![]() It is believed that fullerenes have existed in nature for a long time minute quantities of fullerenes in the form of C 60, C 70, C 76, C 82 and C 84, have been found hidden in soot. Additionally, other smaller metastable species, such as C 28, C 36 and C 50, have been discovered. The C 70 molecule is another spherical fullerene that is known for being chemically stable. The buckminsterfullerene (buckyball/C 60), one of the most common spherical fullerenes, is a nanoscale molecule having 60 carbon atoms, with each atom being bonded to three other adjacent atoms to form hexagons and pentagons, with the ends curved into a sphere. It is a semi-metal, which has an overlap between the valence and conduction bands, i.e. Graphene is an allotrope of carbon, which is comprised of a single layer of carbon atoms, arranged in a two-dimensional hexagonal lattice. Fullerenes are comprised of graphene sheets of linked hexagonal and pentagonal rings, which give them their curved structure. ĬNTs are part of the fullerene family, which are a group of carbon allotropes with atoms linked in the shape of cage-like structures such as a hollow sphere, ellipsoid or cylindrical tube. For example, CNTs are promising for electronics ‘beyond CMOS’ as active devices and interconnects in future integrated circuits. The novel and useful properties of CNTs, such as low-cost, light-weight, high aspect ratios and surface area, distinct optical characteristics, high thermal and electrical conductivity and high mechanical strength make them suitable and of interest for a wide range of electronic, biomedical and other industrial applications. SWCNTs can be further categorized electrically into semiconducting and metallic SWCNTs (s-SWCNTs and m-SWCNTs), while MWCNTs mainly display metallic behavior. Nanotubes could either be single-walled structures, called single-walled carbon nanotubes (SWCNTs) or could have many walls, called multi-walled carbon nanotubes (MWCNTs). CNTs exhibit different electronic properties based on the way these graphene layers are rolled into a cylinder. graphene), with diameters ranging from below 1 nm to 10 s of nm. Finally, some of the challenges in current and emerging applications of CNTs in fields such as energy storage, transistors, tissue engineering, drug delivery, electronic cryptographic keys and sensors are considered.Ĭarbon nanotubes (CNTs) are long, hollow cylindrical tubule structures made of graphite sheets (a.k.a. Various assembly and integration techniques for multiple CNTs based on catalyst patterning, forest growth and composites are considered along with their alignment/placement onto different substrates using photolithography, transfer printing and different solution-based techniques such as inkjet printing, dielectrophoresis (DEP) and spin coating. Advances in CNT structural control (chirality, diameter and junctions) using methods such as catalyst conditioning, cloning, seed-, and template-based growth are then explored in detail, followed by post-growth CNT purification techniques using selective surface chemistry, gel chromatography and density gradient centrifugation. ![]() CNT synthesis based on arc-discharge, laser ablation and chemical vapor deposition (CVD) including details of tip-growth and base-growth models are first introduced. This review focuses on progress to date in the field of CNT assembly and integration for various applications. Controlled growth, assembly and integration of CNTs is essential for the practical realization of current and future nanotube applications. Carbon nanotubes (CNTs) have attracted significant interest due to their unique combination of properties including high mechanical strength, large aspect ratios, high surface area, distinct optical characteristics, high thermal and electrical conductivity, which make them suitable for a wide range of applications in areas from electronics (transistors, energy production and storage) to biotechnology (imaging, sensors, actuators and drug delivery) and other applications (displays, photonics, composites and multi-functional coatings/films).
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