seminar report- functionalization of carbon nanotubes

7/28/2019 Seminar Report- Functionalization of Carbon Nanotubes

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Functionalization of Carbon Nanotubes

A

TECHNICAL SEMINAR REPORT ON


By

Shehaab Savliwala

TE- B- 01 (Gr. No. 101357)

DEPARTMENT OF CHEMICAL ENGINEERING

VISHWAKARMA INSTITUTE OF TECHNOLOGY(An Autonomous Institute, Affiliated to Pune University)

Academic Year 2012-13


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CERTIFICATE

Bansilal Ramnath Agarwal Charitable Trusts

VISHWAKARMA INSTITUTE OF TECHNOLOGY

(An Autonomous Institute affiliated to the University of Pune)

(Academic Year 2012- 13)

Department of Chemical Engineering

It is certified that the seminar work entitled


Submitted by

Shehaab Savliwala (T.E.-B- 01), Gr. No. 101357

Is the original work carried out by him under the supervision of Prof.

Mrs. Shachi Nigam for the partial fulfillment of the requirement of the

University of Pune, for the award of the Bachelor of Chemical

Engineering.

Prof. Mrs. Shachi Nigam, Prof. Dr. D.S. Bhatkhande,Guide He ad of De pa r t me nt ,

Chemical Engineering Dept. Chemical Engineering Dept.


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Department of Chemical Engineering, Vishwakarma Institute Of Technology 3

Acknowledgements

It is matter of great pleasure for me to submit this seminar report on

Functionalization of Carbon Nanotubes, as a part of curriculum for award

ofBachelor ofChemical Engineering.

I am thankful to my seminar guide Prof. Mrs. Shachi Nigam, Chemical

Engineering Department for her constant encouragement and able guidance.

I am also thankful to Prof. D.S. Bhatkande, Head of Chemical

Engineering Department for his valuable support.

I take this opportunity to express my deep sense of gratitude towards

those, who have helped me in various ways, for preparing my seminar. At

the last but not least, I am thankful to my parents, who had encouraged &

inspired me with their blessings.

Shehaab Savliwala.


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Table of Contents

1. Abstract2. Introduction

2.1. Structure of Carbon Nanotubes (CNTs).2.2. Synthesis Methods.2.3. Reactivity of CNTs.2.4. Need for Functionalization: Current, Potential Applications.

3. Functionalization of Carbon Nanotubes3.1. End Functionalization3.2. Modification of the Carbon Nanotube Outerwall3.3. Functionalization of The Innerwall3.4. Physical Chemistry of CNTs3.5. Non-covalent Chemistry.

4. Conclusion.5. References.


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1. Abstract.

Carbon Nanotubes have a unique molecular structure that results in extraordinary

macroscopic properties, including high tensile strength, high electrical

conductivity, high ductility, high heat conductivity, and relative chemical

inactivity. Owing to these properties, carbon nanotubes have myriad potential

applications as structural materials, in electronics, optics and other fields of

materials science and technology. However, these applications are limited by our

capability to mold CNTs according to our requirements. Due to the difficulty in

synthesis and their low reactivity, it is difficult to synthesize CNTs with the

surface and bulk properties demanded for specific applications (e.g.

Biocompatibility for nanotube biosensors or interfacial strength for blending with

polymers). Therefore, chemical modification (including surface and interfacial

modification) of CNTs becomes essential.

Judicious application ofsite-selective reactions to non-aligned and aligned carbon

nanotubes has opened a rich field of carbon nanotube chemistry. The tips of carbon

nanotubes are more reactive than their sidewalls, allowing a variety of chemical

reagents to be attached at the nanotube tips. Recently, some interesting reactions

have also been devised for chemical modification of both the inner and outer

nanotube walls, though the seamless arrangement of hexagon rings renders the

sidewalls relatively unreactive. This report provides a brief summary of the recent

progress made in the research on chemistry of carbon nanotubes.


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2. Introduction.

Since their discovery by Iijima in 1991, carbon nanotubes have received

considerable attention. Carbon Nanotubes (CNTs) are allotropes of carbon with a

cylindrical nanostructure. They can be thought of as cylindrical fullerenes.

Nanotubes have been constructed with length-to-diameter ratio of up to

132,000,000:1[1]

, significantly larger than for any other material. Carbon nanotubes

can be metallic or semi-conductive, depending on their diameters and arrangement

of hexagon rings along the tube length. Apart from the interesting electronic

characteristics, carbon nanotubes exhibit excellent mechanical and thermal

properties. These interesting physicochemical properties make carbon nanotubes

very attractive as electron emitters in field emission displays, reinforcement fillers

in nanocomposite materials, scanningprobe microscopy tips, actuators and sensors,

as well as molecular-scale components in micro- or nano-electronic devices.[1]

However, it is difficult to synthesize carbon nanotubes with the surface

characteristics demanded for specific applications (e.g. strongly interfacing with

polymers in nanocomposites, or good biocompatibility for nanotube sensors).

Therefore, surface modification and interfacial engineering are essential in

making advanced carbon nanotubes of good bulk and surface properties.

Due to the seamless arrangement of hexagon rings without any dangling bonds,

carbon nanotube walls are rather unreactive. Like C60 fullerene, the fullerene-like

tips of nanotubes are known to be more reactive than the cylindrical nanotube

walls, and hence certain reagents can more readily react with the tips[2.3]

. However,

this does not impact significantly on the chemistry of nanotubes as a whole due to

the relatively smallproportionofthetipsinthestructure.Although research on the

chemical modification of carbon nanotubes is still in its infancy, some interesting

work on carbon nanotube chemistry has recently been reported in literature. I shall

now attempt to present an overview on carbon nanotube chemistry, covering both


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the covalent and non-covalent reactions at the tips, outerwalls, and innerwalls of

SWNTs.

2.1. Structure of Carbon Nanotubes (CNTs).

Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled

nanotubes (MWNTs). These elongated tubularmacromolecules consist of carbon

hexagons arranged in a concentric manner with both ends normally capped by

fullerene-like structures.

The structure of a SWNT can be conceptualized by wrapping a one-atom-thick

layer of graphite called graphene into a seamless cylinder. These sheets are rolled

at specific and discrete (chiral) angles. The way the graphene sheet is rolled is

represented by a pair of indices (n, m). The integers n and m denote the number of

unit vectors along two directions in the honeycomb crystal lattice of graphene. A

tube (n,0) has carbon-carbon bonds that are parallel to the tube axis, and form, at

an open end, a zigzag pattern; these tubes are referred to as zigzag tubes. Tubes

with n=m have carbon-carbon bonds that are perpendicular to the tube axis, and

are often called "armchair" tubes. All others, where m does not equal n, and

neither is 0, are chiral, and have left-and right-handed variants.

The (n, m) values decide the radius and the rolling angle of the SWNT, thus

influencing its properties significantly.

The diameter of an ideal nanotube can be calculated from its (n, m) indices as

follows: a = 0.246 nm.

If there are additional graphene tubes around the core of a SWNT the nanotube is

called a Multi-walled carbon nanotube or MWNTs. We shall be focusing only on

SWNTs in this report.


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The figures shown above illustrate the (n, m) coordinate system and the structure

of a typical SWNT.

2.2. Synthesis Methods.

The three main methods of Carbon Nanotube synthesis are Arc Discharge, Laser

Ablation and Chemical Vapor Deposition. Each of them is described briefly

below.

In Arc Discharge, two graphite electrodes are placed millimeters apart and a 100 A

(or more) current is passed through them. The carbon contained in the negative

electrode sublimates in the form of nanotubes because of the high-discharge

temperatures. The yield for this method is up to 30% by weight and it produces

both single- and multi-walled nanotubes with lengths of up to 50 micrometers with

few structural defects. [4]

In laser ablation, a pulsed laser vaporizes a graphite target in a high-temperature

reactor while an inert gas is bled into the chamber. Nanotubes develop on the

cooler surfaces of the reactor as the vaporized carbon condenses. The laser

ablation method yields around 70% and produces primarily single-walled carbon

nanotubes with a controllable diameter determined by the reaction temperature.

However, it is more expensive than either arc discharge or chemical vapor

deposition.[4]

In CVD, a substrate with a layer of metal catalyst particles is heated to 600 oC in
http://en.wikipedia.org/wiki/Temperaturehttp://e/Downloads/Carbon%20Nanotubes-%20Seminar/Supplementary%20Files/Carbon_nanotubes.htm%23cite_note-nanotubes_for_electronics-30http://e/Downloads/Carbon%20Nanotubes-%20Seminar/Supplementary%20Files/Carbon_nanotubes.htm%23cite_note-nanotubes_for_electronics-30http://e/Downloads/Carbon%20Nanotubes-%20Seminar/Supplementary%20Files/Carbon_nanotubes.htm%23cite_note-nanotubes_for_electronics-30http://e/Downloads/Carbon%20Nanotubes-%20Seminar/Supplementary%20Files/Carbon_nanotubes.htm%23cite_note-nanotubes_for_electronics-30http://en.wikipedia.org/wiki/Temperature


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an oven, with slow addition of a carbon-bearing gas such as methane. The

vaporized carbon recrystallizes in the form of CNTs. Easiest to scale to industrial

production; long length MWNTs obtained but riddled with defects.[4]

2.3. Reactivity of CNTs.

The Orbital hybridization theory best describes chemical bonding in nanotubes.

The chemical bonding in graphene sheets, ergo in nanotubes, is composed entirely

ofsp2

bonds. As we already know, the strain of a carbon framework is reflected in

the pyramidalization or strain angle (p) of the carbon constituents. Chemical

reactivity is directly proportional to the strain caused by misalignment of pi-

orbitals. Trigonal carbon atoms (sp2

hybridized) prefer a planar orientation with

p=0 (i.e. graphene). Thus, the reactivity of nanotubes with respect to addition

chemistries is strongly dependent on the curvature of the carbon framework. The

(5, 5) SWNT has p~6 for the sidewall.[5] (This is a very moderate curvature).

Values for other (n, n) nanotubes show a trend of increasing p (sidewall) with

decrease in n. Therefore generally the chemical reactivity of SWNT increases with

decrease in diameter (or n, diameter increases with n)[5]

. However, on a

comparative scale, CNT sidewalls are rather unreactive. This low reactivity drops

even further if we consider any reaction occurring on the innerwall of a CNT, due

to hindrance (or blocking). This leaves the terminal ends of the CNT. As

mentioned earlier, the ends of carbon nanotubes are capped by fullerene- like

(football shaped) structures. Over here, the strain due to misalignment is much

higher, and consequently, the hemispherical (roughly) ends of a CNT are the area

where most chemical bonding takes place.[5]

2.4 The Need for Functionalization: Current and Potential Applications.

SWNTs are an important variety of carbon nanotube because most of their

properties change significantly with the (n, m) values, and this dependence is non-

monotonic (see Kataura plot). In particular, their band gap can vary from zero to


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about 2 eV and their electrical conductivity can show metallic or semiconducting

behavior. Single-walled nanotubes are likely candidates for miniaturizing

electronics. The most basic building block of these systems is the electric wire,

and SWNTs with diameters of an order of a nanometer can be excellentconductors.[6,7] One useful application of SWNTs is in the development of the

intermolecular field-effect transistors (FET). The first intermolecular logic gate

using SWNT FETs was made in 2001.[8]

A logic gate requires both a p-FET and

an n-FET. Because SWNTs are p-FETs when exposed to oxygen and n-FETs

otherwise, it is possible to protect half of an SWNT from oxygen exposure, while

exposing the other half to oxygen. This results in a single SWNT that acts as a

NOT logic gate with both p and n-type FETs within the same molecule.

Apart from the interesting electronic characteristics, carbon nanotubes exhibit

excellent mechanical and thermal properties. In particular, owing to their

extraordinary thermal conductivity and mechanical and electrical properties,

carbon nanotubes find applications as additives to various structural materials.[9]

These interesting physicochemical properties make carbon nanotubes very

attractive as electron emitters in field emission displays, reinforcement fillers in

nanocomposite materials, scanning probe microscopy tips, actuators and sensors,

as well as molecular-scale components in micro- or Nano-electronic devices.[2]

However, it is difficult to synthesize carbon nanotubes with the surface

characteristics demanded for specific applications (e.g. strongly interfacing with

polymers in nanocomposites, or good biocompatibility for nanotube sensors). This

is because synthesis methods are not developed enough yet to produce a uniform

product. Therefore, surface modification and interfacial engineering are essential

in making advanced carbon nanotubes of good bulk and surface properties. This

requires a detailed study of their chemistry; especially in light of the fact that they

are highly resistant to most common reactions. Although research on the chemistry

of carbon nanotubes is still in its infancy, some interesting work on both covalent and

non-covalent modification has recently been reported in literature.
http://en.wikipedia.org/wiki/Logic_gatehttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Logic_gate


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3. Functionalization of Carbon Nanotubes.

3.1. End Functionalization

This section describes the reaction schemes that have been performed on the

terminals of CNTs.

3.1.1. Oxidation of Carbon Nanotubes

Early work on carbon nanotube chemistry can be traced back to the oxidation of

carbon nanotubes at high temperature in air or oxygen. [10] Oxidation of carbon

nanotubes at temperature above 700 C in the presence of air for 10 min results in

the hemispherical end-caps opening, indicating that the hemispherical tips are

more reactive than the graphite sidewall. This work has led to the prospect of

filling foreign materials (e.g. metal oxide nanoparticles, biosensors, enzymes) into

the hollow tubes.

The oxidation may be followed by gas-phase reactions with CO2, N2O, NO, NO2,

O3, and ClO2.[11]

Solution-state chemical oxidation, however, is found to be more efficient for the

purification and/or modification of

carbon nanotubes. Tsang et al.[12]

reported the liquid-phase oxidation of

carbon nanotubes in HNO3 in 1994.

Since then, various oxidants have been

shown to react with carbon nanotubes.

Oxygen-containing acids, including

HNO3, HNO3 + H2SO4, HClO4, H2SO4

+K2Cr2O7 , and H2SO4 +KMnO4[13-20]


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have been extensively used, though several other oxidants (e.g. OsO 4 , H2O2) can

also been used.

The oxidation reactions discussed above often generate various functional groups

(e.g. -COOH, -OH, -CO) at the opened end or defect sites of the carbon nanotubestructure (Scheme 1). Other groups may be also introduced due to side reactions.

For example, a small amount of sulfur-containing groups may be introduced onto

the H2SO4 /HNO3 -oxidized carbon nanotubes, as shown in Scheme 2.[17]

3.1.2. Covalent Coupling via the Oxidized Nanotube Ends

The carboxylic acid and hydroxyl

groups of the oxidized nanotubes

can be further used to covalently

connect other small and polymeric

molecules through reactions

characteristic of the -COOH and -

OH functionalities. In this context,

the reactions of molecular

fluorine, rhodamine B, and p-

carboxytetraphenylporphine (TPP) with oxidized nanotubes have been carried out,

following Scheme 3.[22]

Alkyl chains may also be covalently attached onto the oxidized nanotubes through

a simpler reaction between the carboxylic acid and amine groups, Scheme 5, using

a carboxylateammonium salt, which also improves the solubility of the

nanotubes. [23,24]


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Similarly long alkyl chains and/or polymers have been chemically attached onto

the oxidized nanotubes through, for example, an amidation reaction, Scheme 4. In

this case, the carboxylic acid functionalized nanotubes were firstly converted into

alkyl chloride by treatment with SOCl2; aryl amine then reacts with the alkyl

chloride to form an amide bond between the nanotube and the aryl group. The

attachment of long hydrocarbon chains onto carbon nanotubes improves the

nanotubes solubility significantly,[25,23] allowing the modified SWNTs to be

purified by conventional chromatographic techniques.[26]

Polymers with amino terminal groups, such as poly(propionylethylenimine-co-

ethylenimine) (PPEI-EI), have also been grafted onto oxidized nanotubes through

amide formation, Scheme 6. The resulting polymer-grafted SWNTs and MWNTs

are highly soluble in most common organic solvents and water.[27-29]

Apart from the amide linkage, the etherification reaction has also been used to

covalently attach alkyl groups and polymers onto oxidized carbon nanotubes. For

instance, octadecylalcohol [30] and poly (vinyl acetate-co-vinyl alcohol) (PVA-VA)

[27]have been successfully grafted onto oxidized SWNTs to improve solubility,

Scheme 7.

Interestingly, Sano et al.[31] reported the ring formation from the acid-oxidized

SWNTs through the esterification between the carboxylic acid and hydroxyl end-

groups at the nanotube tips in the presence of a condensation reagent, 1, 3-

dicyclohexylcarbodiimide (Scheme 9). Carbon nanotube rings, with an average

diameter of 540 nm and a narrow size distribution, were obtained.

Nanotube hetero-junctions with two carbon nanotubes joined in either an end-

to-side or end-to-end configuration have been constructed through a bi-


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functionalized amine linkage, as schematically shown in Scheme 10 and Figure

2.[32]


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3.2 Modification of the Carbon Nanotube Outerwall

3.2.1. Sidewall Fluorination of Carbon Nanotubes.

Although carbon nanotubes are generally known to be inert towards fluorine at

room temperature, chemical fluorination of carbon nanotubes has been achieved at

relatively high temperatures. The chemical fluorination of the carbon nanotube

wall at temperatures ranging between 250 and 400C has been achieved.[33]

Fluorination of SWNTs has been carried out in the same manner as fluorination of

graphite,[34]

indicating that there is considerable room for chemical

functionalization of carbon nanotubes under appropriate conditions. Fluorination

above 400C is found to cause the decomposition of the nanotube structure.

Fluorination between 250 and 400C does not damage the structure to that extent,

but it reduces conductivity of the SWNTs due to the partial destruction of the

graphitic structure. Thus, electronic properties of fluorinated SWNTs differ

dramatically from those of their unmodified counterparts. Covalently bonded

fluorine is removable from the fluorinated surface by treatment with hydrazine.

This fluorination reaction is of considerable interest because further

functionalization of carbon nanotubes can be carried out through the fluorine

intermediate. The covalently bonded fluorine can be replaced by alkyl groups

through the alkylation reaction [35], with alkyl lithium or Grignard reagent used as a

reagent. Interestingly enough, these alkyl groups can also be removed by heating

the alkylated nanotubes at about 250C, leading to the recovery of the pure

SWNTs. various physicochemical properties of the fluorinated SWNTs, including

high-resolution electron energy loss[36], thermal recovery behavior[37], and

solvation in alcoholic solvents[38], have been investigated.


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3.2.2 Dichlorocarbene.

As is well known, 1, 1-dichlorocarbene can attack C- C bonds connecting two

adjacent six-membered carbon rings to produce 1, 1-dichlorocyclopropane,

Scheme 11. This reaction has been investigated for both SWNTs and MWNTs

[24]

using 1, 1- dichlorocarbene generated from different sources, including

NaOH/CHCl3 and a mercury complex.

3.2.3 Aniline and Azomethine.

Reactions with aniline (Scheme 13)[39]

, and 1, 3-Dipolar Cycloaddition of

Azomethine Ylides (Scheme 12) [40] have also been carried out.


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3.3 Functionalization of the Carbon Nanotube Innerwall.

Compared with the outerwall modifications discussed above, the functionalization

of the nanotube innerwall is much less discussed in literature. This is becauseinnerwall modifications often require opening the nanotube tip(s) and protection of

the outerwall; these processes are complicated and tedious. In this regard, carbon

nanotubes synthesized by the template technique possess advantages towards

innerwall modification.[41]

The template technique involves direct deposition of carbon nanotubes, or their

precursor polymer nanotubes, followed by high-temperature graphitizing, within

the pores of a Nano porous template (e.g. an alumina membrane or a semi porous

zeolite). The template synthesis often allows the production of monodispersed

carbon nanotubes[42, 43]

with opened ends as well as controllable diameters, lengths,

and orientations.

Based on the template method for the nanotube growth, Kyotani et al.[41]

have

successfully carried out the nitric acid oxidation of nanotube innerwalls within the

pores of Nano porous

alumina, in which the

template acts as a protective

layer for the outerwall. Upon

the completion of the

innerwall oxidation, the

template was removed by

dissolving it in aqueous HF,

thereby releasing the

innerwall-modified

nanotubes (Scheme 15).


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3.4 Physical Chemistry of CNTs.

3.4.1. Mechanochemical Reactions

Mechanochemistry refers to processes in which mechanical motions control

chemical reactions.[44]

Specifically, the mechanochemical reaction involves highly

reactive centers generated by mechanical energy (e.g. ultra sonication or ball-

milling) imparted to the reaction system. Certain organic reactions have been

demonstrated to take place efficiently in the solid state [45]. Ultra sonication has

been demonstrated to significantly enhance many chemical reactions, including the

acid oxidation of carbon nanotubes[46]

. It was envisaged that the strong vibration

arising from the ultrasonication created many defect sites on the SWNT sidewalls

(both the inner and outer ones), which could not only facilitate the oxidation

reaction but also cleaved the SWNTs into short segments. Ultrasonication has also

been found to induce a chemical reaction between SWNTs and

monochlorobenzene in the presence of poly (methyl methacrylate) (PMMA)[47]

. In

particular, SWNTs could be separated from carbonaceous impurities and degraded

to short segments by ultrasonicating SWNTs and PMMA in chlorobenzene [47].

Apart from ultrasonication, various other physicochemical processes, including

microwave irradiation [48] and ball-milling[49], have also been investigated. In

particular, ball-milling of carbon nanotubes in the presence of acid was reported to

cleave the nanotubes into 200300 nm long ropes. [49]


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3.4.2. Electrochemical Reactions.

Owing to the good

electronic propertiesintrinsically associated with

carbon nanotubes [50],

electrochemical

modification of individual

carbon nanotube bundles

has been attempted. To

demonstrate this, Kooi et al.[51] electrochemically

polymerized a thin polymer

layer onto the individual

SWNT bundle (Scheme 16), which was pre-coated on a microelectrode. The

resultant polymer layer was directly observed to be of 6 nm thickness, by means of

in situ AFM imaging (Fig. 6).

3.4.3. Photochemical Reactions

Despite of the well-known fact that carbon nanotubes possess unusual

optoelectronic properties, the recent report on ignition of some dry and fluffy

SWNTs in air by the camera flash is rather intriguing[52]

. In view of the highly

efficient absorption of light by carbon nanotubes, the observed ignition may have

resulted from a rapid temperature increase within the nanotube sample upon

exposure to the flash (estimated to heat to 1500C in a very short time), which is

well above the temperature required for ignition when oxygen is present. While the

mechanism of ignition by a camera flash in this system deserves further

investigation, such an interesting photochemical reaction may find its application

in the remote light-triggered combustion or explosives[52]

.


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3.5. Non-covalent Chemistry of CNTs.

Non-covalent chemistry involves self-assembly of molecules or macromolecules to

thermodynamically stable structures that are held together by weak, non-covalentinteractions. These weak non-covalent interactions include hydrogen bonding,

stacking, electrostatic forces, van der Waals forces, and hydrophobic and

hydrophilic interactions. Non-covalent chemistry offers an important advantage in

not changing the carbon nanotubes structure, and hence its electronic and

mechanical properties are largely retained. A few methods have been devised

which are demonstrated below.

3.5.1. Non-Covalent Attachment of Small Molecules onto the Sidewall of

CNTs.

Chen et al. [53] have recently found that certain aromatic molecules with a planar -

moiety (e.g. pyrenylene) could strongly interact with the basal plane of graphite on

the nanotube sidewall via -stacking. The interaction is so strong that the aromatic

molecule is irreversibly adsorbed onto the hydrophobic surface of carbon

nanotubes, leading to a highly stable, self-assembled structure in aqueous

solutions. As schematically shown in Scheme 17, the long alkyl chains, end-

adsorbed onto the nanotube surface via the aromatic anchors, could significantly

improve the solubility of the nanotubes.

The above approach could be used to attach bio- chemically active molecules, such

as DNA and proteins, on the sidewall of SWNTs through appropriate anchoring

molecules. For example, some amine-containing bioactive molecules, includingferritin, streptavidin, and biotinyl-3, 6- dioxactanediamine, have been attached

onto the sidewall of SWNTs through nucleophilic substitution of the amino

functionality by N -hydroxysuccinimide group, which was pre-anchored onto the

nanotube surface through a succinimidyl ester linkage by pyrenylene (Scheme 18).


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3.5.2 Plasma Activation of Aligned Carbon Nanotubes

Dai and coworkers [54-56] have developed

a novel approach for chemical

modification of aligned carbon nanotubes

by carrying out radio-frequency glow-

discharge plasma treatment, and

subsequent reactions characteristic of

plasma- induced surface groups. They

successfully immobilized polysaccharide

chains onto acetaldehyde plasma

activated carbon nanotubes through the

Schiff-base formation, followed by

reductive stabilization of the Schiff- base

linkage with sodium cyanoborohydride

in water under mild conditions (Scheme

21).


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4. Conclusion.

This ends our discussion on the reaction chemistry involved in synthesis,

purification, and application-specific modifications of Single Walled Carbon

Nanotubes (SWNTs).

The various covalent and non-covalent chemistries that have been devised for

making sophisticated carbon nanotube materials of good bulk and surface

properties as demanded for specific applications. Judicious application of these

site-selective reactions to nonaligned and aligned carbon nanotubes has opened up

the rich field of carbon nanotube chemistry.

With so many covalent and non-covalent methods already reported, and more to be

developed, the possibility of actually producing functionalized carbon nanotubes

of the exact physicochemical properties suitable for practical applications will

soon be in sight. Continued research in chemistry of carbon nanotubes should

overcome some of the major hurdles that carbon nanotubes are facing in the race to

the technological marketplace.


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5. References.

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Nanotubes on Clean Substrates".Nano Letters9 (9): 31373141.

[2]Tong Lin,Vardhan Bajpai,Tao Jiand Liming Dai. Chemistry of Carbon Nanotubes,Laboratory of Functional Polymers and Carbon Nanomaterials, Department of PolymerEngineering, University of Akron, Akron OH 44325-0301, USA.

[3] P. M. Ajayan, T.W. Ebbesen, T. Ichihashi, S. Iijima, K. Tanigaki,

H. Hiura,Nature 1993, 362, 522.

[4] Collins, P.G. (2000). "Nanotubes for Electronics".Scientific American: 6769.

[5] Chen, Z; Thiel, W; Hirsch, A (2003). "Reactivity of the convex and concave surfaces of

single-walled carbon nanotubes (SWCNTs) towards addition reactions: dependence on thecarbon-atom pyramidalization.". Chemphyschem : a European journal of chemical physics and

physical chemistry4 (1): 937.

[6] Mintmire, J.W.; Dunlap, B.I.; White, C.T. (1992). "Are Fullerene Tubules Metallic?". Phys.

Rev. Lett.68 (5): 631.

[7]Dekker, C. (1999). "Carbon nanotubes as molecular quantum wires".Physics Today52 (5):2228.

[8] Martel, R.; Derycke, V.; Lavoie, C.; Appenzeller, J.; Chan, K.; Tersoff, J.; Avouris, Ph.(2001). "Ambipolar Electrical Transport in Semiconducting Single-Wall Carbon Nanotubes".

Phys. Rev. Lett.87 (25): 256805.

[9] Gullapalli, S.; Wong, M.S. (2011). "Nanotechnology: A Guide to Nano-Objects".ChemicalEngineering Progress107 (5): 2832.

[10] P. M. Ajayan, T.W. Ebbesen, T. Ichihashi, S. Iijima, K. Tanigaki,H. Hiura,Nature 1993,362, 522.

[11] C. Niu, D. Moy, A. Chishti, R. Hoch, Int. Patent WO 0 107 694,2001.

[12] S. C. Tsang, Y. K. Chen, P. J. F. Harris, M. L. H. Green, Nature 1994, 372, 159.

[13] A. C. Dillon, T. Gennett, K. M. Jones, J. L. Alleman, P. A. Parilla, M. J. Heben, Adv. Mater.1999, 11, 1354.

[14] E. Dujardin, T. W. Ebbesen, A. Treacy, M. M. J. Krishnan,Adv.Mater. 1998, 10, 611.

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seminar report- functionalization of carbon nanotubes

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