On the efficiency of bile salt for stable suspension and isolation of single-walled carbon nanotubes-spectroscopic and microscopic investigations

In this contribution we present a systematic study on the dispersion of SWCNTs in a water-based solution of biocompatible detergent: sodium deoxycholate (DOC). By avoiding harsh chemical conditions, which are known to damage nanotubes structure, a stable SWCNTs suspension was created. Long term stirring of the solution led to preparation of a stable transparent solution, containing welldispersed isolated SWCNTs. The as-prepared dispersion remained stable and clear for two months. Optical absorption spectroscopy was employed to measure SWCNTs suspension stability. Nanotube aggregation was evaluated through the tangential mode (G mode) present in the Raman spectrum. High-resolution transmission electronmicroscopy was employed to observe the mechanism of debundling process. © 2010 Springer-Verlag

On the efficiency of bile salt for stable suspension and isolation of single-walled carbon nanotubes-spectroscopic and microscopic investigations

In this contribution we present a systematic study on the dispersion of SWCNTs in a water-based solution of biocompatible detergent: sodium deoxycholate (DOC). By avoiding harsh chemical conditions, which are known to damage nanotubes structure, a stable SWCNTs suspension was created. Long term stirring of the solution led to preparation of a stable transparent solution, containing welldispersed isolated SWCNTs. The as-prepared dispersion remained stable and clear for two months. Optical absorption spectroscopy was employed to measure SWCNTs suspension stability. Nanotube aggregation was evaluated through the tangential mode (G mode) present in the Raman spectrum. High-resolution transmission electronmicroscopy was employed to observe the mechanism of debundling process. © 2010 Springer-Verlag

On the formation process of silicon carbide nanophases via hydrogenated thermally induced templated synthesis

A thermally induced templated synthesis for SiC nanotubes and nanofibers using ammonia or nitrogen as a carrier gas, single wall carbon nanotubes (SWCNT) as templates as well as gaseous Si is presented. The bundles of SWCNT act as both the carbon source and as a nanoframe from which SiC structuctures form. Depending on the duration of the thermally induced templated reaction, for a fixed temperature, carrier gas, and gas pressure, various SiC nanostructures are obtained. These structures include SiC nanorods coated in C, SiC nanorods, SiC nanotubes, and SiC nanocrytals. From our analysis using transmission electron microscopy (TEM) and scanning electron microscopy (SEM), electron energy-loss spectroscopy (EELS), electron diffraction (EDX), optical absorption spectroscopy and Raman spectroscopy as probes we prove that H has a key role on the morphology and stochiometry of the different SiC nanostructures.Comment: 9 pages, 2 Figure

Carbon nanostructures as a multi-functional platform for sensing applications

The various forms of carbon nanostructures are providing extraordinary new opportunities that can revolutionize the way gas sensors, electrochemical sensors and biosensors are engineered. The great potential of carbon nanostructures as a sensing platform is exciting due to their unique electrical and chemical properties, highly scalable, biocompatible and particularly interesting due to the almost infinite possibility of functionalization with a wide variety of inorganic nanostructured materials and biomolecules. This opens a whole new pallet of specificity into sensors that can be extremely sensitive, durable and that can be incorporated into the ongoing new generation of wearable technology. Within this context, carbon-based nanostructures are amongst the most promising structures to be incorporated in a multi-functional platform for sensing. The present review discusses the various 1D, 2D and 3D carbon nanostructure forms incorporated into different sensor types as well as the novel functionalization approaches that allow such multi-functionality

Facilitating the CVD synthesis of seamless double-walled carbon nanotubes

In this contribution we present a simple laser assisted chemical vapour (LA-CVD) technique that rapidly determines if a given catalyst and feedstock combination are appropriate for the bulk synthesis of double-walled carbon nanotubes (DWCNT) in conventional thermal CVD (T-CVD). Systematic T-CVD studies across a range of temperatures with a Fe–Co catalyst mix for two carbon feedstocks (ethanol and methane) were conducted to validate the LA-CVD technique. The T-CVD findings confirm that the LA-CVD route is appropriate as a fast and easy means to determine the primary carbon nanotube product for a selected catalyst and feedstock in T-CVD. The LA-CVD route reduces the optimization parameters in T-CVD to only that of temperature. The studies led to the bulk production of seamless DWCNT with yields better than 55%

One-step catalyst-free generation of carbon nanospheres via laser-induced pyrolysis of anthracene

Carbon nanospheres with diameters between 100 and 400 nm have been successfully synthesized via low-power laser-assisted pyrolysis of anthracene in a nitrogen atmosphere. The developed facile route yields homogeneous nanoparticles and requires no supplementary carbon feedstock or catalyst. The sharp thermal gradient afforded by the laser results in two kinds of carbon products that differ in crystallinity and mean particle size. Our detailed findings point to the carbon nanospheres being comprised of small-unclosed aromatic layers that are connected together by simple organic linkers. C-H bonds in the anthracene molecules are partiallly broken by the laser beam enrgy, and as the newly created large radicals aggregate, carbon nanospheres are formed

Confined crystals of the smallest phase-change material

The demand for high-density memory in tandem with limitations imposed by the minimum feature size of current storage devices has created a need for new materials that can store information in smaller volumes than currently possible. Successfully employed in commercial optical data storage products, phase-change materials, that can reversibly and rapidly change from an amorphous phase to a crystalline phase when subject to heating or cooling have been identified for the development of the next generation electronic memories. There are limitations to the miniaturization of these devices due to current synthesis and theoretical considerations that place a lower limit of 2 nm on the minimum bit size, below which the material does not transform in the structural phase. We show here that by using carbon nanotubes of less than 2 nm diameter as templates phase-change nanowires confined to their smallest conceivable scale are obtained. Contrary to previous experimental evidence and theoretical expectations, the nanowires are found to crystallize at this scale and display amorphous-to-crystalline phase changes, fulfilling an important prerequisite of a memory element. We show evidence for the smallest phase-change material, extending thus the size limit to explore phase-change memory devices at extreme scales