CARBON nanotubes1 are expected to have a wide variety of interesting properties. Capillarity in open tubes has already been demonstrated2–5, while predictions regarding their electronic structure6–8 and mechanical strength9 remain to be tested. To examine the properties of these structures, one needs tubes with well defined morphologies, length, thickness and a number of concentric shells; but the normal carbon-arc synthesis10,11 yields a range of tube types. In particular, most calculations have been concerned with single-shell tubes, whereas the carbon-arc synthesis produces almost entirely multi-shell tubes. Here we report the synthesis of abundant single-shell tubes with diameters of about one nanometre. Whereas the multi-shell nanotubes are formed on the carbon cathode, these single-shell tubes grow in the gas phase. Electron diffraction from a single tube allows us to confirm the helical arrangement of carbon hexagons deduced previously for multi-shell tubes1.

Single-shell carbon nanotubes of 1-nm diameter

Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

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Carbon Nanotubes: Present and Future Commercial Applications

Research Development on Sodium-Ion Batteries

Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

SINCE carbon nanotubes1 were first synthesized in macroscopic quantities2, it has become possible to explore their physical and chemical characteristics. There has been much speculation3 about the properties of materials encapsulated within the tubes, but experimental studies of this issue require a reliable means of open-ing and filling the tubes. Various approaches have been developed for opening up4–6 the tube ends and encapsulating material4,6,7, but these work only for a limited range of materials or in low yield. Here we describe a general method that allows carbon nanotubes to be opened at the end and filled with a variety of metal oxides using wet chemical techniques. We anticipate that this method will lead to extensive study of the chemistry and physics of filled nanotubes, which might find applications in catalysis, separation and storage technology and in the development of materials with new magnetic and electrical properties.

A simple chemical method of opening and filling carbon nanotubes

Carbon nanotubes are molecular-scale tubes of graphitic carbon with outstanding properties. They are among the stiffest and strongest fibres known, with Young's moduli as high as 1 TPa and tensile strengths of up to 63 GPa. They also have remarkable electronic properties and can be metallic or semiconducting depending on their structure and diameter. There is currently great interest in exploiting these properties by incorporating carbon nanotubes into some form of matrix. A wide range of polymer matrices have been employed, and there is growing interest in nanotube/ceramic and nanotube/metal composites. This review outlines the properties of carbon nanotubes and describes the preparation and properties of carbon nanotube composites. The prospects for commercial exploitation of these materials are discussed.

http://www.personal.rdg.ac.uk/~scsharip/IMR3.pdf

Carbon nanotube composites

1 Introduction 2 Synthesis 3 Structure 4 The physics of nanotubes 5 Nano-capsules and nano-test-tubes 6 The ultimate carbon fibre? 7 Curved crystals, inorganic fullerenes and nanorods 8 Carbon onions and spheroidal carbon 9 Future directions Index

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Carbon Nanotubes and Related Structures: New Materials for the Twenty-first Century

Mechanical damage of carbon nanotubes by ultrasound

Edge structures of thermally treated graphite have been studied by means of atomically resolved high-resolution TEM. The method for the determination of a monolayer or more than one layer graphene sheets is established. A series of tilting experiments proves that the zigzag and armchair edges are mostly closed between adjacent graphene layers, and the number of dangling bonds is therefore minimized. Surprisingly bilayer graphene often exhibits AA stacking and is very hard to distinguish from a single graphene layer. Open edge structures with carbon dangling bonds can be found only in a local area where the closed (folding) edge is partially broken.

http://www.personal.rdg.ac.uk/~scsharip/Liu_graphene.pdf

Peter J. F. Harris

Papers

A simple chemical method of opening and filling carbon nanotubes

Carbon nanotube composites

Carbon Nanotubes and Related Structures: New Materials for the Twenty-first Century

Mechanical damage of carbon nanotubes by ultrasound

Open and closed edges of graphene layers.