Rebeca Marcilla

Fiber‐Embedded Electrolyte‐Gated Field‐Effect Transistors for e‐Textiles

Electrolyte-gate organic field-effect transistors embedded at the junction of textile microfibers are demonstrated. The fiber transistor operates below I V and delivers large current densities. The ...

Woven Electrochemical Transistors on Silk Fibers

Woven electrochemical transistors on silk fibers from the silkworm Bombyx mori are demonstrated. This is achieved with carefully chosen electrolyte chemistry: electrically conducting silk fibers ar ...

Facile Synthesis of Supramolecular Ionic Polymers That Combine Unique Rheological, Ionic Conductivity, and Self‐Healing Properties

A new family of supramolecular ionic polymers is synthesized by a simple method using (di-/tri-)carboxylic acids and (di-/tri-)alkyl amines. These polymers are formed by carboxylate and ammonium molecules that are weakly bonded together by a combination of ionic and hydrogen bonds, becoming solid at room temperature. The supramolecular ionic polymers show a sharp rheological transition from a viscoelastic gel to a viscous liquid between 30 and 80 °C. This sharp viscosity decrease is responsible for an unprecedented jump in ionic conductivity of four orders of magnitude in that temperature range. As a potential application, this chemistry can be used to develop polymeric materials with self-healing properties, since it combines properties from supramolecular polymers and ionomers into the same material.

Irreversible Thermochromic Behavior in Gold and Silver Nanorod/Polymeric Ionic Liquid Nanocomposite Films

The novel application of gold and silver nanorods as irreversible thermochromic dyes in polymeric ionic liquid (PIL) nanocomposites is proposed here. These materials have been synthesized by anion exchange of an imidazolium-based PIL in a solution that also contained gold nanorods. This resulted in the entrapment of the nanoobjects within a solid polymer precipitate. In this article, the effect of the temperature was studied in relation to the change of shape and, consequently, color of the gold or silver nanorods within the films. For the nanocomposites studied here, a maximum of two visual thermochromic transitions was observed for gold nanorods and up to three transitions were observed for silver nanorods.

A new approach to hydrophobic and water-resistant poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) films using ionic liquids

An effective strategy is presented to produce hydrophobic and water-resistant poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films by replacing the cations associated with the sulfonate polyanion by large organic cations. Addition of specific ionic liquids (ILs) bearing large cations to the commercial PEDOT:PSS aqueous dispersion resulted in the exchange of the proton of PSS by the long hydrophobic cation of the ILs. This exchange made PEDOT:PSS hydrophobic, provoking the precipitation of the polymer in water. Recovered polymers could be dispersed in different organic solvents, preferably polar solvents such as DMF and DMSO. Electrical conductivity of the modified PEDOT:PSS films remained similar (5–8 S cm−1) to that of the commercial PEDOT:PSS but the water resistance was strongly enhanced. A strong dependence of the hydrophobic behaviour of PEDOT:PSS on the nature of the counterion was observed. Thus, the water contact angle could be tuned from 48° in the case of commercial PEDOT:PSS up to 100° for the modified PEDOT:PSS.

Nanostructured porous wires of iron cobaltite: novel positive electrode for high-performance hybrid energy storage devices

The demand for more efficient energy storage systems stimulates research efforts to seek and develop new energy materials with promising properties. In this regard, binary metal oxides have attracted great attention due to their better electrochemical performance as compared to their single oxide analogues. Herein, nanostructured porous wires of FeCo2O4 were grown on nickel foam via a facile hydrothermal route and employed as binder/additive-free electrodes to investigate the electrochemical behavior of FeCo2O4 as electrode materials for supercapacitors. The FeCo2O4 sample exhibits a high specific capacitance of 407 F g−1 at a scan rate of 10 mV s−1 in the initial cycling. After cycling for 2000 cycles, electro-activation of the material results in subsequent increase in capacitance up to 610 F g−1, showing promising characteristics of this material for energy storage. The performance of the prepared FeCo2O4 sample is found to be much better than that of the corresponding single oxides. Furthermore, porous nanostructured FeCo2O4//AC asymmetric supercapacitors were assembled and could achieve a high energy density of 23 W h kg−1 and a maximum power density of 3780 W kg−1.

Vanadium nitride@N-doped carbon nanocomposites: tuning of pore structure and particle size through salt templating and its influence on supercapacitance in ionic liquid media

The facile one-step synthesis of composites of highly porous carbons with functional metal nitride nanoparticles with tunable surface area, pore size, pore volume and nanoparticle size is presented using simple salts as porogens. Vanadium nitride (VN) nanoparticles in high surface area nitrogen-doped carbons are made by a simple heat-treatment of mixtures consisting of a vanadium precursor (VOCl3 or NH4VO3), the ionic liquid 1-ethyl-3-methyl-imidazolium dicyanamide (Emim-dca) as solvent and the nitrogen/carbon source, and salts, i.e. cesium or zinc acetate, as porogens. The synthesis takes advantage of a homogeneous starting solution, while in situ pore generation is obtained through demixing in later stages of the reaction. As compared to other templates such as silica, the salt is easily removed with water. Furthermore, the composite properties can conveniently be controlled by the variation of the salt nature and composition of the precursor mixture. Cesium acetate as a porogen at low concentrations results in microporous materials with small VN nanoparticles with a surface area of around 1000 m2 g−1, while increasing salt amounts promote small mesopores with bigger nanoparticles and surface areas of up to 2400 m2 g−1. The utilization of zinc acetate enables the synthesis of entirely mesoporous composites with very small vanadium nitride nanoparticles and surface areas of 800 m2 g−1. Mixtures of these two salt porogens give access to independently tunable surface area, pore size, pore volume and particle size. Comparative electrochemical testing in two ionic liquid (IL) electrolytes quantifies the accessibility of the surface area in two systematic sample series and indicates optimized surface access even for large electrolytes. A variation of ion radius in similar IL-systems quantifies the accessibility of surface in the different hybrid materials. Optimal energy density of the composites in supercapacitor electrodes can only be realized in a fine balance of charge density and electronic/ionic conductivity, which is here realized by fine-tuning the structural parameters.

Role of textural properties and surface functionalities of selected carbons on the electrochemical behaviour of ionic liquid based-supercapacitors

In the present study, five different activated carbons are used as active electrode materials in Ionic Liquid based-Supercapacitors (IL-SCs). Selection of carbons was made according to their different textural and surface properties and includes microporous, microporous–mesoporous and mesoporous carbons with specific surface areas (SDFT) ranging from 1400 to 2200 m2 g−1 and pore lengths (Lo) ranging from 0.7 to 2.8 nm. These carbons are used to build IL-SCs using the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) as the electrolyte. IL-SCs are electrochemically characterized by electrochemical impedance spectroscopy (EIS) and by galvanostatic charge/discharge (C/D) methods at 25 °C and at 60 °C. The effect of increasing the temperature and the voltage window on electrochemical performance is analysed. The performance of IL-SCs in terms of specific capacitance (Cs) and specific energy (Ereal) strongly increased with temperature and with maximum voltage (Vmax) reaching values as high as 245 F g−1 and 58 Wh kg−1 at 60 °C and 3.5 V. The influence of both textural properties and surface chemistry of the carbons on the performance of IL-SCs is analysed in detail.

Tuning the Properties of Functional Pyrrolidinium Polymers by (Co)polymerization of Diallyldimethylammonium Ionic Liquids

The synthesis and polymerization of novel diallyldimethylammonium ionic liquid monomers is described. A free-radical polymerization follows a ring-closing cyclopolymerization mechanism similar to the one observed previously for diallyldimethylammonium halides that leads to pyrrolidinium functional polymers. As previously observed in other families of polymeric ionic liquids, their physico-chemical properties are seriously affected by the nature of the counter-anion. As an example, the thermal stability increases following the trend SCN(-)  < 

Electrochemical reduction of O2 in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid containing Zn2+ cations: deposition of non-polar oriented ZnO nanocrystalline films

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