Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.

http://science.sciencemag.org/content/sci/297/5582/787.full.pdf

Carbon Nanotubes--the Route Toward Applications

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

Nanotubes from Carbon.

Graphitic carbon nitride, g-C3N4, can be made by polymerization of cyanamide, dicyandiamide or melamine. Depending on reaction conditions, different materials with different degrees of condensation, properties and reactivities are obtained. The firstly formed polymeric C3N4 structure, melon, with pendant amino groups, is a highly ordered polymer. Further reaction leads to more condensed and less defective C3N4 species, based on tri-s-triazine (C6N7) units as elementary building blocks. High resolution transmission electron microscopy proves the extended two-dimensional character of the condensation motif. Due to the polymerization-type synthesis from a liquid precursor, a variety of material nanostructures such as nanoparticles or mesoporous powders can be accessed. Those nanostructures also allow fine tuning of properties, the ability for intercalation, as well as the possibility to give surface-rich materials for heterogeneous reactions. Due to the special semiconductor properties of carbon nitrides, they show unexpected catalytic activity for a variety of reactions, such as for the activation of benzene, trimerization reactions, and also the activation of carbon dioxide. Model calculations are presented to explain this unusual case of heterogeneous, metal-free catalysis. Carbon nitride can also act as a heterogeneous reactant, and a new family of metal nitride nanostructures can be accessed from the corresponding oxides.

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Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts

Polymeric graphitic carbon nitride materials (for simplicity: g-C(3)N(4)) have attracted much attention in recent years because of their similarity to graphene. They are composed of C, N, and some minor H content only. In contrast to graphenes, g-C(3)N(4) is a medium-bandgap semiconductor and in that role an effective photocatalyst and chemical catalyst for a broad variety of reactions. In this Review, we describe the "polymer chemistry" of this structure, how band positions and bandgap can be varied by doping and copolymerization, and how the organic solid can be textured to make it an effective heterogenous catalyst. g-C(3)N(4) and its modifications have a high thermal and chemical stability and can catalyze a number of "dream reactions", such as photochemical splitting of water, mild and selective oxidation reactions, and--as a coactive catalytic support--superactive hydrogenation reactions. As carbon nitride is metal-free as such, it also tolerates functional groups and is therefore suited for multipurpose applications in biomass conversion and sustainable chemistry.

Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry

Nanostructure science and technology now forms a common thread that runs through all physical and materials sciences and is emerging in industrial applications as nanotechnology. The breadth of the subject material is demonstrated by the fact that it covers and intertwines many of the traditional areas of physics, chemistry, biology, and medicine. Within each main topic in this field there can be many subfields. For example, the electrical properties of nanostructured materials is a topic that can cover electron transport in semiconductor quantum dots, self-assembled molecular nanostructures, carbon nanotubes, chemically tailored hybrid magnetic-semiconductor nanostructures, colloidal quantum dots, nanostructured superconductors, nanocrystalline electronic junctions, etc. Obviously, no one book can cope with such a diversity of subject matter. The nanostructured material system is, however, of increasing significance in our technology-dominated economy and this suggests the need for a series of books to cover recent developments.    The scope of the series is designed to cover as much of the subject matter as possible – from physics and chemistry to biology and medicine, and from basic science to applications. At present, the most significant subject areas are concentrated in basic science and mainly within physics and chemistry, but as time goes by more importance will inevitably be given to subjects in applied science and will also include biology and medicine. The series will naturally accommodate this flow of developments in the sciences and technology of nanostructures and maintain its topicality by virtue of its broad emphasis. It is important that emerging areas in the biological and medical sciences, for example, not be ignored as, despite their diversity, developments in this field are often interlinked. The series will maintain the required cohesiveness from a judicious mix of edited volumes and monographs that while covering subfields in depth will also contain more general and interdisciplinary texts.    Thus the series is planned to cover in a coherent fashion the developments in basic research from the distinct viewpoints of physics, chemistry, biology, and materials science and also the engineering technologies emerging from this research. Each volume will also reflect this flow from science to technology. As time goes by, the earlier series volumes will then serve as reference texts to subsequent volumes.

Nanostructure Science and Technology

Superconducting thin films of Y1Ba2Cu3O7−x were fabricated using the process of plasma‐assisted laser deposition. The substrate temperature was as low as 400 °C and high‐temperature post‐annealing in an O2 atmosphere was not necessary. The as‐deposited films have a Tc of ∼85 K, and are oriented mostly with the c axis perpendicular to the substrate surface. The measured Jc at 80 K was 105 A/cm2.

Deposition of superconducting Y‐Ba‐Cu‐O films at 400 °C without post‐annealing

Field emission data from aligned high-density carbon nanotubes (CNTs) with orientations parallel, 45°, and perpendicular to the substrate have been obtained The large-area uniformly distributed CNTs were synthesized on smooth nickel substrates via dc plasma-assisted hot filament chemical vapor deposition CNTs with diameters in the range of 100–200 nm were employed in this study The different orientations were obtained by changing the angle between the substrate and the electrical field direction The growth mechanism for the alignment and orientation control of CNTs has been discussed The CNTs oriented parallel to the substrate have a lower onset applied field than those oriented perpendicular to the substrate This result indicates that electrons can emit from the body of the CNT, which means that the CNT can be used as a linear emitter The small radius of the tube wall and the existence of defects are suggested as the reasons for the emission of electrons from the body of the tubes

Field emission of different oriented carbon nanotubes

High‐energy atomic beams with Mach numbers as high as 5 were observed in excimer laser‐superconducting target interactions. The velocity distributions of the Y, Ba, Cu, and O atoms and ions could be described very well by a supersonic expansion‐type mechanism similar to a molecule beam. The physics of the atomic beam formation process is discussed.

Generation of high‐energy atomic beams in laser‐superconducting target interactions

An oxygen jet placed near the target during plasma‐assisted laser deposition produces a strong atomic oxygen beam with kinetic energies of 5.6 eV, simultaneous with the laser‐induced atomic beams of Ba, Cu, and Y from the target. All atomic beams can be well characterized by a supersonic expansion mechanism. The behavior of the velocity distributions was studied as a function of the distance from the target and laser energy fluence. A target‐substrate separation of 7 cm was found to be optimum in terms of producing the best as‐deposited films. At that distance, the velocity distributions of all atomic beams become nearly the same.

David T. Shaw

Papers

Nanostructure Science and Technology

Deposition of superconducting Y‐Ba‐Cu‐O films at 400 °C without post‐annealing

Field emission of different oriented carbon nanotubes

Generation of high‐energy atomic beams in laser‐superconducting target interactions

Role of the oxygen atomic beam in low-temperature growth of superconducting films by laser deposition