar ratios near to the eutectic one – as catalysts, neither further solvents nor initiators were required to carry out the ROP of ε-caprolactone. The resulting polycaprolactones (PCLs) were highly crystalline (more than 87%) and exhibited an excellent capability to support the growth of murine L929 fibroblasts. We consider that the preparation of biocompatible PCLs at physiological temperatures and in the absence of reagents other than the monomer and the catalyst offers an interesting alternative to both the self-cross-linked oligomers/macromers of acrylate-based PCL-derivatives and the pH/temperature-sensitive PCL copolymers used to date as injectable biomaterials., This work was supported by MINECO under grants MAT2012-34811 and MAT2011-25329, and by the European Union Seventh Framework Programme (FP7/2007-2013/NMP) under grant agreement #263289 (Green Nano Mesh). M.C.S. is grateful to the Instituto de Salud Carlos III-MINECO for a Miguel Servet type I contract.

Ionic liquids (ILs) are being widely used in many diverse areas of social interest, including catalysis, electrochemistry, etc. However, issues related to hygroscopicity of many ILs and the toxic and/or nonbiodegradable features of some of them limit their practical use. Developing materials capable of IL recovery from aqueous media and dehydration, thus allowing their recycling and subsequent reutilization, in a single and efficient process still poses a major challenge. Herein, electrically conductive aerogels composed of carbon nanofibers (CNFs) with remarkable superhydrophobic features are prepared. CNF-based 3D aerogels are prepared through a cryogenic process, so called ice-segregation-induced self-assembly (ISISA) consisting of the unidirectional immersion of an aqueous chitosan (CHI) solution also containing CNFs in suspension into a liquid nitrogen bath, and subsequent freeze-drying. The CNF-based 3D aerogels prove effective for absorption of ILs from aqueous biphasic systems and recovery with quite low water contents just through a single process of filtration. Moreover, the electrical conductivity of CNF-based 3D aerogels is particularly interesting to treat highly viscous ILs because the Joule effect allows not only shortening of the absorption process but also enhancement of the flux rate when operating in flow-through conditions.

Since the seminal work by Pekala in 1989, polycondensation of phenol derivatives with formaldehyde and subsequent carbonization has been one of the most used procedures for preparation of porous carbons. Nitrogen-doped carbons have also been obtained through this approach only by using nitrogen-rich precursors. The list of the most commonly used nitrogen-rich precursors includes melamine, urea, 3-hydroxypyridine, 3-aminophenol and lysine, and despite a few of them can be used in a single fashion, they typically need to be co-condensed with a second precursor. Nitrogen-rich precursors different from these ones have been used rarely because their molecular structure does not favor the nucleophilic substitution through which polycondensation takes place-e.g. p-nitrophenol. This is by no means a trivial issue because, on the one hand, these precursors cannot form a cross-linked network by themselves, and on the other hand, it may be difficult to encompass their different reaction kinetics when combined with more reactive precursors. This is also the situation for other precursors with an amphiphilic molecular structure that could be of interest to control the structure of the resulting porous carbons-e.g. 4-hexylresorcinol. In this work, we have used deep eutectic solvents composed of resorcinol, 4-hexylresorcinol, p-nitrophenol and choline chloride for the preparation of nitrogen-doped carbon monoliths with a hierarchical porous structure. Carbon conversions ranged from 64 to 50%-depending on the carbonization temperature-despite using three different carbon precursors for co-condensation and two of them were uncommon. The nitrogen content ranged from 4.9 to 3.0 wt%, revealing an excellent nitrogen-doping efficiency for p-nitrophenol when used in the form of DES. Finally, the use of 4-hexylresorcinol controlled the formation of a narrow microporosity that, in combination with the nitrogen functionalities, provided a remarkable CO2-sorption capability to the resulting carbons., This work was supported by the MINECO (MAT2012-34811 and MAT2011-25329). NLS acknowledges the MINECO for a FPI contract.

The deep eutectic solvents (DESs) based on the mixtures of a variety of ammonium salts and hydrogen bond donors containing acrylic acids and acrylamides are capable of sustaining frontal polymerization (FP). The selection of ammonium salt affects the reactivity and allows FP at relatively low temperature but with full conversion. Also, full conversion allows us to use these polymers for biomedical applications (e.g., drug delivery systems) as the unreactive ammonium salts can be released from the resulting polymer without by-products. We call these components >active fillers,> which can be ammonium salts with biological or pharmaceutical importance. For instance, we prepared poly(acrylic acid) loaded with lidocaine hydrochloride (a common anesthetic), the release of which was found to occur in a controlled fashion. The ammonium salts also create a sufficiently high viscosity to suppress buoyancy-driven convection without additional materials. The DES here described played an all-in-one role, providing the monomer, the active filler, and the polymerization medium for FPs. © 2013 Wiley Periodicals, Inc., Funded by: CONACYT. Grant Number: 181678.

This work describes a simple synthetic route to induce chitosan (CHI) gelation by the in situ formation of gold nanoparticles (AuNPs). AuNPs were obtained by thermal treatment (e.g., 40 and 80 °C) of CHI aqueous solutions containing HAuCl(4) and in the absence of further reducing agents. The CHI hydrogels resulting after AuNP formation were submitted to unidirectional freezing and subsequent freeze-drying via ISISA (ice-segregation-induced self-assembly) process for the preparation of CHI scaffolds. The study of AuNP-CHI scaffolds by SEM and confocal fluorescence microscopy revealed a morphological structure characteristic of the hydrogel nature of the samples subjected to the ISISA process. Interestingly, not only the morphology but also the dissolution and swelling degree of the resulting CHI scaffolds were strongly influenced by the strength of the hydrogels obtained by the in situ formation of AuNP. We have also studied the catalytic activity AuNP-CHI scaffolds in the reduction of p-nitrophenol. The negligible dissolution and low swelling degree obtained in certain AuNP-CHI scaffolds allowed them to be used for more than four cycles with full preservation of the reaction kinetics.

Deep eutectic solvents are a new class of ionic liquids obtained via the complexion of quaternary ammonium salts with hydrogen-bond donors (such as acids, amines, and alcohols, among others). The charge delocalization that occurs through hydrogen bonding between the halide anion with the hydrogen-donor moiety is responsible for the decrease in the freezing point of the mixture, relative to the melting points of the individual components. We have recently reported on the use of deep eutectic solvents as suitable solvents, to carry out the polycondensation of resorcinol−formaldehyde. [Chem. Mater. 2010, 22, 2711−2719.] Herein, we describe the synthesis of deep eutectic solvents (DESs) based on resorcinol, the use of which as both carbonaceous precursors and structure-directing agents allowed the preparation of hierarchical porous (bimodal, with micropores and mesopores) carbon monoliths via formaldehyde polycondensation and subsequent carbonization. The performance of resorcinol-based DESs as carbonaceous p...

Deep eutectic solvents (DESs) composed of resorcinol, either 2-cyanophenol or 4-cyanophenol, and choline chloride were used for the synthesis of hierarchical nitrogen-doped carbon molecular sieves. Carbons were obtained with high conversions by polycondensation of resorcinol and either 2-cyanophenol or 4-cyanophenol with formaldehyde, and subsequent carbonization at 800 °C in nitrogen atmosphere. The nitrogen content was ca. 2.4 wt%, revealing an excellent nitrogen-doping efficiency for cyanophenol derivatives when used in the form of DES. The use of either 2-cyanophenol or 4-cyanophenol modified the contribution of quaternary-Nvalley groups in the resulting carbons, being larger in carbons coming from 4-cyanophenol than in those coming from 2-cyanophenol. The hierarchical porous structure was composed of micro-, meso- and macropores, and the diameter distribution of mesopores was also related to the use of either 2-cyanophenol or 4-cyanophenol. These structural and compositional differences were critical for the use of the resulting hierarchical nitrogen-doped carbons as efficient metal-free electrocatalysts. In particular, the carbons coming 4-cyanophenol proved particularly effective in the direct reduction of oxygen to OH− (H2O in acidic solution) through a four-electron (4e−) process with high catalytic activity and selectivity, and longer stability and stronger tolerance to crossover effects than platinum-based electrocatalysts.

Eutectic mixtures of the monohydrated form of p-toluenesulfonic acid (pTsOH·HO) and triethyl phosphate (TEP) in a 1: 1 molar ratio were used as the medium to disperse previously functionalized multiwalled carbon nanotubes (MWCNTs), and to catalyse the polycondensation of furfuryl alcohol. Hierarchically structured P-doped carbon-CNT composites were obtained after carbonization. The high surface area, the phosphate functionalization, the hierarchical structure and the good electrical conductivity exhibited by these composites provided remarkable metrics when they were used as electrodes in a supercapacitor cell, with energy densities of around 22.6 W h kg and power densities of up to 10 kW kg for operational voltages of up to 1.5 V. This performance surpasses any performance previously reported for electrodes weighing (at least) 10 mg per cm of current collector and using an aqueous electrolyte. Actually, the supercapacitor cell built up with these electrodes provided enough neat energy to turn an IR LED of 30 mW on and emit light over a certain period., This study was supported by MINECO (MAT2012-34811). J. P. and N. L.-S. acknowledge MINECO for their respective FPI contracts.

Poly(octanediol-co-citrate) elastomers containing high loading of lidocaine were synthesized at temperatures below 100 °C by means of using deep eutectic mixtures of 1,8-octanediol and lidocaine. The preservation of lidocaine integrity resulted in high-capacity drug-eluting elastomers.

This chapter discusses the use of deep eutectic solvent-assisted syntheses which allow the preparation of both chemically and structurally modified carbon monoliths suitable as electrodes in supercapacitor cells. Either carbons or carbon–carbon nanocomposites exhibiting a hierarchical structure and a tailored composition (either nitrogen or phosphorus doped) could be attained by the use of different mixtures of deep eutectic solvents (DESs). Carbons prepared from DESs are also suitable for CO2 adsorption and CO2–N2 and/or CO2–CH4 separation processes. These features, besides the low-cost character of our carbons, open interesting perspectives for their application as sorbents in separation technologies for CO2 low-pressure post-combustion processes and natural gas upgrading.

A template‐free approach based on the use of eutectic mixtures composed of 2‐hydroxymethylthiophene and furfuryl alcohol has been designed for the preparation of hierarchical sulfur‐doped carbons (SPCs) in monolithic form. The temperature used for carbonization, for example, 600, 800, or 900 °C, determined most of the physicochemical properties of the resulting SPCs. Thus, the surface area increased from below 400 to up 775 m2 g−1, along with the carbonization temperature, whereas the sulfur content decreased from approximately 15 to 5 wt %. The oxygen reduction reaction performance in samples carbonized at 900 °C was good, with the four‐electron‐transfer reaction prevailing over the two‐electron‐transfer one. Interestingly, the methanol tolerance and stability of these SPCs were also remarkable, with less than 5 % current decrease immediately after methanol addition, whereas, in terms of stability, the current decrease was below 8 % after 20000 s. This performance was in the range of that found not only for other SPCs, but also for many nitrogen‐doped and even some dual‐doped (S and N) ones., This work was supported by MINECO (MAT2012‐34811 and MAT2011‐25329). N.L.S. acknowledges MINECO for a FPI contract.

The use of deep eutectic solvents (DESs) that act as all-in-one solvent-template-reactant systems offers an interesting green alternative to conventional syntheses in materials science. This Review aims to provide a comprehensive overview to emphasize the similarities and discrepancies between DES-assisted and conventional syntheses and rationalize certain green features that are common for the three DES-assisted syntheses described herein: one case of radical polymerization and two cases of polycondensations. For instance, DESs contain the precursor itself and some additional components that either provide certain functionality (e.g., drug delivery and controlled release, or electrical conductivity) to the resulting materials or direct their formation with a particular structure (e.g., hierarchical-type). Moreover, DESs provide a reaction medium, so polymerizations are ultimately carried out in a solventless fashion. This means that DES-assisted syntheses match green chemistry principles 2 and 5 because of the economy of reagents and solvents, whereas the functionality incorporated by the second component allows the need for any post-synthesis derivatization to be minimized or even fully avoided (principle 8). DESs also provide new precursors that favor more efficient polymerization (principle 6) by decreasing the energy input required for reaction progress. Finally, the use of mild reaction conditions in combination with the compositional versatility of DESs, which allows low-toxic components to be selected, is also of interest from the viewpoint of green chemistry because it opens up the way to design biocompatible and/or eco-friendly synthetic methods (principle 3). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., MINECO. Grant Numbers: MAT2009-10214, MAT2011-25329, MAT2012-34811.

Deep Eutectic Solvents (DESs) formed between Acrylic Acid (AA) and Choline Chloride (CCl) exhibit certain properties of ionic liquids (e.g. high viscosity) that make them suitable for frontal polymerization (FP). The use of DESs not only as a monomer but also as the solvent prevents the use of additional solvents (i.e. typically of organic nature) and offers a green tool for the synthesis of functional composites. We have recently explored this approach for the preparation of poly(acrylic acid) (PAA) and poly(methacrylic acid). In this work, we have taken advantage of the outstanding capability of DESs to solubilize and/or disperse a number of substances to incorporate-in a homogeneous fashion-carbon nanotubes (in this particular case, N-doped MWCNT-CNxMWCNTs) in the polymerizable DES. Interestingly, CNxMWCNTs also played the role of an inert filler in FP. The resulting PAA-CNxMWCNT composites exhibited some distinct features as compared to previous PAA also obtained via DES-assisted FP. For instance, PAA-CNxMWCNT composites can undergo swelling depending on the pH, as bare PAA. However, the presence of CNxMWCNTs allows the formation of a macroporous structure after submission to a freeze-drying process, the achievement of which was not possible in bare PAA. The combination of structural (e.g. macroporosity) and functional (e.g. stimuli responsive) properties exhibited by these materials besides an eventually high biocompatibility-coming from the green character of the DES-assisted synthesis-should make the resulting macroporous PAA-CNxMWCNT composites excellent candidates for their future application as biomaterials. © 2013 The Royal Society of Chemistry., F. dM. acknowledges support from Grant reference numbers MAT2009-10214, MAT2011-25329,MAT2012-34811. P. Santiago acknowledges financial support from DGAPA-UNAM, through grant IN113411.

Bacterial infection related to the implantation of medical devices represents a serious clinical complication, with dramatic consequences for many patients. In past decades, numerous attempts have been made to develop materials with antibacterial and/or antifouling properties by the incorporation of antibiotic and/or antiseptic compounds. In this context, deep eutectic solvents (DESs) are acquiring increasing interest not only as efficient carriers of active principle ingredients (APIs) but also as assistant platforms for the synthesis of a wide repertoire of polymer-related materials. Herein, we have successfully prepared biodegradable poly(octanediol-co-citrate) polyesters with acquired antibacterial properties by the DES-assisted incorporation of quaternary ammonium or phosphonium salts into the polymer network. In the resulting polymers, the presence of these salts (i.e., choline chloride, tetraethylammonium bromide, hexadecyltrimethylammonium bromide, and methyltriphenylphosphonium bromide) inhibits bacterial growth in the early postimplantation steps, as tested in cultures of Escherichia coli on solid agar plates. Later, positive polymer cytocompatibility is expected to support cell colonization, as anticipated from in vitro preliminary studies with L929 fibroblasts. Finally, the attractive elastic properties of these polyesters permit matching those of soft tissues such as skin. For all of these reasons, we envisage the utility of some of these antibacterial, biocompatible, and biodegradable polyesters as potential candidates for the preparation of antimicrobial wound dressings. These results further emphasize the enormous versatility of DES-assisted synthesis for the incorporation, in the synthesis step, of a wide palette of APIs into polymeric networks suitable for biomedical applications. © 2013 American Chemical Society., M.C.S. is greatly indebted to MINECO for a Juan de la Cierva fellowship. M. T. Portolés (Department of Biochemistry and Molecular Biology I, Universidad Complutense de Madrid) is acknowledged for generous supplying L929 fibroblasts. This work was supported by MINECO (grant reference numbers MAT2009-10214, MAT2011-25329, MAT2012-34811, and BFU2012-32797).

The stability of hen's egg white lysozyme in different choline chloride-based pseudo-concentrated and neat deep eutectic solvents (DESs) has been studied by means of intrinsic fluorescence and CD spectroscopy. Thermal unfolding experiments carried out in non-diluted urea:choline chloride and glycerol:choline chloride eutectic solvents (UCCl-DES and GCCl-DES, respectively) showed the accumulation at certain temperatures of discrete, partially folded intermediates that displayed a high content of secondary structure and a disrupted tertiary structure. Reversibility of the unfolding process was incomplete in these circumstances, with the urea-based DES showing higher protein structure destabilization upon thermal treatment. On the other hand, aqueous dilution of the eutectic mixtures allowed the recovery of a reversible, two-state denaturation process. Lysozyme activity was also affected in neat and pseudo-concentrated GCCl-DES, with an increasing recovery of activity upon aqueous dilution, and full restoration after DES removal through extensive dialysis. These results suggest that protein interactions at room temperature are reversible and depend on the DES components and on the aqueous content of the original DES dilution. © 2013 the Owner Societies., This work was supported by grants MAT2009-10214, MAT2012-34811, MAT2008-05670 and BFU2010-17824 from the Spanish Ministry of Economy and Competitiveness. R. Esquembre acknowledges a predoctoral fellowship (BES-2006-12514) from MINECO. F. del Monte acknowledges a travel grant (PA1003268) from CSIC.

Microwave irradiation combined with mild heating was demonstrated as a suitable synthetic method for the preparation of NiCo2O4 nanowires and NiCo2O4-graphene oxide nanocomposites. In both cases, the synthesis was carried out in just a few minutes, at relatively low temperatures and with a certain economy of reagents. In the particular case of the nanocomposites, NiCo2O4 was deposited in form of not only nanowires, but also ultrafine nanoparticles on the surface of graphene oxide sheets due to the preferred activation of these sheets under microwave irradiation. The nanocomposites exhibited a superior performance to NiCo 2O4 nanowires as electrodes in pseudocapacitors with capacitance retentions of nearly 735 F g-1 at current densities of up to 33 A g-1. © 2013 The Royal Society of Chemistry.

Ionic liquids and deep eutectic solvents (a new class of ionic liquids obtained by complexation of quaternary ammonium salts with hydrogen bond donors such as acids, amines, and alcohols among others) have been recently used as solvents and even as precursors in the synthesis of carbonaceous materials. The use of long-alkyl-chain derivatives of ionic liquids that, playing the role of structure directing agents, were capable of designing the mesoporous structure of the resulting carbons is of particular interest. Meanwhile, deep eutectic solvents proved efficient in tailoring the structure comprised between large mesopores and small macropores, but the control over the smaller ones (e.g. small mesopores and micropores) is still a challenge as compared to ILs. Herein, we have used deep eutectic solvents composed of resorcinol, 4-hexylresorcinol and tetraethylammonium bromide for the synthesis of carbon monoliths with a tailor-made narrow microporosity. Behaving as molecular sieves, these carbons exhibited not only good capacities for CO2 adsorption (up to 3 mmol g−1) but also an outstanding – especially at low pressures – CO2–CH4 selectivity., This work was supported by MINECO (MAT2009‐10214 and MAT2011‐25329). DC acknowledges MINECO for a JdelaC research contract. JP acknowledges MINECO for a FPI fellowship. COA and JBP thank the financial support of FICYT (EQUIP08‐36, file num. 04010208000281).

The immobilization of more than one single substance within the structure of a biocompatible polymer provides multifunctional biomaterials with attractive and enhanced properties. In the context of bone tissue engineering, it could be of great interest to synthesize a biomaterial that simultaneously contains amorphous calcium phosphate (ACP), to favor calcium and phosphate precipitation and promote osteogenesis, and an antibiotic such as ciprofloxacin (CFX) that can, eventually, avoid infections resulting after surgical scaffold implantation. However, the co-immobilization of multiple substances is by no means a trivial issue because of the enhanced number of interactions that can take place. One of the main issues is controlling not only the diverse solid forms that individual substances can eventually adopt, but also the forces responsible for the self-organization of the individual components. The latter determines whether phase-separated structures or conjugated architectures are obtained and, consequently, may dramatically affect their functionality. Herein, we have observed-by SEM, TEM, and solid-state NMR-that enzymatically-assisted coprecipitation of ACP and CFX resulted in phase-separated structures. Thus, CFX crystals showed identical morphology to that obtained in the absence of ACP, but the size was smaller. Neither the size nor the morphology of ACP exhibited significant differences whether precipitated with or without CFX, but, in the former case, ACP was stabilized over a wider range of pH and temperature. Finally, by using this methodology and the ice segregation induced self-assembly process (ISISA), we have successfully co-immobilized ACP and CFX in chitosan-based scaffolds. Interestingly, the presence of ACP exerted significant control on the CFX release from these materials.

Deep eutectic solvents (DESs) have been used in the synthesis of nitrogen-doped carbons exhibiting a hierarchical porous structure. The CO2 sorption capacity of these solid sorbents was extraordinary because of their relatively high nitrogen content and their bimodal porous structure where micropores provide high surface areas (ca. 700 m2 g−1) and macropores provide accessibility to such a surface. DESs were composed of resorcinol, 3-hydroxypyridine and choline chloride in 2 : 2 : 1 and 1 : 1 : 1 molar ratios. Polycondensation of resorcinol and 3-hydroxypyridine (with formaldehyde) promoted DES segregation in a spinodal-like decomposition process by the formation of a polymer rich phase and a depleted polymer phase. Thus, DESs played a multiple role in the synthetic process; the liquid medium that ensured reagents homogenization, the structure-directing agent that is responsible for the achievement of the hierarchical structure, and the source of carbon and nitrogen of the solid sorbent obtained after carbonization. Interestingly, the homogeneous incorporation of nitrogen at the solution stage of the synthetic process (rather than by post-treatment of the preformed carbon) allowed the achievement of significant nitrogen contents even in carbons obtained at relatively high temperatures (e.g. 8–12 at% for 600 °C and ca. 5 at% for 800 °C). It is worth noting that, despite thermal treatments at high temperatures tend to decrease the nitrogen content, the high surface area of the solid sorbents obtained at 800 °C contributed to a significant enhancement of CO2 capture while providing superior selectivity, recyclability and stability.