THE ROLE OF SYNTHESIS IN MATERIALS TECHNOLOGY:The Holy Bible

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CHAPTER - 10

THE ROLE OF SYNTHESIS IN MATERIALS TECHNOLOGY

And he said unto them, it is not for you to know the times or the seasons, which the

Father hath put in his own power.

The Holy Bible (The Acts 1:7)

My times are in thy hand.

The Holy Bible (Psalm 1:15)

To every thing there is a season, and a time to every purpose under the heaven:

A time to be born, and a time to die; a time to plant, and a time to pluck that which is

planted;

A time to kill, and a time to heal; a time to breakdown, and a time to build up;

A time to weep, and a time to laugh; a time to mourn, and a time to dance;

A time to cast away stones, and a time to gather stones together; a time to embrace, and a

time to refrain from embracing;

A time to get, and a time to lost; a time to keep, and a time to cast away;

A time to rend, and a time to sew; a time to keep silence, and a time to speak;

A time to love, and a time to hate; a time of war, and a time of peace.

The Holy Bible (Ecclesiastes 3:1-8)

Noah's Ark The Technological Marvel

13. And God said unto Noah, The end of all flesh is come before me; for the earth is

filled with violence through them; and, behold I will destroy them with the earth.

14. Make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch

it within and without with pitch.

15. And this is the fashion which thou shalt make it of: The length of the ark shall be

three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits.

16. A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and

the door of the ark shalt thou set in the side thereof; with lover, second, and third stories

shalt thou make it.

Genesis 6: 13-16, The Holy Bible

10.2

Role of Synthesis in Materials Technology

What is new in Materials Technology?

The Living Cell is the All Time Marvel of Almighty God, The Creator. The Living Cell

can apparently handle enormous number of unimaginable, uncomprehendable and

difficult problems (functions) with ease and spontaneity.

The Living Cell performs

multiple functions (reproduction, growth, defense, protein synthesis, transport of

nutrients, information storage, site directed information transfer, communication, energy

conversion and energy storage, sensing) simultaneously. All vital functions for the

sustenance of life takes place in the living cells. Thus the Living Cells are self-

replicating, self-containing and self-maintaining.

One of the goals of Materials

Technology is to design and synthesize the material with artificial intelligence that

replicate Living Cell in all aspects.

An inquisitive mind now poses the following questions:

What is the Living Cell? What does a Cell mean? Where does the term `Cell' originate

from? How can the Living Cell be multifunctional and versatile? How cells form

complex organisms? What is the structure of the Cell? What are the dimensions of the

Living Cell? What are the constituents of the Cell? Can the Living Cells be mimicked?

Can such mimics of the Living Cells act as molecular machines and revolutionize

Materials Technology? The queries are recurring.

The Cell is the basis of life. The Cell is the smallest unit of all living organisms

whether it be unicellular (eg., bacteria) or multicellular (eg., human beings). Human

beings have an estimate of 100 trillion (1014) cells. A typical cell is of 10 µm size and 1

nanogram mass [1].

Robert Hooke is the originator of the term "Cell" and has been derived from the latin

word `Cellula' meaning `a small room'. It is worth knowing few good things about

Robert Hooke which are depicted in the next few lines.

Robert Hooke (18th July, 1635 - 3rd March 1703)

Robert Hooke was a remarkably industrious scientist and philosopher. He was an active,

restless, indefatigable genius even almost to the last days of his life. One of the important

contributions of Robert Hooke to Biology is his book "Micrographia" published in 1665

[Fig. 10.1 (a)]. Robert Hooke coined the term "Cells". This has originated from his

microscopical observation of thin slices of cork (tissue of light soft bark of Mediterranean

Synthetic Strategies in Chemistry

10.3

tree). He coined the word `Cell' to the pores separated by walls because the observation

reminded him of the cell of a monastery (small rooms where monks lived in) [Fig. 10.1

(b)].

He has recorded his study of the plant tissue in "Observation XVIII" of the

Micrographia as follows [2]:

"I could exceedingly, plainly perceive it to be all perforated and porous, much like a

honey-comb, but that the pores, or cells, ........ were indeed the first microscopical pores

I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person,

that had made any mention of them before this ....".

Truly, history owes to this industrious scientist and philosopher.

(a)

(b)

Fig. 10.1. (a) Title page of Micrographia (1665) [3], (b) Robert Hooke's drawings of the

cellular structure of cork (plant tissue) and a spring of sensitive plant from Micrographia

[4].

Living cells are divided into two types, namely, the Procaryotic Cells and the

Eucaryotic Cells. Procaryotic cells possess simple structure (eg. Bacteria cell) [5]. Cells

10.4

Role of Synthesis in Materials Technology

without a nucleus were grouped together as "Prokaryotes'. We human beings, and most

of the animals and plants, belongs to the life form enjoying cell nucleus and are

collectively called Eukaryotes [6]. Eucaryotic cell (they carry their DNA wrapped in a

cell nucleus) possesses complex structure as represented in Fig. 10.2. The cells are

surrounded by a double layer membrane. In many cases the cells are further shielded by

a cell wall. As a result chemical processes taking place in a cell would not easily get

disturbed by the surrounding environment.

Golgi

Apparatus

Cell

Nucleus

Membrane

Rough

Lysosome

Endoplasmic

Reticulum

Cytoplasm

Chloroplast

Smooth

Endoplasmic

Mitochondria

Reticulum

Fig. 10.2. Schematic representation of a eukaryotic cell and its compartments [6]

The cell possesses secluded areas for specific functions.

The major organelles

(specialized subunit with in a cell that has a specific function to perform) and cellular

structure include the nucleus, ribosomes, mitochondria, golgi apparatus, cytoplasm, rough

endoplasmic reticulum and smooth endoplasmic reticulum. As houses are divided into

living room, dining room, kitchen and bed room, living cells too are compartmentalized

as shown in Fig. 10.2. Each compartment has a specific set of functional tasks. For

instance, the nucleus contains most of the DNA which is the carrier of genetic

information in all the cellular life forms. The mitochondria are the power houses of the

Synthetic Strategies in Chemistry

10.5

cells. These are the sites where cellular respiration and a consequent release of chemical

energy from food takes place. Ribosomes are the protein synthesizing machines of the

cell. Ribosomes are the cells protein factory.

Can we imagine a data storage device of micrometer (10-6 m) size but can squeez

the data equivalent of five high-density floppy disks (5 x 1.44 MB = 7.2 MB) ?

Yes, such a data device is existing in Nature. The chromosome, a very long stretch of

DNA wound up in a complicated way, which determines the genetic identity of every

living organism on this plant is an example of such data storing device.

Can we imagine a motor that is running on and on and on but only of size

measuring a few hundredths of a thousandth of a millimeter?

For your surprise the motor is already in existence. It is a system mainly consisting of the

proteins actin and myosin. The system serves to power our muscles. Actin is a soluble

protein found in muscle cells. It is the main component of the thin filaments. Myosin is

the motor protein that generates the force and movement in contraction of muscles.

Myosin is the oxygen storage protein of the muscle. When Myosin carries an oxygen

molecule, the oxygen molecule is deeply burried within the structure of the protein.

Because of the weak interations present the protein is capable of rearranging its structure

to be able to take up oxygen or to set it free by way of rearranging itself so that a tunnel is

opened between the oxygen binding site and the rest of the world. For such rapid

rearrangments to take place weak interactions should be present with in the protein

structure as well as with the substrate. The following are some of the weak interactions

found in biological systems (The Cell).

i. Hydrogen bonding: Hydrogen atom is normally bound to just one atom of oxygen or

nitrogen. In Hydrogen bonding the Hydrogen atom starts interacting with a second atom.

Hydrogen bonding is responsible for the extremely high boiling point in spite of its

modest molecular weight. If hydrogen bonding did not exist, water would be a gas at

ambient temperatures.

ii. Salt bridges: This is because of the electrostatic attraction between parts of molecules

having opposite electrical charges.

iii. Van der Waals forces: These forces exist between the negatively-charged cloud of

electrons of one atom and the positively-charged nucleus of the other.

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Role of Synthesis in Materials Technology

iv. The Hydrophobic interaction: The tendency of oily, water-avoiding molecular

surfaces to stick together and shut out any water molecules.

Thus the first lesson one need to learn is that the key to generate materials that replicate

living cells or biological systems lies in designing synthetic strategies based on weak

interations between the reacting systems as represented pictorially in Fig. 10.3..

Fig. 10.3. Interactions that stabilize the local structures in proteins: (a) Hydrogen bonds

(secondary structure), (b) disulfide bridges (tertiary or even Intermolecular, (c) salt

bridges, (d) hydrophobic interaction. The oval shape symbolizes the hydrophobic area

from which water is excluded [6].

Synthetic Strategies in Chemistry

10.7

Can we imagine a catalyst capable of converting the inert nitrogen gas from the air

into nitrogen fertilizer at room temperature and atmospheric pressure?

The enzyme nitrogenase present in nodule bacteria that live in symbiosis with certain

plants and provide them with freshly made nitrogen fertilizer produced from air and

water. There is no technical catalyst producing ammonia from elemental hydrogen and

nitrogen at ambient temperature and pressure as the nitrogenase of nodule bacteria. Thus

it is the dream not yet realized by the scientists all over the world.

Can we dream of the synthesis of natural products with 100 % enantiomeric excess

(ee)?

In organic chemistry, particularly in the synthesis of natural products, one of the major

issues of concern even today is to synthesize exclusively one of the two mirror-imaged

structures of chiral compounds. Literally, synthetic chemists are battling for every single

digit enhancement in the value of ee beyond the statistically 50%. Interestingly enzymes

can distinguish the mirror images with 100% reliability.

Can we synthesize catalysts

(nonnatural) which are on a par with natural enzymes in their performance? This is yet

another challenge facing materials technology today.

Other important challenges ahead in Materials Technology are achieving computer

technology that matches with human brain, achieving telecommunications technology

that matches with nervous system of human body. The only means of realizing such

breakthroughs in materials technology is through the evolving synthetic strategies in

Chemistry.

Some Benefits from Materials Technology

Audio tapes, audio tape players, audio tape recorders, calculators, cameras, compact disks

(CD's), CD players, Barcode, Colour Printers, Computers, Digital video disk (DVD),

Electronic commerce, Electronic data interchange, E-mail, Internet, Fax machines,

Laboratory equipment, Laser printers, Laser pointers, Liquid crystal display, LCD,

Mailing services, Measuring instruments, Modem, Network/cable television, Periodicals,

News papers, Over head projectors, Photocopy machines, Play ground equipment, Radio,

Refrigerators, Slide Projectors, Scanner, Search Engines, Switching technology,

Telephones, Transparencies, Type writers, Video cameras, Vedio conferencing are all

some of the marvels of Materials Technology [7].

10.8

Role of Synthesis in Materials Technology

Materials Technology Vs Material's Technology

Materials technology is a science and a knowledge area that describes properties,

functions and applications of different materials [8]. Materials technology is dependent

on Material's technology, i.e. the way materials are architectured or build or constructed

or fabricated or synthesized. To gain knowledge of Materials technology one should

understand the role of synthesis in generating the materials. New materials, improved

production techniques, and miniaturization are the three essential ingredients that have

tremendous potential to trigger major technological revolutions.

Role of Synthesis

Materials synthesis is so vital that the early history of man kind (from the stone age to the

iron age) is classified based on the materials that started new eras.

So far the

classification of eras is associated with or based on materials that have revolutionized the

respective eras.

But the role of synthesis has now become so crucial in materials

technology that the production methods are going to be used as milestones of

development rather than the material itself. Initially materials that are either simply

found or gathered from nature (wood, bones, stones) served mankind. Progress has been

made from such naturally existing materials to the use of metals retrieved from ores using

fire. Metals were found to be more versatile in their use rather than naturally occurring

materials.

Currently, metals, glass and other materials are being replaced by polymers. This age

which we live can be truly regarded as polymer age because the survival of mankind

becomes questionable with out polymers (substances that are chemically assembled from

smaller molecules).

Again polymers are more versatile than metals and naturally

occurring materials like wood or stone. Milestones in the use of materials during the last

10, 000 years have been illustrated in Fig. 10. 4.

But still we have not our destination in technological advancement. Even though

polymers have the potential to cater to many of our needs they can not fulfill all the

demands we have for advanced materials. The problems associated with polymers are:

valuable resources and energy are used up in the production of polymers. Also they are

neither biodegradable like wood nor recyclable like iron.

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10.9

Fig. 10.4. Time line illustrating the use of materials during the past 10, 000 years [6].

10.10

Role of Synthesis in Materials Technology

Even though polymers have revolutionized the way we live, in comparison to biological

materials they are far inferior as they in no way contain any significant amount of

information, also they cannot store energy, or they cannot act in an intelligent way. Thus

the focus of the evolving synthetic strategies has been to produce materials mimicking

biological materials. Such materials should be functional and adaptive on a molecular

scale.

Like our fore fathers and ancestors we may be of the opinion that our present

technology is modern, advanced, accomplished and ultimate. Also we may tend to

believe that only incremental improvements can be brought about in the present day

technology. Major technological breakthroughs are believed to be hardly possible. But

this is not true. There is large room for the change to betterment as change happens to be

the law of life. The enormous scope and potential for such a major advancement can be

noticed if we compare our present day synthetic strategies or production methodologies

with the synthetic strategies adopted by molecular machinery in living cells. So long

almost all the available synthetic strategies handled bulk amounts (countless atoms or

molecules) which yielded materials whose properties can only be controlled with in a

limit. But the properties of materials obtained by adopting such synthetic strategies

dealing with bulk amounts are not adaptive or intelligent. Even though the tools and

machinery that one currently uses to carry out simple processes automatically they can no

way go down below macroscopic or at the most microscopic levels. In sharp contrast, in

the living cells, the structures of inorganic building materials are controlled at the

molecular level guiding the precipitation of the mineral from solution for instance.

Incidentally, the most complex machines of the cell are not bigger than 25 50 nm. Thus

there is ample scope and also the way is long to meet the materials technology mimicking

the Living Cell. At the moment The Time of reaching the destination is not clear.

Information technology, Nanotechnology and Biotechnology are regarded as the three

eyes of the new millennium. New synthetic strategies can open access to new materials.

Materials are transformed into useful products by working on them with hands and tools.

Production technology underwent a drastic change. From millennia useful products are

made manually. Now most of them are made by machines. Except those processes

where decision-making is involved all others are being carried out by machines. As a

Synthetic Strategies in Chemistry

10.11

consequence length scale is no longer limited to such parts that human workers could

grasp with their hands. Thus miniaturization of production has paved the way for the

miniaturization of the products.

INFORMATION TECHNOLOGY:

The Beginning of Information Technology The Age of the Printed Book:

Now this very second you are reading this book. It means you are getting benefited by

the revolution of book publishing technology that has started in 15th century. Johannes

Gutenberg (1397 1468) conceived the idea of printing books with movable type. He

developed his idea into a working technology. It is no easy job to achieve uniform

dimensions of letters. Such sufficiently uniform dimensions of letter type facilitates a flat

printing surface. Hence smooth lines are obtained.

Through years of persistent hard

work Johannes Gutenberg could overcome this problem by making the type from metal.

He could cast all of them in the same mold, which could be combined with different

letter shapes and adjusted in its width. This development is a result of several years of

hard work. To achieve this objective he has to borrow considerable amounts of money.

He could not have given the world the printing technology if he were not to be

knowledgeable in metallurgy. His major success involves producing 160-170 copies of

the 42-line Bible shown in Fig. 10.5. The name 42-line Bible refers to the number of

lines of print on each page. This work of Johannes Gutenberg is of iconic status as this

marked the beginning of `Gutenberg Revolution' and `the Age of the Printed Book'.

The printing of 42-line Bible by Gutenberg is a remarkable development in the history of

mankind as this has broken the information monopoly. The new technology has put an

end to the Dark Ages. It has brought about the reformation, the enlightenment and the

rise of modern science. Interestingly, with in a span of 50 years after the production of

Bible with printing technology developed by Johannes Gutenberg, more books were

produced than in the 1000 years before. The technology Johannes Gutenberg developed

lasted for more than 500 years. Later on this printing technology of Gutenberg was

replaced by light reprography. This is followed by the new information revolution

brought about with the invention of personal computers.

10.12

Role of Synthesis in Materials Technology

Fig. 10. 5. (a) A copy of the 42-line Holy Bible, the major work of Johannes Gutenberg

[9].

Advent of Computers and Internet Information Explosion:

Advent of computers and widespread growth of availability and use in internet has

brought about revolution in the field of information technology. Since this development

has only taken place over the past two decades we are fortunate enough to witness the

progress. But how could this happen? What is the driving force for such a drastic

explosion in information technology? Literally with computers and internet the whole

world is at our finger tips. The marvelous progress can be attributed to the new synthetic

strategies that facilitated miniaturization of electronic elements and circuits.

Miniaturization means not alone saving space or materials but miniaturization of

electronic circuits made them cost effective, efficient and faster. 1000 fold enhancement

is memory capabilities and calculation speeds have been achieved with in a short span of

10 years i.e., from early 1980's to 1990's. The number of transistors in typical microchip

kept on increasing exponentially from 1971.

For every 18 months the number of

transistors on a microchip doubled.

In 1971 the microchip contained only 2300

transistors when Intel launched the world's first microchip.

Nearly a hundred fold

increase in the number of transistors has been achieved by 1985 with the creation of Intel

386 processor with 2, 75, 000 transistors. And today the Tukwila contained 2 billions

transistors. Very recently, i.e., on 14th April 2008, Intel, the microchip leader, unveiled

Synthetic Strategies in Chemistry

10.13

two drastically different processors. They succeeded in creating the worlds smallest

microchip (computer processor) namely the atom chip as well as the worlds biggest chip

namely the Tukwila. The size of the atom chip is of a baby's finger nail. The chip packs

47 million transistors. But consumes only over a half of a watt of power. The atom chip

can power hand held internet devices namely the mobile internet devices, small hand held

computers that will help in emailing, letter writing and calculations. On the contrary the

Tukwila, the new Intel chip possessing the highest number of transistors ever put on the

slab of silicon with 2 billion transistors can do the work of four computers. This world's

biggest microchip consumes 130-170 watts of power. This will help scientists to build

gaint `number crunchers' far more powerful than the Tata-CRL `Eka' super computer

built in India (the Tata-CRL `Eka', computer is the world's forth-fastest computing

machine). With the help of such super computers fuelled by microchips with 2 billion

transistors complete genetic simulation of a human cell can be achieved with in a span of

a decade or even lesser time period. This facilitates doctors to precisely simulate an

unhealthy cell in a human. Thus exact medication can be possible. With the advent of

nanotechnology unimaginable advancements in the field of information technology are

anticipated.

NANOTECHNOLOGY:

The word Nanotechnology was used for the first time by Taniguchi at the University of

Tokyo, Japan, in 1974. He was then referring to need of electronics industry to engineer

materials at nanometer scale [10].

On 29th of December, 1959, Richard P. Feynman took the shiny example of the

living cell to drive home his point that individual atoms can be arranged in the way we

want them to be.

With this ultimate degree of miniaturization all the information

contained in all the books in the world can be stored in the grain of a sand. Living cell is

not only capable of storing enormous amount of information in a very small volume but

also equipped with the hard ware to read out the information and retrieve the same when

needed and put the same into action. In an analogous way Richard P. Feynman professed

that it should be possible to write the entire Encyclopaedia Britannica onto the point of a

needle. In those days when computers were huge machines the wiring of which filled the

10.14

Role of Synthesis in Materials Technology

whole room completely, he is genius enough and fore sighted to profess that computers

of the future should be made of wires that would only be 10 or 100 atoms in diameter.

Role of Synthesis in Nanotechnology:

Carbon materials are very important for Nanotechnology to flourish. Carbon materials

are vital, versatile, amazing and unique. Carbon exists in different allotropic forms,

namely, graphite, diamond, fullerene, and nanotube. Graphite with its two dimentional

hexagonal array of carbon atoms and diamond with its three dimensional structure are

well known. Fullerene and nanotubes are newly discovered allotropic forms of carbon.

Synthetic Strategy that lead to the formation of Fullerenes:

A dream team of five scientists namely Kroto, Heath, O'Brien, Curl and Smally in Rice

Quantum Institute, Texas were trying to understand how long-chain carbon molecules

(cyclopolyynes) are formed in interstellar space.

To find an answer, they started

vapourizing graphite, the grand old allotrope of carbon, by irradiating with laser. This

experiment has lead to the serendipitous discovery of C60 molecule, named as

Buckminsterfullerene. The structure of C60 molecule consisted of 32 faces, 12 of which

are pentagonal and the remaining 20 are hexagonal. The structure of C60 is analogous to

common foot ball shown in Fig. 10. 6. (a) The experimental set up containing the

vapourization chamber is shown in Fig. 10. 6. (b). Later on many studies have been

carried out on the properties and applications of fullerens and fullerene derivatives. Not

oniy that, fullerene research paved path for the discovery of multiwalled carbon

nanotubes by Ijima. Simply the synthetic methodology adopted has changed the course

and destination of carbon science and technology.

Carbon species from the surface of a solid graphite disk are vapourized using a pulsed

laser source in the presence of He environment. Nd:YAG laser producing pulse energies

of ~ 30 mJ is used. In a typical experiment the pulsed valve is opened. Vapourization

laser is fired onto the rotating graphite disk. Carbon species start vaporizing into the

helium stream, cooled and partially equilibrated in the expansion. As a result molecular

beam is formed which travels into the ionization region. The clusters were ionized by a

laser pulse and the products were analysed by mass spectrometer. During the process

graphite disk is rotated slowly to produce a smooth vaporization surface.

The

vaporization laser beam is focused through the nozzle to strike the graphite. The species

Synthetic Strategies in Chemistry

10.15

in the vaporized graphite plasma are cooled and clustered by the thermalizing collisions

of He carrier gas. Also the carrier gas provides necessary wind to carry the cluster

through the remaining of the nozzle. The cluster filled gas expands freely at the nozzle

and form a supersonic beam which is probed by mass spectrometer [11]. Kroto, Smalley

and Curl were awarded nobel prize for Chemistry in 1996 for their discovery of

Fullerenes in 1985.

Fig. 10.6. (a) A football (the C60 molecule is supposed to have the structure formed when

each vertex on the seams of such a ball is replaced by carbon atm, (b) Schematic diagram

of the pulsed supersonic nozzle used to generate carbon cluster beams

Even though Fullerens were discovered in 1985, it is not until 1991 when Kratschmer and

Huffman evolved a synthetic strategy based on arc discharge for the mass production of

fullerenes that fullerene research grew rapidly and in one way this is a foundation stone

for the future discovery of nanotubes by Ijima in 1991. Hence synthetic strategies play a

pivotal role in the birth as well as destination of any new technology.

With the ways being available for the mass production of Fullerenes, derivatives of

fullerenes could be synthesized.

Endohedral compounds, exohedral compounds and

heterofullerenes are the three classes of fullerene derivative [12].

Fullerene derivatives with atleast one atom or ion located inside the 7 Å cage of

fullerene are called endohedral fullerenes.

Endohedral compounds are more polar

compared to the parent fullerene making the separation of fullerenes easier. Electronic

properties of fullerenes can be tuned by forming endohedral derivatives. Endohedral

compounds find utility in the fabrication of solar cells, linear optical units and in photo

conductors. Some of the ways of synthesizing endohedral derivatives are by heating the

fullerene directly with the guest gas under pressure; evaporating fullerene in presence of

10.16

Role of Synthesis in Materials Technology

metals or metal oxide to be hosted by using laser source or by generating an arc.

Endohedral compounds with noble gases, alkali metals and lanthanides are well known.

Recently N@C60 has also been synthesized. La@C82 could be synthesized by evaporating

graphite impregnated with La2O3 using a laser. Rg@C60 (Rg-rare gas), Li@C60 have also

been synthesized [13].

Exohedral compounds: By reacting C60 with CrO2(NO3)2 a compound C60Cr2N6O21 was

obtained. In this compound 50% Cr species are in Cr3+ and the other 50% were found to

be in Cr6+ state. Such exohedral compounds are useful for catalytic and medicinal

applications.

Intercalation Compounds: Alkalimetal intercalated fullerene compounds were found to

be super conductors. For instance, K3C60 has a transition temperature of 19.8 K and

Cs3C60 exhibited a transition temperatures upto 40 K. Compounds like (NH3)6Na3C60

(NH3)8Na2C60 showed improvements in transition temperatures. Ba6C60 and Sm3C60 have

also been found to be superconductors.

Carbon Nanotubes

Synthesis of carbon nanotubes with desired properties in large quantities is a challenge

ahead. The second problem in the successful utilization of CNT's for a variety of

Technologies is to remove the impurities present such as the catalyst nanoparticles (Fe,

Co, Ni-Y and few others), amorphous carbon and fullerenes. The third hurdle is to

develop synthetic strategies that exclusively give either SWNT's or MWNT's as

currently there is no path available to separate them. Making them soluble is also a note

worthy problem.

Carbon nanotubes are a key component of nanotechnology. Carbon nanotubes

(multiwalled tubes) were discovered by the Japanese scientist Iijima in 1991. Carbon

nanotubes were obtained as a by-product during fullerene synthesis. Discoovery of

carbon tubes has supplemented the fullerene research to a major extent. Multiwalled

carbon nanotubes should be distinguished from single walled carbon nanotubes. The

difference between them is pictorically represented in Fig. 10. 7. Single walled carbons

nanotubes contain one single cylinder whose wall is made up of hexagonal carbon

structure. Multiwalled carbon nanotube contains concentric cylinders (one inside the

other) with each cylindrical wall being made of a graphene sheet.

Synthetic Strategies in Chemistry

10.17

Fig. 10.7. Schematic representation of single walled and multiwalled carbon nanotubes

[12]

The discovery of single walled carbon nanotubes (SWCNT's) is incidental. A series of

failed attempts to synthesize MWCNT's (multiwalled carbon nanotube's) filled with

transition metals resulted in the formation of single walled carbon nanotubes. The credit

of the discovery of single walled carbon nanotubes should be given to two research

groups who worked independently, namely Iijima and Ichihashi, NEC (Nippon Electric

Company), Japan as well as Bethune et al., from IBM, California [14].

Nanotubes of carbon are not soluble. As a result separation and purification are a

problem. This has hindered the large scale production of carbon naotubes partially.

Fortunately these tubes are less susceptible to combustion. So heating in oxygen can

brun the impurities (other forms of carbon namely amorphous carbon) and can yield pure

CNT's [13].

Single walled carbon nanotubes can be envisaged or conceptualized or understood as

seamless (continuous and uniform through out) cylinders rolled up from graphene sheet

as represented in Fig. 10. 8. A graphene sheet is a monolayer of sp2 bonded carbon

atoms.

10.18

Role of Synthesis in Materials Technology

Single walled nano tube

Graphene Sheet

Fig. 10.8. Hexagonal net work of carbon atoms rolled upto make a seamless cylinder

[15].

Depending on the way in which the graphene sheet is rolled up there can be three types

of carbon nanotubes, namely, zigzag, armchair and chiral. In zigzag tubes some of the C-

C bonds lie parallel to the tube axis. The name zigzag comes from the fact that the edge

of the tube possesses zigzag structure (

). In armchair tube some of the C-C bonds

lie perpendicular to the tube axis. The name armchair comes from the very shape of the

edge of the tube which looks like arm chair (

Intermediate orientations of

the graphene sheet result in `chiral' carbon nanotubes.

Thus the classification of

nanotubes into zigzag or arm chair is based on the appearance of the rim of the tube

formed. The formation of the three types of nanotubes by changing the way of rolling the

graphene sheet is represented schematically in Fig. 10.9

Cabon nanotubes have several potential applications. This is because of their unique

properties. Due to the high mechanical stability carbon nanotubes are now being used in

carbon-carbon composites. As carbon nanotubes are capable of emitting electrons from

the tube ends they are used for flat screen applications. Carbon nanotues serve as host

materials for Li or H2 and can be exploited in energy storage applications.

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10.19

Fig. 10. 9. Schematic representation of the relation between nanotube and graphene [16].

Evolution in Synthetic Strategies

Some of the ways of synthesizing nanotubes include:

1. Arch-discharge or vaporization process (in the presence of transition metal catalyst)

2. Laser-evaporation of graphite (Laser furnace process)

3. Chemical Vapour Deposition, CVD (Catalytic Pyrolysis of hydrocarbons) or Catalytic

Chemical Vapour Deposition (CCVD)

4. Template Carbonization Method

The fine details of the synthetic strategies are given in the next few pages.

1. The Arc-Discharge Process:

Carbon nanotubes were first introduced to the world by using this synthetic methodology.

As stated earlier carbon nanotubes occurred as a by-product during the synthesis of

fullerenes. Kratschmer and coworkers have used the same arc discharge method in 1990

for the mass production of fullerene. The method they have employed comprises of

10.20

Role of Synthesis in Materials Technology

evaporating the graphitic anode. The two electrodes were made to contact with each

other by applying an ac voltage in an inert gas atmosphere. This results in the generation

of an arc that evaporates the anodic graphite. Thus fullerenes were generated in bulk

amounts.

Fig. 10. 10. Schematic representation of the apparatus used for the synthesis of CNT's

[17]

The arc-discharge apparatus used for the production of carbon nanotubes is shown in Fig.

10.10. The chamber is first made free from atmospheric air by evacuating the reaction

chamber with a vacuum pump. Ambient gas (He or Ar or CH4) is introduced into the

chamber. A dc (direct current) arc voltage is applied between the two graphite electrodes

(rods of carbon). The anodic graphite evaporates. Fullerenes in the form of sooth are

deposited in the chamber. In addition to fullerenes, the great treasure, CNT's were also

found to be deposited on to the cathode from the evaporating anode. These CNT's were

found to be made of coaxial (concentric) graphene sheets and are termed as multiwalled

carbon nanotubes. These results are obtained when pure graphite rods free from any

Synthetic Strategies in Chemistry

10.21

metal impurities are used as anode and cathode. By using this arc discharge method and

by employing He environment large scale synthesis of MWCNT's could be achieved.

If the synthetic condition is slightly changed by using metal catalyst (Fe or Co)

containing graphite rod as anode instead of pure graphite rod, single walled carbon

nanotubes could be obtained instead of multiwalled carbon nanotubes. In either cases the

cathode is only pure cathode.

Experiments have been carried out by changing the

atmosphere with in the reaction chamber. Among He, Ar and CH4, CH4 gas was found to

be the best as it resulted in the formation of highly crystalline nanotubes with few

coexisting nanoparticles which are not wanted. The major and essential distinguishing

feature in the synthesis of fullerens and CNTs is that, fullerene cannot be produced when

reaction chamber contains hydrogen containing gases (CH4 or even H2). At the same

time presence of environment of H2 facilitates the formation of CNT. During the process

of arc evaporation in CH4, thermal decomposition of methane takes place leading to the

insitu generation of H2 as indicated in the following equation.

C2H2 + 3 H2

CH4

In presence of CH4, the evaporation of graphitic anode thus takes place in pure

hydrogen gas environment. Thus hydrogen arc discharge is effective in the generation of

highly crystalline carbon nanotubes (multiwalled). As hydrogen arc results in high

temperature and resultant high activity, production of MWCNT's in hydrogen

atmosphere (CH4 environment) is more effective than either He or Ar atmosphere. Not

only that, the unwanted carbon nanoparticles (amorphous carbon) which are ubiquitous

and unavoidable can be minimized by using hydrogen arc process

SWNT's were synthesized in the year 1993, just two years after the discovery of

MWNT's in the year 1991. SWNT's were synthesized by the arc discharge process using

a graphite anode but with metal catalyst (either Fe or Co or metal alloys in some cases

like Ni-Y). In sharp contrast to the synthesis of MWCNT's, SWNT's were not found on

the carbon deposit on cathode but were obtained from the soot in the gas phase.

Xinluo Zhao and coworkers has succeeded in synthesiszing highly crystalline

SWCNT's with a clean surface in large quantities by employing arc discharge process.

The SWNT's were obtained with 70 at.% purity.

10.22

Role of Synthesis in Materials Technology

Fig. 10.11. Arc discharge chamber with a web of SWNT's [18] (Arrow A shows the

starting point of the SWNT web; arrow B shows the black thick region of SWNT's;

arrow C shows the half-transparent thin region of SWNT's growth; arrow D points

towards the roof of the arc discharge chamber where the thin film of SWNT's is located.

This film can be peeled of into large slices)

The carbon electrode employed comprises of 1 at% Fe catalyst. Inert atmosphere is

maintained in the reaction chamber by H2-Ar mixture. The catalyst Fe nanoparticles

present in the product CNT's could be completely eliminated by heating the product in

air at 693 K and also by the subsequent acid treatment with HCl.

The two graphite electrodes were held vertically one over the other with the anode at

the lower end and the cathode at the upper end separated by 2 mm distance. The

electrode assembly was held in the centre of the vacuum chamber. The anode is the

carbon containing Fe catalyst and the cathode is pure carbon.

Inert atmosphere is

maintained in the reaction chamber by passing H2-Ar mixture. The synthesis time was

roughly 3 mm.

This has resulted in the formation of macroscopic web of SWNT's as

Synthetic Strategies in Chemistry

10.23

shown in Fig. 10.11. The length of the SWNT's is nearly 30 cm. H2-Ar gas mixture

played a crucial role in the synthesis of SWNT's.

Fig. 10.12. TEM images of (a) as grown CNT's (low magnification, iron particles are

seen along with tubes), (b) as grown CNT's (high magnification, iron particles are seen

along with the graphene layers) (c) purified CNT's (low magnification, only CTN's and

no Fe particles) (d) purified CNT's (high magnification, only graphene folded sheets and

no Fe particles) [18].

TEM images of as-grown and purified SWNT's are shown in Fig. 10.12. Both the

low magnification and high magnification images are shown. It is clear from the TEM

images that after heat treatment and the subsequent acid treatment with HCl the

particulate impurities (catalyst as well as amorphous carbon) were completely removed

yielding clean and pure SWNT's.

2. Laser Furnace Process

The energy density of lasers is higher compared to any other vaporizing device. So lasers

are appropriate means to vaporize materials like carbon with high boiling temperature

[17].

Typical laser furnace experimental set up is shown in Fig. 10.13. The essential

components are a furnace, a quartz tube provided with a window at one end and a trap for

10.24

Role of Synthesis in Materials Technology

CNT's provided with a water circulation at the other end, flow system for inert gas (Ar),

laser source and the carbon target.

Fig. 10.13. Laser-furnace (vaporization) apparatus [19]

The carbon target used is a composite of carbon doped with catalytic Co-Ni alloy. The

carbon composite (Co-Ni/graphite) is placed at the centre of the quartz tube having

window at one end through which the laser beam penetrates into the quartz tube. The

laser source used is Nd:YAG (Neodymium : Yttrium-aluminium-garnet) and this can

produce a temperature of 1200 ºC in the furnace. CO2 can also be used. A laser beam

from the afore mentioned source is introduced into the quartz tube through the window

and is focused on to the carbon composite. Ar gas is circulated through out the furnace.

The carbon composite is vapourized when the laser beam hit the target and forms

SWNT's. The SWNT's produced are carried to the other end of the quartz tube provided

with a trap (with water circulation facility) where the SWNT's are collected.

It is important to note that the surface of the carbon composite should be kept as fresh

as possible for the process of vaporization to be homogeneous. Since there is no way the

target can be moved, the focus of the laser onto the target should be changed from time to

time. Laser furnace synthesis is an efficient route to synthesize bundles of single-walled

carbon nanotubes with a narrow diameter distribution.

Synthetic Strategies in Chemistry

10.25

3. Chemical Vapour Deposition

In this method of synthesis a hydrocarbon (acetylene, ethylene, benzene or methane) is

thermally decomposed in the presence of a transition metal catalyst (Fe, Co or Ni) or

catalyst support (alumina, silica or zeolite serve as useful supports for transition metals)

The process of synthesis can be carried out even at relatively lower temperatures (600-

1200 ºC) than those which are normally encountered in either arc discharge process or

laser vaporization processes.

But we have to forgo the quality of the nanotubes

obtained interms of crystallinity when the synthesis temperatures are lower. Since this

synthetic methodology can be employed at relatively lower temperatures and ambient

pressure, CVD is simple and also forms a viable means of producing large amounts of

nanotubes.

Hydrocarbons in either liquid (benzene, alcohols) or solid (camphor,

napthelene) or gaseous (CH4 or C2H2) can be virtually employed as carbon precursors.

Fig. 10.14. Experimental set up for Chemical Vapour Deposition Synthesis, (b) probable

models of CNT growth [17]

The experimental set up used for a CVD or CCVD (catalytic chemical vapour deposition)

synthesis is shown in Fig. 10.14 (a) and the possible ways in which the nanostructures

grow on catalyst particles is represented pictorially in Fig. 10.14 (b).

In a typical process of CVD, the catalyst is placed in the middle of a quartz tube.

The quartz tube with the catalyst is placed in a furnace capable of generating and

sustaining temperatures between (600-1200 ºC). The hydrocarbon vapour is allowed to

pass through the quartz tube containing catalyst material present at sufficiently high

10.26

Role of Synthesis in Materials Technology

temperature. The hydrocarbon gets decomposed. CNT's start growing on the catalyst

particles. The temperature of the furnace is then cooled to room temperature. The

CNT's are collected. If the carbon precursors were to be in liquid form as in the case of

either benzene or alcohols then an inert gas like Ar is bubbled through the flask

containing the liquid hydrocarbon.

The liquid hydrocarbon in the flask is heated

simultaneously so that vapours of the hydrocarbon are generated. The vapours of the

hydrocarbon are thus carried by the inert gas through the catalyst particles located in the

hot zone of the furnace. If the carbon precursors were to be in solid state like those of

naphthalene or camphor, the hydrocarbon vapours in such cases are generated by placing

them in another furnace kept at a lower temperature prior to the main furnace where the

deposition of carbon takes place over the catalyst particles. Analogous to the carbon

precursors the catalyst materials can also be in either solid or liquid or gaseous state. In

the high temperature zone the hydrocarbon vapour gets decomposed. A variety of carbon

species are formed.

Such carbon species are capable of dissolving in the metal

nanoparticles of the catalyst. Once a catalyst particle is supersaturated, carbon species

starts precipitating out. Initially, fullerene dome like structure will petrude out of the

catalyst particle which extends into carbon cylinders. The position and direction of

growth of carbon from the metal nanoparticle depends on the interaction between the

metal particle and the support .If the interaction beween the metal particle and the support

is strong, the particle is literally immovable. The decomposed carbon species will be

adsorbed into the particle initially from all the direction where the catalyst particle

surface is exposed to the carbon species. Once a level of super saturation of the particle

with carbon species is reached no more carbon species are adsorbed in to the metal

particle. Now carbon has to precipitate out from the metal particle. Since the particle is

strongly held by the support, the only direction in which the carbon can precipitate out is

from the tip. The process of dissolution now takes place from the sides of the particle

near the base and the excess carbon is precipitated at the mouth or tip of the particle.

Since the grown process starts at the sides of the base this is known as base grown

carbon. On the contrary, if there were to exist weak interaction between the catalyst

particle and the support, the particle can now be easily lifted vertically up above the

support surface the movement when the particle gets supersaturated with carbon that is

Synthetic Strategies in Chemistry

10.27

being absorbed from the tip. Since the growth of the tube is now originating at the tip of

the metal particle the mechanism is regarded at tip grown CNT process. Depending on

the size of catalyst particle, we get either SWNT's or MWNT's.

4. Template Carbonization Method:

The structure directing material (template) used for preparing nanotubes in this method is

the porous aluminium plate. Channels are created in the aluminium plate by the process

of anodic oxidation in the presence of sulphuric acid. Carbon is deposited pyrolytically

onto the channels in aluminium oxide film at 800 ºC in inert atmosphere.

Fig. 10.15. Synthesis of carbon nanotubes by template carbonization method [12]

After the process of carbon deposition and subsequent carbonization the aluminium oxide

template is removed by treatment with HF (hydrofluoric acid) solution. (Note: HF should

be handled with utmost care. Proper hand gloves should be used while handling HF. It is

so hazardous that through skin it can damage even the bones). This resulted in uniform

monodisperse carbon nanotubes with uniform length, diameter and thickness. As the

temperature of the carbonization is not high (800 ºC only), the tubes contained structural

imperfections. Typical synthetic steps involved in a template assisted synthesis are

pictorially represented in Fig. 10.15.

10.28

Role of Synthesis in Materials Technology

Can a carbon source as common as kerosene be used for the synthesis of nanoforms

of carbon materials?

Kerosene is used as a fuel for cooking and lightening. It is a residue of the petroleum

refinery. Kerosene contains a mixture of various short and long chain aromatic and

aliphatic hydrocarbons.

Sharon and coworkers have used kerosene as precursor for

preparing various nanoforms of carbon. The method of synthesis comprises of pyrolysis

of kerosene at 1000 ºC. The experimental arrangement comprises of a quartz tube held

horizontally in a furnace.

Kerosene is placed in a round bottom flask and heated

thermostatically at 90 ºC. The vapours of kerosene along with Ar gas were allowed to

pass through the quartz tube held in a furnace. Stainless steal plates in rectangular shape

were placed in the center of the quartz tube. The stainless steal plate serves as a substrate

for the deposition of various forms of carbon materials. Straight, stiff and long fibers,

flexible, thin hair like threads, soft wool like clusters of carbon, uniform nanotubes,

bitter-gourd-like rough fibers, earth worm-like nanofibers and carbon thin film deposits

were found around and on the stainless steal substrate.

SEM (scanning electron

microscope) images of the various nanoforms of carbon synthesized are shown in Fig.

10.16. It is to be noted that the substrate stainless steal is a complex catalyst of different

compositions which govern the growth and orientation of the nanostructures. Important

questions one should now consider are: How a single carbon precursor under given

conditions of synthesis yields different nanostructures simultaneously? What factors are

responsible for control of size and shape of the nanostructures? Can each of the different

carbon nano structures be separated? How does the synthetic strategy adopted dictates

the ultimate materials technology? Or in other words, what impact does this synthetic

strategy have on the ultimate materials technology? The ultimate materials technology is

a function of material structure as well as material property which are controlled by the

specific synthetic strategy employed.

For instance, as in the present case, the fibers

obtained were found to be conducting and such conducting fibers are useful in

biosensors, ion-activated molecular switches and for the fabrication of microelectrodes

for medicinal applications. Composite fibers can be obtained from hair-like and wool-

like fibers. The bitter gourd like fibers with extremely irregular outer surface yields large

specific surface area values and will be useful for catalytic applications. The electrodes

Synthetic Strategies in Chemistry

10.29

fabricated from the thin film carbon synthesized was found to be a substitutes to an

expensive RuO2 coated titanium sheet which is used as anode against a mercuric cathode

for the electrolysis of brine solution. The electrochemical potential range of the electrode

fabricated from carbon thin film material was found to be -1.24 to 1.67 V Vs SCE

(standard calomel electrode) indicating that water will not be electrolysed by using the

electrodes (both anode and cathode) fabricated by this carbon material. The electrodes

fabricated from thin film carbon could electrolyze 30 % NaCl solution at 300 mAcm-2 for

more than 110 h continuously with out any deterioration [21]. Thus the electrodes

fabricated from the carbon obtained by kerosene pyrolysis are useful for Chloro-alkali

industry offering a solution for toxicity problem by eliminating the hazardous mercury

contamination [20].

(a)

(b)

(c)

Fig. 10.16. SEM (scanning electron microscope) images of (a) hair like fibers, (b) bitter

gourd - like rough fibers and (c) carbon thin film grown on a stainless steel substrate

Carbon Nanotubes as STM and AFM Tips:

Gerd Binnig and Heinrich Rohrer at the IBM (International Business Machines

Corporation) research laboratories in Zurich in the late 1970's developed a method of

structural analysis namely the STM, scanning tunneling microscopy. Few details on the

principle of operation of STM are worth knowing. Electron is not only a particle but also

a wave. In our daily life walking through a brick wall is not possible [7]. Imagine a

nanometer scale equivalent of a brick wall. Let this be an energy barrier that an electron

following prequantum physics would not be able to overcome. But quantum mechanics

tells us that there is still a certain probability that the electron is found on the other side of

the wall since electron is not only a particle but also a wave. In this case the electron

10.30

Role of Synthesis in Materials Technology

behaves more like a wave and this effect is called tunneling which forms the basis of

STM analysis. The empty space between the surface to be studied and the probe is

regarded as the barrier or the wall through which an electron normally but occasionally

will not passes. The tip of the probe should be one atom wide. The next layer can

contain more atoms. The probability of tunneling decreases by a factor of ten for each

0.1 nm of additional distance. So the second layer has no virtual significance. The one

atom tip is suspended above the object just a few atomic radii. This distance is readjusted

using the measured tunneling current. From the distance between the STM tip and the

surface to be probed and the measured tunneling current one can feel the structure of the

surface. The peaks and troughs of the surface can be felt at atomic scales with out ever

touching it. It has now become possible to control the placement of the tip with sufficient

accuracy establishing STM as a standard method of analysis in materials science.

A variation of the theme of electron tunneling found as in the case of STM was

presented in 1986 by Binnig, C. F. Quate and C. Gerber which was latter called as

Atomic Force Microscopy (AFM). In this technique the probe will actually touch the

surface. The vertical movement of the tip of the probe will be controlled by the repulsive

force measured when the surface is touched. By 1990's individual biomolecules such as

the double-stranded DNA could be pictured which made the researchers elated. Thus

both STM and AFM techniques are in principle suitable for "feeling" the fine structure of

a surface atom by atom.

The performance of STM and AFM instruments has been limited by the quality of the

tip which acts as a probe that either exchanges electron with the surface as in the case of

STM or touches the surface as in the case of AFM. The virtual characteristics a tip

should possess to be used as probe are: such tips should end in a single atom; possess a

well defined geometry, should be conductive and chemically inert. So far the tool that

worked as a good probe tip is obtained by simply cutting a metal wire with an ordinary

pair of scissors.

Is it not surprising?

Even though the afore mentioned material

possessed no such virtual attributes as mentioned previously for an ideal probe, the

material derived by cutting through a metal wire with a pair of scissors worked very well.

The diameter of such a tip is of a few hundred nanometers indicating that the outer most

Synthetic Strategies in Chemistry

10.31

layer contains thousands of atoms. Interestingly, alternative methods like etching the

wire tips or some other improvements in shaping the metal wire only failed to function.

Tremendous improvements have been brought about in the advancement of utility of

STM and AFM techniques for probing the surface structure when carbon nanotubes

(CNT's) were used for the first time as AFM tips by the researchers from the laboratory

of Nobel Laureate Richard Smalley. A single carbon nanotube of 10 nm wide and 100

nm to 1 µm long capped with fullerene like hemisphere is glued as molecular antenna

onto a conventional probe. The conventional probe was coated initially with a suitable

glue and then dipped into a bundle of nanotubes. In most cases, this effort culminated

into the gluing of just one tube onto the tip.

The new probe onto which carbon nanotube is glued fulfilled the ideal conditions the

STM or AFM tip should satisfy. The probe with CNT tips has a well-defined and well-

known molecular structure, is conductive, chemically inert and also very thin. Use of

carbon nanotubes as AFM tips provided additional advantages by being stable to

withstand the forces applied to the tip and also being elastic enough to avoid unwanted

collisions with the surface. More over, now-a-days, reliable and reproducible synthetic

strategies are at disposal for making such new probes (carbon nanotubes).

Role of Synthesis in Leather Technology:

Transformation of animal hides and skins into attractive, aesthetic and useful artifacts has

been one of the oldest technologies of mankind.

When wet the animal skins are

susceptible to bacterial attack and putrefy.

On the contrary drying makes the skin

inflexible and useless for clothing and other applications. Such problems can be over

come by the use of bactericide during soaking . This forms a good solution for the short

term preservation of skins and hides. Addition of bactericide prevent the bacterial attack

on hide and skin. Addition of bactericide convert the putrescible biological materials into

a stable material resistant to microbial activities with enhanced resistance to wet and dry

heat. The bactericide kill the growth of microorganism there by preventing the damage

to skin and hide.

Mercury compounds as well as a mixture of sulfite and acetic acid were extensively

used as bactericides. Even though the afore mentioned materials are effective they are

damageable and harmful to the environment. So they are no longer used for protecting

10.32

Role of Synthesis in Materials Technology

the hides and skins from bacterial attack. Instead, bronopol which is a highly active

antimicrobial chemical compound has been the ubiquitous choice to leather industry to

prevent bacteria attacking the skins and hides. Bronopol is 2-bromo-2-nitro propane 1,

3 diol. Bronopol was invented by The Boots Company PLC, Nottingham, England in

the early 1960's. It was used as a preservative for pharmaceuticals for the first time [21].

Earlier reports on the synthetic path ways of bronopol include reaction of bromo-nitro-

methyl-cyclohexanol with aliphatic aldehyde. The main drawbacks associated with this

method of synthesis are the use of cyclohexanol which is expensive and also the use of

hazardous sodium ethoxide. Lakshimi Muthusubramanian and Rajat B Mitra [22] have

succeeded in deloping a simple but cleaner synthetic strategy that helped Leather

manufacturing technology.

Scheme 10.1. Synthetic strategy for Bronopol

This method of synthesis of bronopol includes reaction of formaldehyde with nitro alkane

in the presence of sodium hydroxide (in MeOH) which on bromination yielded bronopol

as represented in Scheme 10.1.

The advantages of this method include complete

replacement of hazardous and expensive hydroxide and methanol which are inexpensive

and readily available. Currently scale up studies are being carried out for the production

of bronopol using this environmentally benign synthetic strategy.

CONCLUSION:

The living cells are versatile in its design and function. They provide all necessary

inspiration to design and synthesize new materials with specific functions that bring

Synthetic Strategies in Chemistry

10.33

about revolutions in Technology and also give birth to Advanced Technologies.

Understanding and imitation of natural machinery of the living cells holds great rewards.

But such endeavours are not free from barriers and obstacles. For instance, molecular

level details of the working of ribosomes (their function of protein synthesis) is unclear

even today and remains one of the hardest problems in biology.

Therefore our

knowledge and understanding of the processes going on in a living cell and also the

mechanochemical functions of various cell components is limited. Any improvements in

such an understanding facilitate imitation and mimicking of the synthetic strategies

involved in life process (a unique network of chemical reactions). This knowledge will

in turn bring about drastic changes and advancements in Materials Technology.

REFERENCES:

1. http://en.wikipedia.org/wiki/cell_(biology)

2. http://www.ucmp.berkeley.edu/history/hooke.html

3. http://www.roberthooke.org.uk/

4.http://images.google.co.in/imgres?imgurl=http://cache.eb.com/eb/image%3Fid%3D997

68%26rendTypeId%3D4&imgrefurl=http://www.britannica.com/ebc/art-99713/Robert-

Hookes-drawings-of-the-cellular-structure-of-cork

and&h=450&w=339&sz=44&hl=en&start=1&um=1&tbnid=8NZeLWw7jw9MzM:&tbn

h=127&tbnw=96&prev=/images%3Fq%3DRobert%2BHooke%2Bcell%26um%3D1%26

hl%3Den%26sa%3DN

5. http://www.cellsalive.com/cells/3dcell.htm

6. Travels to the nanoworld Miniature Machinery in Nature and Technology, Michael

Gross, Perseus Publishing, Cambridge, Massachusetts, 1999.

7. North Central Regional Eductional Laboratory, 1-800-356-2735, 1997-99.

8. http://www.sp.se/en/areas/material/Sidor/default.aspx

9. http://en.wikipedia.org/wiki/Gutenberg_Bible

10. Warren H. Hunt, Jr. JOM, October 2004, 13.

11. H. W. Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl and R. E. Smalley, Nature 318

(1985) 162

12. P. Scharff, Carbon 36 (1998) 481

13. T. Pradeep, Current Science, 72 (1997) 124

10.34

Role of Synthesis in Materials Technology

14. Marc Monthionx, Vladimir L. Kuznetsov, Carbon 44 (2006) 1621

15. Purushottam Chakraborty, Everyman's Science, Vol. XXXIX, No. 4, October-

November' 04

16. Nanotube and Nanofibers, Yury Gogotsi (Ed.,) Taylor & Francis, 2006

17. Yoshinori Ando, Xinluo Zhao, Toshiki Sugai, and Mukul Kumar, Materials Today,

October 2004, 22-29

18. Xinluo Zhao, Sakae Inone, Makoto Jinno, Tomoko Suzuki, Yoshinori Ando,

Chemical Physics Letters, 373 (2003) 266

19. R. Saito, G. Dresselhaus and M. S. Dresselhaus, Physical Properties of Carbon

Nanotubes, Imperial College Press, 1998

20. Mukul Kumar, P. D. Kichambare, Maheshwar Sharon, Yoshinori Ando and Xinluo

Zhao, Materials Research Bulletin 34 (1999) 791

21. http://en.wikipedia.org/wiki/Bronopol

22. Lakshmi Muthusubramanian, Rajat B Mitra, Journal of cleaner production, 14 (2006)

536

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