Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

Energy-storage technologies, including electrical double-layer capacitors and rechargeable batteries, have attracted significant attention for applications in portable electronic devices, electric vehicles, bulk electricity storage at power stations, and “load leveling” of renewable sources, such as solar energy and wind power. Transforming lithium batteries and electric double-layer capacitors requires a step change in the science underpinning these devices, including the discovery of new materials, new electrochemistry, and an increased understanding of the processes on which the devices depend. The Review will consider some of the current scientific issues underpinning lithium batteries and electric double-layer capacitors.

Challenges Facing Lithium Batteries and Electrical Double‐Layer Capacitors

This review is an attempt to illustrate the different alternatives in the field of 2D materials. Graphene seems to be just the tip of the iceberg and we show how the discovery of alternative 2D materials is starting to show the rest of this iceberg. The review comprises the current state-of-the-art of the vast literature in concepts and methods already known for isolation and characterization of graphene, and rationalizes the quite disperse literature in other 2D materials such as metal oxides, hydroxides and chalcogenides, and metal–organic frameworks.

2D materials: to graphene and beyond

Two-dimensional (2D) nanosheets, which possess atomic or molecular thickness and infinite planar lengths, are regarded as the thinnest functional nanomaterials. The recent development of methods for manipulating graphene (carbon nanosheet) has provided new possibilities and applications for 2D systems; many amazing functionalities such as high electron mobility and quantum Hall effects have been discovered. However, graphene is a conductor, and electronic technology also requires insulators, which are essential for many devices such as memories, capacitors, and gate dielectrics. Along with graphene, inorganic nanosheets have thus increasingly attracted fundamental research interest because they have the potential to be used as dielectric alternatives in next-generation nanoelectronics. Here, we review the progress made in the properties of dielectric nanosheets, highlighting emerging functionalities in electronic applications. We also present a perspective on the advantages offered by this class of materials for future nanoelectronics.

Two‐Dimensional Dielectric Nanosheets: Novel Nanoelectronics From Nanocrystal Building Blocks

A wide variety of cation-exchangeable layered transition metal oxides and their relatively rare counterparts, anion-exchangeable layered hydroxides, have been exfoliated into individual host layers, i.e., nanosheets. Exfoliation is generally achieved via a high degree of swelling, typically driven either by intercalation of bulky organic ions (quaternary ammonium cations, propylammonium cations, etc.) for the layered oxides or by solvation with organic solvents (formamide, butanol, etc.) for the hydroxides. Ultimate two-dimensional (2D) anisotropy for the nanosheets, with thickness of around one nanometer versus lateral size ranging from submicrometer to several tens of micrometers, allows them to serve either as an ideal quantum system for fundamental study or as a basic building block for functional assembly. The charge-bearing inorganic macromolecule-like nanosheets can be assembled or organized through various solution-based processing techniques (e.g., flocculation, electrostatic sequential deposition, or the Langmuir-Blodgett method) to produce a range of nanocomposites, multilayer nanofilms, and core-shell nanoarchitectures, which have great potential for electronic, magnetic, optical, photochemical, and catalytic applications.

Nanosheets of oxides and hydroxides: Ultimate 2D charge-bearing functional crystallites.

PROBLEM TO BE SOLVED: To provide a capsule type endoscope which never has blind spots in imaging a detecting region of a stomach or the like and facilitates the understanding of a position of an abnormal part in the detecting region when the abnormality is detected. SOLUTION: The capsule type endoscope 1 has four cameras 4a, 4b placed in a spherically formed capsule 2 and enables the simultaneous acquisition of "image information" in all directions while keeping the same posture. Moreover, a posture sensor 5 is placed in the capsule 2 and "posture information" on its postures detected by the posture sensor 5 is output to the outside. COPYRIGHT: (C)2006,JPO&NCIPI

Spherical capsule type omnidirectional endoscope

Ultrathin films composed of ruthenate nanosheets (RuO2ns) were fabricated via electrostatic self-assembly of unilamellar RuO2ns crystallites derived by total exfoliation of an ion-exchangeable layered ruthenate. Ultrathin films with submonolayer to monolayer RuO2ns coverage and multilayered RuO2ns thin films were prepared by controlled electrostatic self-assembly and layer-by-layer deposition using a cationic copolymer as the counterion. Electrical properties of a single RuO2ns crystallite were successfully measured by means of scanning probe microscopy. The sheet resistance of an isolated single RuO2ns crystallite was 12 kΩ sq−1. Self-assembled submonolayer films behaved as a continuous conducting film for coverage above 70%, which was discussed based on a two-dimensional percolation model. Low sheet resistance was attained for multilayered films with values less than 1 kΩ sq−1. Interestingly, the grain boundary resistance between nanosheets seems to contribute only slightly to the sheet resistance of se...

Conductivity of Ruthenate Nanosheets Prepared via Electrostatic Self-Assembly: Characterization of Isolated Single Nanosheet Crystallite to Mono- and Multilayer Electrodes

Swelling, intercalation, and exfoliation behavior of layered ruthenate derived from layered potassium ruthenate

PROBLEM TO BE SOLVED: To provide a solid catalyst component for production of propylene block copolymer enabling production of propylene block copolymer excellent in powder properties and a catalyst for production of propylene block copolymer and to provide a method for producing the propylene block copolymer. SOLUTION: The solid catalyst component for production of the propylene block copolymer is obtained by bringing (a) a specific solid catalyst component precursor into contact with (b) a halogenated compound and (c) an electron donor. The specific solid catalyst component precursor is obtained by reducing a titanium compound represented by general formula [I] in the presence of an organosilicon compound having an Si-O bond with an organomagnesium compound and has ≥25 μm average particle diameter. The catalyst for production of the propylene block copolymer is obtained by bringing (A) the solid catalyst component for production of the propylene block copolymer into contact with (B) an organoaluminum compound and (C) an electron-donating compound. The method for producing the propylene block copolymer comprises using the catalyst for production of the propylene block copolymer. COPYRIGHT: (C)2004,JPO&NCIPI

Solid catalyst component for producing propylene block copolymer, catalysts for producing propylene block copolymer and method for producing propylene block copolymer

Graphite oxide nanosheets with three different sheet sizes were prepared from different graphite materials. The graphite oxide nanosheets were used as precursors to prepare three 20 mass% Pt/graphene composite electrocatalysts composed of different sizes of graphene. The structure and electrochemical properties in 0.1 M HClO4 at 60°C of the three Pt/graphene electrocatalysts were studied. Well dispersed Pt nanoparticles with 2.2 nm average diameter and electrochemically active surface area of ∼50 m2 (g-Pt)−1 were obtained irrespective of the size of graphene. Despite the similarity in Pt nanoparticle state, the oxygen reduction reaction was strongly affected by the size of graphene. Smaller sized graphene afforded higher mass and specific activity towards the oxygen reduction reaction.

Oxygen Reduction Reaction Activity of Pt/Graphene Composites with Various Graphene Size

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