Water soluble carbon nanotubes

Multi-walled Carbon nanotube, its role and implications in biological systems are currently under evaluation and became interesting for many researchers primarily working on the interface of chemistry, physics and biology. However, concerns about the potential toxicity of multi-walled carbon nanotubes have been raised. To carry such affords, herein we investigate the effects of carboxylic acid functionalized water soluble carbon nanotube (wsCNT) on the growth of gram Cicer arietinum plant. The growth of gram plants was observed with and without the presence of wsCNT to demonstrate that carboxylated functionalized multi-walled carbon nanotubes showed better growth and under more wsCNT, the growth was enhanced without showing apparent toxicity. Although this is a preliminary study with a small group of plants, our results encourage further confirmation studies with larger groups of plants.


Since the discovery of carbon nanotube (CNT)1, exploitation of its application is sought in all possible arena of life and role of CNT in biological systems and medicine is highly important and these area needs newer approaches to do so. For the biological application the important task to make CNT first fairly water soluble is crucial. We have made a simple approach to achieve that and started using water soluble CNT 2 as probe in different biological aspects. The present study deals with its effect on the growth of gram C. arietinum seed under different concentrations of wsCNT.

There are many reports of ingesting of single wall carbon nanotube in macrophage cells without showing any toxic effect3. Gas and water flow measurement through micro fabricated membranes in which aligned CNTs having diameters less than 2 nm served as pores to show that the gas and water permeability of nanotube based membranes were several orders of magnitude higher than those of commercial polycarbonate membranes4. Molecular dynamic simulation on osmotically driven transport of water molecules through hexagonally packed carbon nanotube membrane were simulated in relevance to CNT semi permeable membrane to separate components of pure water and salt solution5. Molecular dynamics simulation of flows of water inside CNTs was also studied6 . However, experimental findings on such phenomena are lacking. Molecular transport across cellular membranes is essential to many of life’s processes. In the molecular life, water and minerals are essential components for growth and their transport to different cells and organs are critically important for survival of a living entity. In vascular plants, root helps plant in transport of water and solutes7 and involved in pumping of water across the plasma membrane into the cytoplasm of cells8 . Pumping of water is due to the water potential caused by the transpiration. We used dicotyledonous plant of gram – C. arietinum seed as it has a very short life cycle, and its vascular bundles are arranged in ring in comparison to monocotyledonous plant in which the vascular bundles are scattered. The growth of gram C. arietinum seed were observed under different concentrations of wsCNT; and it was found that the plant grown in solution having maximum concentration of wsCNT showed maximum growth.

Materials and Methods

Water soluble multiwalled carbon nanotubes (wsCNT) wsCNT which were synthesized as by the prescribed method with slight modification from the previous method2 like standing the carbon soot in concentrated nitric acid overnight and decanted off the sample to remove excess of acid and the black mass was washed with distilled water several times till it was neutral. At the final stage of washing, decantation resulted loss of materials and so the residual water was removed under boiling water bath. Repeated adding water and evaporation under boiling water bath removed trace amount of volatile nitric acid and the nitrate free final wash has been tested using Griess reagent9 . The black residue was finally vacuum dried (300 mg) and subjected to analysis. The highly cabroxylated CNT (wsCNT) thus formed became readily soluble in water under sonication and remained in solution for months without precipitation.


Seeds

eeds of common gram C. arietinum were kept in a dry place in the dark under room dark under room temperature before use. Sprouted (one day) gram seeds were grown in different concentrations of wsCNT (a stock of wsCNT with its concentration 1.45gm /liter was used after sonication to dissolve).


Germination

Seeds were immersed in a 10% sodium hypochlorite solution for 10 min to ensure surface sterility (USEPA, 1996), then, they were soaked in DI-water for germination for one day. Then, sprouted one day gram seeds were then transferred onto the sample vials, which were grown in different concentrations of wsCNT. After 13 days, growth in different parts of the plants like shoot and roots were observed



For Fluorescence

Stock solution of 0.009 gm wsCNT and 0.001 gm CdSO4, (0.004 mmol) (purchased from Sigma Aldrich) was prepared in 10 ml double distilled water and refluxed for 3.5 hrs followed by stirring for 1 hour. Ammonium sulphide was prepared with 25 ml NH4OH in which H2S was passed for 1 minute. 300 µl stock solution was taken in vial 1ml water, into which 1-2 drops of ammonium sulphide was added, to the transverse section (T.S.) and lateral section (L.S) of root. Slides were then prepared and watched under fluorescence microscopy. Ammonium sulphide addition is a necessary step as it converts the CdSO4 into CdS which in turn fluorescence the channel made by wsCNT. After two hours of this exposure, the solution mixture was removed and the root part of the sprouted seed was washed with running distilled water to free it from external CdSO4. The washed sprouted seed root was now dipped into 2ml of distilled water pre-saturated with H2S gas. After 30 minutes, the entire sprouted seed was washed with running distilled water and slides were then prepared from the T.S section of the root. Florescence microscopic images of CdS incorporated into wsCNT showed very distinct tubular structures due to the fluorescence of CdS inside the wsCNT. The excitation wavelength used was 371 nm.





In this study, we report the comparative growth of sprouted (one day) gram seed in the presence of different concentrations of wsCNT in comparison with controlled one, which were imaged by Scanning electron microscope (SEM) equipped with an energy-dispersive X-ray analysis and were recorded with FEI Quanta 200 Hv and “Tecnai 20 G2” 200 kV STWIN used for Transmission electron microscopic (TEM) analysis (Figure 1).








Figure 1 -(A) Scanning electron microscopy image having the scale bar of 5µm; (B) its EDAX analysis showing the presence of carbon and oxygen only; (C) Transmission electron microscopy scale bar 100 nm; (D) High Resolution transmission electron microscopy (inner diameter approx 12 nm) having the scale bar of 5 nm.


To compare the growth in different parts of the plants like shoot and roots, three different sets of five vials were used. In the first set, seeds were grown under controlled condition in the second set 100µl wsCNT solution is added in 5ml double distilled water ; in the third set of vials the concentration of the wsCNT is 200µl wsCNT in 5 ml double distilled water . And for comparison the water level; shoot length, root numbers and root length were observed for 13 days (Figure 2).





showing the comparative growth of gram plants in controlled, 100µl and 200µl wsCNT solution . Comparing the size of wsCNT (10-30 nm) shown in (Figure 1) and xylem (few microns), it can be assumed that the CNT capillary structure may get introduced inside the lumen of treachery elements since the size difference between these two, drifts wsCNT to be incorporated within the xylem according to the concept of the formation of a “large capillary”. This is formed inside the treachery elements of the xylem by head to tail arrangement of one carbon nanotube to the second and thus it provides channelling through which water is conducted. Carbon nanotube thus providing channels through which water can be conducted (Figure 3).




Here in, effects were observed that wsCNT which were initially in the form of cluster aggregates like spaghetti; get aligned in the vascular bundle due to endo-osmotic root pressure caused by xylem10. These vascular bundles run all through the plant and consist of xylem and phloem. Alignment of carbon nanotubes within the treachery elements of xylem has been established by optical microscopy (Figure 4) from the wsCNT treated sprouted gram seed Florescence microscopic images of CdS incorporated into wsCNT showed very distinct tubular structures due to the fluorescence of CdS inside the wsCNT. The excitation wavelength used was 371 nm. The presence of wsCNT in the plant root (especially in the xylem) can be detected by the images obtained from optical microscope shown





(Figure 4) in the absence and in the presence of wsCNT.



(Figure 5) clearly showed the channels fluoresces through the passage of Cd+2 ion subsequently exposed with sulfide to precipitate fluorescing material CdS. To understand the mechanism, inducing growth of the plants, it might be possible that wsCNTs after attaching with the root surface or inner portion of root (such as vascular bundles, cortical region etc.) enhances the capillary action of water absorption as shown by simulated work5,10. Our present work suggested that water is not only occupies these channels but also molecular transport takes place faster inside the plant via xylem where wsCNT acts as membrane that offers both high selectivity and high flux. This consequences almost frictionless and very rapid flow, and the transport is predicted by molecular dynamics, which correlates this enhancement of flux to atomic smoothness of the nanotube surface and to molecular ordering phenomena that may occur on confined length scales in the 1-2 nm range 6 . In atomically smooth pores, the nature of water–wall collision can change from purely diffuse to a combination of Specular and diffused collisions leading to the observed fast transport. This faster transport of water leads to high absorption of water by the roots containing nanotube in the xylem resulting increased length of root, shoot, and root hairs which ultimately increase the productivity. It might be possible that after being adsorbed within the root surface (mainly root hair region) carbon nanotubes retard the salt uptake by making xylem tracheids less porous. As a result of less porosity, it permits the uptake of only small molecules by xylem tracheids where as large molecules became unable to pass through CNTs.
The rate of the survival of the plants (under laboratory condition) grown in CNT solution is more than the plants grown in distilled water only. In the first table it is shown that out of five plants only two plants survived, plants grown with 100 micro liter CNT solution three plants

survived and the plants grown with 200 micro liter CNT solution out of five plants four plants survived, by the end of experiment. The water absorption rate by the plants in the vials containing wsCNT was more than the plants grown in distilled water only. Plants grown in distilled water showed least water absorption, while plants grown with CNT were found to absorb more water and the depletion in water level is more in these vials. The root system of the plants grown with CNT was found to be more branched. The root length (the longest branch of the root) is longest of the plants grown in CNT

MECHANICAL PROPERTIES OF CARBON NANOTUBES

Carbon nanotubes are cylindrical all-carbon molecules composed of concentric graphitic shells with extremely strong covalent bonding of atoms within the shells but very weak van der Waals type interaction between them. Due to the unique atomic structure nanotubes have exceptional electronic and mechanical properties which imply a broad range of possible applications as constituents of nanometer-scale devices and novel composite materials.

In this work we are using computational methods to study the atomistic structure of twist grain boundaries of different rotation angles. We are interested in knowing if the interface of all grain boundaries is comprised of a thin amorphous layer, or if there are certain angles for which the interface is crystalline. We are also interested in the grain boundary energy, since it can be compared to experimental results.

The properties of a carbon nanotube depend on the local atomic configuration and defects. For composite and device development it is essential to understand how structural changes affect the properties and our work strives after shedding some more light on the occurring phenomena. Current projects concentrate on evaluating irradiation and irradiation induced defects as a means to improve carbon nanotube strength, load transfer and inter-shell friction. The tools employed are both classical molecular dynamics and dynamical tight binding methods. Fig. 1 shows an example of a defect typical to irradiation and how such defects can link tubes which efficiently prevents tube-tube slippage

Figure 1. A defect typical to irradiation, a vacancy.

Figure 2.Example of a nanotube bundle in which the nanotubes are linked together by the presence of vacancies

It is becoming clear from recent experiments3-9 that carbon nanotubes (CNTs) are

fulfilling their promise to be the ultimate high strength fibres for use in materials applications.

There are many outstanding problems to be overcome before composite materials, which

reflect the exceptional mechanical properties of the individual nanotubes, can be fabricated.

Arc-discharge methods are unlikely to produce sufficient quantities of nanotubes for such

applications. Therefore, catalytically grown tubes are preferred, but these generally contain

more disorder in the graphene walls and consequently they have lower moduli than the arc-

grown ones. Catalytic nanotubes, however, have the advantage that the amount of disorder

(and therefore their material properties) can be controlled through the catalysis conditions, as

mentioned before. As well as optimizing the material properties of the individual tubes for

any given application, the tubes must be bonded to a surrounding matrix in an efficient way to

enable load transfer from the matrix to the tubes. In addition, efficient load bearing within the

tubes themselves needs to be accomplished, since, for multi-walled nanotubes (MWNTs),

experiments have indicated that only the outer graphitic shell can support stress when the

tubes are dispersed in an epoxy matrix10, and for single wall nanotube (SWNT) bundles (also

known as ropes), it has been demonstrated that shearing effects due to the weak intertube

cohesion gives significantly reduced moduli compared to individual SWNTs6. The reduced

bending modulus of these SWNT bundles is a function of their diameter. An individual tube

has an elastic modulus of about 1 TPa, but this falls to around 100 GPa for bundles 15 to 20

nm in diameter. In summary, there are two main challenges to address: to enable strong

bonding between the CNTs and the surrounding matrix; to create crosslinks between the

shells of MWNTs and also between the individual SWNTs in SWNT bundles, so that loads

can be homogeneously distributed throughout the CNTs. Ideally, both these goals should be

achieved without compromising the mechanical properties of the CNTs too drastically. Efforts

within this group have begun to address these problems using post production modification of

CNTs via chemical means and controlled irradiation.

High resolution transmission electron microscopy (HRTEM) can be used to give

invaluable information about the structure of CNTs, in particular, the amount of

order/disorder within the walls of MWNTs. Atomic force microscopy (AFM) can be used to

measure the mechanical properties of individual CNTs4-7. Use of both techniques has allowed

us to make a correlation between the strength of MWNTs, grown in different ways, with the

amount of disorder within the graphene walls (see below).

The AFM technique developed in our laboratories has already enabled characterisation

of the moduli of SWNT bundles6 and MWNTs, both arc-grown and catalytically grown7. The

method has been described in detail previously6,7. Briefly, it involves depositing CNTs from a

suspension in liquid onto well-polished alumina ultrafiltration membranes with a pore size of

about 200 nm (Whatman anodisc). By chance, CNTs occasionally span the pores and these

can be subjected to mechanical testing on the nanometer length scale. Contact mode AFM

(M5 Park Scientific Instruments) under ambient conditions is used to collect images of the

suspended CNTs at various loading forces. Fig. 4 shows an AFM image of a SWNT bundle

suspended across a pore and a schematic representation of the mechanical test. The maximum

deflection of the CNT into the pore as a function of the loading force can be used to ascertain

whether the behavior is elastic. If the expected linear behavior is observed, the YoungÕs

modulus can be extracted using a continuum mechanics model for a clamped beam

configuration6,7. The suspended length of the CNT, its deflection as a function of load and its

diameter can all be determined from the images, enabling the modulus to be deduced. The

diameter is taken as the height of the tube above the membrane surface at the clamped ends.

Although tip convolution can be a problem in measuring lateral dimensions using AFM, the

height is a reliable measure because the CNTs are essentially incompressible at these loads

(nominal loading forces are in the range 1 to 5 nN). The suspended length can be determined

from line profiles taken either side of the tube. A minimum suspended length is measured

because of the convolution of the tip with the edge of the pore. This means that all the

determined moduli quoted here are minimum values.

The powerful advantage of the AFM technique employed in our laboratory is its

simplicity. There is no need for complex lithographic techniques for suspending and clamping

tubes. The surface forces between the CNTs and the alumina membrane are sufficiently high

to maintain the clamped beam condition in the majority of cases. In addition, the nanotubes

are never exposed to electron radiation during measurement, which is the case for TEM

studies. Radiation will induce defects, if the energy of the electrons is high enough, and

thereby alter the material properties. This is one effect that we are currently utilising in a

positive way in an effort to modulate CNTsÕ mechanical properties. The relative ease of

sample preparation in our AFM method enables a high measurement throughput allowing us

to measure a variety of CNTs synthesized in different ways and to compare the results.

Described below are new data on catalytic MWNTs, and arc-grown SWNT bundles that have

been hydrogenated and exposed to a low-level of radiation. Catalytic MWNTs were produced

through decomposition of acetylene over a cobalt/silica catalyst. The previously measured

catalytic MWNTs were produced at a temperature of 900oC 11, whereas the new data

presented here were obtained on MWNTs fabricated at 720oC. The microstructure of the

catalytic MWNTs has a strong dependence on the synthesis temperature which can be readily

seen via HRTEM.

Figure 4. (a) 3D rendering of an AFM image of a SWNT bundle adhered to the alumina ultrafiltration membrane, leading to a clamped beam configuration for mechanical testing. (b) Schematic representation of the measurement technique. The AFM applies a load, F, to the portion of nanotube with a suspended length of L and the maximum deflection d at the center of the beam is directly measured from the topographic image, along with L and the diameter of the tube (measured as the height of the tube above the membrane).

To produce crosslinks between the shells of MWNTs and between the SWNTs of

SWNT bundles, the sp2 carbon bonding must be disrupted to sp3 bonding so that dangling

bonds are available for crosslinking. Since the sp2 bonding is the essence of the CNTs

strength, this must not be disrupted to such a degree that the properties of the individual shells

in MWNTs or individual SWNTs in bundles are degraded. Hydrogenating CNTs is a first step

towards producing them with internal crosslinking. The MWNTs and SWNT bundles were

hydrogenated using a modified Birch reduction using Lithium and methanol in liquid

ammonia12. The SWNT bundles were subsequently exposed to 2.5 MeV electrons with a total

radiation dose of 11 C/cm2. A theoretical estimation of the number of displacements that this

dose produces suggests that it will create about 1 defect per 360 carbon atoms13.

AFM measurements on the hydrogenated, irradiated SWNT bundles are shown in Fig.

5, along with the previous measurements of untreated SWNT bundles6. As before, the bundles

were dispersed in ethanol using an ultrasonic probe and deposited on the alumina membranes

for measurement by AFM in air. Within the errors of our measurement technique a

strengthening of the bundles was not observed: the YoungÕs modulus still decreases in a

similar trend to the as-grown bundles. However, the treatment does not appear to have

compromised the strength of the individual SWNTs either, since the lower diameter bundles

have comparable moduli. In addition, it was noticed that the treated bundles were more

difficult to disperse in ethanol and the morphology of the sample in the AFM showed that the

bundles exhibited a higher degree of aggregation. Taken together these data suggest that the

radiation treatment produced bonding between the tubes but was not sufficient to produce

enough crosslinks within the bundles to reduce shearing effects and produce bundles with

higher YoungÕs moduli. Future efforts will concentrate on optimising the chemistry and

irradiation doses to improve their mechanical properties.

ELECTRONIC PROPERTIES OF CARBON NANOTUBES

Interest in carbon nanotubes has grown at a very rapid rate because of their many

exceptional properties, which span the spectrum from mechanical and chemical robustness to

novel electronic transport properties. Their physics, chemistry and perspectives for

applications are very challenging. Below we highlight the main results of the Lausanne group

and their collaborators on transport, electron spin resonance, elastic and field emission

properties of single wall (SWNT) and multi-wall (MWNT) carbon nanotubes.

SAMPLES

We use MWNTs produced by arc discharge or by thermal decomposition of

hydrocarbons, and SWNTs either prepared by the arc discharge method in the presence of

catalysts or commercially available (Carbolex, Rice University, MER, DEL). The first step in

the study of CNTs is technological: their purification. This is especially true for SWNTs,

which are severely contaminated with magnetic catalyst particles. The purity of the arc-

discharge fabricated MWNTs is much better, since magnetic materials are not used in their

production. Nevertheless they have to be separated from graphitic flakes, polyhedral particles

and amorphous carbon present in the raw soot. For MWNTs, we have developed a soft

purification method, which uses the properties of colloidal suspensions1. We started the

purification with a suspension prepared from 500 ml of distilled water, 2.5 g of SDS (sodium

dodecyl sulfate; a common surfactant) and 50 mg of MWNT arc powder sonicated for 15

minutes. Sedimentation and centrifugation (at 5000 rpm for 10 minutes) removed all graphitic

particles larger than 500 nm from the solution, as confirmed by low magnification SEM

observations (upper part of Fig. 1). We then added surfactant to the solution to reach 12 CMC

(critical micelle concentration). At these surfactant concentrations, micelles form and induce

flocculation, i.e. the formation of aggregates. These aggregates mostly contain large objects,

while smaller objects remain dispersed, and sediment after a certain time, typically a few

days. After decanting the suspension one week later, we repeat the procedure once or twice.

Fig. 1 (lower part) shows scanning electron microscopy images of a MWNT deposit after the

separation procedure. The untreated material contains a large proportion of nanoparticles

(typically 70 % in number and 40 % in weight). After the purification, the material remaining

in suspension consisted nearly exclusively of nanoparticles, while the sediment contained

nanotubes with a content of over 80 % in weight.

Figure 1. Scanning electron (SEM) micrographs of a MWNT deposit (top) and MWNTs after purification and as a Òside-productÊÓ, nanoparticles of carbon.

For SWNTs, the purification of the raw soot has been carried out by oxidative

dissolution of the carbon encapsulated metal particles with concentrated acid, which ensures

maximum efficacy of the process of metal elimination. A weighed amount of the raw soot

was sonicated in an ultrasonic bath at 25 ûC with concentrated nitric acid for a few minutes

and subsequently refluxed for 4-6 h. Thick brown fumes containing oxides of nitrogen were

seen, indicating the rapid oxidation of carbon to carbon dioxide. After cooling, water was

added so as to leave the samples in 6M HNO3 for the next 8-12h, after which, it was

centrifuged several times and the supernatant rejected until the pH of the solution was around

6.5. High resolution transmission electron microscopy of the material from this solution

showed the presence of long ropes of bundled nanotubes accompanied by small amounts of

carbon-coated metal particles. Parallel examination of the unpurified soot indicated that more

than 80% of the metal had been dissolved. The SWNTs in suspension were stabilized by

using a surfactant such as SDS and left undisturbed for 3-5 days until the slow aggregation of

the nanotubes allowed their separation from the nanoparticles in solution. The nanotube

suspension was filtered through a polycarbonate membrane (1 µm pore size) in order to

eliminate most of the particles. On drying, the sediment on the filter paper peeled away to

form a self supporting sheet of carbon nanotubes. Scanning electron micrographs of such a

sediment, like the one in Fig. 2 shows a network of SWNTs.

Figure 2. Scanning electron (SEM) micrographs of (a) a SWNT deposit and (b) a mat of SWNTs after purification. A few nanoparticles and embedded catalyst particles are still present.

MWNTs are also prepared by catalytic decomposition of acetylene (or other carbon-

containing materials) over supported transition metal catalysts in a temperature range of 700800oC.

This reaction can be carried out under relatively mild conditions in a fixed bed flow

reactor at atmospheric pressure. After optimization, the catalytic method can be suitable for

the production of either single and multiwall or spiral carbon nanotubes.

Figure 3. Scanning electron (SEM) micrographs of MWNTs prepared by catalytic decomposition of acetylene

A further advantage of this method is that it enables the deposition of carbon

nanotubes on pre-designed lithographic structures2, producing ordered arrays which can be

used in applications such as thin-screen technology, electron guns etc. The feasibility of the

deposition of carbon nanotubes on a ceramic membrane and its field emission properties was

demonstrated.

Carbon Nanotubes and Graphene for Electronics Applications

Carbon Nanotubes (CNTs) and graphene exhibit extraordinary electrical properties for organic materials, and have a huge potential in electrical and electronic applications such as sensors, semiconductor devices, displays, conductors and energy conversion devices (e.g., fuel cells, harvesters and batteries). This report brings all of this together, covering the latest work from 78 organizations around the World to details of the latest progress applying the technologies. Challenges and opportunities with material production and application are given.

Applications of Carbon Nanotubes and Graphene for electronics applications



Depending on their chemical structure, carbon nanotubes (CNTs) can be used as an alternative to organic or inorganic semiconductors as well as conductors, but the cost is currently the greatest restraint. However, that has the ability to rapidly fall as new, cheaper mass production processes are established, which we cover in this report. In electronics, other than electromagnetic shielding, one of the first large applications for CNTs will be conductors. In addition to their high conductance, they can be transparent, flexible and even stretchable. Here, applications are for displays, replacing ITO; touch screens, photovoltaics and display bus bars and beyond.




In addition, interest is high as CNTs have demonstrated mobilities which are magnitudes higher than silicon, meaning that fast switching transistors can be fabricated. In addition, CNTs can be solution processed, i.e. printed. In other words, CNTs will be able to provide high performing devices which can ultimately be made in low cost manufacturing processes such as printing, over large areas. They have application to supercapacitors, which bridge the gap between batteries and capacitors, leveraging the energy density of batteries with the power density of capacitors and transistors. Challenges are material purity, device fabrication, and the need for other device materials such as suitable dielectrics. However, the opportunity is large, given the high performance, flexibility, transparency and printability. Companies that IDTechEx surveyed report growth rates as high as 300% over the next five years.

Graphene, a cheap organic material, is being enhanced by companies that are increasing its conductivity, to be used in some applications as a significantly cheaper printed conductor compared to silver ink. All this work is covered in this new report from IDTechEx.
Activity from 78 organizations profiled
IDTechEx has researched 78 companies and academic institutions working on carbon nanotubes and graphene, all profiled in the report. While manufacturers in North America focus more on single wall CNTs (SWCNTs); Asia and Europe, with Japan on top and China second, are leading the production of multi wall CNTS (MWCNTs) with Showa Denko, Mitsui and Hodogaya Chemical being among the largest suppliers. The split of number of organizations working on the topic by territory is shown below.


Split of organizations working on carbon nanotubes and graphene for electronics applications by territory

Source IDTechEx



Opportunities for Carbon Nanotube material supply


A number of companies are already selling CNTs with metallic and semiconducting properties grown by several techniques in a commercial scale but mostly as raw material and in limited quantities. However, the selective and uniform production of CNTs with specific diameter, length and electrical properties is yet to be achieved in commercial scale. A significant limitation for the use of CNTs in electronic applications is the coexistence of semiconducting and metallic CNTs after synthesis in the same batch. Several separation methods have been discovered over the last few years which are covered in the report, as is the need for purification.

Opportunities for Carbon Nanotube device manufacture


There are still some hurdles to overcome when using printing for the fabrication of thin carbon nanotube films. There is relatively poor quality of the nanotube starting material, which mostly shows a low crystallinity, low purity and high bundling. Subsequently, purifying the raw material without significantly degrading the quality is difficult. Furthermore there is also the issue to achieve good dispersions in solution and to remove the deployed surfactants from the deposited films. The latest work by company is featured in the report.


Key benefits:


This concise and unique report from IDTechEx gives an in-depth review to the applications, technologies, emerging solutions and players. It addresses specific topics such as:


* Activities of 78 global organizations which are active in the development of materials or devices using carbon nanotubes or graphene.
* Application to conductors, displays, transistors, super capacitors, photovoltaics and much more
* Types of carbon nanotubes and graphene and their properties and impact on electronics
* Current challenges in production and use and opportunities
* Forecasts for the entire printed electronics market which carbon nanotubes and printed electronics could impact


For those involved in making or using carbon nanotubes, or those developing displays, photovoltaics, transistors, energy storage devices and conductors and want to learn about how they can benefit from this technology, this is a must-read report.

Top Ten Nanotech Products

The overwhelming majority of commercially-available nanotech products on the market today are in sports. Last year, we featured Nanogate/Holmenkol's Cerax Nanotech Ski Wax, Babolat Tennis Racquets using nanotubes and longer-lasting nanoparticle tennis balls from Inmat/Wilson. In 2004, sports led the way for nanotechnology commercialization yet again. From golf balls to footwarmers, athlete skin care to new tennis racquets, consumer demand for better exercise equipment and materials is still driving nanotech revenues