EFFECT OF TEMPERATURE ANDEFFECT OF TEMPERATURE AND

MAGNESIUM FOR THE LITHIUM MAGNESIUM FOR THE LITHIUM

NIOBATE NANO CRYSTALS NIOBATE NANO CRYSTALS

ABSTRACTABSTRACT

• My aim is synthesis of quantum dots of Lithium Niobate, a non linear-material.

• It has various special properties like, high curie temperature and low loss optical transmission.

• The effects of nano scale on these properties have been aimed.

• Various spectroscopic techniques are being used to characterize the synthesized quantum dots.

Nanotechnology

• In 4th century AD, Roman glass makers were fabricating glasses containing nanosized metals.

• Varieties of beautiful colors of the windows of churches are due to the presence of metal nanoparticles in the glass.

• Particles of different sizes scatter different wavelengths of light, imparting different colors to theglass.

Nanotechnology :- The vision

1959 Richard Feynman Lecture

Nanotechnology has been inspired by Richard Feynman (Noble Prize 1965) who already predicted back in 1959.

“ There is plenty of room at the bottom “

“ Ultimately in the future we will be able to arrange atoms as we want all the way down ”

“ as far as I see, the principles of physics do not speak against this possibility”

Nanomaterials• A hydrogen atom is 0.1 nm• Nanoparticles range from 1 to 100 nm• Fullerenes (C60 / Buckyballs) are 1

nm• DNA (Deoxyribonucleic acid ( (width)

is 2 nm• Quantum Dots of CdSe are 8-10 nm• Proteins range from 5 to 50 nm• Viruses range from 75 to 100 nm• Bacteria range from 1,000 to 10,000

nm• Red blood cells are ~ 7,000 nm in

diameter, and ~ 2000 nm in height• White blood cells are ~10,000 nm in

diameter

• To visualize a nanometer• A sheet of paper is about

1,00,000 nanometers thick.• a nanometer is about the width

of six bonded carbon atoms

Nanotechnology At the nanoscale, the physical, chemical, and

biological properties of materials differ in fundamental and valuable ways from the properties of individual atoms and molecules or bulk matter.

R&D in Nanotechnology is directed toward understanding and creating improved materials, devices, and systems that exploit these new properties.

One area of nanotechnology R&D is in the biological applications including medicine. Medical researchers work at the nano-scales to develop new drug delivery methods, to develop biosensors and treatment of diseases.

The other area of nanotechnolgoy R&D is energy. Energy researchers work at the nanomaterials to develop alternative energy materials.

Nanotechnology :- Top down & Bottom up

Top-down approach uses the microfabrication methods where externally-controlled tools are used to cut, mill and shape materials into the desired shape and order.

Bottom-up approach use the chemical properties of single molecules to automatically arrange themselves by utilizing the concepts of molecular self-assembly.

Nanotechnology :- Top down & Bottom up

Removing unwanted area of PCB bychemical or photolithography technique

Arranging atom by atom

Different types of Nanomaterials

1. Metals 2. Metal oxides 3. Bio-functional nanomaterials 4. Semiconductors 5. Polymer nano-

composites

Different methods of Synthesis a) Ball milling b) Sol-gel c) Solution process

6. Carbon Nanostructures

Different methods of Synthesis a) Arc discharge b) PLD c) CVD

Ball milling technique (Top-down approach)

High energy ball milling will grind samples down to less than 1μm, and can be used for mixing, homogenising, and alloying.

Grinding bowls and balls are offered in nine different materials and three different sizes.

Therefore the instrument can be used universally and enables contamination-free grinding.

Crucial factors involve milling time, speed, ball to powder ratio and atmosphere

sol- gel process (Bottom-up approach)

Sol gel is a colloidal suspension that can be gelled to form a solid.

• Sol-gel process involves the transition of a system from a liquid (the colloidal “sol") into a solid (the "gel") phase.

Applying the sol-gel process, it is possible to fabricate ceramic or glass materials in a wide variety of forms:

1. ultra-fine or spherical shaped powders

2. thin film coatings 3. ceramic fibers 4. microporous inorganic membranes 5. ceramics and glasses 6. porous aerogel materials.

a low-density solid stateMaterial derived from gel

an excess amount of the solvent is placed on the substrate, which is then rotated at high speed in order to spread the fluid by centrifugal force.

Crucial factors involve precursor, sol viscosity,seed materials & pre-treatment procedures

Nanosized particles produced by Solutionprocess

ZnO has a direct band gap of 3.37 eV possesses a wide range of technological applications

1. transparent conducting electrodes for solar cells 2. flat panel displays 3. chemical & biological sensors

Synthesis of flower-shaped ZnO nanostructures of ZnO nanorods

solution process

zinc acetate dihydrate and sodium hydroxide at 90 C in 30 min

Size dependence of Size dependence of PropertiesProperties

In materials where strong chemical bonding is present, delocalization of valence electrons can be extensive.

The extent of delocalization can vary with the size of the system.

Surface effects: atoms at the surfaces of nanomaterials have less neighbours than atoms in the bulk.

The above changes can lead to different physical and chemical properties, depending on the size.

The energy levels in the nanomaterials are quantized. Even when such nanoparticles are consolidated into

macro scale solids, new properties of bulk materials are possible.

Melting pointOptical absorption/emissionSuperplastivitySuperparamagnetism

New properties enable new applications

Quantum confinement A quantum well is a structure

where the height is approximately the Bohr exciton radius while the length and breadth can be large.

A quantum wire is a structure where the height and breadth is made small while the length can be long.

A quantum dot is a structure where all dimensions are near the Bohr exciton radius, typically a small sphere.

A quantum dot is confined in all three dimensions,

a quantum wire is confined in two dimensions, and

a quantum well is confined in one dimension.

Properties of nanomaterialsMelting point of Gold

Gold is known as a shiny, yellow noble metal, is non-magnetic and melts at 1337 K.

The melting point decreases dramatically as the particle size gets below 5 nm. As the size of a gold particle decreases from 10 to 5 nm, the surface melting point has been experimentally observed to decrease from 900 to 450 C.Surface effects:atoms on surfaces have fewer neighbours than atoms in the bulk.

Because of this lower coordination and unsatisfied bonds, surface atoms are less stabilized than bulk atoms. Quantum size effects:The electronic wave functions of conduction electrons are delocalized over the entire particle.

Melting Point – 10640 C

Optical properties of Au Nanoparticles

Changing colors with size

The light absorption depends on the oscillation of theconducting electrons in gold atoms in the cluster(plasmon oscillation)Variation of the size, shape, or electrical properties of the particles’ surroundings should influence the frequency of the oscillation and thus the color of the absorbed light.Gold particle suspensions scatter colored light when illuminated by

a beam of white light and that the color depends on particle size.

A gold nanoparticle contains as less as eleven atoms which can be a

perfect quantum dot.

The energy states in a molecule are the molecule orbital (MO) for

electrons in a molecule.

The optical properties of a particle which adsorb or emit light will be

altered while the MOs are distorted.

In other words, for colloidal gold, the change of size can be verified

by visual inspecting its color from red to blue.

Applications of nano-Au:- detection of cancer

Gold nanoparticles stick to cancer cells and make them shine

Gold nanoparticles don’t stick to noncancerous cells. The results can be seen with a simple microscope

Antibodies and DNA probes can be readilyattached to Au and Ag without altering theirlight-scattering properties.Binding Au nanoparticles to a specific antibody for cancer cells could make cancer detection much easier, suggests research at the Georgia Institute of Technology and the University of California at San Francisco (UCSF).

“Gold nanoparticles are very good at scattering and absorbing light,” said Mostafa El-Sayed, director of the Laser Dyanamics Laboratory and chemistry professor at Georgia Tech. “We wanted to see if the scattering property in a living cell to make cancer detection easier”.

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