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NANOPARTICLES AND QUANTUM DOTS

Presented byYashvant Rao


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5.NANOPARTICLES & QUANTUM DOTS

fine particles: cover a range 100 - 2500 nm.

ultrafine particles, 1 and 100 nm.

Similar to ultrafine particles, nanoparticles1-100nm.

Nanoparticles may or may not exhibit size-relatedproperties that differ significantly from those observed

in fine particles or bulk materials.

Nanoparticle research is currently an area of intense

scientific interest due to a wide variety of potentialapplications in biomedical, optical and electronic

fields.


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SILICA NANOPARTICLES

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.
http://en.wikipedia.org/wiki/File:Mesoporous_Silica_Nanoparticle.jpg


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NANOSTARS OF VANADIUM(IV) OXIDE

At the small end of the size range, nano-particles are often referred

to as clusters( ). Spheres(), rods(), fibers(), and cupsare just a few of the shapes that have been grown.
http://en.wikipedia.org/wiki/Vanadium(IV)_oxidehttp://en.wikipedia.org/wiki/File:Nanostars.jpghttp://en.wikipedia.org/wiki/Vanadium(IV)_oxide


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LONG HISTORY OF THE NANOPARTICLE

Although nano-particles are generallyconsidered an invention of modernscience, they actually have a very longhistory. Nano-particles were used byartisans as far back as the 9th century in

Mesopotamia for generating a glitteringeffect on the surface of pots.

Deep Dish from Spain, after 1475[1]Tin-

glazed earthenware with lustred

decoration, Victoria and Albert Museum,

London

Earthenwarecup with lustre

decoration, 10th century, from

Susa, Iran
http://en.wikipedia.org/wiki/Earthenwarehttp://en.wikipedia.org/wiki/Susahttp://en.wikipedia.org/wiki/Susahttp://en.wikipedia.org/wiki/Earthenwarehttp://en.wikipedia.org/wiki/File:Cup_archs_Louvre_MAO571.jpghttp://en.wikipedia.org/wiki/File:Cup_archs_Louvre_MAO571.jpghttp://en.wikipedia.org/wiki/File:Lustreware.jpg


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Application of Nanoparticles

nanoparticles of usually yellow gold and gray silicon are red in color;

absorption of solar radiation in photovoltaic cells is much higher in

materials composed of nanoparticles than it is in thin films of continuous

sheets of material the smaller the particles, the greater the solar

absorption.

the presence of titanium dioxide nanoparticles imparts what we call the

self-cleaning effect, and the size being nanorange, the particles can not

be observed. Zinc oxideparticles have been found to have superior UV

blocking properties compared to its bulk substitute.

Clay nanoparticles when incorporated into polymer matrices increase

reinforcement, leading to stronger plastics, verifiable by a higher glass

transition temperature and other mechanical property tests. These

nanoparticles are hard, and impart their properties to the polymer

(plastic).
http://en.wikipedia.org/wiki/Zinc_oxidehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Glass_transition_temperaturehttp://en.wikipedia.org/wiki/Zinc_oxidehttp://en.wikipedia.org/wiki/Zinc_oxidehttp://en.wikipedia.org/wiki/Zinc_oxide


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Nanoparticles have also been attached to textile fibers in order

to create smart and functional clothing.

Metal, dielectric, and semiconductor nanoparticles have been

formed, as well as hybrid structures (e.g., core-shell

nanoparticles). Nanoparticles made of semiconducting material

may also be labeled quantum dots if they are small enough(typically sub 10 nm) that quantizationof electronic energy levels

occurs. Such nanoscale particles are used in biomedical

applications as drug carriersor imaging agents.

Application of Nanoparticles
http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Resonance_(chemistry)http://en.wikipedia.org/wiki/Quantization_(physics)http://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Drug_carrierhttp://en.wikipedia.org/wiki/Imaging_agenthttp://en.wikipedia.org/wiki/Imaging_agenthttp://en.wikipedia.org/wiki/Imaging_agenthttp://en.wikipedia.org/wiki/Imaging_agenthttp://en.wikipedia.org/wiki/Drug_carrierhttp://en.wikipedia.org/wiki/Drug_carrierhttp://en.wikipedia.org/wiki/Drug_carrierhttp://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Quantization_(physics)http://en.wikipedia.org/wiki/Resonance_(chemistry)http://en.wikipedia.org/wiki/Resonance_(chemistry)http://en.wikipedia.org/wiki/Resonance_(chemistry)http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Metal


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WHAT ARE QUANTUM DOTS?

Quantum dots are semiconductor

nanocrystals that are so small they are

considered dimensionless.

Quantum dots range from 2-10

nanometers (10-50 atoms)in diameter.


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Quantum dot

What is quantum dot?is a semiconductor whose excitons are

confined in all three spatial dimensions.

Consequently, such materials have

electronic properties intermediate

between those of bulk semiconductors

and those of discrete molecules

Researching fields:

have studied quantum dots in

transistors, solar cells, LEDs, and diode

lasers. They have also investigatedquantum dots as agents for medical

imagingand hope to use them as qubits

Colloidal quantum dots irradiated with a UV

light. Different sized quantum dots emitdifferent color light due to quantum

confinement.

WHY? HOW?
http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Excitonhttp://en.wikipedia.org/wiki/Potential_wellhttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Laser_diodehttp://en.wikipedia.org/wiki/Laser_diodehttp://en.wikipedia.org/wiki/Stainhttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Quantum_computinghttp://en.wikipedia.org/wiki/File:QD_mini_rainbow.jpghttp://en.wikipedia.org/wiki/Quantum_computinghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Stainhttp://en.wikipedia.org/wiki/Laser_diodehttp://en.wikipedia.org/wiki/Laser_diodehttp://en.wikipedia.org/wiki/Laser_diodehttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Potential_wellhttp://en.wikipedia.org/wiki/Excitonhttp://en.wikipedia.org/wiki/Semiconductor


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Several important

quantumconfinement

structures,

(a)quantum well,

(b) quantum wire, and(c) quantum dot.


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Besides confinement in all three dimensions i.e. Quantum

Dot - other quantum confined semiconductors include:

quantum wires, which confine electrons or holes in two

spatial dimensionsand allow free propagation in the third.

quantum wells, which confine electrons or holes in one

dimension and allow free propagation in two dimensions.

Quantum Dot , Quantum Wires and Quantum Well


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COLORIFIC PROPERTIES

The height,and energy difference,between

energy levels increases as the size of the

quantum dot decreases.

Smaller Dot=Higher Energy=SmallerWavelength=Blue Color


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COLOR & QUANTUM DOTS


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CHARACTERISTICS OF QUANTUM DOT

In addition to such tuning, a main advantage with quantum dots is

that, because of the high level of control possible over the size of

the crystals produced, it is possible to have very precise control

over the conductive properties of the material

this equates to higher frequencies of light emitted after

excitation of the dot as the crystal size grows smaller, resulting

in a color shift from red to blue in the light emitted.

Generally, the smaller the size of the crystal, the larger the band

gap, the greater the difference in energy between the highest

valence bandand the lowest conduction bandbecomes, therefore

more energy is needed to excite the dot, and concurrently, more

energy is released when the crystal returns to its resting state.
http://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/File:QD_mini_rainbow.jpg


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Researchers at Los Alamos National Laboratoryhave developed a wireless device that efficiently

produces visible light, through energy transfer

from thin layers of quantum wells to crystals

above the layers.

Optical Properties

quantum dots of the same material, but

with different sizes, can emit light ofdifferent colors. The physical reason is the

quantum confinementeffect.

The larger the dot, the redder (lower

energy) its fluorescence spectrum.

Conversely, smaller dots emit bluer

(higher energy) light. The coloration is

directly related to the energy levels of the

quantum dot.

As with any crystalline semiconductor,

a quantum dot's electronic wave functions

extend over the crystal lattice. Similar to a

molecule, a quantum dot has both a

quantized energy spectrum and a

quantized density of electronic statesnear

the edge of the band gap.
http://en.wikipedia.org/wiki/Los_Alamos_National_Laboratoryhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Quantum_confinementhttp://en.wikipedia.org/wiki/Spectral_colorhttp://en.wikipedia.org/wiki/Fluorescencehttp://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/Spectral_colorhttp://en.wikipedia.org/wiki/Wave_functionhttp://en.wikipedia.org/wiki/Crystal_structurehttp://en.wikipedia.org/wiki/Quantization_(physics)http://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Density_of_stateshttp://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/Quantization_(physics)http://en.wikipedia.org/wiki/Crystal_structurehttp://en.wikipedia.org/wiki/Crystal_structurehttp://en.wikipedia.org/wiki/Crystal_structurehttp://en.wikipedia.org/wiki/Wave_functionhttp://en.wikipedia.org/wiki/Wave_functionhttp://en.wikipedia.org/wiki/Wave_functionhttp://en.wikipedia.org/wiki/Spectral_colorhttp://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/Fluorescencehttp://en.wikipedia.org/wiki/Spectral_colorhttp://en.wikipedia.org/wiki/Quantum_confinementhttp://en.wikipedia.org/wiki/Quantum_confinementhttp://en.wikipedia.org/wiki/Quantum_confinementhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Los_Alamos_National_Laboratoryhttp://en.wikipedia.org/wiki/File:Achermann7RED.jpg


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APPLICATIONS OF QUANTUM DOTS


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APPLICATIONS

Quantum dots are particularly significant for optical applications due to their

high extinction co-efficient , single-electron transistor, implementations of

qubitsfor quantum information process

Computing

Biology

Photovoltaic device

Light emitting device
http://en.wikipedia.org/wiki/Qubithttp://en.wikipedia.org/wiki/Quantum_information_processinghttp://en.wikipedia.org/wiki/Quantum_information_processinghttp://en.wikipedia.org/wiki/Qubit


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CONCLUSIONS

Quantum Dots are a new and innovative

perspective on the traditional semiconductor. Quantum Dots can be synthesized to be

essentially any size,and therefore,produce

essentially any wavelength of light. There are many possible applications of Quantum

Dots in many different areas of industry/science.

The future looks bright and exciting on all thepossible applications of Quantum Dots.

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