201,110 research outputs found
Sorting and transmission electron microscopy analysis of single or double wall carbon nanotubes
On the basis of the recent progress on the sorting of carbon nanotubes’ structure with respect to their diameter or number of walls, we investigate by transmission electron microscopy the sorting efficiency, with a comparison with optical absorption spectroscopy measurements. We study density gradient ultracentrifugation sorted single walled or double walled carbon nanotubes, showing obviously the ability to separate carbon nanotubes of different diameters or/and number of walls. This microscopic approach affords accurate information about the sorted samples such as the real mean diameter, the relative concentration of double walled carbon nanotubes over single walled carbon nanotubes, standard deviation, and the real diameter distribution of carbon nanotubes, even beyond any possible accurate analysis from optical absorption spectroscopy. Therefore, we demonstrate that the diameter analysis of the sorted samples by TEM can indeed afford some information about the relevant optical properties of carbon nanotubes
Strong correlation effects in single-wall carbon nanotubes
We present an overview of strong correlations in single-wall carbon
nanotubes, and an introduction to the techniques used to study them
theoretically. We concentrate on zigzag nanotubes, although universality
dictates that much ofthe theory can also be applied to armchair or chiral
nanotubes. We show how interaction effects lead to exotic low energy properties
and discuss future directions for studies on correlation effects in nanotubes
Optimising DNA binding to carbon nanotubes by non-covalent methods
The use of carbon nanotubes as a gene delivery system has been extensively studied in recent years owing to its potential advantages over viral vectors. To achieve this goal, carbon nanotubes have to be functionalized to become compatible with aqueous media and to bind the genetic material. To establish the best conditions for plasmid DNA binding, we compare the dispersion properties of single-, double- and multi-walled carbon nanotubes (SWCNTs, DWCNTs and MWCNTs, respectively) functionalized with a variety of surfactants by non-covalent attachment. The DNA binding properties of the functionalized carbon nanotubes were studied and compared by electrophoresis. Furthermore, a bilayer functionalization method for DNA binding on SWCNTs was developed that utilized RNA-wrapping to solubilize the nanotubes and cationic polymers as a bridge between nanotubes and DNA
Complement activation and protein adsorption by carbon nanotubes
As a first step to validate the use of carbon nanotubes as novel vaccine or drug delivery devices, their interaction with a part of the human immune system, complement, has been explored. Haemolytic assays were conducted to investigate the activation of the human serum complement system via the classical and alternative pathways. Western blot and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques were used to elucidate the mechanism of activation of complement via the classical pathway, and to analyse the interaction of complement and other plasma proteins with carbon nanotubes. We report for the first time that carbon nanotubes activate human complement via both classical and alternative pathways. We conclude that complement activation by nanotubes is consistent with reported adjuvant effects, and might also in various circumstances promote damaging effects of excessive complement activation, such as inflammation and granuloma formation. C1q binds directly to carbon nanotubes. Protein binding to carbon nanotubes is highly selective, since out of the many different proteins in plasma, very few bind to the carbon nanotubes. Fibrinogen and apolipoproteins (AI, AIV and CIII) were the proteins that bound to carbon nanotubes in greatest quantit
Field-effect transistors assembled from functionalized carbon nanotubes
We have fabricated field effect transistors from carbon nanotubes using a
novel selective placement scheme. We use carbon nanotubes that are covalently
bound to molecules containing hydroxamic acid functionality. The functionalized
nanotubes bind strongly to basic metal oxide surfaces, but not to silicon
dioxide. Upon annealing, the functionalization is removed, restoring the
electronic properties of the nanotubes. The devices we have fabricated show
excellent electrical characteristics.Comment: 5 pages, 6 figure
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