scispace - formally typeset
Search or ask a question
Author

Luca Ortolani

Bio: Luca Ortolani is an academic researcher from National Research Council. The author has contributed to research in topics: Graphene & Graphene oxide paper. The author has an hindex of 26, co-authored 87 publications receiving 2287 citations. Previous affiliations of Luca Ortolani include University of Toulouse & Max Planck Society.


Papers
More filters
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

DOI
Claudia Backes1, Claudia Backes2, Amr M. Abdelkader3, Concepción Alonso4, Amandine Andrieux-Ledier5, Raul Arenal6, Raul Arenal7, Jon Azpeitia6, Nilanthy Balakrishnan8, Luca Banszerus9, Julien Barjon5, Ruben Bartali10, Sebastiano Bellani11, Claire Berger12, Claire Berger13, Reinhard Berger14, M.M. Bernal Ortega15, Carlo Bernard16, Peter H. Beton8, André Beyer17, Alberto Bianco18, Peter Bøggild19, Francesco Bonaccorso11, Gabriela Borin Barin20, Cristina Botas, Rebeca A. Bueno6, Daniel Carriazo21, Andres Castellanos-Gomez6, Meganne Christian, Artur Ciesielski18, Tymoteusz Ciuk, Matthew T. Cole, Jonathan N. Coleman2, Camilla Coletti11, Luigi Crema10, Huanyao Cun16, Daniela Dasler22, Domenico De Fazio3, Noel Díez, Simon Drieschner23, Georg S. Duesberg24, Roman Fasel20, Roman Fasel25, Xinliang Feng14, Alberto Fina15, Stiven Forti11, Costas Galiotis26, Costas Galiotis27, Giovanni Garberoglio28, Jorge M. Garcia6, Jose A. Garrido, Marco Gibertini29, Armin Gölzhäuser17, Julio Gómez, Thomas Greber16, Frank Hauke22, Adrian Hemmi16, Irene Hernández-Rodríguez6, Andreas Hirsch22, Stephen A. Hodge3, Yves Huttel6, Peter Uhd Jepsen19, I. Jimenez6, Ute Kaiser30, Tommi Kaplas31, HoKwon Kim29, Andras Kis29, Konstantinos Papagelis32, Konstantinos Papagelis27, Kostas Kostarelos33, Aleksandra Krajewska34, Kangho Lee24, Changfeng Li35, Harri Lipsanen35, Andrea Liscio, Martin R. Lohe14, Annick Loiseau5, Lucia Lombardi3, María Francisca López6, Oliver Martin22, Cristina Martín36, Lidia Martínez6, José A. Martín-Gago6, José I. Martínez6, Nicola Marzari29, Alvaro Mayoral7, Alvaro Mayoral37, John B. McManus2, Manuela Melucci, Javier Méndez6, Cesar Merino, Pablo Merino6, Andreas Meyer22, Elisa Miniussi16, Vaidotas Miseikis11, Neeraj Mishra11, Vittorio Morandi, Carmen Munuera6, Roberto Muñoz6, Hugo Nolan2, Luca Ortolani, A. K. Ott3, A. K. Ott38, Irene Palacio6, Vincenzo Palermo39, John Parthenios27, Iwona Pasternak40, Amalia Patanè8, Maurizio Prato41, Maurizio Prato21, Henri Prevost5, Vladimir Prudkovskiy13, Nicola M. Pugno42, Nicola M. Pugno43, Nicola M. Pugno44, Teófilo Rojo45, Antonio Rossi11, Pascal Ruffieux20, Paolo Samorì18, Léonard Schué5, Eki J. Setijadi10, Thomas Seyller46, Giorgio Speranza10, Christoph Stampfer9, I. Stenger5, Wlodek Strupinski40, Yuri Svirko31, Simone Taioli28, Simone Taioli47, Kenneth B. K. Teo, Matteo Testi10, Flavia Tomarchio3, Mauro Tortello15, Emanuele Treossi, Andrey Turchanin48, Ester Vázquez36, Elvira Villaro, Patrick Rebsdorf Whelan19, Zhenyuan Xia39, Rositza Yakimova, Sheng Yang14, G. Reza Yazdi, Chanyoung Yim24, Duhee Yoon3, Xianghui Zhang17, Xiaodong Zhuang14, Luigi Colombo49, Andrea C. Ferrari3, Mar García-Hernández6 
Heidelberg University1, Trinity College, Dublin2, University of Cambridge3, Autonomous University of Madrid4, Université Paris-Saclay5, Spanish National Research Council6, University of Zaragoza7, University of Nottingham8, RWTH Aachen University9, Kessler Foundation10, Istituto Italiano di Tecnologia11, Georgia Institute of Technology12, University of Grenoble13, Dresden University of Technology14, Polytechnic University of Turin15, University of Zurich16, Bielefeld University17, University of Strasbourg18, Technical University of Denmark19, Swiss Federal Laboratories for Materials Science and Technology20, Ikerbasque21, University of Erlangen-Nuremberg22, Technische Universität München23, Bundeswehr University Munich24, University of Bern25, University of Patras26, Foundation for Research & Technology – Hellas27, Center for Theoretical Studies, University of Miami28, École Polytechnique Fédérale de Lausanne29, University of Ulm30, University of Eastern Finland31, Aristotle University of Thessaloniki32, University of Manchester33, Polish Academy of Sciences34, Aalto University35, University of Castilla–La Mancha36, ShanghaiTech University37, University of Exeter38, Chalmers University of Technology39, Warsaw University of Technology40, University of Trieste41, Queen Mary University of London42, University of Trento43, Instituto Politécnico Nacional44, University of the Basque Country45, Chemnitz University of Technology46, Charles University in Prague47, University of Jena48, University of Texas at Dallas49
29 Jan 2020
TL;DR: In this article, the authors present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures, adopting a 'hands-on' approach, providing practical details and procedures as derived from literature and from the authors' experience, in order to enable the reader to reproduce the results.
Abstract: © 2020 The Author(s). We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a 'hands-on' approach, providing practical details and procedures as derived from literature as well as from the authors' experience, in order to enable the reader to reproduce the results. Section I is devoted to 'bottom up' approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section II covers 'top down' techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers' and modified Hummers' methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by employing a theoretical data-mining approach. The exfoliation of LMs usually results in a heterogeneous dispersion of flakes with different lateral size and thickness. This is a critical bottleneck for applications, and hinders the full exploitation of GRMs produced by solution processing. The establishment of procedures to control the morphological properties of exfoliated GRMs, which also need to be industrially scalable, is one of the key needs. Section III deals with the processing of flakes. (Ultra)centrifugation techniques have thus far been the most investigated to sort GRMs following ultrasonication, shear mixing, ball milling, microfluidization, and wet-jet milling. It allows sorting by size and thickness. Inks formulated from GRM dispersions can be printed using a number of processes, from inkjet to screen printing. Each technique has specific rheological requirements, as well as geometrical constraints. The solvent choice is critical, not only for the GRM stability, but also in terms of optimizing printing on different substrates, such as glass, Si, plastic, paper, etc, all with different surface energies. Chemical modifications of such substrates is also a key step. Sections IV-VII are devoted to the growth of GRMs on various substrates and their processing after growth to place them on the surface of choice for specific applications. The substrate for graphene growth is a key determinant of the nature and quality of the resultant film. The lattice mismatch between graphene and substrate influences the resulting crystallinity. Growth on insulators, such as SiO2, typically results in films with small crystallites, whereas growth on the close-packed surfaces of metals yields highly crystalline films. Section IV outlines the growth of graphene on SiC substrates. This satisfies the requirements for electronic applications, with well-defined graphene-substrate interface, low trapped impurities and no need for transfer. It also allows graphene structures and devices to be measured directly on the growth substrate. The flatness of the substrate results in graphene with minimal strain and ripples on large areas, allowing spectroscopies and surface science to be performed. We also discuss the surface engineering by intercalation of the resulting graphene, its integration with Si-wafers and the production of nanostructures with the desired shape, with no need for patterning. Section V deals with chemical vapour deposition (CVD) onto various transition metals and on insulators. Growth on Ni results in graphitized polycrystalline films. While the thickness of these films can be optimized by controlling the deposition parameters, such as the type of hydrocarbon precursor and temperature, it is difficult to attain single layer graphene (SLG) across large areas, owing to the simultaneous nucleation/growth and solution/precipitation mechanisms. The differing characteristics of polycrystalline Ni films facilitate the growth of graphitic layers at different rates, resulting in regions with differing numbers of graphitic layers. High-quality films can be grown on Cu. Cu is available in a variety of shapes and forms, such as foils, bulks, foams, thin films on other materials and powders, making it attractive for industrial production of large area graphene films. The push to use CVD graphene in applications has also triggered a research line for the direct growth on insulators. The quality of the resulting films is lower than possible to date on metals, but enough, in terms of transmittance and resistivity, for many applications as described in section V. Transfer technologies are the focus of section VI. CVD synthesis of graphene on metals and bottom up molecular approaches require SLG to be transferred to the final target substrates. To have technological impact, the advances in production of high-quality large-area CVD graphene must be commensurate with those on transfer and placement on the final substrates. This is a prerequisite for most applications, such as touch panels, anticorrosion coatings, transparent electrodes and gas sensors etc. New strategies have improved the transferred graphene quality, making CVD graphene a feasible option for CMOS foundries. Methods based on complete etching of the metal substrate in suitable etchants, typically iron chloride, ammonium persulfate, or hydrogen chloride although reliable, are time- and resourceconsuming, with damage to graphene and production of metal and etchant residues. Electrochemical delamination in a low-concentration aqueous solution is an alternative. In this case metallic substrates can be reused. Dry transfer is less detrimental for the SLG quality, enabling a deterministic transfer. There is a large range of layered materials (LMs) beyond graphite. Only few of them have been already exfoliated and fully characterized. Section VII deals with the growth of some of these materials. Amongst them, h-BN, transition metal tri- and di-chalcogenides are of paramount importance. The growth of h-BN is at present considered essential for the development of graphene in (opto) electronic applications, as h-BN is ideal as capping layer or substrate. The interesting optical and electronic properties of TMDs also require the development of scalable methods for their production. Large scale growth using chemical/physical vapour deposition or thermal assisted conversion has been thus far limited to a small set, such as h-BN or some TMDs. Heterostructures could also be directly grown.

330 citations

Journal ArticleDOI
TL;DR: It is shown that homogeneous stable dispersions of single-layer graphene (SLG) in water can be obtained by mixing graphenide (negatively charged graphene) solutions in tetrahydrofuran with degassed water and evaporating the organic solvent.
Abstract: Dispersing graphite in water to obtain true (single-layer) graphene in bulk quantity in a liquid has been an unreachable goal for materials scientists in the past decade. Similarly, a diagnostic tool to identify solubilized graphene in situ has been long awaited. Here we show that homogeneous stable dispersions of single-layer graphene (SLG) in water can be obtained by mixing graphenide (negatively charged graphene) solutions in tetrahydrofuran with degassed water and evaporating the organic solvent. In situ Raman spectroscopy of these aqueous dispersions shows all the expected characteristics of SLG. Transmission electron and atomic force microscopies on deposits confirm the single-layer character. The resulting additive-free stable water dispersions contain 400 m2 l–1 of developed graphene surface. Films prepared from these dispersions exhibit a conductivity of up to 32 kS m–1.

165 citations

Journal ArticleDOI
TL;DR: An unambiguous correlation is found between the graphene-dye interaction energy, the molecular structure and the amount of graphene flakes solubilized and that the molecular dipole is not important per se, but because it facilitates adsorption on graphene by a "sliding" mechanism of the molecule into the solvent layer.
Abstract: We study the mechanism of surface adsorption of organic dyes on graphene, and successive exfoliation in water of these dye-functionalized graphene sheets A systematic, comparative study is performed on pyrenes functionalized with an increasing number of sulfonic groups By combining experimental and modeling investigations, we find an unambiguous correlation between the graphene–dye interaction energy, the molecular structure and the amount of graphene flakes solubilized The results obtained indicate that the molecular dipole is not important per se, but because it facilitates adsorption on graphene by a “sliding” mechanism of the molecule into the solvent layer, facilitating the lateral displacement of the water molecules collocated between the aromatic cores of the dye and graphene While a large dipole and molecular asymmetry promote the adsorption of the molecule on graphene, the stability and pH response of the suspensions obtained depend on colloidal stabilization, with no significant influence of molecular charging and dipole

124 citations

Journal ArticleDOI
TL;DR: This work used automatized image processing of Atomic Force Microscopy (AFM) data to measure the exact shape and size of thousands of nanosheets obtained by exfoliation of an important 2D-material, boron nitride, and used different statistical functions to model the asymmetric distribution ofnanosheet sizes typically obtained.
Abstract: The main advantage for applications of graphene and related 2D materials is that they can be produced on large scales by liquid phase exfoliation. The exfoliation process shall be considered as a particular fragmentation process, where the 2D character of the exfoliated objects will influence significantly fragmentation dynamics as compared to standard materials. Here, we used automatized image processing of Atomic Force Microscopy (AFM) data to measure, one by one, the exact shape and size of thousands of nanosheets obtained by exfoliation of an important 2D-material, boron nitride, and used different statistical functions to model the asymmetric distribution of nanosheet sizes typically obtained. Being the resolution of AFM much larger than the average sheet size, analysis could be performed directly at the nanoscale and at the single sheet level. We find that the size distribution of the sheets at a given time follows a log-normal distribution, indicating that the exfoliation process has a “typical” scale length that changes with time and that exfoliation proceeds through the formation of a distribution of random cracks that follow Poisson statistics. The validity of this model implies that the size distribution does not depend on the different preparation methods used, but is a common feature in the exfoliation of this material and thus probably for other 2D materials.

110 citations


Cited by
More filters
Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

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