I. Introduction to NanoscienceNanoscience, a field of science which has emerged during the last three decades, nowadays comprises many different fields and starts to play an important role as key technology in applications and business. Nanotechnology means any technology done on nanoscale that has applications in the real world. Science and technology research in nanotechnology promises breakthroughs in areas such as materials and manufacturing, medicine and health care, energy and national security [1, 2].

The term nano comes from the Greek word nanos, which means dwarf. Scientists use this prefix to indicate 10-9 or one billionth. Thus a nanosecond is one billionth of one second; a nanometer is one billionth of one meter, and so on [3]. A nanoparticle is an aggregate of atoms bonded together with a radius between 1 and 100 nm. It is typically consists of 10 to 105

atoms. Thus, the science of nanostructures is defined as dealing with objects on a size scale 1-100nm. The nano word has existed for a long time and it is up to chemists to study the structures and properties of molecules. They have learnt (with the help with physicists) to manipulate them and build more and more complex structures. A number of new materials with nano elements such as ceramics, glass, polymers and fibers making their way to the market and present in all shapes and forms in everyday life, from washing machine to architecture [1,4 ].

Fig.I.1.Objects Size. Adapted from reference [3].

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The properties of materials at the nanoscale can be very different from those at a larger scale. When the dimension of a material is reduced from a large size, the properties remain the same at first, then small changes occurs, until finally, when the size drops below 100nm, dramatic changes in properties can occur. To demonstrate the changes that occur to a material when it is nanosized, let’s consider the element gold. We are familiar with gold as shiny yellow metal that can be worked in to a variety of shapes for our adornment. If you cut a piece of gold in half, each of the halves retains the properties of the whole except that each piece has half the mass and half the volume of the original. Cut each half in half again and any one would still recognize the pieces as gold and so on. You can keep doing this down to a certain size and then the properties of the pieces begin to change. One of these may be the apparent color of the material. When gold is nanoscopic, that is, clusters of gold atoms measuring 1nm across, the particles appear red [2, 3].

In biological systems, nanosized structures plays an important role from proteins to deoxyribonucleic acid (DNA) carrying the genetic code and the ribonucleic acid (RNA). Nanostructures are fundamentals for the properties of bone and teeth. In medical applications, nanosized particles will play a role in diagnosis, therapy and drug delivery. For example, diabetes treatment could be improved by injecting nanoparticles in to the blood that automatically delivered a dose of insulin up on sensing an imbalance in blood glucose level and also cancer may be treated someday soon with an injection of nanoparticles that latch on to cancerous tissue and cook it to death upon external applications of light source that poses no threat to healthy tissue, therefore many scientists think that nanotechnology will eventually affect how people work, what they eat, how they communicate. It will change their medical care, energy sources and water environment [1, 3].

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Fig.I.2. Biological Nanostructures. Adapted from reference[1].

I.1.Characterization Techniques in Nanoscience Research :

Observation is the key to make new discoveries, and this especially true in the nanoscale. In fact as far as nano objects are concerned, one cannot proceed further with the investigations without observing these objects. Characterization tools are crucial in the study of emerging materials to evaluate their full potential in applications and to know their physical and chemical properties [5, 6].

Characterization Techniques Using Electrons:

We use microscopy in order to see objects in more details. Microscope is an instrument used to form enlarged images. The word microscope is derived from two Greek words micros meaning small and skopos meaning to look at [5].

The following definitions must be listed before discussing microscopes:

Resolution :

A measure of capacity of the instrument to distinguish two closely spaced points as separate points given in terms of distance [5].

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Resolving Power :

The resolution achieved by a particular instrument under optimum conditions [5].

Electron microscope is an important lab instrument which depends in its operation on the wave nature of electrons. It resembles an optical microscope in many ways. The important difference is the resolving power. The electron microscope has high resolving power because electrons can carry high kinetic energy and hence very small λ according to de Broglie equation, λ=h/mv. Thus its magnification is so high that it can detect very small objects that optical microscope cannot observe which make e-microscope more appropriate in investigating nanoparticles, the electron beam used travel in vacuum emitted from electron gun such as cathode ray tubes used in television sets and focused using certain type of lens [4, 5].

There are two kinds of microscopy:

1. Transmitting:

The beam passed through the specimen is differentially refracted and absorbed [4, 7].

2. Scanning:

The beam is scanned over the surface. The image is created point- by- point [4, 7].

I.1.1. Types of Electron Microscopes:

I.1.1.1. Transmitting Electron Microscope (TEM):

Equipment which let the incident electron beam to transmit a thin specimen at high acceleration voltage, 80-30,000 KV, which results in generating signals caused by the interaction between the specimen and incident electrons. Structures, compositions and chemical bonding of the specimen can be determined from these signals [4, 8].

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In general there are three types of transmitted electrons observed by TEM:

a. Unscattered electrons:

Caused by incident electrons transmitted through the thin specimen without any interaction occurring inside the specimen. Since the amount of unscattered electrons is inversely proportional to the specimen thickness, thicker areas of the specimen have fewer unscattered electrons and appear darker [5, 8].

b. Elastically scattered electrons:

Caused by the incident electrons that are scattered by atoms without losing energy. Elastic scattering occurs from well-ordered arrangements of atoms as in crystals, result in coherent scattering, giving spot patterns and each spot is corresponding to a specific atomic spacing [5, 8].

c. Inelastically scattered electrons:

Caused by the incident electrons that interact with atoms in specimen with losing their energy. Inelastic loss of energy by the incident electrons is characteristic to the elements. These energies are unique to each bonding state of each element and thus can be used to extract both compositional and chemical bonding information of the specimen [5, 8].

TEM offers high magnification ranging from 50 to 106 . The final resolution is related to the associated wave length of the electrons and therefore to their energy [5, 8].

I.1.1.2. Scanning Electron Microscope (SEM):

It is one of the most widely used techniques used in characterization of nanomaterials and nanostructures [7]. The surface of sample under study is scanned with an electron beam, the interaction between the electrons and sample surface give rise to different signals which when gathered and analyzed bring together the image of the surface of the observed sample

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without using mathematical process, contrary to process of the TEM. The resolution of this type of instrument enables scientists to view objects at an atomic scale (1/10 of a nanometer) [4, 5].

Fig.I.3. An image of an ant in a Scanning Electron Microscope. Adapted from www.wikipedia.org

I.2.Top down and Bottom up Approaches to Nanotechnology :

Top down Approach:

Involves the breaking down of large pieces of material to generate the nanostructures from them [2, 4].

Bottom up Approach:

This implies assembling single atoms and molecules in to larger nanostructures [2, 4].

Fig.I.4.Top down and Bottom up Approaches. Adapted from www.gitam.edu

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I.3.Nanoparticles Synthesis Methods :

Nanoparticles can be synthesized by a variety of methods using gas, liquid or solid phase processes. These includes gas phase processes of flame pyrolysis, high temperature evaporation, microwave irradiation, physical and chemical vapor deposition synthesis, colloidal or liquid phase methods in which chemical reactions in solvent lead to the formation of colloids , molecular self assembly and mechanical processes of size reduction including grinding and milling [8,9].

Gas phase synthesis approaches are based on homogenous nucleation of a supersaturated vapor and subsequent particle growth by condensation, coagulation and capture [8, 9].

Fig.I.5.Mechanism of nanoparticle production using vapor phase or liquid phase/colloidal methods. Adapted from reference [9].

The supersaturated vapor can be generated in many ways depending on chemical nature of the material, but typically by heating a solid and evaporating it in to carrier gas phase. The supersaturation is achieved by cooling or by chemical reaction or by some combination of these. The supersaturated vapor can nucleate homogenously in the gas phase and also heterogeneously by contact with surfaces. The nuclei grow by collision and condensation to give rise to distribution of particle sizes and morphologies.

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Depending on the heating and cooling processes used, there are a wide range of gas phase methods such as flame pyrolysis and laser ablation [8, 9].

Colloidal methods depend on precipitation processes in solutions. For example, solutions of different ions can be mixed under controlled conditions of temperature and pressure to form insoluble precipitates. By controlling the nucleation and growth kinetics, particles of various sizes and morphologies can be produced [8, 9].

The molecular self assembly method is a spontaneous process by which nanoparticles are created starting from molecules. This is a particularly effective method for production of polymeric nanoparticles. An added advantage of this approach is the ability to produce thermodynamically stable nanoparticles whose size and shape can be controlled [8, 9].

In addition to nanoparticles approaches in gas or liquid phases, it is also possible to use solid substrates as heterogeneous nucleating sites to build up nanoparticles at solid-liquid interfaces. By using patterned surfaces, one may be able to control the nucleation and growth processes thereby affecting the nature of nanoparticles produced [8, 9].

All of the above synthesis approaches starts at the molecular level to build up or create the nanoparticles. In the opposite direction, mechanical size reduction methods such as grinding and milling have also been employed to generate nanoparticles. These methods are the traditional approaches to produce nanoparticles [8, 9].

To avoid particle aggregation in the course of the size reduction process, the grinding and milling operations are often carried out with colloidal stabilizers [8, 9].

Once the nanoparticles are produced and purified to a satisfactory level it is often necessary to introduce surface modifications [8, 9].

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The surface modification can be for the purposes of:

1. Passivating a very reactive nanoparticle [9].

2. Stabilizing very aggregative nanoparticles in a medium where the nanoparticles are to be dispersed [9].

3. Functionalizing nanoparticles for applications [9].

4. Promoting the assembly of nanoparticles [9].

Fig.I.6.Surface Modifications. Adapted from reference [9].

a) Surface treatment to make interfacial tension at the nanoparticle-medium interface close to zero allowing for thermodynamic stability of the nanoparticles dispersion.

b) Surface adsorption of a surfactant to provide inter-particle electrostatic and/or steric repulsion that would provide kinetic stability of nanoparticles dispersion.

c) Surface modification to make the nanoparticle functional in one of many ways including hydrophobic or hydrophilic, the ability to bind to specific molecular recognition elements, DNA, enzymes, etc.

For most practical application, the nanoparticles have to be assembled, similar to how atoms and molecules are assembled in to matter. For example, a sensing device may require that nanoparticles be arranged with specified inter- particle separation [9].

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Fig. I.7.Assembling nanoparticles for applications such as nanoparticles with stabilizing polymer molecules around them in a random arrangement to create porous nanoparticle system for catalytic or adsorption applications. Adapted from reference [9].

Nanoparticles constitute the building blocks for nanotechnology and thus for numerous potential applications in energy and power, health and biomedicine, electronics and computers, environmental applications, new engineering materials, consumer goods, personal care products, foods and transportation. To perform these functions nanoparticles have to be synthesized, passivated to control their chemical reactivity, stabilized against particle aggregation, and functionalized to achieve performance goals and in table I.1 some of this applications[4,9].

Table I.1. Nanoscience Applications adapted from reference [9]

Biomedicine Antibacterial creams and powder (Ag).

Bone growth promoters

Consumer goods and personal care products

Sunscreens(ZnO and TiO2) Tennis balls and rackets

Environmental Self-cleaning glass Water treatment

Food Flavors and colors in food and beverages

Food packing materials Food pathogen sensing

Transportation High strength, light weight

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composites for increasing fuel efficiency

Wear-resistant tiresEngineering materials Chemical sensors

Molecular sieves Lubricants Pigments(metals and metals

oxides) Wear-resistant coatings

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II. Carbon NanotubesII.1. Definition : A flat layer of graphite rolled in to a tube [5].

Fig.II.1. Structure of Diamond and Graphite. Adapted from http://www.tutorvista.com

Fig.II.2. Single-Walled Carbon Nanotube. Adapted from http://www.guardian.co.uk

II.2. Structure of Carbon Nanotubes:

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Carbon NanotubesSingle-Walled

(SWNT)a)zigzag

b)arm-chair

c)helical

Multi-Walled(MWNT)

Fig.II.3.Types of Carbon Nanotubes

There are two main types of Carbon Nanotubes:

II.2. 1. Single- Walled Nanotubes (SWNT):

it is relatively easy to imagine a single wall carbon nanotube .Ideally it is enough to consider a perfect graphene sheet (Graphene is a polyaromatic monoatomic layer consisting of sp2-hybridized carbon atoms arranged in hexagons, graphite consist of layers of this graphene) and to roll it in to a cylinder as shown in fig.II.2 SWNT can be produced by laser ablation, high pressure CO conversion (HiPCO), or the arc discharge technique [2, 10].

Fig.II.4a-c.showing three different structures of SWNT (a) zigzag (b) arm-chair (c) helical. Adapted from reference [2]

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Zigzag, arm-chair and helical refers to the arrangement of hexagons around the circumference. Zigzag and arm-chair structures have plane of symmetry while helical structure has no plane of symmetry [2, 10].

Fig.II.5a,b.High resolution (TEM) of a bundle of SWNTs (a) Longitudinal view (b) cross-sectional view. Adapted from reference [2].

II.2. 2. Multi-Walled Nanotubes (MWNT)

The easiest MWNT to imagine is the concentric type(c-MWNT), in which SWNTs with regularly increasing diameters are coaxially arranged in to a multiwall nanotube [2,11].

Fig.II.6. Concentric MWNT. Adapted from http://www.umi.surrey.ac.uk

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Such nanotubes are generally formed either by electric arc technique, by catalyst enhanced thermal cracking of gaseous hydrocarbons, or by CO disproportionation [2, 11].

Fig.II.7. TEM image of an MWNT. Adapted from reference [2].

II.3 . Synthesis of Carbon Nanotubes II.3.1 . Solid Carbon-Based Production

II.3.1.1. Laser Ablation

In the laser ablation process, a pulsed laser vaporizes a graphite target in a high-temperature reactor while an inert gas is inserted into the reactor

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which swept carbon species that deposited on cooler surfaces of the reactor forming nanotubes [2, 11].

Fig.II.8. laser Ablation. Adapted from reference [2]

II.3.1.2. Electric Arc Method

Principle:

Vaporizing carbon in presence of catalyst (ex.Fe and Ni) in atmosphere of inert gas (Ar or He) [2, 11].

After triggering an arc between 2 electrodes, plasma is formed which consists of a mixture of carbon vapors, gas and catalyst vapors which deposited on different parts of the reactor as carbon nanotubes [2, 11].

Fig.II.9. Electric Arc Method. Adapted from reference [10].

II.3.2 .Gaseous Carbon Based Production

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The catalysis enhanced thermal cracking of gaseous carbon source (hydrocarbons, carbon monoxide) commonly referred to catalytic chemical vapor deposition (CCVD) [2, 11].

There are two types of CCVD:

A) Homogenous

If everything takes place in gas phase [2].

B) Heterogeneous

If a solid substrate is involved [2].

II.3.2.1. Homogeneous Process

Typical reactor for this method is a quartz tube placed in an oven in to which gaseous feed stock containing metal precursor, carbon source ,some H2 and gases as (N2, Ar or He) is passed[2, 11].

First zone of the reactor kept at lower temperature and the second zone where formation of nanotubes occurs heated to 700-1200 oC[2].

Metal precursor is generally metal-organic compound as Fe (CO)5 which decomposes in the first zone generating nanosized metallic particles that catalyze nanotubes formation [2, 11].

In the second part of the reactor, the carbon source is decomposed to atomic carbon which is responsible for the formation of nanotubes[2, 11].

II.3.2.2. Heterogeneous Process

Passing a gaseous flow containing a given proportion of hydrocarbons (ex.CH4) as a mixture with either H2 or Ar over small transition metals particles that are deposited on inert substrate by spraying suspension of metal particles on it[2, 11].

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Decomposition of hydrocarbons represented by:

In case of carbon monoxide:

Fig.II.10. Heterogeneous CCVD adapted from reference [2]

II.3.3 .Templating Technique:

Another interesting technique, that is not suitable for mass production, is the templating technique. It is able to synthesize carbon nanotubes without any catalyst. The principle of this technique is to deposit the hydrocarbon on to the walls of a porous substrate whose pores are arranged in parallel channels. The substrate may be alumina or zeolite which contain natural channel pores. The whole system is heated to the temperature that cracks the hydrocarbon selected as carbon source [2, 11].

Both MWNT (exclusively concentric type) and SWNTs can be obtained. The smallest SWNTs (diameters ≈ 0.4nm) were actually obtained by this technique. The nanotube lengths are determined by the channel lengths , in other words by the thickness of the substrate plate[2, 11].

One main advantage of the technique is the purity of the tubes. On the other hand, the nanotube structure is not closed at both ends, which can be advantage or a drawback depending on the application. The

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porous matrix must be dissolved using one of the chemical treatments previously cited in order to recover the tubes [2, 11].

Fig.II.11. Templating Technique adapted from reference [2]

II.4 . Purification: Purification is an important problem faced in the use of SWNTs for various purposes. Synthesized SWNTs prepared by processes as arc- discharge, laser ablation, HiPCO and pyrolysis of hydrocarbons or organometallic precursors, contain carbonaceous impurities, typically amorphous carbon and graphite nanoparticles, as well as particles of transition metal catalyst. Generally, dilute mineral acids are used to remove the catalyst metal nanoparticles, as concentrated acid tend to functionalize and even destroy the nanotube. Amorphous carbon cannot be eliminated completely by air oxidation due to the presence of metal nanoparticles that catalyze the oxidation of SWNTs at relatively low temperature. A typical procedure for purification of SWNTs synthesized by the arc method is to carry out intial air oxidation at 300 oC followed by acid washing, and then heating in H2 at 700-1000 oC.whereas, in air; oxidation converts amorphous carbon to CO2 which converted to CH4 on hydrogen treatment [11, 12].

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II.5. Filling and Functionalizing Carbon Nanotubes: To further modify the properties of carbon nanotubes in a controlled manner, several functionalization have been thought to make them chemically active and also by filling them with certain substances for certain application.

CNTs filled with metals could provide potential application in catalysis [1, 11]. On the surface of carbon nanotubes, the outside functionalization is of interest for material science, nanoelectronics and biological applications. Making use of the extremely strong SWNTs together with polymers, the mechanical properties such as stiffness of these composites could, in theory, be enhanced by a factor of ten or more. In present, the materials are far from approaching these values because of inability to disperse CNTs effectively in polymers. A step in the direction of solving this problem is functionalization of SWNTs with pH-sensitive poly (acrylic acid) molecules providing pH-controlled solubility and dispersion in water [1].

At lower pH, the polymer is highly coiled, allowing CNTs to bundle together. At high pH, the polymer is negatively charged and becomes more extended as the side groups repel each others.

Fig. II.12. SWNTs with pH-sensitive poly (acrylic acid) molecules adapted from reference [1].

II.6. CNTs Growth Mechanisms: The growth mechanisms of CNTs are still the source of much debate. However, research have been impressively imaginative, and have come up

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with a number of hypothesis. One reason for the debate is that the conditions that allow carbon nanofilaments to grow are very diverse, which means that there are many related growth mechanisms. For a given set of conditions, the true mechanism is probably a combination or a compromise between some of the proposals. Another reason is that the phenomenon that occurs during growth is pretty rapid and difficult to observe insitu [2, 11].

II. 6.1. Floating Catalyst Method :

Synthesis routes that use floating catalysts include arc discharge, laser ablation, HiPCO and thermal CVD methods. In the arc discharge and laser evaporation routes that the catalyst material and the carbon are evaporated due to the arc or laser, respectively. In CVD, the decomposition of metal-based compound (ex: Ferrocene) is the way to provide metal catalyst species, the carbon is provided via the decomposition of hydrocarbon. Once the catalyst and carbon species have been vaporized they begin to form clusters as they cool. As they cool further they coalesce yielding catalyst particles saturated with carbon. As the system cool further the catalyst particles precipitate carbon, forming a nucleation cap and as more carbon is added, a carbon nanotube is extruded. With floating catalyst system, usually SWNTs are obtained [2, 11].

Fig. II.13. CNT Growth adapted from [13]

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If the particle is too small, insufficient carbon would be available for a stable cap to form and if the particle was too big, the particle would have an excess of carbon that would encapsulate the particle. However, if the catalyst particles volume to surface area is just right, a graphitic hemisphere would form providing the nucleation cap [2, 11].

II. 6 .2. Supported Catalyst Routes :

In supported catalysis of CNTs, the effect of the substrate on the catalytic process is still unknown since there are many chemical reactions between the substrate and the catalyst metal. Two modes of growth mechanisms in supported catalyst have been identified: the base growth mode, in which the catalyst particle resides on the support throughout the process, and the tip growth mode, in which the catalyst detaches from the support [2, 11].

The number of walls increases as the catalyst particles size increases. This is in keeping with the catalyst volume to surface area model described for floating catalyst, but modified to account for catalyst particle interaction with the support. In this scenario encapsulation of a catalyst particle is prevented and results in a multicap formation [2, 11].

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Fig.II.14. Supported Catalyst Modes. Adapted from reference [14]

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Fig.II.15. Floating and Supported Catalyst. Adapted from reference [11]

II. 6 .3. Catalyst Free Routes :

Catalyst free routes in which no catalyst particle is used. An example is the template synthesis of carbon nanotubes in porous alumina with no catalyst particle present in pores. The porous alumina is subjected to CVD conditions similar to catalytic CVD and graphitic walls are found to form in the pores forming MWNTs. Similar studies using a variety of oxide nanoparticles found several layers of graphene to form on the surface. They appear to root from step sites on the oxide surface. Step sites are well known as catalytic sites. Another route to form CNTs is via the decomposition of SiC in presence of CO at temperature between 1400-1700 oC . As the SiC decomposes, graphitic structures like CNTs emerge [11, 14]. The decomposition argued to occur as the following:

Fig. II.16. Catalyst Free Route Example. Adapted from reference [14]

II.7 . Physical Properties of CNTs : 1. Nanotubes have high strength to weight ratio (density of 1.8g/cm3

for MWNTs and 0.8g/cm3for SWNTs)and this useful for light weight applications[2,5].

2. The surface area of nanotubes is in order of 10-20 cm2/g which is higher than that of graphite [2, 5].

3. Nanotubes are expected to have high thermal conductivity and the value increases with decrease in diameter [2, 5].

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II. 8. General Properties of SWNTs:

They are stable up to 750 oC in air and they are stable up to 1500-1700

oC in inert atmosphere [2, 5]. They have half the mass density of aluminum. The properties of SWNTs, like any molecule, are heavily influenced by the way that its atoms are arranged. The physical and chemical behavior of SWNTs is therefore related to its structure [2, 5].

II. 8.1. Adsorption Properties of SWNTs :

An interesting feature of a SWNTs that it has the highest surface area of any molecule due to the fact that a graphene sheet is probably the only example of a sheet like molecule that is energetically stable under conditions[2,5].

In reality, nanotubes specifically SWNTs are usually associated with other nanotubes in bundles rather than a single entity. Each of these associations has a specific of porosities that determines its adsorption properties. Theoretical calculations have predicted that the adsorption on to the outer or inner surface of a bundle of a nanotube bundle is stronger than that on to an individual tube. The adsorption of gases in to a SWNT bundle can occur inside the tubes (pore), in the interstitial triangular channels between the tubes, on the outer surface of the bundle and in the grooves formed at contacts between adjacent tubes on the outside of the bundle[2,5].

Fig.II.17.SWNT Bundle. Adapted from reference [2]

II. 8.2. Mechanical Properties :

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CNTs are unique due to the particularly strong bonding between carbons (SP2hybridization) of the curved graphene sheet, which is stronger than diamond (SP3hybridization), as revealed by the difference in C-C bond length (0.142 vs. 0.154nm for graphene and diamond respectively); this makes CNTs particularly stable against deformations. The tensile strength of SWNTs can be 20 times of steel [2, 5].

II. 8.3 . Electronic Properties:

Nanotubes can have distinctly different electronic properties depend on chirality; early calculations show that they can be semiconducting or metallic depending on the type of structure, for example arm chair is always metallic. As the diameter increases tubes resembles graphite which can be metallic. The presence of defects on the body of the surface can alter electronic structures and can make regions of specific electronic properties, such as metallic and semiconducting [2, 5].

III. Carbon nanotubes applications III.1 . Increasing octane number of gasoline using functionalized CNTs

The octane number is one of characteristic of spark ignition fuels such as gasoline. Octane number can be improved by addition of oxygenates such as ethanol, MTBE (methyl tertiary butyl ether), TBF (tertiary butyl formate) and TBA (tertiary butyl alcohol) and also CNTs containing amide group can be added to gasoline to increase the octane number[15,16].

In this study, using octadecylamine (CH3 (CH2)17NH2) and dodecylamine (C12H25NH2), CNTs were amidated and the amino-functionalized CNTs were added to gasoline. Addition of oxygenates improve ignition and combustion efficiency, stabilize fuel mixture, protect the motor from abrasion and reduce pollutant emission. Emissions from gasoline engines seriously threaten the environment and are considered as one of the major sources of air pollution which can cause serious health. Nanomaterials can act as burning rate catalyst because when added to liquid fluids, they accelerate burning rate and

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promote clean burning as they decrease the hazardous such as particular matter(PM) and carbon monoxide(CO) emissions to the environment[15,16].

III.1.1. Synthesis of Functionalized CNTs

a.Ozonolysis:

By using ozone and hydrogen peroxide to produce MWNTs with high content of carboxyl functional group [15].

B.Acyl chlorination of CNTs :

Achieved by thionyl chloride (SOCl2) [15].

c.Amidation :

By adding acyl chlorinated MWNTs to dodecylamine (dda) or octadecylamine (oda) [15].

Fig.III.1. Synthesis of Functionalized CNTs. Adapted from reference [15].

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III.1.2. Addition of Functionalized CNTs to Gasoline :

An amount of functionalized CNTs were added to an amount of gasoline for achieving two samples containing 5 and 7 ppm [15].

Fig.III.2. samples of gasoline. Adapted from reference [15].

III.1.3. Octane Number Analysis :

Adding amido-funcationalized MWNTs to the gasoline, the octane number increases, and the effect of octadecylamine is more than dodecylamine in increasing octane number [14]

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Fig. III.3. Octane Number Analysis. Adapted from [15].

III.2. The adsorption of resorcinol from water using MWCNTs:

Phenolic compounds used as industrial raw materials for many drugs, dyes, weed killers, insecticides, and explosives. They are typical examples of waste water pollutants of high toxicity to human health and environment, the increasing public concerns for environmental problems as the pollution of water resources; highlight the treatment process of waste water [16, 17]. Therefore, the adsorption of resorcinol and other phenolic derivatives on MWCNTs has been investigated in attempt to use MWCNTs as efficient adsorbents for pollutant. MWCNTs showed higher adsorption ability in a rather wide pH range of 4-8 for resorcinol. Other phenolic derivatives such as phenol, catechol and pyrogallol were employed to study the influence of number and position of hydroxyl groups on adsorption capacity. The amount adsorbed by MWCNTs increased with the increasing number of hydroxyl. The substitution of phenol with hydroxyl in a meta position leads to a much higher absorption ability than substitution in ortho or para positions, which suggested that MWCNTs possess a great potential in removal of resorcinol from water [17, 18].

When pH is lower than 6, there is a slight increase in the uptake of resorcinol with the decrease of pH value. The solubility of resorcinol is dependent on pH due to weak acidity of resorcinol in nature, the solubility of resorcinol decreases with the decrease of pH value, thus the uptake of resorcinol on MWCNTs increased with the decrease of pH value [17, 18].

The amount adsorbed of the adsorbed phenolic derivatives on to MWCNTs calculated by the initial concentration minus the equilibrium concentration as shown in the following equation:

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Where qe is the adsorbed amounts by MWCNTs (mg/g) after equilibrium, Co the initial concentration (mg/ml), Ce the equilibrium concentration (mg/ml), m is the MWCNTs dosage (g), V the solution volume (ml) [17].

III.3. NaCl adsorption in MWCNTs/active carbon combination electrode

A new process for fabricating electrochemical double layer capacitors employing active carbon and MWCNTs to adsorbs Na+and Cl- from NaCl solution. Due to their unique mesoporosity (A mesoporous material containing pores with diameters between 2 and 50 nm), active carbons have high ability to desalt NaCl.But they have many defects such as high electrical resistance, high energy consumption and since CNTs is a new material which has low electrical resistance, we can composite the merits of active carbon and carbon nanotube and develop carbon nanotube/active carbon materials combination electrode, the pores of the electrode are used to store ions and the ions moved to the electrodes which has reverse polarity [20, 21].

Fig.III.4a,b. Desalination Theory (a) NaCl adsorption (b)process of regeneration. Adapted from reference [20]

Fresh water is obtained, as in fig.III.4 (a) shows. When ions are saturated in the electrodes, we change the polarity of electrodes, as fig.III.4 (b) shows; the ions can flow from electrodes by repulsive force, and the electrodes regenerated.

III.4. Cancer Treatment:

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CNTs are so small they might one day be used to target and destroy individual cancer cells. By treating CNTs with certain proteins, scientists are developing a method to bind them specifically to cancerous cells. Once attached, the CNTs, which are excellent conductors of heat, could be exposed to infrared light shone through the patient's skin. The light would heat the CNTs to a temperature high enough to destroy the cancer cells while leaving surrounding tissue undamaged. While more research must be done, this method could offer a way to treat certain cancers without harming healthy tissue [11, 19].

IV. CNTs HazardsIV.1.Occupational Exposure to CNTs can occur:

1. During manufacture.2. Through incorporation in other material (ex: medical applications and

electronics).3. Generating nanoparticles in non-enclosed systems. 4. During research in to their properties and uses.5. As result of incorrect disposal.6. As a result of accident spillage [23].

The following figure shows the risk management steps

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Fig.IV. Risk Management Steps .Adapted from reference [23]

IV.2.Effect of CNTs on Health:

Emerging data indicates that when CNTs are breathed they cause lung inflammation and fibrosis. The type of CNT, its physical form and presence of impurities and surface modifications influence the severity of the response but at present there is not enough information which factors of high concern. It is also not clear that if inhaled CNT have a role in the development of adverse health effects at other sites in the body. There is an increasing body of evidence to suggest that CNTs and other nanomaterials with a long, thin and straight shape may be particularly hazardous. There is some evidence to that CNTs may be able to provoke inflammatory reactions in the skin but more

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information is required to properly understand the conditions of exposure that are required to produce such effects[22, 23].

Mass production of CNTs and their application in nanomedicine lead to increased exposure risk of nanomaterials to human beings. They are tested as new materials for biological and biomedical application. Because of their abilities to bind cells and across cell membrane, functionalized CNTs can be used as nanovectors for drug delivery and cancer phototherapy. On the other hand, when injected intravenously, CNTs will interact directly with immune cells and proteins in blood and tissues. Immunotoxicity is one of results of using nanoparticles. Immunity is the function of the body to eliminate the pathogens and foreign particles [22, 23].

V.Conclusion

The universe is 10 billion years old and for several years out of these 10 billion years we have been developing nanoscience. Now it is time for nanoscience.

To catch up with the nanotechnology era, first thing to be done is should be to educate the future’s scientists in this field. People should be knowledgeable about every aspects of nanotechnology such as its applications importance .The National Science Foundation predicts that the global market place for goods and services using nanotechnologies will grow to $1 trillion by 2015.The United States invest approximately$3 billion dollar annually in nanotechnology research and

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development. This dollar figure accounts for approximately one-third of total public and private sector investments worldwide thus we must unify our efforts in nanotechnology research to face problems in the future.

Nano =

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