Advanced synthesis of conductive polyaniline using laccase as biocatalyst

18 p.-7 fig.-1 tab.Polyaniline is a conductive polymer with distinctive optical and electrical properties. Its enzymatic synthesis is an environmentally friendly alternative to the use of harsh oxidants and extremely acidic conditions. 7D5L, a high-redox potential laccase developed in our lab, is the biocatalyst of choice for the synthesis of green polyaniline (emeraldine salt) due to its superior ability to oxidize aniline and kinetic stability at the required polymerization conditions (pH 3 and presence of anionic surfactants) as compared with other fungal laccases.Doses as low as 7.6 nM of 7D5L catalyze the polymerization of 15 mM aniline (in 24 h, room temperature, 7% yield) in the presence of different anionic surfactants used as doping templates to provide linear and water-soluble polymers. Aniline polymerization was monitored by the increase of the polaron absorption band at 800 nm (typical for emeraldine salt). Best polymerization results were obtained with 5 mM sodium dodecylbenzenesulfonate (SDBS) as template. At fixed conditions (15 mM aniline and 5mM SDBS), polymerization rates obtained with 7D5L were 2.5-fold the rates obtained with commercial Trametes villosa laccase. Moreover, polyaniline yield was notably boosted to 75% by rising 7D5L amount to 0.15 μM, obtaining 1g of green polyaniline in 1L-reaction volume. The green polymer obtained with the selected system (7D5L/SDBS) holds excellent electrochemical and electro-conductive properties displayed in water-dispersible nanofibers,which is advantageous for the nanomaterial to be readily cast into uniform films for different applications.This work was funded by INDOX (KBBE-2013-7-613549) European project and NOESIS (BIO2014-56388-R) Spanish national project.Peer reviewe

Injectable hybrid hydrogels physically crosslinked based on carrageenan and green graphene for tissue repair

Injectable and biocompatible novel hybrid hydrogels based on physically crosslinked natural biopolymers and green graphene for potential use in tissue engineering are reported. Kappa and iota carrageenan, locust bean gum and gelatin are used as biopolymeric matrix. The effect of green graphene content on the swelling behavior, mechanical properties and biocompatibility of the hybrid hydrogels is investigated. The hybrid hydrogels present a porous network with three-dimensionally interconnected microstructures, with lower pore size than that of the hydrogel without graphene. The addition of graphene into the biopolymeric network improves the stability and the mechanical properties of the hydrogels in phosphate buffer saline solution at 37 °C without noticeable change in the injectability. The mechanical properties of the hybrid hydrogels were enhanced by varying the dosage of graphene between 0.025 and 0.075 w/v%. In this range, the hybrid hydrogels preserve their integrity during mechanical test and recover the initial shape after removing the applied stress. Meanwhile, hybrid hydrogels with graphene content of up to 0.05 w/v% exhibit good biocompatibility for 3T3-L1 fibroblasts; the cells proliferate inside the gel structure and show higher spreading after 48 h. These injectable hybrid hydrogels with graphene have promising future as materials for tissue repair.The research leading to these results received funding from the Xunta de Galicia Government: program of consolidation and structuring competitive research units [grant number: ED431C 2019/17]. Y.F. is a ‘Sara Borrell’ researcher funded by Instituto de Salud Carlos III (ISCIII) and co-funded by Fondo Europeo de Desarrollo Regional (FEDER) [CD21/00042]. Thanks to Corfo 22CVID-206836, CIPA, ANID Regional, GORE BIO BIO, R17A10003, ACE210016, ACE210012. Funding for open access charge was provided by Universidade da Coruna/CISU

Chemistry below graphene: Decoupling epitaxial graphene from metals by potential-controlled electrochemical oxidation

While high-quality defect-free epitaxial graphene can be efficiently grown on metal substrates, strong interaction with the supporting metal quenches its outstanding properties. Thus, protocols to transfer graphene to insulating substrates are obligatory, and these often severely impair graphene properties by the introduction of structural or chemical defects. Here we describe a simple and easily scalable general methodology to structurally and electronically decouple epitaxial graphene from Pt(111) and Ir(111) metal surfaces. A multi-technique characterization combined with ab-initio calculations was employed to fully explain the different steps involved in the process. It was shown that, after a controlled electrochemical oxidation process, a single-atom thick metal-hydroxide layer intercalates below graphene, decoupling it from the metal substrate. This decoupling process occurs without disrupting the morphology and electronic properties of graphene. The results suggest that suitably optimized electrochemical treatments may provide effective alternatives to current transfer protocols for graphene and other 2D materials on diverse metal surfacesWe acknowledge funding from the Spanish MINECO (Grants MAT2014-54231-C4-1-P, MAT2014-54231-C4-4-P, MAT2013- 47898-C2-2-R and MAT2017-85089-C2-1-R), the EU via the ERCSynergy Program (Grant ERC-2013-SYG-610256 NANOCOSMOS), the innovation program under grant agreement No. 696656 (GrapheneCore1- Graphene-based disruptive technologies), the Comunidad Aut_onoma de Madrid (CAM) MAD2D-CM Program (S2013/ MIT-3007) and computing resources from CTI-CSIC. GOI acknowledges financial support from FCT, Ministry of Science and Technology, Portugal (Grant No. PTDC/CTM-NAN/121108/2010 and IF/ 01054/2015). EL acknowledges funding from Spanish “Consolider” project CSD2010-00024. JIM acknowledges the financial support by the “Ramón y Cajal” Program of MINECO (Grant RYC-2015-17730) and NANOCOSMO

Monolithic mesoporous graphitic composites as super capacitors : From Starbons to Starenes®

In this study, we present a new class of monolithic mesoporous carbonaceous materials produced via the carbonisation of a mesoporous starch aerogel highly doped with graphite. Consecutive ball milling, microwave assisted gelation and carbonization treatment produced a high concentration of dispersed graphite. These treatments induce a strong interaction between the graphite particles and the developing carbonaceous matrix, including partial delamination of graphite and the merging of the nanoflakes into the carbonaceous structure. From a combination of SEM and TEM it was found that the graphite particles reduced in size to 24 and 37 nm, matching the pore wall sizes of the produced materials. From XRD, ball milling and heating helped reduce the number of graphene layers by 40%, with presence within the porous starch matrix reducing this a further 13%. The high degree of graphite dispersion/incorporation induces a pronounced increase in conductivity, and excellent capacitance retention, in excess of 10 000 charge-discharge cycles, offering a cost efficient and sustainably produced alternative to activated carbon based EDLCs and importantly, the resultant monolithic structures mitigate the need for additional binders

Nanocompuestos poliméricos a partir de grafeno

10 páginas, 7 figuras.-- El Pdf es la versión de autor.[EN]: Graphene sheets have recently attracted considerable attention as a viable and inexpensive filler substitute for carbon nanotubes in nanocomposites, given the predicted excellent in-plane mechanical, structural, thermal, and electrical properties of graphite. Recent studies have shown that individual graphene sheets have extraordinary electronic transport properties. Exfoliation of graphite oxide represents an attractive route to functionalized graphene as versatile 2D carbon nanomaterials and components of a variety of polymer nanocomposites. This review presents a general approach for preparing polymer/graphene composites via complete exfoliation of graphite and molecular–level dispersion of individual, chemically modified graphene sheets within polymer hosts.[ES]: Las láminas de grafeno tienen, en la actualidad, un gran interés como posible carga barata que sustituya a los nanotubos de carbono en nanocompuestos, como consecuencia de las excelentes propiedades mecánicas, estructurales, térmicas y eléctricas del grafito. Además, estudios recientes demuestran que las láminas individuales de grafeno presentan extraordinarias propiedades de transporte electrónico. La exfoliación del óxido de grafito representa un método atractivo para conseguir grafeno funcionalizado como nanomaterial de carbono en 2D y preparar una amplia variedad de nanocompuestos poliméricos. Este trabajo ofrece una visión general de los métodos de preparación de nanocompuestos polímero/grafeno a partir de la exfoliación completa del grafito y la dispersión molecular de los grafenos individuales o grafenos modificados, dentro de la matriz polimérica.Este trabajo ha sido financiado por el Ministerio de Ciencia e Innovación MICINN (MAT2009-09335).Peer reviewe

Promising alternative routes for graphene production and functionalization

A decade after scientists from Manchester University isolated a single graphene sheet, the development of a method for mass-scale production of graphene of a similar quality to that obtained, and the implementation of a modular chemical route to incorporate graphene into multicomponent/ multifunctional materials are still fundamental challenges. The methods for graphene production and the synthetic procedures for its modification are limited to a handful of established methodologies, each with important limitations. In this manuscript a non-conventional electrochemical method for the preparation of high-quality graphene, and a recently reported general chemical approach for graphene functionalization through thiol-ene click reactions are highlighted. © the Partner Organisations 2014.Peer Reviewe

Procedimiento de obtención de materiales nanocompuestos de polímeros clorados y nanoestructuras de carbono

La presente invención proporciona procedimiento para la obtención un material nanocompuesto de polímero clorado unido covalentemente a nanoestructuras de carbono, y los sus usos de dicho material como refuerzo de nanocompuestos poliméricos.Peer reviewedConsejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic

Synthesis of sulfonated graphene/polyaniline composites with improved electroactivity

The sulfonation of graphene by coupling with the diazonium salts of sulfanilic (SA) acid and amino-4-hydroxy-2-naphthalenesulfonic (NSA) acid is studied. Coupling with the diazonium salt of NSA gives the highest degree of sulfonation. Composites of polyaniline (PANI) and sulfonated graphene (SG) are prepared by the polymerization of aniline in the presence of the SG. The materials have been characterized by Raman, Fourier transformed infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry. These materials are electrochemically active at pHs close to physiological pH due to the doping of PANI with the sulfonic groups in SG trapped in the polymer. Furthermore, good conductivity values are obtained. © 2011 Elsevier Ltd. All rights reserved.Peer Reviewe