nanoscience (ug 2007)

8/14/2019 Nanoscience (UG 2007)

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What Exactly is NANOSCIENCE??What Exactly is NANOSCIENCE??

NanoscienceNanoscience is the science of the extremelyis the science of the extremely

tiny.tiny.

Nano (from the Greek for dwarf) is the prefixNano (from the Greek for dwarf) is the prefix

for units of 10for units of 1099 . So one nanometre is a. So one nanometre is a

billionth of a metre or a millionth of abillionth of a metre or a millionth of amillimetre.millimetre.

Nanoparticle size ranges from 0.1nm to 100nm.Nanoparticle size ranges from 0.1nm to 100nm.


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Why Nanoscience so Special??

At Nanoscales, materials have strikinglyAt Nanoscales, materials have strikingly

different properties.different properties.

Nanotechnologies aim to exploit them to createNanotechnologies aim to exploit them to create

novel structures, devices and systems for a varietynovel structures, devices and systems for a variety

of different industries.of different industries.


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Nano Structured Materials..

Nanostructured materials are single phase orNanostructured materials are single phase or

multiphase polycrystalline solids with a typicalmultiphase polycrystalline solids with a typical

average grain size of a few nanometres,average grain size of a few nanometres,typically less than 100nm.typically less than 100nm.


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Classification of Nano Structured

Materials..

Nanostructured materials are classified in toNanostructured materials are classified in to

different categories depending on the number ofdifferent categories depending on the number of

dimensions in which the material has nanometredimensions in which the material has nanometremodulations.modulations.


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a) Layered or Lamellar structures :

It is a one-dimensional (1D) nanostructure inIt is a one-dimensional (1D) nanostructure in

which the magnitudes of length and width arewhich the magnitudes of length and width are

much greater than the thickness, which is only amuch greater than the thickness, which is only afew nanometers in size.few nanometers in size.

a) Layered or Lamellar structures :

It is a one-dimensional (1D) nanostructure inIt is a one-dimensional (1D) nanostructure in

which the magnitudes of length and width arewhich the magnitudes of length and width are

much greater than the thickness, which is only amuch greater than the thickness, which is only afew nanometers in size.few nanometers in size.


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b) Filamentary structures

It is a two-dimensional (2D) rod shapedIt is a two-dimensional (2D) rod shaped

nanostructure in which the magnitude of length isnanostructure in which the magnitude of length is

substantially greater than the width or diametre.substantially greater than the width or diametre.


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c) Equiaxed nanostructured materials :

The most common of the nanostructures whichThe most common of the nanostructures which

is in three-dimensional (3D) form.is in three-dimensional (3D) form.

Here, all the three dimensions are of nanometerHere, all the three dimensions are of nanometersize. And they are termedsize. And they are termedNanostructuredNanostructured

CrystallitesCrystallites..


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a) Activation of particle surface :

As the particles are micronized, they tend to beAs the particles are micronized, they tend to be

affected by the behaviour of atoms or theaffected by the behaviour of atoms or the

molecules themselves and to show differentmolecules themselves and to show differentproperties from those of the bulk solid of theproperties from those of the bulk solid of the

same material. It is attributable to the change ofsame material. It is attributable to the change of

the bonding state of the atoms or the moleculesthe bonding state of the atoms or the moleculesconstructing the particles.constructing the particles.


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For Example :

Here the fraction of the atoms or the moleculesHere the fraction of the atoms or the molecules

located at the surface on the particles plays a greatlocated at the surface on the particles plays a great

role, since they are more active than those insiderole, since they are more active than those inside

the solid particles because of the free hand, whichthe solid particles because of the free hand, whichleads to easy bonding with the contactingleads to easy bonding with the contacting

materials and causes various changes in particlematerials and causes various changes in particle

properties.properties.

No. of cubes = 10121 cm

divided 1m

CUBE

No. of cubes = 1018

divided 10nm


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b) Increase in Surface area

As the micronization of solid particles, theAs the micronization of solid particles, the

specific surface area increases generally inspecific surface area increases generally in

reversal proportion to the particle size.reversal proportion to the particle size.


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No. of cubes = 10121 cm

divided 1m

CUBE

No. of cubes = 1018

divided 10nm

For Example :

Here increase in the specific surface areaHere increase in the specific surface area

directly influences such properties like thedirectly influences such properties like the

solution and reaction rates of the particles, it issolution and reaction rates of the particles, it is

one of major reasons for the unique propertiesone of major reasons for the unique propertiesof the nanoparticles different from the bulkof the nanoparticles different from the bulk

material together with the change in the surfacematerial together with the change in the surface

properties of the particles itself.properties of the particles itself.


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The Bohr radius rThe Bohr radius rBB of an electron moving in aof an electron moving in a

condensed phase is given bycondensed phase is given by

*2

2

me

hrB=

Where h is Planks constant. m is the electronWhere h is Planks constant. m is the electron

mass. Typical values ranges from a few tomass. Typical values ranges from a few to

hundred nanometres. Therefore it is practicallyhundred nanometres. Therefore it is practically possible to create particles whose radius r is possible to create particles whose radius r is

smaller than rsmaller than rBB..


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Fluorescence induced by ultraviolet rays on Cadmium Selinide quantum

dots.
http://en.wikipedia.org/wiki/Image:Fluorescence_in_various_sized_CdSe_quantum_dots.png


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Applications .. Nanosensors :Nanosensors :

Electrode, Semiconductor

Quartz, crystal, microbalance

Photomultiplier, photodiode

Sound detector

Thermister

Transducers


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Controls the flow of liquids or gases throughControls the flow of liquids or gases through

a series of tiny channels and valves.a series of tiny channels and valves.

Manipulate living matter by mixingManipulate living matter by mixing

separating and handling components atseparating and handling components at

nanoscale.nanoscale.

Nanofluids :Nanofluids :


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Nanorobots :Nanorobots :


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Nanoeyes :Nanoeyes :

Using Dragon flies

and house flies as

models.


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Electronic Nose :Electronic Nose :

Microorganisms produce characteristicMicroorganisms produce characteristic

volatile compoundsvolatile compounds

Presence of odor is the indication for foodPresence of odor is the indication for foodrottingrotting

E-nose device mimicking human noseE-nose device mimicking human nose

Uses an array of gas sensors to identify theUses an array of gas sensors to identify theodorsodors


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THANK YU

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