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 reaction of [W(PMe3)3H6] with cycloheptatriene at 80 °C gives the compounds [W(η5-C7H9)(η3-C7H7)(PMe3)2] and [W(η-C7H7)(η3-C7H11)(PMe3)] in moderate yields. [W(η5-C7H9)(η3-C7H7)(PMe3)2] reacts with carbon monoxide giving [W(η5-C7H9)(η3-C7H7)(CO)], both of which have been characterised using two-dimensional n.m.r. spectroscopy.

η3- and η7-Cycloheptatrienyltungsten Chemistry: Synthesis of (W(η5-C7H9)(η3-C7H7)(PMe3)2) and (W(η-C7H7)(η3-C7H11)(PMe3)).

Irradiation of the metallocyclobutane derivatives [W(η5-C5H5)2(-CH2CHR2CHR1-)], where R1= R2= H, R1= H, R2= Me, or R1= Me, R2= H, gives rise to the olefins CH2CHR1 and CH2CHR2 in good yield.

Photochemical reactions of metallocyclobutane derivatives of tungsten- evidence for the mechanism of olefin metathesis

Treatment of [Nb(η-C5H5)2H3] with pentaborane(9) gives the novel arachno-metallaboranes [Nb(η-C5H5)2B4H9] (1) and [Nb(η-C5H5)2B3H8] (2). Compound 1 is the first reported base subrogated analogue of the neutral arachno-pentaborane(11) and has an apex to niobium hydrogen bridge. Compound 2, for which the X-ray crystal structure has been determined, is an analogue of the neutral arachno-tetraborane(10).

Niobium Metallaboranes: A Novel Metallaborane Analogue of Pentaborane(11).

The cis-ethylenehydride compounds [Mo(η-C6H6)(L2)(η-C2H4)H]PF6[L2= Me2PCH2CH2PMe2(dmpe) or o-C6H4(EMe2)2(E = P, pdmp, or As, pdma)] react with trimethylphosphine to give the η-ethylbenzene compounds [Mo(η-C6H5Et)(L2)(PMe3)H]PF6. Detailed studies of the mechanism of this reaction show that there is an initial reaction, at low temperatures, giving isomeric mixtures of thermally unstable η-cyclohexadienyl derivatives [Mo(η-C6H7)(dmpe)(PMe3)(η-C2H4)]+. The combined evidence from n.m.r. spectra, including kinetic studies, and from the preparation and reactions of intermediates shows that the η-ethylbenzene compound is formed by the sequence [Mo(η-C6H6)(dmpe)(η-C2H4)H]+→[Mo(η-C6H6)(dmpe)(PMe3)Et]+→[Mo(η-C6H6Et-endo)(dmpe)(PMe3)(solvent)]+→[Mo(η-C6H5Et)(dmpe)(PMe3)]+ H+→[Mo(η-C6H5Et)(dmpe)(PMe3)H]+. The following new compounds have been prepared and characterised: [Mo(η-C6H6){P(OMe)3}2(η-C3H5)] PF6, [Mo(η-C6H6)(pdmp)(η-C3H5)]PF6, [Mo(η-C6H6)(pdma)(η-C3H5)]PF6, [Mo(η-C6H6)(pdmp)(η-C2H4)], [Mo(η-C6H6)(pdma)(η-C2H4)], [Mo(η-C6H6)(pdmp)(η-C2H4)H]PF6, [Mo(η-C6H6)(pdma)(η-C3H5)]PF6, [Mo(η-C6H6)(pdmp)(η-C2H4)], [Mo(η-C6H6)(pdma)(η-C2H4)], [Mo(η-C6H6)(pdmp)(η-C2H4)H]PF6, [Mo(η-C6H6)(pdma)(η-C2H4)H]PF6, [Mo(η-C6H5Et)(pdmp)(PMe3)H]PF6, [Mo(η-C6H5Et)(pdma)(PMe3)H]PF6, [Mo(η-C6H6)(dmpe)(PMe3)D]PF6, [Mo(η-C6H6)(dmpe)(η-C2H4)], [Mo(η-C6H6Et-endo)(dmpe)2]PF6, [Mo(η-C6H6)(dmpe){P(OMe)3}H]PF6, [Mo(η-C6H6)(dmpe)(CO)H]PF6, [Mo(η-C6H6)(dmpe)(2,6-Me2C6H3 NC)]PF6, [Mo(η-C6H5Me)(dmpe)(η-C2H4)H]PF6, [Mo(C6H4Me-2-Et-1)(dmpe)(PMe3)H]PF6, [Mo(C6H4Me-3-Et-1)(dmpe)(PMe3)H]PF6, [Mo(C6H5Me-1-Et-6-endo)(dmpe)2]PF6, [Mo(C6H5Me-2-Et-6-endo)(dmpe)2]PF6, and [Mo(η-C6H6Et-endo)(pdmp)2]PF6.

Mechanism of the Reaction of (Mo(η-C6H6)(Me2PCH2CH2PMe2)(η-C2H4)H)+ with PMe3 Giving (Mo(η-C6H5Et)(dmpe)(PMe3)H)+: Metal-to-Ring Migration of an Ethyl Group.

The chiral ditosylate (I) reacts with the phosphide (II) to give the phosphine (III), together with the bisphosphine (IV).

Synthesis of (4S,5S)‐trans‐4‐(Cyclopentadien‐1‐ylmethyl)‐5‐diphenylphosphinomethyl‐2,2‐dimethyl‐1,3‐dioxolane and the Ferrocene Derivative. Cyclic trans‐(Fe(η‐C5H4CH2(CHOC(CH3)2OCH)CH2PPh2)2).

Malcolm L. H. Green

Papers

η3- and η7-Cycloheptatrienyltungsten Chemistry: Synthesis of (W(η5-C7H9)(η3-C7H7)(PMe3)2) and (W(η-C7H7)(η3-C7H11)(PMe3)).

Photochemical reactions of metallocyclobutane derivatives of tungsten- evidence for the mechanism of olefin metathesis

Niobium Metallaboranes: A Novel Metallaborane Analogue of Pentaborane(11).

Mechanism of the Reaction of (Mo(η-C6H6)(Me2PCH2CH2PMe2)(η-C2H4)H)+ with PMe3 Giving (Mo(η-C6H5Et)(dmpe)(PMe3)H)+: Metal-to-Ring Migration of an Ethyl Group.

Synthesis of (4S,5S)‐trans‐4‐(Cyclopentadien‐1‐ylmethyl)‐5‐diphenylphosphinomethyl‐2,2‐dimethyl‐1,3‐dioxolane and the Ferrocene Derivative. Cyclic trans‐(Fe(η‐C5H4CH2(CHOC(CH3)2OCH)CH2PPh2)2).