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Cristina Vallés

Bio: Cristina Vallés is an academic researcher from University of Manchester. The author has contributed to research in topics: Graphene & Oxide. The author has an hindex of 26, co-authored 51 publications receiving 2753 citations. Previous affiliations of Cristina Vallés include Centre national de la recherche scientifique & Spanish National Research Council.


Papers
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Journal ArticleDOI
TL;DR: Negatively charged graphene layers from a graphite intercalation compound spontaneously dissolve in N-methylpyrrolidone, yielding stable, air-sensitive, solutions of laterally extended atom-thick graphene sheets and ribbons with dimensions over tens of micrometers.
Abstract: Negatively charged graphene layers from a graphite intercalation compound spontaneously dissolve in N-methylpyrrolidone, without the need for any sonication, yielding stable, air-sensitive, solutions of laterally extended atom-thick graphene sheets and ribbons with dimensions over tens of micrometers. These can be deposited on a variety of substrates. Height measurements showing single-atom thickness were performed by STM, AFM, multiple beam interferometry, and optical imaging on Sarfus wafers, demonstrating deposits of graphene flakes and ribbons. AFM height measurements on mica give the actual height of graphene (ca. 0.4 nm).

456 citations

Journal ArticleDOI
01 Jun 2018
TL;DR: In this paper, the progress in graphene-polymer composites for electrical applications is discussed and the current optimal composites are presented, and the example of strain sensors is used to demonstrate their application.
Abstract: Electrically conductive composites comprising polymers and graphene are extremely versatile and have a wide range of potential applications. The conductivity of these composites depends on the choice of polymer matrix, the type of graphene filler, the processing methodology, and any post-production treatments. In this review, we discuss the progress in graphene-polymer composites for electrical applications. Graphene filler types are reviewed, the progress in modelling these composites is outlined, the current optimal composites are presented, and the example of strain sensors is used to demonstrate their application.

269 citations

Journal ArticleDOI
01 Mar 2012-Carbon
TL;DR: In this paper, the authors report the fabrication of flexible conductive graphene paper through a direct and gentle annealing process of graphene oxide paper, which leads to a significant removal of disruptive oxygen-containing functional groups, and to a considerable recovery of the sp2 network structure.

216 citations

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TL;DR: In this paper, a detailed study has been undertaken of the mechanisms of stress transfer in polymeric matrices with different values of Young's modulus, Em, reinforced by graphene nanoplatelets (GNPs).

205 citations

Journal ArticleDOI
TL;DR: In this paper, the authors show that the two-component model of graphene oxide (GO), composed of highly oxidized carbonaceous debris complexed to oxygen functionalized graphene sheets, is a generic feature of the synthesis of GO, independent of oxidant or protocol used.
Abstract: We show that the two-component model of graphene oxide (GO), that is, composed of highly oxidized carbonaceous debris complexed to oxygen functionalized graphene sheets, is a generic feature of the synthesis of GO, independent of oxidant or protocol used. The debris present, roughly one-third by mass, can be removed by a base wash. A number of techniques, including solid state NMR, demonstrate that the properties of the base-washed material are independent of the base used and that it contains similar functional groups to those present in the debris but at a lower concentration. Removal of the oxidation debris cleans the GO, revealing its true monolayer nature and in the process increases the C/O ratio (i.e., a deoxygenation). By contrast, treating GO with hydrazine both removes the debris and reduces (both deoxygenations) the graphene sheets.

193 citations


Cited by
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Journal ArticleDOI
TL;DR: Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability as discussed by the authors, and its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability.
Abstract: The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.

6,863 citations

Journal ArticleDOI
TL;DR: The use of colloidal suspensions to produce new materials composed of graphene and chemically modified graphene is reviewed, which is both versatile and scalable, and is adaptable to a wide variety of applications.
Abstract: Interest in graphene centres on its excellent mechanical, electrical, thermal and optical properties, its very high specific surface area, and our ability to influence these properties through chemical functionalization. There are a number of methods for generating graphene and chemically modified graphene from graphite and derivatives of graphite, each with different advantages and disadvantages. Here we review the use of colloidal suspensions to produce new materials composed of graphene and chemically modified graphene. This approach is both versatile and scalable, and is adaptable to a wide variety of applications.

6,178 citations

Journal ArticleDOI
15 Feb 2010-ACS Nano
TL;DR: The resultant N-graphene was demonstrated to act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction via a four-electron pathway in alkaline fuel cells.
Abstract: Nitrogen-doped graphene (N-graphene) was synthesized by chemical vapor deposition of methane in the presence of ammonia. The resultant N-graphene was demonstrated to act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction via a four-electron pathway in alkaline fuel cells. To the best of our knowledge, this is the first report on the use of graphene and its derivatives as metal-free catalysts for oxygen reduction. The important role of N-doping to oxygen reduction reaction (ORR) can be applied to various carbon materials for the development of other metal-free efficient ORR catalysts for fuel cell applications, even new catalytic materials for applications beyond fuel cells.

3,604 citations

Journal ArticleDOI
TL;DR: The status of graphene research is presented, which includes aspects related to synthesis, characterization, structure, and properties.
Abstract: Every few years, a new material with unique properties emerges and fascinates the scientific community, typical recent examples being high-temperature superconductors and carbon nanotubes. Graphene is the latest sensation with unusual properties, such as half-integer quantum Hall effect and ballistic electron transport. This two-dimensional material which is the parent of all graphitic carbon forms is strictly expected to comprise a single layer, but there is considerable interest in investigating two-layer and few-layer graphenes as well. Synthesis and characterization of graphenes pose challenges, but there has been considerable progress in the last year or so. Herein, we present the status of graphene research which includes aspects related to synthesis, characterization, structure, and properties.

3,513 citations

Journal ArticleDOI
TL;DR: A critical review of the synthesis methods for graphene and its derivatives as well as their properties and the advantages of graphene-based composites in applications such as the Li-ion batteries, supercapacitors, fuel cells, photovoltaic devices, photocatalysis, and Raman enhancement are described.
Abstract: Graphene has attracted tremendous research interest in recent years, owing to its exceptional properties. The scaled-up and reliable production of graphene derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO), offers a wide range of possibilities to synthesize graphene-based functional materials for various applications. This critical review presents and discusses the current development of graphene-based composites. After introduction of the synthesis methods for graphene and its derivatives as well as their properties, we focus on the description of various methods to synthesize graphene-based composites, especially those with functional polymers and inorganic nanostructures. Particular emphasis is placed on strategies for the optimization of composite properties. Lastly, the advantages of graphene-based composites in applications such as the Li-ion batteries, supercapacitors, fuel cells, photovoltaic devices, photocatalysis, as well as Raman enhancement are described (279 references).

3,340 citations