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Butt H.,University of Cambridge | Dai Q.,University of Cambridge | Rajesekharan R.,University of Cambridge | Wilkinson T.D.,University of Cambridge | And 2 more authors.
ACS Nano

Highly dense periodic arrays of multiwalled carbon nanotubes behave like low-density plasma of very heavy charged particles, acting as metamaterials. These arrays with nanoscale lattice constants can be designed to display extended plasmonic band gaps within the optical regime, encompassing the crucial optical windows (850 and 1550 nm) simultaneously. We demonstrate an interesting metamaterial waveguide effect displayed by these nanotube arrays containing line defects. The nanotube arrays with lattice constants of 400 nm and radius of 50 nm were studied. Reflection experiments conducted on the nanoscale structures were in agreement with numerical calculations. © 2011 American Chemical Society. Source

Haworth B.,Loughborough University | Ratnayake U.N.,Sri Lanka Institute of Nanotechnology SLINTEC
International Polymer Processing

Layered structures in inorganic minerals are not easily intercalated when combined with conventional non-polar polymers such as polypropylene (PP). A new co-intercalation method is reported whereby the combined influence of low molecular weight polar additives and polyolefin-based compatibilizers on PP-clay nanocomposites (PPCN) has been investigated. Our research has shown that the interlayer spacing of montmorillonite clay increases dramatically, and increased particle dispersion is achieved, when short chain, organic additives (typically amidetype, AM) are included. In this work, the migration of these additives into the clay galleries has been confirmed by surface energy data (from contact angle experiments) and by various capillary flow measurement techniques. Shear flow data have been used to interpret the mechanism of intercalation, following compound preparation using melt-state mixing processes. At relatively low concentrations, the erucamide molecules assist the intercalation process in nanocomposites; however if an excess of AM is apparent within the bulk polymer melt, unusual flow behavior is observed which can be attributed to wall slip. Modified melt elasticity is also obtained with the PPCN's leading to reduced die swell characteristics in extrusion processes. Significant differences in melt flow behavior can therefore be attributed to the presence of AM; a mechanism for co-intercalation has been proposed in terms of hydrogen bonding between the additives and the silicate layers. © Carl Hanser Verlag GmbH & Co. KG. Source

Hiralal P.,Nokia Inc. | Hiralal P.,University of Cambridge | Unalan H.E.,Middle East Technical University | Amaratunga G.A.J.,University of Cambridge | Amaratunga G.A.J.,Sri Lanka Institute of Nanotechnology SLINTEC

As a result of their morphology, nanowires bring new properties and the promise of performance for a range of electronic devices. This review looks into the properties of nanowires and the multiple ways in which they have been exploited for energy generation, from photovoltaics to piezoelectric generators. © 2012 IOP Publishing Ltd. Source

Dai Q.,University of Cambridge | Dai Q.,CAS National Center for Nanoscience and Technology | Rajasekharan R.,University of Cambridge | Butt H.,University of Cambridge | And 4 more authors.

An ultrasmall tunable microlens with a diameter of 1.5 μm is fabricated using nematic liquid crystals (electrically tunable medium) and vertically aligned carbon nanofibers (CNFs, electrodes). Individual CNFs are grown at the center of circular dielectric regions. This allows the CNFs to produce a more Gaussian electric field profile and hence more uniformity in lens array switching. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Rajasekharan R.,University of Cambridge | Butt H.,University of Cambridge | Dai Q.,University of Cambridge | Wilkinson T.D.,University of Cambridge | And 2 more authors.
Advanced Materials

Reflective binary Fresnel lenses fabricated so far all suffer from reflections from the opaque zones and hence degradation in focusing and lensing properties. Here a solution is found to this problem by developing a carbon nanotube Fresnel lens, where the darkest man-made material ever, i.e., low-density vertically aligned carbon nanotube arrays, are exploited. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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