next generation technology 1

8/8/2019 Next Generation Technology 1

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BY

Ratneshwar kumar

M.Tech(nano technology)

Jamia milliya islamiya(central university)

New Delhi


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CoverChapter

1. Introduction of nanotechnology.

Ancient history & detail of past time uses of nanotechnology.

2. What is nanotechnology.

Generation of nanotechnology.

3. fullerene and nanotech introduction

-Structure of fullerene

-property

4. Introduction of CNT(carbon nano tube)

-Types of carbon nanotube.

- single walls

- multiwalls

- nanotorous

- nanobirds etc written again

* Property of carbon nano tube

5. size effect of CNT.(carbon nano tube)

6. colour Shifting in CNT

7. Classification of Structure

- 3 D Bulk ,its structure and property



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8. Procedure to Development or growth of nano particles.

a) via physical root .(these include number of root to develop nano particles)

b) via chemical root

classification of Chemical vapour deposition technique

- LPCVD(low pressure chemical vapour deposition)Many more written

c) pros and coins related to both these development method(physical & chemical

root.)

- Application of Nanotube in electronics and other engg fielg.

9. Future scope of this technology.

10. Introduction of MEMS and NEMS Devices

- Application,uses,and ,Material use for MEMS & NEMS devises.

11. Top Down and Bottom up Approach.

12. daxluar and Smallyies Debates on top Down &Bottom up approach

And how this approach is useful in nanotechnology.

13.challenges of this emerging technology.

14. Abuses of NANOTECHNOLOGY.

15. Instrument use to Measure and watch the Nanoscale Materials.

-SEM,TEM,HRTEM,XRD,RAMAN Spectroscopy,ratherford back scattering(RBS)

etc


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History of nanotechnology

Although nanotechnology is a relatively recent development in scientific research, thedevelopment of its central concepts happened over a longer period of time.

In 1965, Gordon Moore, one of the founders ofIntel Corporation, made the outstandingprediction that the number of transistors that could be fit in a given area would double every 18months for the next ten years. This it did and the phenomenon became known as Moore's Law.This trend has continued far past the predicted 10 years until this day, going from just over 2000transistors in the original 4004 processors of1971 to over 700,000,000 transistors in the Core 2.There has, of course, been a corresponding decrease in the size of individual electronic elements,going from millimeters in the 60's to hundreds of nanometers in modern circuitry.

At the same time, the chemistry,biochemistry and molecular genetics communities have beenmoving in the other direction. Over much the same period, it has become possible to direct thesynthesis, either in the test tube or in modified living organisms.

Finally, the last quarter of a century has seen tremendous advances in our ability to control andmanipulate light. We can generate light pulses as short as a few femtoseconds (1 fs = 1015 s).Light too has a size and this size is also on the hundred nanometer scale.

Thus now, at the beginning of a new century, three powerful technologies have met on acommon scale the nanoscale with the promise of revolutionizing both the worlds ofelectronics and of biology. This new field, which we refer to as biomolecular nanotechnology,holds many possibilities from fundamental research in molecular biology and biophysics toapplications in biosensing, biocontrol, bioinformatics, genomics, medicine, computing,information storage and energy conversion.

Historical background

Humans have unwittingly employed nanotechnology for thousands of years, for example inmaking steel, paintings and in vulcanizing rubber.[1] Each of these processes rely on theproperties ofstochastically-formed atomic ensembles mere nanometers in size, and aredistinguished from chemistry in that they don't rely on the properties of individual molecules.But the development of the body of concepts now subsumed under the term nanotechnology hasbeen slower.

The first mention of some of the distinguishing concepts in nanotechnology (but predating use ofthat name) was in 1867 by James Clerk Maxwell when he proposed as a thought experiment atiny entity known as Maxwell's Demon able to handle individual molecules.

The first observations and size measurements of nano-particles was made during the first decadeof the 20th century. They are mostly associated with Richard Adolf Zsigmondy who made adetailed study of gold sols and other nanomaterials with sizes down to 10 nm and less. Hepublished a book in 1914.

[2]. He used ultramicroscope that employes the dark fieldmethod for

seeing particles with sizes much less than lightwavelength. Zsigmondy was also the first who


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used nanometer explicitly for characterizing particle size. He determined it as 1/1,000,000 ofmillimeter. He developed the first system classification based on particle size in the nanometerrange.

There have been many significant developments during the 20th century in characterizing

nanomaterials and related phenomena, belonging to the field ofinterface and colloid science. Inthe 1920s, Irving Langmuirand Katharine B. Blodgett introduced the concept of a monolayer, alayer of material one molecule thick. Langmuir won aNobel Prize in chemistry for his work. Inthe early 1950s, Derjaguin and Abrikosova conducted the first measurement of surface forces

[3].

There have been many studies ofperiodic colloidal structures and principles ofmolecular self-assembly that are overviewed in the paper

[4]. There are many other discoveries that serve as the

scientific basis for the modern nanotechnology which can be found in the "Fundamentals ofInterface and Colloid Science by H.Lyklema [5].

Conceptual origins

The topic of nanotechnology was again touched upon by "There's Plenty of Room at theBottom," a talk given by physicist Richard Feynman at an American Physical Society meeting atCaltech on December 29, 1959. Feynman described a process by which the ability to manipulateindividual atoms and molecules might be developed, using one set of precise tools to build andoperate another proportionally smaller set, so on down to the needed scale. In the course of this,he noted, scaling issues would arise from the changing magnitude of various physicalphenomena: gravity would become less important, surface tension and Van der Waals attractionwould become more important, etc. This basic idea appears feasible, and exponential assemblyenhances it withparallelism to produce a useful quantity of end products. At the meeting,Feynman announced two challenges, and he offered a prize of $1000 for the first individuals to

solve each one. The first challenge involved the construction of a nanomotor, which, toFeynman's surprise, was achieved by November 1960 by William McLellan. The secondchallenge involved the possibility of scaling down letters small enough so as to be able to fit theentire Encyclopedia Britannica on the head of a pin; this prize was claimed in 1985 by TomNewman.[6]

In 1965 Gordon Moore observed that silicon transistors were undergoing a continual process ofscaling downward, an observation which was later codified as Moore's law. Since hisobservation transistor minimum feature sizes have decreased from 10 micrometers to the 45-65 nm range in 2007; one minimum feature is thus roughly 180 silicon atoms long.

The term "nanotechnology" was first defined byNorio Taniguchi of the Tokyo ScienceUniversity in a 1974 paper

[7]as follows: "'Nano-technology' mainly consists of the processing

of, separation, consolidation, and deformation of materials by one atom or one molecule." Sincethat time the definition of nanotechnology has generally been extended to include features aslarge as 100 nm. Additionally, the idea that nanotechnology embraces structures exhibitingquantum mechanical aspects, such as quantum dots, has further evolved its definition.


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Also in 1974 the process ofatomic layer deposition, for depositing uniform thin films one atomiclayer at a time, was developed and patented by Dr. Tuomo Suntola and co-workers in Finland.

In the 1980s the idea of nanotechnology as deterministic, rather than stochastic, handling ofindividual atoms and molecules was conceptually explored in depth by Dr. K. Eric Drexler, who

promoted the technological significance of nano-scale phenomena and devices through speechesand the books Engines of Creation: The Coming Era of Nanotechnology and Nanosystems:Molecular Machinery, Manufacturing, and Computation, (ISBN 0-471-57518-6). Drexler'svision of nanotechnology is often called "Molecular Nanotechnology" (MNT) or "molecularmanufacturing," and Drexler at one point proposed the term "zettatech" which never becamepopular.

In 2004 Richard Jones wrote a book called Soft Machines (nanotechnology and life), is a bookabout nanotechnology for the general reader, published by Oxford University. In this book hedescribes radical nanotechnology as a deterministic/mechanistic idea of nano engineeredmachines that does not take into account the nanoscale challenges such as wetness, stickness,

brownian motion, high viscosity (Drexler view).H

e also explains what is soft nanotechnology ormore appropriatellybiomimetic nanotechnology which is the way forward, if not the best , todesign functional nanodevices that can cope with all the problems at nanoscale. One can think ofsoft nanotechnology as the development of nanomachines that uses the lessons learned frombiology on how things work, chemistry to precisely engineer such devices and stochastic physicsto model the system and its natural processes in detail.

Experimentaladvances

Nanotechnology and nanoscience got a boost in the early 1980s with two major developments:the birth ofclusterscience and the invention of the scanning tunneling microscope (STM). This

development led to the discovery offullerenes in 1985 and the structural assignment ofcarbonnanotubes a few years later. In another development, the synthesis and properties ofsemiconductornanocrystals were studied. This led to a fast increasing number ofsemiconductornanoparticles ofquantum dots.

In the early 1990s Huffman and Kraetschmer, of the University of Arizona, discovered how tosynthesize and purify large quantities of fullerenes. This opened the door to their characterizationand functionalization by hundreds of investigators in government and industrial laboratories.Shortly after, rubidium doped C60 was found to be a mid temperature (Tc = 32 K)superconductor. At a meeting of the Materials Research Society in 1992, Dr. T. Ebbesen (NEC)described to a spellbound audience his discovery and characterization of carbon nanotubes. This

event sent those in attendance and others downwind of his presentation into their laboratories toreproduce and push those discoveries forward. Using the same or similar tools as those used byHuffman and Kratschmere, hundreds of researchers further developed the field of nanotube-based nanotechnology.

At present in 2007 the practice of nanotechnology embraces both stochastic approaches (inwhich, for example, supramolecular chemistry creates waterproof pants) and deterministicapproaches wherein single molecules (created by stochastic chemistry) are manipulated on


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substrate surfaces (created by stochastic deposition methods) by deterministic methodscomprising nudging them with STM orAFM probes and causing simple binding or cleavagereactions to occur. The dream of a complex, deterministic molecular nanotechnology remainselusive. Since the mid 1990s, thousands of surface scientists and thin film technocrats havelatched on to the nanotechnology bandwagon and redefined their disciplines as nanotechnology.

This has caused much confusion in the field and has spawned thousands of "nano"-papers on thepeer reviewed literature. Most of these reports are extensions of the more ordinary research donein the parent fields.

For the future, some means has to be found for MNT design evolution at the nanoscale whichmimics the process of biological evolution at the molecular scale. Biological evolution proceedsby random variation in ensemble averages of organisms combined with culling of the less-successful variants and reproduction of the more-successful variants, and macroscale engineeringdesign also proceeds by a process of design evolution from simplicity to complexity as set forthsomewhat satirically by John Gall: "A complex system that works is invariably found to haveevolved from a simple system that worked. . . . A complex system designed from scratch never

works and can not be patched up to make it work. You have to start over, beginning with asystem that works." [8] A breakthrough in MNT is needed which proceeds from the simpleatomic ensembles which can be built with, e.g., an STM to complex MNT systems via a processof design evolution. A handicap in this process is the difficulty of seeing and manipulation at thenanoscale compared to the macroscale which makes deterministic selection of successful trialsdifficult; in contrast biological evolution proceeds via action of what Richard Dawkins has calledthe "blind watchmaker" [9] comprising random molecular variation and deterministicreproduction/extinction.


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What is Nanotechnology

Nanotechnology is a part ofscience and technology that is about the control ofmatter on the atomic

and molecular scale - this means things that are about 100 nanometers or smaller. Nanotechnology

includes making products that use parts this small, such as electronic devices, catalysts, and sensors etc.

Nanotechnology is defined as the study of structures between 1 nanometer and 100 nanometers in size.

To give you an idea of how small that is, it would take eight hundred one hundred nanometer particles

side by side to match the width of a human hair!

Nanotechnology brings together scientists from many different subjects, such as applied physics,materials science, interface and colloid science, device physics, chemistry, supramolecularchemistry (which refers to the area of chemistry that focuses on the noncovalent bondinginteractions of molecules), self-replicating machines and robotics, chemical engineering,

mechanical engineering, biology,biological engineering, and electrical engineering

Generally when people talk about nanotechnology, they mean structures of the size 100nanometers or smaller. There are one million nanometers in a millimeter. Nanotechnology triesto make materials or machines of that size. People are doing many different types of work in thefield of nanotechnology. Most current work looks at making nanoparticles (particles withnanometer size) that have special properties, such as the way they scatter light, absorb X-rays,transport electrical currents or heat, etc. etc. At the more "science fiction" end of the field areattempts to make small copies of bigger machines or really new ideas for structures that makethemselves. New materials are possible with nano size structures. It is even possible to work withsingle atoms.

There has been a lot of discussion about the future of nanotechnology and its dangers.Nanotechnology may be able to invent new materials and instruments which would be veryuseful, such as in medicine, computers, and making clean electricity (nanotechnology is helpingdesign the next generation of solar panels, and efficient low-energy lighting). On the other hand,nanotechnology is new and there could be unknown problems. For example if the materials arebad for people's health or for nature. They may have a bad effect on the economy or even bignatural systems like the Earth itself. Some groups argue that there should be rules about the useof nanotechnology.

The BeginningofNanotechnology

The first use of the ideas in 'nano-technology' (but before the name was invented) was in "There'sPlenty of Room at the Bottom," a talk given by the scientist Richard Feynman at an AmericanPhysical Society meeting at Caltech on December 29, 1959. Feynman described a way to moveindividual atoms and molecules using very small apparatus to build and operate even smallerinstruments and so on down to the needed scale. In the course of this, he noted, sometimesproblems will appear because of the changes in scale. The weight of things under study wouldbecome less important, but for example, surface tension and Van der Waals force would becomemore important.


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Feynman's simple idea seemed possible. The word "nanotechnology" was explained by TokyoScience University Professor Norio Taniguchi in a 1974 paper. He said that nanotechnology wasthe work of changing materials by one atom or by one molecule. In the 1980s this idea wasstudied by Dr. K. Eric Drexler, who spoke and wrote about how important nano-scale events andthings are.

"Engines of Creation: The Coming Era of Nanotechnology" (1986) is thought to be the first bookon nanotechnology. Nanotechnology and nanoscience got started in the early 1980s with two keydevelopments: the start of cluster science and the invention of the scanning tunneling microscope(STM). Soon afterwards, new molecules made of carbon were discovered - first fullerenes in1986, and carbon nanotubes a few years later. In another development, people studied how tomake semiconductor nanocrystals. Many metal oxide nanoparticles are now used as quantumdots (nanoparticles where the behaviour of single electrons becomes important). In 2000, theUnited States National Nanotechnology Initiative was begun to help develop the science inAmerica.

ImportantIdeas

One nanometer (nm) is one billionth, or 10-9, of a meter. When two carbon atoms join together tomake a molecule the distance between them is in the range 0.12-0.15 nm, and a DNA double-helix is about 2 nm from one side to the other. On the other hand, the smallest living thing with acell is a bacteria about 200 nm long... To understand the scale better think about the differencebetween a nanometer and a meter. It is the same size difference as a golf ball and the earth. Oranother way of putting it: a nanometer is the amount that a hair on a man's face grows in the timeit takes him to lift his hand to shave. There are two common approaches in the field ofnanotechnology. In the "bottom-up" idea, materials and instruments are built from moleculeswhich join together because of their chemistry. In the "top - down" idea, nano-objects are made

out of bigger things without trying to move parts of them at the level of atoms.

Top - down (Largertosmaller):alookatthe problembasedonmaterials

Some of the laws of physics become more obvious as the system gets smaller. For example theeffects of very small movements, as well as quantum mechanical effects, like the quantum sizeeffect where electrons in solids move differently for very small sizes of particle. This effectdoes not come into play by going from macro to micro sizes. However, it becomes the mostimportant thing when working in the nanometer size range. A number of physical (mechanical,electrical, optical, etc.) properties also change when a macroscopic system becomes amicroscopic one. One example is the increase in amount of surface area for the volume inside it.

This changes how heat and chemicals interact with the material. The new types of interaction innanosystems are of interest in nanomechanics research. Nanomaterials can be catalysts, i.e. theyhelp chemical reactions happen more easily. This can be very useful for the chemical industry toreduce energy use and production of expensive or toxic by-products, but care has to be taken toavoid catalysing unwanted reactions, such as in their interaction with biomaterials.[6]

Materials made very small can show different properties which we do not see on a macroscale,this makes some completely new inventions possible. For example, substances which usually


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stop light become transparent (copper); it becomes possible to burn some materials (aluminum);solids turn into liquids at room temperature (gold); insulators become conductors (silicon). Amaterial such as gold, which does not react with other chemicals at normal scales, can be apowerful chemical catalyst at nanoscales. These special properties which we can only see at thenano scale are one of the most interesting things about nanotechnology.

Bottom - up (Smallertolarger)

Modern scientists can now make small molecules with almost any structure. These techniquesare used today to make a wide variety of useful chemicals such as medicines orpolymers. Thisability lets us ask questions about using this kind of method at a larger level: to try to put thesesingle molecules together into structures containing many molecules organised into a system.

This idea uses molecules that move themselves or organise themselves into some useful structurelike building blocks. Here it is very important for molecules to find exactly the other moleculesthat they should connect with. Molecules can be designed so that a certain structure is more

likely to appear, because of the forces between the molecules. The Watson-Crick basepairingrules are a way of doing this, so is the way a lot of enzymes work, or the structures that proteinsmake. In this way, two or more parts of a structure can be designed to find each other and worktogether to make a bigger and more useful system.

Such techniques should be able to make a lot of small structures at the same time and muchcheaper than top-down methods, but it may be difficult for them to design bigger and morecomplicated structures. Most useful structures need a lot of atoms, organised into a structure thathas a small probability of making itself. But there are many examples of these structures inbiology, especially Watson-Crick basepairing and enzyme interactions. The interesting job fornanotechnologists is to use the same techniques to make new systems which do not happen in

nature.

What is Nanotechnology?

A basic definition: Nanotechnology is the engineering of functional systems at themolecular scale. This covers both current work and concepts that are moreadvanced.

In its original sense, 'nanotechnology' refers to the projected ability to construct itemsfrom the bottom up, using techniques and tools beingdeveloped today to makecomplete, high performance products.

The Meaning of Nanotechnology

When K. Eric Drexler (right) popularized the word 'nanotechnology' in the 1980's, he

was talking about building machines on the scale of molecules, a few nanometers

widemotors, robot arms, and even whole computers, far smaller than a cell. Drexler

spent the next ten years describing and analyzing these incredible devices, and


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responding to accusations of science fiction. Meanwhile, mundanetechnology was

developing the ability to build simple structures on a molecular scale. As

nanotechnology became an accepted concept, the meaning of the word shifted to

encompass the simpler kinds of nanometer-scale technology. The U.S. National

Nanotechnology Initiative was created to fund this kind of nanotech: their definition

includes anything smaller than 100 nanometers with novel properties.

Much of the work being done today that carries the name 'nanotechnology' is not

nanotechnology in the original meaning of the word. Nanotechnology, in its traditional sense,

means building things from the bottom up, with atomic precision. This theoretical capability

was envisioned as early as 1959 by the renowned physicist Richard Feynman.

I want to build a billion tiny factories, models of each other, which are manufacturing

simultaneously. . .The principles of physics, as far as I can see, do not speak against the

possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it issomething, in principle, that can be done; but in practice, it has not been done because we are

too big. Richard Feynman, Nobel Prize winner in physics

Based on Feynman's vision of miniature factories using nanomachines to build complex

products, advanced nanotechnology (sometimes referred to as molecular

manufacturing) will make use of positionally-controlled mechanochemistry guided by

molecular machine systems. Formulating a roadmap for development of this kind of

nanotechnology is now an objective of a broadly based technology roadmap project

led by Battelle (the manager of several U.S. National Laboratories) and the Foresight

Nanotech Institute.

Shortly after this envisioned molecular machinery is created, it will result in a manufacturing

revolution, probably causing severe disruption. It also has serious economic, social,

environmental, and military implications.


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With 15,342 atoms, this parallel-shaft speed reducer gear is one of the largest

nanomechanical devices ever modeled in atomic detail.

Structural DNA Nanotechnology Gallery

Here we feature models created by NanoEngineer-1 of DNA structures that have actually been

synthesized and imaged.

Carbon Nanotube Gallery

A collection of theoretical designs in which one or more components are carbon nanotubes.


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MolecularMachinery Gallery

Theoretical designs in which assemblies are composed of rigid covalently bonded components.

MolecularManufacturing Gallery

Theoretical models of mechanosynthesis tools designed for atomically precise manufacturing.

Generation of Nanotechnology:

Four Generations

Mihail (Mike) Roco of the U.S. National Nanotechnology Initiative has describedfourgenerations of nanotechnology development (see chart below). The current era, asRoco depicts it, is that of passive nanostructures, materials designed to perform one


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task. The second phase, which we are just entering, introduces active nanostructuresfor multitasking; for example, actuators, drug delivery devices, andsensors. The thirdgeneration is expected to begin emerging around 2010 and will feature nanosystemswith thousands of interacting components. A few years after that, the first integratednanosystems, functioning (according to Roco) much like a mammalian cell with

hierarchical systems within systems, are expected to be developed.

Some experts may still insist that nanotechnology can refer to measurement orvisualization at the scale of 1-100 nanometers, but a consensus seems to be formingaround the idea (put forward by the NNI's Mike Roco) that control and restructuring ofmatterat the nanoscale is a necessary element. CRN's definition is a bit more precise

than that, but as work progresses through the four generations of nanotechnologyleading up to molecular nanosystems, which will include molecular manufacturing, wethink it will become increasingly obvious that "engineering of functional systems atthe molecular scale" is what nanotech is really all about.


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Conflicting Definitions

Unfortunately, conflicting definitions of nanotechnology and blurry distinctionsbetween significantly different fields have complicated the effort to understand thedifferences and develop sensible, effective policy.

The risks of today's nanoscale technologies (nanoparticle toxicity, etc.) cannot betreated the same as the risks of longer-term molecular manufacturing (economicdisruption, unstable arms race, etc.). It is a mistake to put them together in onebasket for policy considerationeach is important to address, but they offer differentproblems and will require different solutions. As used today, the term nanotechnologyusually refers to a broad collection of mostly disconnected fields. Essentially,anything sufficiently small and interesting can be called nanotechnology. Much of it isharmless. For the rest, much of the harm is of familiar and limited quality. But as wewill see, molecular manufacturing will bring unfamiliar risks and new classes ofproblems.

General-Purpose Technology

Nanotechnology is sometimes referred to as ageneral-purpose technology. That's

because in its advanced form it will have significant impact on almost all industries

and all areas of society. It will offer better built, longer lasting, cleaner, safer, and

smarter products for the home, for communications, for medicine, for transportation,

for agriculture, and for industry in general.

Imagine a medical device that travels through the human body to seek out and destroy small

clusters of cancerous cells before they can spread. Or a box no larger than a sugar cube thatcontains the entire contents of the Library ofCongress. Or materials much lighter than steel that

possess ten times as much strength. U.S. National Science Foundation

Dual-Use Technology

Like electricity or computers before it, nanotech will offer greatly improved

efficiency in almost every facet of life. But as a general-purpose technology, it will be

dual-use, meaning it will have many commercial uses and it also will have many

military usesmaking far more powerful weapons and tools of surveillance. Thus it

represents not only wonderful benefits for humanity, but also grave risks.

A key understanding of nanotechnology is that it offers not just better products, but a

vastly improved manufacturing process. A computer can make copies of data files

essentially as many copies as you want at little or no cost. It may be only a matter of

time until the building of products becomes as cheap as the copying of files. That's


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the real meaning of nanotechnology, and why it is sometimes seen as "the next

industrial revolution."

My own judgment is that the nanotechnology revolution has the potential to change America on

a scale equal to, if not greater than, the computer revolution. U.S. Senator Ron Wyden (D-

Ore.)

The power of nanotechnology can be encapsulated in an apparently simple device

called apersonal nanofactorythat may sit on your countertop or desktop. Packed

with miniature chemical processors, computing, and robotics, it will produce a wide-

range of items quickly, cleanly, and inexpensively, building products directly from

blueprints.

Application ofNano Technology:

With nanotechnology, a large set of materials and improved products rely on a change inthe physical properties when the feature sizes are shrunk. Nanoparticles, for example,take advantage of their dramatically increased surface area to volume ratio. Their opticalproperties, e.g. fluorescence, become a function of the particle diameter. When brought

into a bulk material, nanoparticles can strongly influence the mechanical properties of thematerial, like stiffness or elasticity. For example, traditionalpolymers can be reinforcedby nanoparticles resulting in novel materials which can be used as lightweightreplacements for metals. Therefore, an increasing societal benefit of such nanoparticlescan be expected. Such nanotechnologically enhanced materials will enable a weightreduction accompanied by an increase in stability and improved functionality. Practicalnanotechnology is essentially the increasing ability to manipulate (with precision) matteron previously impossible scales, presenting possibilities which many could never have


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imagined - it therefore seems unsurprising that few areas of human technology areexempt from the benefits which nanotechnology could potentially bring.

Medicine

The biological and medical research communities have exploited the unique properties ofnanomaterials for various applications (e.g., contrast agents for cell imaging andtherapeutics for treating cancer). Terms such as biomedical nanotechnology,nanobiotechnology, and nanomedicine are used to describe this hybrid field.Functionalities can be added to nanomaterials by interfacing them with biologicalmolecules or structures. The size of nanomaterials is similar to that of most biologicalmolecules and structures; therefore, nanomaterials can be useful for both in vivo and invitro biomedical research and applications. Thus far, the integration of nanomaterialswith biology has led to the development of diagnostic devices, contrast agents, analyticaltools, physical therapy applications, and drug delivery vehicles.

Nanomedicine

Nanomedicine is the medical application ofnanotechnology.[1] Nanomedicine ranges

from the medical applications ofnanomaterials, to nanoelectronic biosensors, and

even possible future applications ofmolecular nanotechnology. Current problems

for nanomedicine involve understanding the issues related to toxicity and

environmental impactofnanoscale materials.

Nanomedicine research is receiving funding from the USNational Institute ofHealth. Ofnote is the funding in 2005 of a five-year plan to set up four nanomedicine centers. InApril 2006, the journalNature Materials estimated that 130 nanotech-based drugs anddelivery systems were being developed worldwide.[2]

Nanomedicine seeks to deliver a valuable set of research tools and clinically usefuldevices in the near future.[3][4] TheNational Nanotechnology Initiative expects newcommercial applications in thepharmaceutical industry that may include advanced drugdelivery systems, new therapies, and in vivo imaging.[5] Neuro-electronic interfaces and

othernanoelectronics-based sensors are another active goal of research. Further down theline, the speculative field ofmolecular nanotechnology believes that cell repair machinescould revolutionize medicine and the medical field.

Nanomedicine is a large industry, with nanomedicine sales reaching 6.8 billion dollars in2004, and with over 200 companies and 38 products worldwide, a minimum of 3.8 billiondollars in nanotechnology R&D is being invested every year.[6] As the nanomedicineindustry continues to grow, it is expected to have a significant impact on the economy.


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Medical useofnanomaterials

Drug delivery

Nanomedical approaches to drug delivery center on developing nanoscale particles or molecules

to improve drugbioavailability. Bioavailability refers to the presence of drug molecules wherethey are needed in the body and where they will do the most good. Drug delivery focuses onmaximizing bioavailability both at specific places in the body and over a period of time. This canpotentially be achieved by molecular targeting by nanoengineered devices.[7][8] It is all abouttargeting the molecules and delivering drugs with cell precision. More than $65 billion arewasted each year due to poor bioavailability. In vivo imaging is another area where tools anddevices are being developed. Using nanoparticlecontrast agents, images such as ultrasound andMRI have a favorable distribution and improved contrast. The new methods of nanoengineeredmaterials that are being developed might be effective in treating illnesses and diseases such ascancer. What nanoscientists will be able to achieve in the future is beyond current imagination.This might accomplished by self assembled biocompatible nanodevices that will detect, evaluate,

treat and report to the clinical doctor automatically.

Drug delivery systems, lipid- or polymer-based nanoparticles[9], can be designed to improve thepharmacological and therapeutic properties of drugs.[10] The strength of drug delivery systems istheir ability to alter thepharmacokinetics andbiodistribution of the drug. Nanoparticles haveunusual properties that can be used to improve drug delivery. Where larger particles would havebeen cleared from the body, cells take up these nanoparticles because of their size. Complex drugdelivery mechanisms are being developed, including the ability to get drugs through cellmembranes and into cell cytoplasm. Efficiency is important because many diseases depend uponprocesses within the cell and can only be impeded by drugs that make their way into the cell.Triggered response is one way for drug molecules to be used more efficiently. Drugs are placed

in the body and only activate on encountering a particular signal. For example, a drug with poorsolubility will be replaced by a drug delivery system where both hydrophilic and hydrophobicenvironments exist, improving the solubility. Also, a drug may cause tissue damage, but withdrug delivery, regulated drug release can eliminate the problem. If a drug is cleared too quicklyfrom the body, this could force a patient to use high doses, but with drug delivery systemsclearance can be reduced by altering the pharmacokinetics of the drug. Poor biodistribution is aproblem that can affect normal tissues through widespread distribution, but theparticulates fromdrug delivery systems lower the volume of distribution and reduce the effect on non-target tissue.Potential nanodrugs will work by very specific and well-understood mechanisms; one of themajor impacts of nanotechnology and nanoscience will be in leading development of completelynew drugs with more useful behavior and less side effects.

Proteinand peptidedelivery

Protein and peptides exert multiple biological actions in human body and they have beenidentified as showing great promise for treatment of various diseases and disorders. Thesemacromolecules are calledbiopharmaceuticals. Targeted and/or controlled delivery of thesebiopharmaceuticals using nanomaterials like nanoparticles and Dendrimers is an emerging fieldcalled nanobiopharmaceutics, and these products are called nanobiopharmaceuticals.


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Nanoparticle

In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms ofits transport and properties. It is further classified according to size: in terms ofdiameter, fineparticles cover a range between 100 and 2500 nanometers, while ultrafine particles, on the other

hand, are sized between 1 and 100 nanometers. Similar to ultrafine particles, nanoparticles aresized between 1 and 100 nanometers. Nanoparticles may or may not exhibit size-relatedproperties that differ significantly from those observed in fine particles or bulk materials.[1][2]Although the size of most molecules would fit into the above outline, individual molecules areusually not referred to as nanoparticles.

Nanoclusters have at least one dimension between 1 and 10 nanometers and a narrow sizedistribution.Nanopowders[3] are agglomerates of ultrafine particles, nanoparticles, ornanoclusters. Nanometer-sized single crystals, or single-domain ultrafine particles, are oftenreferred to as nanocrystals. Nanoparticle research is currently an area of intense scientific interestdue to a wide variety of potential applications in biomedical, optical and electronic fields.

TEM (a, b, and c) images of prepared mesoporous silica nanoparticles with mean outer diameter: (a)

20nm, (b) 45nm, and (c) 80nm. SEM (d) image corresponding to (b). The insets are a high magnification

of mesoporous silica particle.


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Background

Although nanoparticles are generally considered an invention of modern science, they actuallyhave a very long history. Nanoparticles were used by artisans as far back as the 9th century inMesopotamia for generating a glittering effect on the surface of pots

[citation needed].

Even these days,pottery from the Middle Ages and Renaissance often retain a distinct gold orcopper colored metallic glitter. This so called lusteris caused by a metallic film that was appliedto the transparent surface of a glazing. The luster can still be visible if the film has resistedatmospheric oxidation and other weathering.

The luster originated within the film itself, which contained silver and copper nanoparticlesdispersed homogeneously in the glassy matrix of the ceramic glaze. These nanoparticles werecreated by the artisans by adding copperand silversalts and oxides together with vinegar, ochreand clay, on the surface of previously-glazed pottery. The object was then placed into a kiln andheated to about 600 C in a reducing atmosphere.

In the heat the glaze would soften, causing the copper and silverions to migrate into the outerlayers of the glaze. There the reducing atmosphere reduced the ions back to metals, which thencame together forming the nanoparticles that give the colour and optical effects.

Luster technique showed that ancient craftsmen had a rather sophisticated empirical knowledgeof materials. The technique originated in the islamic world. As Muslims were not allowed to usegold in artistic representations, they had to find a way to create a similar effect without using realgold. The solution they found was using luster.

[5]

Michael Faraday provided the first description, in scientific terms, of the optical properties of

nanometer-scale metals in his classic 1857 paper. In a subsequent paper, the author (Turner)points out that: "It is well known that when thin leaves of gold or silver are mounted upon glassand heated to a temperature which is well below a red heat (~500 C), a remarkable change ofproperties takes place, whereby the continuity of the metallic film is destroyed. The result is thatwhite light is now freely transmitted, reflection is correspondingly diminished, while theelectrical resistivity is enormously increased."

Uniformity

The chemical processing and synthesis of high performance technological components for theprivate, industrial and military sectors requires the use of high purity ceramics,polymers, glass-

ceramics and material composites. In condensed bodies formed from fine powders, the irregularparticle sizes and shapes in a typical powder often lead to non-uniform packing morphologiesthat result in packing density variations in the powder compact.

Uncontrolled agglomeration of powders due to attractivevan der Waals forces can also give riseto in microstructural inhomogeneities. Differential stresses that develop as a result of non-uniform drying shrinkage are directly related to the rate at which the solvent can be removed,and thus highly dependent upon the distribution ofporosity. Such stresses have been associated


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with a plastic-to-brittle transition in consolidated bodies, and can yield to crack propagation inthe unfired body if not relieved.

In addition, any fluctuations in packing density in the compact as it is prepared for the kiln areoften amplified during the sintering process, yielding inhomogeneous densification. Some pores

and other structural defects associated with density variations have been shown to play adetrimental role in the sintering process by growing and thus limiting end-point densities.Differential stresses arising from inhomogeneous densification have also been shown to result inthe propagation of internal cracks, thus becoming the strength-controlling flaws.

It would therefore appear desirable to process a material in such a way that it is physicallyuniform with regard to the distribution of components and porosity, rather than using particlesize distributions which will maximize the green density. The containment of a uniformlydispersed assembly of strongly interacting particles in suspension requires total control overinterparticle forces. Monodisperse nanoparticles and colloids provide this potential.

Monodisperse powders of colloidal silica, for example, may therefore be stabilized sufficiently toensure a high degree of order in the colloidal crystal orpolycrystalline colloidal solid whichresults from aggregation. The degree of order appears to be limited by the time and spaceallowed for longer-range correlations to be established. Such defective polycrystalline colloidalstructures would appear to be the basic elements of submicrometer colloidal materials science,and, therefore, provide the first step in developing a more rigorous understanding of themechanisms involved in microstructural evolution in high performance materials andcomponents.

Colloidal crystal composed ofamorphoushydratedcolloidalsilica (particle diameter 600 nm)

Properties

Nanoparticles are of great scientific interest as they are effectively a bridge between bulkmaterials and atomic ormolecularstructures. A bulk material should have constant physicalproperties regardless of its size, but at the nano-scale size-dependent properties are often


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observed. Thus, the properties of materials change as their size approaches the nanoscale and asthe percentage of atoms at the surface of a material becomes significant. For bulk materialslarger than one micrometer (or micron), the percentage of atoms at the surface is insignificant inrelation to the number of atoms in the bulk of the material. The interesting and sometimesunexpected properties of nanoparticles are therefore largely due to the large surface area of the

material, which dominates the contributions made by the small bulk of the material.

For example, nanoparticles of usually yellow gold and gray silicon are red in color; goldnanoparticles melt at much lower temperatures (~300 C for 2.5 nm size) than the gold slabs(1064 C);[18] and absorption of solar radiation in photovoltaic cells is much higher in materialscomposed of nanoparticles than it is in thin films of continuous sheets of material the smallerthe particles, the greater the solar absorption.

Other size-dependent property changes include quantum confinement in semiconductorparticles,surface plasmon resonance in some metal particles and superparamagnetism in magneticmaterials. Ironically, the changes in physical properties are not always desirable. Ferroelectric

materials smaller than 10 nm can switch their magnetisation direction using room temperaturethermal energy, thus making them unsuitable for memory storage.[19]

Suspensions of nanoparticles are possible since the interaction of the particle surface with thesolvent is strong enough to overcome density differences, which otherwise usually result in amaterial either sinking or floating in a liquid. Nanoparticles also often possess unexpected opticalproperties as they are small enough to confine their electrons and produce quantum effects. Forexample gold nanoparticles appear deep red to black in solution.

The high surface area to volume ratio of nanoparticles provides a tremendous driving force fordiffusion, especially at elevated temperatures. Sintering can take place at lower temperatures,

over shorter time scales than for larger particles. This theoretically does not affect the density ofthe final product, though flow difficulties and the tendency of nanoparticles to agglomeratecomplicates matters. Moreover, nanoparticles have been found to impart some extra properties tovarious day to day products. For example the presence of titanium dioxide nanoparticles impartswhat we call the self-cleaning effect, and the size being nanorange, the particles can not beobserved. Zinc oxide particles have been found to have superior UV blocking propertiescompared to its bulk substitute. This is one of the reasons why it is often used in the preparationof sunscreen lotions.[20], and is completely photostable.[21]

Clay nanoparticles when incorporated into polymer matrices increase reinforcement, leading tostronger plastics, verifiable by a higherglass transition temperature and other mechanicalproperty tests. These nanoparticles are hard, and impart their properties to the polymer (plastic).Nanoparticles have also been attached to textile fibers in order to create smart and functionalclothing.[22]

Metal, dielectric, and semiconductornanoparticles have been formed, as well as hybridstructures (e.g., core-shell nanoparticles). Nanoparticles made of semiconducting material mayalso be labeled quantum dots if they are small enough (typically sub 10 nm) that quantization of


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electronic energy levels occurs. Such nanoscale particles are used in biomedical applications asdrug carriers orimaging agents.

Semi-solid and soft nanoparticles have been manufactured. A prototype nanoparticle of semi-solid nature is the liposome. Various types of liposome nanoparticles are currently used clinically

as delivery systems for anticancer drugs and vaccines.

Silicon nanopowder

Synthesis

There are several methods for creating nanoparticles, including both attrition andpyrolysis. Inattrition, macro or micro scale particles are ground in aball mill, a planetaryball mill, or othersize reducing mechanism. The resulting particles are air classified to recover nanoparticles. Inpyrolysis, a vaporous precursor (liquid or gas) is forced through an orifice at high pressure andburned. The resulting solid (a version of soot) is air classified to recover oxide particles from by-product gases. Pyrolysis often results in aggregates and agglomerates rather than singletonprimary particles.

A thermal plasma can also deliver the energy necessary to cause evaporation of smallmicrometer size particles. The thermal plasma temperatures are in the order of 10,000 K, so thatsolid powder easily evaporates. Nanoparticles are formed upon cooling while exiting the plasmaregion. The main types of the thermal plasma torches used to produce nanoparticles are dcplasma jet, dc arc plasma and radio frequency (RF) induction plasmas. In the arc plasma reactors,the energy necessary for evaporation and reaction is provided by an electric arc which is formedbetween the anode and the cathode. For example, silica sand can be vaporized with an arc plasmaat atmospheric pressure. The resulting mixture of plasma gas and silica vapour can be rapidlycooled by quenching with oxygen, thus ensuring the quality of the fumed silica produced. In RFinduction plasma torches, energy coupling to the plasma is accomplished through theelectromagnetic field generated by the induction coil. The plasma gas does not come in contactwith electrodes, thus eliminating possible sources of contamination and allowing the operation of


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such plasma torches with a wide range of gases including inert, reducing, oxidizing and othercorrosive atmospheres.

The working frequency is typically between 200 kHz and 40 MHz. Laboratory units run at powerlevels in the order of 3050 kW while the large scale industrial units have been tested at power

levels up to 1 MW. As the residence time of the injected feed droplets in the plasma is very shortit is important that the droplet sizes are small enough in order to obtain complete evaporation.The RF plasma method has been used to synthesize different nanoparticle materials, for examplesynthesis of various ceramic nanoparticles such as oxides, carbours/carbides and nitrides of Tiand Si .Inert-gas condensation is frequently used to make nanoparticles from metals with lowmelting points. The metal is vaporized in a vacuum chamber and then supercooled with an inertgas stream. The supercooled metal vapor condenses into nanometer-sized particles, which can beentrained in the inert gas stream and deposited on a substrate or studied in situ.

Sol-gel

The sol-gel process is a wet-chemical technique (also known as chemical solution deposition)

widely used recently in the fields of materials science and ceramic engineering. Such methods are

used primarily for the fabrication of materials (typically a metal oxide) starting from a chemical

solution (sol, short for solution) which acts as the precursor for an integrated network (orgel) of

either discrete particles or network polymers.

Typicalprecursors are metal alkoxides and metal chlorides, which undergo hydrolysis andpolycondensation reactions to form either a network "elastic solid" or a colloidalsuspension (ordispersion) a system composed of discrete (often amorphous) submicrometer particlesdispersed to various degrees in a host fluid. Formation of a metal oxide involves connecting themetal centers with oxo (M-O-M) or hydroxo (M-OH-M) bridges, therefore generating metal-oxo

or metal-hydroxo polymers in solution. Thus, the sol evolves towards the formation of a gel-likediphasic system containing both a liquid phase and solid phase whose morphologies range fromdiscrete particles to continuous polymer networks.[24]

In the case of the colloid, the volume fraction of particles (or particle density) may be so low thata significant amount of fluid may need to be removed initially for the gel-likeproperties to berecognized. This can be accomplished in any number of ways. The most simple method is toallow time forsedimentation to occur, and then pour off the remaining liquid. Centrifugation canalso be used to accelerate the process ofphase separation.

Removal of the remaining liquid (solvent) phase requires a drying process, which is typically

accompanied by a significant amount ofshrinkage and densification. The rate at which thesolvent can be removed is ultimately determined by the distribution ofporosity in the gel. Theultimate microstructure of the final component will clearly be strongly influenced by changesimplemented during this phase of processing. Afterwards, a thermal treatment, or firing process,is often necessary in order to favor further polycondensation and enhance mechanical propertiesand structural stability via final sintering, densification and grain growth. One of the distinctadvantages of using this methodology as opposed to the more traditional processing techniques isthat densification is often achieved at a much lower temperature.


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Theprecursorsol can be eitherdeposited on a substrate to form a film (e.g. by dip-coating orspin-coating), cast into a suitable container with the desired shape (e.g. to obtain a monolithicceramics, glasses, fibers, membranes, aerogels), or used to synthesizepowders (e.g.microspheres, nanospheres). The sol-gel approach is a cheap and low-temperature technique thatallows for the fine control of the products chemical composition. Even small quantities of

dopants, such as organic dyes and rare earth metals, can be introduced in the sol and end upuniformly dispersed in the final product. It can be used in ceramics processing andmanufacturing as an investment casting material, or as a means of producing very thin films ofmetal oxides for various purposes. Sol-gel derived materials have diverse applications in optics,electronics, energy, space, (bio)sensors, medicine (e.g. controlled drug release) and separation(e.g. chromatography)technology.

Colloids

Nanostars ofvanadium(IV) oxide

The term colloid is used primarily to describe a broad range of solid-liquid (and/or liquid-liquid)mixtures, all of which contain distinct solid (and/or liquid) particles which are dispersed tovarious degrees in a liquid medium. The term is specific to the size of the individual particles,which are larger than atomic dimensions but small enough to exhibit Brownian motion. If theparticles are large enough, then their dynamic behavior in any given period of time in suspensionwould be governed by forces ofgravity and sedimentation. But if they are small enough to becolloids, then their irregular motion in suspension can be attributed to the collectivebombardment of a myriad of thermally agitated molecules in the liquid suspending medium, as

described originally by Albert Einstein in his dissertation. Einstein proved the existence of watermolecules by concluding that this erratic particle behavior could adequately be described usingthe theory of Brownian motion, with sedimentation being a possible long-term result. Thiscritical size range (or particle diameter) typically ranges from nanometers (109 m) tomicrometers (106 m).

Morphology


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Scientists have taken to naming their particles after the real world shapes that they mightrepresent. Nanospheres[28], nanoreefs [29], nanoboxes [30] and more have appeared in the literature.These morphologies sometimes arise spontaneously as an effect of a templating or directingagent present in the synthesis such as miscellaremulsions or anodized alumina pores, or from theinnate crystallographic growth patterns of the materials themselves.[31] Some of these

morphologies may serve a purpose, such as long carbon nanotubes being used to bridge anelectrical junction, or just a scientific curiosity like the stars shown at right.

Amorphous particles usually adopt a spherical shape (due to their microstructural isotropy) whereas the shape of anisotropic microcrystalline whiskers corresponds to their particular crystalhabit. At the small end of the size range, nanoparticles are often referred to as clusters. Spheres,rods, fibers, and cups are just a few of the shapes that have been grown. The study of fineparticles is called micromeritics.

Characterization

TEM image of magnetic Fe3O4 nanoparticle.[32]

Nanoparticle characterization is necessary to establish understanding and control of nanoparticlesynthesis and applications. Characterization is done by using a variety of different techniques,mainly drawn from materials science. Common techniques are electron microscopy (TEM,SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), x-ray photoelectronspectroscopy (XPS),powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FTIR), matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry (MALDI-TOF), ultraviolet-visible spectroscopy, dual polarisation interferometry and nuclear magneticresonance (NMR).

Whilst the theory has been known for over a century (see Robert Brown), the technology forNanoparticle tracking analysis (NTA) allows direct tracking of the Brownian motion and thismethod therefore allows the sizing of individual nanoparticles in solution.

Cancer

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