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

The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

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

Nanoparticles — particles in the size range 1–100 nm — are emerging as a class of therapeutics for cancer. Early clinical results suggest that nanoparticle therapeutics can
show enhanced efficacy, while simultaneously reducing side effects, owing to properties such as more targeted localization in tumours and active cellular uptake. Here, we
highlight the features of nanoparticle therapeutics that distinguish them from previous anticancer therapies, and describe how these features provide the potential for
therapeutic effects that are not achievable with other modalities. While large numbers of preclinical studies have been published, the emphasis here is placed on preclinical and clinical studies that are likely to affect clinical investigations and their implications for advancing the treatment of patients with cancer.

Nanoparticle therapeutics: an emerging treatment modality for cancer

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

The size distribution, imaging and obstructing properties of C60 and higher fullerenes formed within arc-grown single walled carbon nanotubes

The synthesis of high-surface-area molybdenum carbides has been studied by the temperature-programmed carburization of molybdenum trioxide MoO3. The feedstocks used were mixtures of methane and ethane with hydrogen. The solid reaction products were characterized at selected intervals using thermogravimetric analysis differential scanning calorimetry (TGA-DSC), surface area measurement (BET), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The gaseous products of the carburization process were monitored using a gas chromatograph equipped with a mass spectrometer (GC-MS). The structural properties of the product carbides are shown to depend on the conditions of synthesis. The C2H6/H2 feedstock gave the highest-surface-area material. The presence of H2 in the feed mixture reduced the amount of amorphous carbon deposited an the molybdenum carbide material. The surface area was found to increase most rapidly during the initial H2-reduction stage. Initially, the MoO3 is re...

Study on the Structure and Formation Mechanism of Molybdenum Carbides

Carbon-hydrogen bonds, especially those of saturated (s$) carbon centres, are normally regarded as being chemically inert. Generally, the C-H group is not thought of as a potential ligand which can have a structural role or play an energetically significant part in ground states or in reaction intermediates. In this article we review recent observations which show that there are in fact many circumstances in which a carbon-hydrogen group will interact with a transition metal centre with formation of a two-electron three-centre bond and that the extent of the interaction is such as to have a marked effect on the molecular and electronic structure and hence reactivity of the molecule. We propose the term “agostic” which will be used to discuss the various manifestations of covalent interactions between carbon-hydrogen groups and transition metal centres in organometallic compounds l . The word agostic will be used to refer specifically to situations in which a hydrogen atom is covalently bonded simultaneously to both a carbon atom and to a transition metal atom. The agostic C-H-M bond is similar to the familiar and long known bridging hydrogen systems which occur in B-H-B, M-H-M, and B-H-M groups. The C-H-M bonds are a recent observation but as will be discussed below, they are probably very much more common than hitherto suspected. Since carbon-hydrogen bonds are a ubiquitous feature of organometallic compounds we have found it useful to define

Carbon-Hydrogen-Transition Metal Bonds

The respiratory muscles provide the motive power for breathing. Despite this central role in ventilation their physiology has been relatively neglected, perhaps partly because of the complexity of their function, and the difficulties of studying them. However, in the last decade, there has been considerable increase in interest, and a number of new concepts have arisen [l-31. It is now appreciated that the translation of central nervous output into ventilation requires a sophisticated integration of the respiratory muscles, which have to subserve the requirements of posture and body movement, simultaneously with breathing. The importance of the shape (configuration) of the respiratory system to muscle action has been emphasized. Analysis has shown that the functions of the diaphragm are complex: it is anatomically and embryologically derived from two muscles, and these parts may have different physiological actions. The abdominal muscles appear to be not only powerful muscles of expiration, but also facilitate inspiration. Both internal and external intercostal muscles now seem to be inspiratory at low lung volumes and expiratory at high lung volumes. Like all skeletal muscles the respiratory muscles are capable of fatigue after heavy loads. It is increasingly believed that respiratory muscle fatigue may play an important part in the pathogenesis of respiratory failure, and part of the value of artificial ventilation may lie in resting the respiratory muscles. The respiratory muscles comprise the diaphragm, the intercostal muscles, the abdominal muscles, and the so-called ‘accessory’ muscles including the sternomastoid and scalene muscles. However, probably all of the muscles of the trunk and neck can be recruited as respiratory muscles under heavy loads.

The respiratory muscles.

Cobalt nanoparticles encapsulated in carbon shells have been synthesized by catalytic chemical vapor deposition (CCVD) in high yield by reducing with a H2/CH4 gas mixture a Mg0.9Co0.1O solid soluti...

Malcolm L. H. Green

Papers

The size distribution, imaging and obstructing properties of C60 and higher fullerenes formed within arc-grown single walled carbon nanotubes

Study on the Structure and Formation Mechanism of Molybdenum Carbides

Carbon-Hydrogen-Transition Metal Bonds

The respiratory muscles.

CCVD Synthesis and Characterization of Cobalt-Encapsulated Nanoparticles