nano materials

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NANOMATERIALS Seminar: 2013 ACKNOWLEDGEMENT I wish to express my sincere and respectful gratitude to Sri.J.MAHENDRAN NAIR, Chairman of PKCET for providing all our needs during the course of this seminar. I wish to express my deep sense of gratitude to Prof: S. CHIDAMBARAM, the Principal and Head Of Department of Mechanical Engineering Department of PKCET for his constant support and guidance. My deepest thanks to our respected Director of academics, Dr. A.KOMALAVALLI AMMA for her encouragement and support. It would be unfair not to mention about the valuable assistance from our registrar Mr.G.MOHANAN NAIR. I express my sincere gratitude to our seminar coordinator Mr. AKHIL SASI, for his valuable suggestions without which the successful completion of this seminar would not have been possible. I am grateful to Mr. AKHIL SASI, Guide of my seminar, who has contributed both directly and indirectly throughout the completion of the seminar. Dept: Of Mechanical Eng 1 PKCET, Kandala

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Page 1: nano materials

NANOMATERIALS Seminar: 2013

ACKNOWLEDGEMENT

I wish to express my sincere and respectful gratitude to Sri.J.MAHENDRAN NAIR,

Chairman of PKCET for providing all our needs during the course of this seminar.

I wish to express my deep sense of gratitude to Prof: S. CHIDAMBARAM, the

Principal and Head Of Department of Mechanical Engineering Department of PKCET

for his constant support and guidance.

My deepest thanks to our respected Director of academics, Dr. A.KOMALAVALLI

AMMA for her encouragement and support. It would be unfair not to mention about the

valuable assistance from our registrar Mr.G.MOHANAN NAIR.

I express my sincere gratitude to our seminar coordinator Mr. AKHIL SASI, for his

valuable suggestions without which the successful completion of this seminar would

not have been possible.

I am grateful to Mr. AKHIL SASI, Guide of my seminar, who has contributed both

directly and indirectly throughout the completion of the seminar.

I wish to thank all the teachers and friends of PKCET, who helped me for making this

seminar successful. Also I wish to express my deep sense of gratitude to my family

members for their constant encouragement and support throughout my academic

carrier.

Last, but not the least, I am grateful to the almighty for guarding and keeping me safe

from any and all misfortunes befalling on me.

Dept: Of Mechanical Eng 1 PKCET, Kandala

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NANOMATERIALS Seminar: 2013

AKHIL KUMAR S

ABSTRACT

Nanotechnology and molecular manufacturing allows for manipulation of

material size and composition. This expands the promise of application of

nanomaterials in addressing environmental problems, but also has the

potential for adversely impacting the natural environment and human

health. The primary focus is to use nanomaterials for environmental

remediation and to study the impact of the release of such materials in the

environment. The first part of this talk will focus on the aggregation

behavior of carbon nanotubes (CNTs) in environmentally relevant solution

chemistries. The MWNTs were thoroughly characterized using Raman

scattering (for state of defect), total gravimetric analysis (for metal

impurities), transmission electron microscopy(for length and diameter

distribution), Fourier transformed infrared spectroscopy (for functional

groups), and electrophoretic mobility (for surface charge). The aggregation

kinetics of MWNTs was consistent with classical DLVO theory of

colloidal stability in presence of Na, Ca, and Mg salts. Humic acid

effectively stabilized the MWNTs by steric interactions. The second part

will demonstrate the use of surface-modified nano-scale zero-valent iron

(NZVI) for remediation of dense non-aqueous-phase liquid (DNAPL).

Surface modification using novel block-copolymer and surfactants

enhanced transport through porous media. Amphiphilic block copolymer

modification helped the NZVI to localize at DNAPL/water interface. The

concluding part of the talk will focus on my research interests that include

studying the effect of functionalization on CNT aggregation and deposition

Dept: Of Mechanical Eng 2 PKCET, Kandala

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NANOMATERIALS Seminar: 2013

behavior, development of nano-sensors for microbial mapping of the

subsurface, and toxicity of CNTs to microbes.

CONTENTS

INTRODUCTION……………………………………………………………….5

DEFINITION ……...……………………………………………………………6

ADVANCES IN NANOMATERIALS…....……………………………………8

TYPES OF NANO MATERIALS……………………….……………………..9

NANOMATERIAL COMPOSITION………...……………………………….14

PROPERTIES OF NANOMATERIALS…………….………………………..15

APPLICATIONS OF NANO MATERIALS…………………………….…….18

SAFETY……………………………………………………………………….24

DISADVANTAGES………………………………………………………...…25

CONCLUSION………………………………………………………………...27

BIBILIOGRAPHY……………………………………………………………..29

Dept: Of Mechanical Eng 3 PKCET, Kandala

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NANOMATERIALS Seminar: 2013

LIST OF FIGURES

“HOW BIG IS 1 NANOMETER”

FULLERENES

OPTICAL PROPERTIES

ELECTRICAL PROPERTIES

MICROBIAL FUEL CELL

CARBON NANOTUBE

NANOWIRES FOR JUNCTIONLESS TRANSISTORS

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NANOMATERIALS Seminar: 2013

INTRODUCTION

Nanomaterials are chemical substances or materials that are manufactured

and used at a very small scale (down to 10,000 times smaller than the

diameter of a human hair).

Nanomaterials are developed to exhibit novel characteristics (such as

increased strength, chemical reactivity or conductivity) compared to the

same material without nanoscale features.

Hundreds of products containing nanomaterials are already in use.

Examples are batteries, coatings, anti-bacterial clothing etc. Analysts

expect markets to grow to hundreds of billions of Euros by 2015.

Nano innovation will be seen in many sectors including public health,

employment and occupational safety and health, information society,

industry, innovation, environment, energy, transport, security and space.

Nanomaterials have the potential to improve the quality of life and to

contribute to industrial competitiveness in Europe. However, the new

materials may also pose risks to the environment and raise health and

safety concerns.

These risks, and to what extent they can be tackled by the existing risk

assessment measures in the EU, have been the subject of several opinions

of the Scientific Committee on Emerging and Newly Identified Health

Risks (SCENIHR). The overall conclusion so far is that, even though

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nanomaterials are not per se dangerous, there still is scientific uncertainty

about the safety of nanomaterials in many aspects and therefore the safety

assessment of the substances must be done on a case-by-case basis.

DEFINITION OF NANOMATERIAL

A natural, incidental or manufactured material containing particles, in an

unbound state or as an aggregate or as an agglomerate and where, for 50 %

or more of the particles in the number size distribution, one or more

external dimensions is in the size range 1 nm - 100 nm.

In specific cases and where warranted by concerns for the environment,

health, safety or competitiveness the number size distribution threshold of

50 % may be replaced by a threshold between 1 and 50 %.

By derogation from the above, fullerenes, graphene flakes and single wall

carbon nanotubes with one or more external dimensions below 1 nm

should be considered as nanomaterials.

The definition will be used primarily to identify materials for which

special provisions might apply (e.g. for risk assessment or ingredient

labelling). Those special provisions are not part of the definition but of

specific legislation in which the definition will be used.

Nanomaterials are not intrinsically hazardous per se but there may be a

need to take into account specific considerations in their risk assessment.

Therefore one purpose of the definition is to provide clear and

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NANOMATERIALS Seminar: 2013

unambiguous criteria to identify materials for which such considerations

apply.

It is only the results of the risk assessment that will determine whether the

nanomaterial is hazardous and whether or not further action is justified.

Today there are several pieces of EU legislation, and technical guidance

supporting implementation of legislation, with specific references to

nanomaterials. To ensure conformity across legislative areas, where often

the same materials are used in different contexts, the purpose of the

Recommendation is to enable a coherent cross-cutting reference.

Therefore another basic purpose is to ensure that a material which is a

nanomaterial in one sector will also be treated as such when it is used in

another sector.

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NANOMATERIALS Seminar: 2013

ADVANCES IN NANOMATERIALS

The history of nanomaterials began immediately after the big bang when Nanostructure were formed in the early meteorites. Nature later evolved many other Nanostructures like seashells, skeletons etc. Nanoscaled smoke particles were formed during the use of fire by early humans. The scientific story of nanomaterials however began much later. One of the first scientific report is the colloidal gold particles synthesised by Michael Faraday asearly as 1857. Nanostructured catalysts have also been investigated for over 70 years. By the early 1940’s, precipitated and fumed silica nanoparticles were being manufactured and sold in USA and Germany as substitutes for ultrafine carbon black for rubber reinforcements.Nanosized amorphous silica particles have found large-scale applications in many every-day consumer products, ranging from non-diary coffee creamer to automobile tires,optical fibers and catalyst supports. In the 1960s and 1970’s metallic nanopowders for magnetic recording tapes were developed. In 1976, for the first time, nanocrystals produced by the now popular inert- gas evaporation technique was published by

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Granqvist and Buhrman. Recently it has been found that the Maya blue paint is a nanostructured hybrid material. The origin of its color and its resistance to acids and biocorrosion are still not understood but studies of authentic samples from Jaina Island show that the material is made of needle-shaped palygorskite (clay) crystals that form asuperlattice with a period of 1.4 nm, with intercalates of amorphous silicate substrate containing inclusions of metal (Mg) nanoparticles. The beautiful tone of the blue color is obtained only when both these nanoparticles and the superlattice are present, as has been shown by the fabrication of synthetic samples.

TYPES OF NANOMATERIALS

For the purpose of this article, most current nanomaterials could be

organized into four types:

• Carbon Based Materials

• Metal Based Materials

• Dendrimers

• Composites

Carbon Based Materials

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These nanomaterials are composed mostly of carbon, most commonly

taking the form of a hollow spheres, ellipsoids, or tubes.

Spherical and ellipsoidal carbon nanomaterials are referred to as

fullerenes, while cylindrical ones are called nanotubes.

These particles have many potential applications, including improved

films and coatings, stronger and lighter materials, and applications in

electronics.

Metal Based Materials

These nanomaterials include quantum dots, nanogold, nanosilver and metal

oxides, such as titanium dioxide.

A quantum dot is a closely packed semiconductor crystal comprised of

hundreds or thousands of atoms, and whose size is on the order of a few

nanometers to a few hundred nanometers.

Changing the size of quantum dots changes their optical properties.

Dendrimers

These nanomaterials are nanosized polymers built from branched units.

The surface of a dendrimer has numerous chain ends, which can be tailored

to perform specific chemical functions.

This property could also be useful for catalysis. Also, because three-

dimensional dendrimers contain interior cavities into which other

molecules could be placed, they may be useful for drug delivery.

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Composites

Composites combine nanoparticles with other nanoparticles or with larger,

bulk-type materials.

Nanoparticles, such as nanosized clays, are already being added to products

ranging from auto parts to packaging materials, to enhance mechanical,

thermal, barrier, and flame-retardant properties.

Materials referred to as "nanomaterials" generally fall into two categories:

fullerenes, and inorganic nanoparticles.

Fullerenes

The fullerenes are a class of allotropes of carbon which conceptually

are graphene sheets rolled into tubes or spheres. These include the carbon

nanotubes(or silicon nanotubes) which are of interest both because of their

mechanical strength and also because of their electrical properties.

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For the past decade, the chemical and physical properties of fullerenes have

been a hot topic in the field of research and development, and are likely to

continue to be for a long time. In April 2003, fullerenes were under study

for potential medicinal use: binding specific antibiotics to the structure of

resistantbacteria and even target certain types of cancer cells such

as melanoma. The October 2005 issue of Chemistry and Biology contains

an article describing the use of fullerenes as light-

activated antimicrobial agents. In the field of nanotechnology, heat

resistance and superconductivity are among the properties attracting

intense research.

A common method used to produce fullerenes is to send a large current

between two nearby graphite electrodes in an inert atmosphere. The

resulting carbon plasma  arc between the electrodes cools into sooty residue

from which many fullerenes can be isolated.

There are many calculations that have been done using ab-initio Quantum

Methods applied to fullerenes. By DFT and TDDFT methods one can

obtain IR,Raman and UV spectra. Results of such calculations can be

compared with experimental results.

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Nano particles

Nanoparticles or nanocrystals made of metals, semiconductors, or oxides

are of particular interest for their mechanical, electrical, magnetic, optical,

chemical and other properties. Nanoparticles have been used as quantum

dots and as chemical catalysts.

Nanoparticles are of great scientific interest as they are effectively a bridge

between bulk materials and atomic or molecular structures. A bulk material

should have constant physical properties regardless of its size, but at the

nano-scale this is often not the case. Size-dependent properties are

observed such as quantum confinement in semiconductor particles, surface

plasmon resonance in some metal particles

and superparamagnetism in magnetic materials.

Nanoparticles exhibit a number of special properties relative to bulk

material. For example, the bending of bulk copper (wire, ribbon, etc.)

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occurs with movement of copper atoms/clusters at about the 50 nm scale.

Copper nanoparticles smaller than 50 nm are considered super hard

materials that do not exhibit the same malleability and ductility as bulk

copper. The change in properties is not always desirable. Ferroelectric

materials smaller than 10 nm can switch their magnetisation direction using

room temperature thermal energy, thus making them useless for memory

storage.Suspensions of nanoparticles are possible because the interaction of

the particle surface with the solvent is strong enough to overcome

differences in density, which usually result in a material either sinking or

floating in a liquid. Nanoparticles often have unexpected visual properties

because they are small enough to confine their electrons and produce

quantum effects. For example goldnanoparticles appear deep red to black

in solution.

Nanomaterial Composition

Comprised of many different elements such as carbons and metals

Combinations of elements can make up nanomaterial grains such as

titanium carbide and zinc sulfide

Allows construction of new materials such as C60 (Bucky Balls or

fullerenes) and nanotubes

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Properties of C60 and its derivatives

Black crystalline solid, thermally stable up to 400 °C

Very difficult to oxidize

Doped with alkali metals: conductor and superconductor

Fluorescence

Acceptors of electrons and electronic energy

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PROPERTIES OF NANOMATERIALS

Mechanical properties

The large amount of grain boundaries in bulk materials made of

nanoparticles allows extended grain boundary sliding leading to high

plasticity.

Catalytic Properties

Due to their large surface, nanoparticles made of transition element oxides

exhibit interesting catalytic properties. In special cases, catalysis may be

enhanced and more specific by decorating these particles with gold or

platinum clusters.

Magnetic Properties

In magnetic nanoparticles, the energy of magnetic anisotropy may be that

small that the vector of magnetization fluctuates thermally; this is called

superparamagnetism. Such a material is free of remanence, and

coercitivity. Touching superparamagnetic particles are loosing this special

property by interaction, except the particles are kept at distance.

Combining particles with high energy of anisotropy with

superparamagnetic ones leads to a new class of permanent magnetic

materials.

Optical Properties

Distributions of non-agglomerated nanoparticles in a polymer are used to

tune the index of refraction. Additionally, such a process may produce

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materials with non-linear optical properties. Gold or CdSe nanoparticles in

glass lead to red or orange coloration. Semi-conducting nanoparticles and

some oxide-polymer nanocomposites exhibit fluorescence showing blue

shift with decreasing particle size.

Unique Properties

The unique properties of these various types of intentionally produced

nanomaterials give them novel electrical, catalytic, magnetic, mechanical,

thermal, or imaging features that are highly desirable for applications in

commercial, medical, military, and environmental sectors.

These materials may also find their way into more complex nanostructures

and systems. As new uses for materials with these special properties are

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identified, the number of products containing such nanomaterials and their

possible applications continues to grow.

Electrical properties

Electrical Properties of Nanoparticles” discuss about fundamentals of

electrical conductivity in nanotubes and nanorods, carbon nanotubes,

photoconductivity of nanorods, electrical conductivity of nanocomposites.

One interesting method which can be used to demonstrate the steps in

conductance is the mechanical thinning of a nanowire and measurement of

the electrical current at a constant applied voltage. The important point

here is that, with decreasing diameter of the wire, the number of electron

wave modes contributing to the electrical conductivity is becoming

increasingly smaller by well-defined quantized steps.

In electrically conducting carbon nanotubes, only one electron wave mode

is observed which transport the electrical current. As the lengths and

orientations of the carbon nanotubes are different, they touch the surface of

the mercury at different times, which provides two sets of information: (i)

the influence of carbon nanotube length on the resistance; and (ii) the

resistances of the different nanotubes. As the nanotubes have different

lengths, then with increasing protrusion of the fiber bundle an increasing

number of carbon nanotubes will touch the surface of the mercury droplet

and contribute to the electrical current transport.

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APPLICATIONS OF NANOMATERIALS

Nanomaterials having wide range of applications in the field of electronics,

fuel cells,batteries, agriculture, food industry, and medicines, etc... It is

evident that nanomaterials split their conventional counterparts because of

their superior chemical, physical, and mechanical properties and of their

exceptional formability.

Fuel cells

A fuel cell is an electrochemical energy conversion device that converts the

chemical energy from fuel (on the anode side) and oxidant (on the cathode

side) directly into electricity. The heart of fuel cell is the electrodes. The

performance of a fuel cell electrode can be optimized in two ways; by

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improving the physical structure and by using more active electro catalyst.

A good structure of electrode must provide ample surface area, provide

maximum contact of catalyst, reactant gas and electrolyte, facilitate gas

transport and provide good electronic conductance. In this fashion the

structure should be able to minimize losses.

Carbon nanotubes - Microbial fuel cell

Microbial fuel cell is a device in which bacteria consume water-soluble

waste such as sugar, starch and alcohols and produces electricity plus clean

water. This technology will make it possible to generate electricity while

treating domestic or industrial wastewater.

Microbial fuel cell can turn different carbohydrates and complex substrates

present in wastewaters into a source of electricity. The efficient electron

transfer between the microorganism and the anode of the microbial fuel

cell plays a major role in the performance of the fuel cell. The organic

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molecules present in the wastewater posses a certain amount of chemical

energy, which is released when converting them to simplermolecules like

CO2. The microbial fuel cell is thus a device that converts the chemical

energy present in water-soluble waste into electrical energy by the catalytic

reaction of microorganisms.

Carbon nanotubes (CNTs) have chemical stability, good mechanical

properties

and high surface area, making them ideal for the design of sensors and

provide very high surface area due to its structural network. Since carbon

nanotubes are also suitable supports for cell growth, electrodes of

microbial fuel cells can be built using of CNT.

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Due to three-dimensional architectures and enlarged electrode surface area

for the entry of growth medium, bacteria can grow and proliferate and get

immobilized. Multi walled CNT scaffolds could offer self-supported

structure with large surface area through which hydrogen producing

bacteria (e.g., E. coli) can eventually grow and proliferate. Also CNTs and

MWCNTs have been reported to be biocompatible for different eukaryotic

cells. The efficient proliferation of hydrogen producing bacteria throughout

an electron conducting scaffold of CNT can form the basis for the potential

application as electrodes in MFCs leading to efficient performance.

Catalysis

Higher surface area available with the nanomaterial counterparts, nano-

catalysts tend to have exceptional surface activity. For example, reaction

rate at nano-aluminum can go so high, that it is utilized as a solid-fuel in

rocket propulsion, whereas the bulk aluminum is widely used in utensils.

Nano-aluminum becomes highly reactive and supplies the required thrust

to send off pay loads in space. Similarly, catalysts assisting or retarding the

reaction rates are dependent on the surface activity, and can very well be

utilized in manipulating the rate-controlling step.

Phosphors for High-Definition TV

The resolution of a television, or a monitor, depends greatly on the size of

the pixel.

These pixels are essentially made of materials called "phosphors," which

glow when struck by a stream of electrons inside the cathode ray tube

(CRT). The resolution improves with a reduction in the size of the pixel, or

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the phosphors. Nanocrystalline zinc selenide, zinc sulfide, cadmium

sulfide, and lead telluride synthesized by the sol-gel techniques are

candidates for improving the resolution of monitors. The use of

nanophosphors is envisioned to reduce the cost of these displays so as to

render highdefinition televisions (HDTVs) and personal computers

affordable to be purchase.

Next-Generation Computer Chips

The microelectronics industry has been emphasizing miniaturization,

whereby the circuits, such as transistors, resistors, and capacitors, are

reduced in size. By achieving a significant reduction in their size, the

microprocessors, which contain these components,can run much faster,

thereby enabling computations at far greater speeds. However, there are

several technological impediments to these advancements, including lack

of the ultrafine precursors to manufacture these components; poor

dissipation of tremendous amount of heat generated by these

microprocessors due to faster speeds; short mean time to failures (poor

reliability), etc. Nanomaterials help the industry break these barriers down

by providing the manufacturers with nanocrystalline starting materials,

ultra-high purity materials, materials with better thermal conductivity, and

longer-lasting, durable interconnections (connections between various

components in the microprocessors).

Example: Nanowires for junctionless transistors

Transistors are made so tiny to reduce the size of sub assemblies of

electronic systems and make smaller and smaller devices, but it is difficult

to create high-quality junctions.

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In particular, it is very difficult to change the doping concentration of a

material overdistances shorter than about 10 nm. Researchers have

succeeded in making thejunctionless transistor having nearly ideal

electrical properties. It could potentiallyoperate faster and use less power

than any conventional transistor on the market today.

The device consists of a silicon nanowire in which current flow is perfectly

controlled by a silicon gate that is separated from the nanowire by a thin

insulating layer. The entire silicon nanowire is heavily n-doped, making it

an excellent conductor. However, the gate is p-doped and its presence has

the effect of depleting the number of electrons in the region of the

nanowire under the gate. The device also has near-ideal electrical

properties and behaves like the most perfect of transistors without suffering

from current leakage like conventional devices and operates faster and

using less energy.

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SAFETY

Nanomaterials behave differently than other similarly-sized particles. It is

therefore necessary to develop specialized approaches to testing and

monitoring their effects on human health and on the environment. The

OECD Chemicals Committee has established the Working Party on

Manufactured Nanomaterials to address this issue and to study the

practices of OECD member countries in regards to nanomaterial safety.

While nanomaterials and nanotechnologies are expected to yield numerous

health and health care advances, such as more targeted methods of

delivering drugs, new cancer therapies, and methods of early detection of

diseases, they also may have unwanted effects. Increased rate of absorption

is the main concern associated with manufactured nanoparticles.

When materials are made into nanoparticles, their surface area to volume

ratio increases. The greater specific surface area (surface area per unit

weight) may lead to increased rate of absorption through the skin, lungs, or

digestive tract and may cause unwanted effects to the lungs as well as other

organs. However, the particles must be absorbed in sufficient quantities in

order to pose health risks.

As the use of nanomaterials increases worldwide, concerns for worker and

user safety are mounting. To address such concerns,

the Swedish Karolinska Institute conducted a study in which various

nanoparticles were introduced to human lung epithelial cells. The results,

released in 2008, showed that iron oxide nanoparticles caused

little DNA damage and were non-toxic. Zinc oxidenanoparticles were

slightly worse. Titanium dioxide caused only DNA damage. Carbon

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nanotubes caused DNA damage at low levels. Copper oxide was found to

be the worst offender, and was the only nanomaterial identified by the

researchers as a clear health risk.

DISADVANTAGES OF NANOMATERIALS

(i) Instability of the particles - Retaining the active metal nanoparticles is

highly challenging, as the kinetics associated with nanomaterials is rapid.

In order to retain nanosize of particles, they are encapsulated in some other

matrix. Nanomaterials are thermodynamically metastable and lie in the

region of high-energy local-minima. Hence they are prone to attack and

undergo transformation. These include poor corrosionresistance, high

solubility, and phase change of nanomaterials. This leads to deteriorationin

properties and retaining the structure becomes challenging.

(ii) Fine metal particles act as strong explosives owing to their high surface

area coming in direct contact with oxygen. Their exothermic combustion

can easily cause explosion.

(iii) Impurity - Because nanoparticles are highly reactive, they inherently

interact with impurities as well. In addition, encapsulation of nanoparticles

becomes necessary when they are synthesized in a solution (chemical

route). The stabilization of nanoparticles occurs because of a non-reactive

species engulfing the reactive nano-entities. Thereby,these secondary

impurities become a part of the synthesized nanoparticles, and synthesis of

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pure nanoparticles becomes highly difficult. Formation of oxides, nitrides,

etc can also get aggravated from the impure environment/ surrounding

while synthesizing nanoparticles. Hence retaining high purity in

nanoparticles can become a challenge hard to overcome.

(iv) Biologically harmful - Nanomaterials are usually considered harmful

as they become transparent to the cell-dermis. Toxicity of nanomaterials

also appears predominant owing to their high surface area and enhanced

surface activity. Nanomaterials have shown to cause irritation, and have

indicated to be carcinogenic. If inhaled, their low mass entraps them inside

lungs, and in no way they can be expelled out of body. Their interaction

with liver/blood could also prove to be harmful (though this aspect is still

being debated on).

(v) Difficulty in synthesis, isolation and application - It is extremely hard

to retain the size of nanoparticles once they are synthesized in a solution.

Hence, the nanomaterials have to be encapsulated in a bigger and stable

molecule/material. Hence free nanoparticles are hard to be utilized in

isolation, and they have to be interacted for intended use via secondary

means of exposure. Grain growth is inherently present in

nanomateirals during their processing. The finer grains tend to merge and

become bigger and stable grains at high temperatures and times of

processing.

(vi) Recycling and disposal - There are no hard-and-fast safe disposal

policies evolved for nanomaterials. Issues of their toxicity are still under

question, and results of exposure experiments are not available. Hence the

uncertainty associated with affects of nanomaterials is yet to be assessed in

order to develop their disposal policies.

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CONCLUSION

Nanoparticles show great promise, yet much discovery and

development still remains to be done. The examples presented in

this review were selected to exemplify the ability to significantly

alter the biodistribution of nanostructures by minor structural

changes, highlighting the importance of well-defined chemistries

for their preparation, in concert with rigorous analytic tools for their

physicochemical characterization, and PET for study of their in

vivo performance. PET serves as a highly sensitive imaging tool to

assist in the development of these materials to realize the potential

of nanomedicine for early-stage detection, diagnosis, treatment, and

monitoring of disease progression, regression, and recurrence.

The primary challenges over the next 5 y will be to accomplish

truly tissue-selective targeting, without the significant MPS organ

uptake, and full clearance of the nanomaterials once they have servedtheir

purpose. Toxicity and immunogenicity are measured routinely

for nearly every new nanomaterial being investigated. The examples

presented here included materials that have not displayed adverse

biologic responses, and they are also structures that are robust—the

robust character was important in the early studies to probe the

behavior of the nanostructures while they remained as intact

nanoscale objects. However, as development moves forward, it will

be important to replace the chemically stable components with others

that are biodegradable. In this aspect, again, organic polymer

materials have advantages over inorganic substrates, because several

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NANOMATERIALS Seminar: 2013

families of organic polymers are used regularly with Food and Drug

Administration approval for biomedical applications (poly[lactic

acid] and poly[glycolic acid], among many others).

BIBILIOGRAPHY

Applied nanotechnology. Jeremy Ramsden

http://en.wikipedia.org/wiki/Nanomaterials

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NANOMATERIALS Seminar: 2013

http://en.wikipedia.org/wiki/Atomic_force_microscopy

http://en.wikipedia.org/wiki/Nanoelectronics

Zhao H and Ning Y 2000 Gold Bull 33 103

Faraday M 1857 Philosophical Transactions 147 145

Feynman R P 1961 Miniaturization (New York: Reinhold)

Moore G 1975 IEDM Technical Digest 11

Maserjian J and Petersson G P 1974 Applied Physics Letters 25 50

Dept: Of Mechanical Eng 30 PKCET, Kandala