Nanostructured Polythiophene Hybrid Charge-Transfer Complexes

Este trabajo se centra en la síntesis de nuevos nanohíbridos dador-aceptor (D/A) de politiofeno solubles en medios acuosos y en la elucidación de la interacción electrónica entre las unidades D/A como en el funcionamiento de los nanohíbridos en forma de películas delgadas en aplicaciones optoelectrónicas.Utilizando técnicas de auto-ensamblaje in-situ de politiofeno en presencia de diferentes nanomateriales como son el óxido de grafeno, puntos cuánticos de semiconductores o láminas de dicalcogenuros de metales de transición se ha conseguido la formación de complejos de transferencia de carga, solubles en agua y con superiores propiedades electrónicas de relevancia para el desarrollo de dispositivos optoelectrónicos basados en películas delgadas <br /

Fluorescent polymeric carbon dots: from synthesis and elucidation of chemical struture towards photoactive hybrid materials

En este trabajo se cubren tres aspectos fundamentales de la investigación en el campo de los carbón dots (CDs). A través de detallados estudios estructurales, caracterización óptica y cálculos teóricos, la primera parte de la tesis consigue identificar las estructuras orgánicas y las fuerzas que producen la fluorescencia azul. En la segunda parte, se ha presentado un nuevo método para controlar la estructura y las propiedades químicas de nanopartículas poliméricas, ofreciendo una herramienta muy versátil para el diseño de materiales basados en CDs como sensores y vectores de fármacos. En la tercera y última parte de la tesis, a partir de los CDs y dicalcogenuros de metales de transición (MoS2 y WS2) se han preparado materiales híbridos, con vistas a su posible uso en aplicaciones de fotocatálisis y conversión de energía. <br /

Electroactive polymer-carbon nanotube composites: smart organic materials for optoelectronic applications

Los nanotubos de Carbono combinados con polímeros conductores intrínsecos contribuirán en un futuro al progreso en nanoelectrónica y al desarrollo de nuevos y mejores dispositivos electrónicos y optoelectrónicos. Este artículo resume nuestro trabajo en materiales compuestos polianilina-nanotubos de carbono altamente funcionales y procesables, y muestra la estrecha relación existente entre las interacciones polímeronanotubo y la funcionalidad y comportamiento en el procesado de los materiales obtenidos.Carbon nanotubes combined with intrinsically conducting polymers may contribute to further progress in nanoelectronics and to the development of improved electronic and optoelectronic devices. This article summarizes our work on highly functional and processable polyaniline-carbon nanotube composite materials. It also demonstrates the close relation between functionality and processing behavior and describes nanotube-polymer interactions

Nanotubos de carbono : estructura, propiedades y química

págs.: 139-193Capítulo incluido en el libro: Desarrollo y aplicaciones de materiales avanzados de carbón. Miguel Ángel Álvarez Merino, Francisco Carrasco Marín, Francisco José Maldonado Hódar (Editores). Sevilla: Univeridad Internacional de Andalucía, 2014. ISBN: 978-84-7993-247-3. Enlace: http://hdl.handle.net/10334

Revisiting graphene oxide chemistry via spatially-resolved electron energy loss spectroscopy

The type and distribution of oxygen functional groups in graphene oxide and reduced graphene oxide remain still a subject of great debate. Local analytic techniques are required to access the chemistry of these materials at a nanometric scale. Electron energy loss spectroscopy in a scanning transmission electron microscope can provide the suitable resolution, but GO and RGO are extremely sensitive to electron irradiation. In this work we employ a dedicated experimental set-up to reduce electron illumina- tion below damage limit. GO oxygen maps obtained at a few nanometres scale show separated domains with diferent oxidation levels. The C/O ratio varies from about 4:1 to 1:1, the latter corresponding to a complete functionalization of the graphene flakes. In RGO the residual oxygen concentrates mostly in regions few tens nanometres wide. Specific energy-loss near-edge structures are observed for diferent oxidation levels. By combining these findings with first principles simulations we propose a model for the highly oxidized domains where graphene is fully functionalized by hydroxyl groups forming a 2D-sp3 carbon network analogous to that of graphane.AT, AZ and OS acknowledge support from the Agence Nationale de la Recherche (ANR), program of future investment TEMPOS-CHROMATEM (No. ANR-10-EQPX-50). The work has also received funding from the European Union in Seventh Framework Programme (No. FP7/2007 -2013) under Grant Agreement No. n312483 (ESTEEM2). AMB and WKM are grateful for Financial support from the Spanish Ministry MINECO and the European Regional development Fund (project ENE2013-48816-C5-5-R) and from the Regional Government of Aragon and the European Social Fund (DGA-ESF-T66 Grupo Consolidado). The authors are grateful to P. Launois, S. Rouziere and C.P. Ewels for useful discussion.Peer reviewe

Carbon nanotube film electrodes with acrylic additives: Blocking electrochemical charge transfer reactions

Carbon nanotubes (CNTs) processed into conductive films by liquid phase deposition technologies reveal increasing interest as electrode components in electrochemical device platforms for sensing and energy storage applications. In this work we show that the addition of acrylic latex to water-based CNT inks not only favors the fabrication of stable and robust flexible electrodes on plastic substrates but, moreover, sensitively enables the control of their electrical and electrochemical transport properties. Importantly, within a given concentration range, the acrylic additive in the films, being used as working electrodes, effectively blocks undesired faradaic transfer reactions across the electrode–electrolyte interface while maintaining their capacitance response as probed in a three-electrode electrochemical device configuration. Our results suggest a valuable strategy to enhance the chemical stability of CNT film electrodes and to suppress non-specific parasitic electrochemical reactions of relevance to electroanalytical and energy storage applications

Oil-in-Water Pickering Emulsions Stabilized with Nanostructured Biopolymers: A Venue for Templating Bacterial Cellulose

Pickering emulsions (PEs) differ from conventional emulsions in the use of solid colloidal particles as stabilizing agents instead of traditional amphiphilic molecules. Nanostructured biopolymers (NBs) emerge as a promising alternative for PE stabilization owing to their remarkable biocompatibility, abundant availability, and low cost. To explore this potential, a study is herein presented, in which cellulose nanocrystals (CNCs), both type I and type II allomorphs, and chitin nanocrystals (ChNCs) were used for stabilizing oil-in-water PEs prepared by the use of ultrasound. Sunflower oil was selected as the oil phase as it offers the advantages of being edible, renewable, and inexpensive. By utilizing ζ-potential, static light diffraction, and visual observations, we determined the optimal oil/water ratio for each type of NB to obtain stable emulsions after 14 days. The optimized PEs were used to form bacterial nanocellulose composites through emulsion templating. To our knowledge, this study represents a pioneering work in exploiting oil-in-water PEs for this approach. Additionally, it entails the first utilization of nonmercerized type II CNCs as stabilizers for PEs, while also establishing a direct comparison among the most relevant NBs. The resulting composites exhibited a unique morphology, composed of larger pores compared to standard bacterial nanocellulose aerogels. These findings highlight the notable potential of NBs as stabilizers for PEs and their ability to generate green nanocomposites with tailored properties

Platelet-like catalyst design for high yield production of multi-walled carbon nanotubes by catalytic chemical vapour deposition

We investigated the effect of catalyst design on the synthesis of multi-walled carbon nanotubes (MWCNTs) by chemical vapor deposition (CVD). A set of highly active supported sol–gel Co–Mo/MgO and Ni–Mo/MgO catalysts was prepared systematically modifying the calcination temperature. First, the evolution of catalysts’ crystallographic phases and their morphology were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron (SEM) and transmission electron (TEM) microscopy. Second, the catalysts were used for the CVD growth of MWCNTs. The resulting materials were analysed by SEM and TEM, Raman and XRD to establish a relation between catalyst design and MWCNT yield. We show that our catalyst synthesis route leads to the formation of laminar non-porous catalyst systems, which at a calcination temperature of 800 °C stabilize in a crystallographic phase of MexMg1−xMoO4 (Me = Co or Ni). We give evidence that increased MWCNT yields of more than 3000 wt.% with respect to the catalysts are directly related to the aforementioned crystallographic phase. Finally, we propose a growth model based on the continuous exfoliation of platelet-like catalyst systems. This consistently explains the high catalytic activity towards MWCNT production using a non-porous catalyst. Our findings provide important insights for catalyst design strategies towards large-scale MWCNT production.Peer reviewe

Diseño de catalizadores laminares para la síntesis de nanotubos de carbono con altos rendimientos

La obtención de nanotubos de carbono CNT por el método de deposición catalítica en forma de vapor CCVD, está limitada por la falta de un modelo de crecimiento de CNT que pueda explicar satisfactoriamente los diversos resultados que se encuentran en la literatura. Las más recientes investigaciones en la síntesis de CNT se enfocan en la optimización de las condiciones de operación y el diseño del catalizador. Este trabajo enfatiza la importancia de la temperatura de calcinación para el diseño de catalizadores con una mayor actividad catalítica en la producción de nanotubos de carbono multicapa MWCNT. El proceso CCVD se realiza mediante la descomposición de metano a 1000ºC durante 30 min en una atmósfera CH4/H2 (97:3 v/v) en contacto con 50 mg de catalizador depositado sobre una navecilla de cerámica. Se emplearon 2 catalizadores compuestos Mx-Mg-Mo (Mx=Co,Ni) sintetizados por el método sol-gel. Se estableció una relación directa entre la temperatura de calcinación, las fases cristalográficas predominantes y los rendimientos de MWCNT obtenidos, empleando técnicas de DSC, XRD y Raman. Se obtuvieron rendimientos superiores a 3000 wt.% en presencia de las fases (Co/Ni)xMg1-xMoO4, las cuales se asocian con una buena dispersión del metal activo en la matriz soporte, lo que evita la desactivación del catalizador por sinterización masiva durante el proceso de nucleación. Se propuso un mecanismo de crecimiento de MWCNT empleando catalizadores laminares no porosos, que explica satisfactoriamente los altos rendimientos obtenidos en correspondencia con la morfología de los catalizadores y de los MWCNT observados por microscopía SEM y TEM