Mass balance of the normalized weight percent of all components including SWNT, metal, carbonaceous impurities, and weight loss of the SWNT samples under various nitric acid treatment conditions. ![]() 24, 25 Electronic transitions between these singularities give rise to distinct features in the optical absorption spectra, which have been widely used to study the electronic structure of SWNTs, 25 – 29 and have been shown to provide a diagnostic tool for the study of the effect of chemistry on the electronic structure of as-prepared and chemically modified SWNTs. As a result of the quantum confinement of electrons in the radial direction, the continuous density of states in graphite splits into a number of sharp peaks (van Hove singularities) that appear at energies that depend on the inverse of the nanotube diameter. 21 – 23 All armchair nanotubes are metallic, while zig-zag and chiral nanotubes can be metallic or semiconducting. SWNTs are either metallic or semiconducting depending on their diameter and helicity. 2) it is possible to identify armchair nanotubes, formed when n = m and the chiral angle is 30° zig-zag nanotubes, formed when either n or m are zero and the chiral angle is 0° and chiral tubes, with chiral angles intermediate between 0° and 30°. The hexagonal lattice structure of CNTs, gives rise to three types of SWNTs. 20 Their growth requires a metal catalyst, usually Fe, Ni, Co, Y or Mo. SWNTs are produced by electric arc, 15 laser ablation, 16 CVD 17 – 19 and gas-phase catalytic processes (HiPco). 8, 13, 14 SWNTs usually occur as hexagonal close-packed bundles in which the nanotubes are held together by van der Walls forces. SWNTs consist of a single graphene cylinder and their diameter varies between 0.4 and 2 nm. The TEM micrographs shown in (a) and (b) were kindly provided by Sumio Iijima, NEC, Japan and reproduced with the permission of Nature Publishing Group. (d, e) Schematics of (d) MWNT and (e) SWNT. ![]() The dark spots are catalyst particles used for nanotube growth. TEM micrographs of (a) MWNTs 7 and (b) SWNTs 8 (c) TEM micrograph showing bundles of SWNTs. This review highlights two aspects of the interaction between biology and CNTs: the use of biological principles for manipulation and self-assembly of functional structures and devices based on CNTs, and the utilization of modified CNTs to manipulate and study living cells. Biology and medicine are rapidly emerging as new areas for the application of CNTs. Because of their unique quasi one-dimensional structure and fascinating mechanical and electronic properties, CNTs have captured the attention of physicists, chemists and materials scientists. ![]() After more than a century of interest, carbon has found its apogee in the fullerenes and carbon nanotubes (CNTs)-arguably the most promising of all nanomaterials. The synergetic future of nano- and bio-technologies holds great promise for further advancement in tissue engineering, prostheses, genomics, pharmacogenomics, drug delivery, surgery and general medicine.Įver since Edison discovered that carbon changes its resistance with pressure and a carbon filament glows when an electric current is passed through it, the unique properties of carbon have intrigued scientists. Nanodevices with biorecognition properties provide tools at a scale, which offers a tremendous opportunity to study biochemical processes and to manipulate living cells at the single molecule level. The feasibility of the bottom-up approach which is based on molecular recognition and self-assembly properties of proteins has already been proved in many inorganic-organic hybrid systems and devices. The application of the principles of biology to nanotechnology provides a valuable route for further miniaturization and performance improvement of artificial devices. 5, 6 Whereas nanotechnology may provide novel materials which can result in revolutionary new structures and devices, biotechnology already offers extremely sophisticated tools to precisely position molecules and assemble hierarchal structures and devices. Nanomaterials have been designed for a variety of biomedical and biotechnological applications, including bone growth, 1 enzyme encapsulation, 2 biosensors 3, 4 and as vesicles for DNA delivery into living cells. Although nanomaterials have existed in nature long before mankind was able to identify forms at the nanoscale level, advances in synthetic chemistry have been one of the driving forces in the development of a biological nanotechnology.
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