Introduction to Nanotechnology

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Submitted by

SALONI SHARMA

Assoc. Prof. PG Deptt. of Physics

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CONTENTS

• Introduction
• What is Nanotechnology?
• Why nanoscale?
• What is nanomaterial?
• Nanomaterials’ characteristics
• Origin of Nanotechnology
• Approaches of Nanotechnology
• Bottom-up Vs top-down
• Applications of Nanotechnology

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What is Nanotechnology

• The design, characterization, and application of structures, devices, and systems by controlled manipulation of size and shape of materials at the nanometer scale (atomic, molecular, and macromolecular scale) ,
• To produce materials with at least one novel/superior characteristic or property

Why Nanoscale?

• A nanometer (nm) is one thousand millionth of a meter. People are interested in the nanoscale because at this scale physical and chemical properties of materials differ significantly from those at a larger scale.

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�What is Nanomaterial?�

Noble metal nanocrystals with cyclic penta-twinned structures �

Nanopowder

�Carbon Nanotubes�

Why Nanomaterials?

• Nanomaterials are interesting because at the small scale, materials have fundamentally different properties than at the bulk due to increased surface area to volume ratios.
• Increased interaction and reactivity is one of the by products of materials that are nanoscale, which means potentially using less of the material or that even on the nanoscale the properties are so utterly different from that of the bulk scale.

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• Nanotubes are extremely strong mechanically and very pure conductors of electric current.
• Applications of the nanotube include resistors, capacitors, inductors, diodes and transistors.

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Nano Materials-Novel Materials?

Novel materials means, new forms of existing materials with characteristics that differ significantly from familiar or naturally-occurring forms. Nanomaterials can have one, two or three dimensions in the nanoscale:

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Origin of Nanotechnology

• In some senses, nanoscience and nanotechnologies are not new. Chemists have been making polymers, which are large molecules made up of nanoscale subunits, for many decades and nanotechnologies have been used to create the tiny features on computer chips for the past 20 years.

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• However, advances in the tools that now allow atoms and molecules to be examined and probed with great precision have enabled the expansion and development of nanoscience and nanotechnologies.

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Approaches of Nanotechnology

Methods of synthesis may be broadly classified as: Bottom-up methods or top-down methods

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Classification of Synthesis methods

• Physical Methods: These methods work at high temperatures. Highest working temperatures are usually greater than 350 ⁰C. These can be further divided into mechanical type and vapour deposition type.
• Chemical Methods: These are simple and inexpensive method of synthesis. Highest working temperature are usually below 350 ⁰C. Large quantities of materials can be produced with variety of sizes and shapes of particles.
• Biological Methods: These methods are based on use of micro-organism or plant extracts or templates such as DNA , Viruses and membranes. These synthesis methods are environment friendly and least toxic and therefore called Green synthesis.

PHYSICAL METHODS

• Arc Discharge Method
• Electron Beam Lithography
• Mechanical Grinding
• Inert Gas Condensation
• Ion Implantation
• Ball Milling
• Spray Pyrolysis
• Vapour-Phase Synthesis

CHEMICAL METHODS

• Co-precipitation Method
• Micro-emulsion Method
• Electro-chemical Method ( Electrolysis)
• Chemical reduction of metal salts
• Pyrolysis
• Phytochemical method (Irradiation)
• Solvo-thermal synthesis
• Sol-Gel Method
• Sono-chemical Method

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BIOLOGICAL METHODS

• Using Plants and their extracts
• Using Micro-organisms like bacteria, fungi and actinomycetes)
• Using Algae
• Using enzymes and biomolecules
• Using industrial and agricultural wastes

Factors affecting synthesis of Nanoparticles

• Temperature
• Pressure
• Time
• Particle Size And Shape
• Cost Of Preparation
• Pore Size
• Ph Value
• Environment

Top Down Approach

• The top-down approach often uses the traditional workshop or micro-fabrication methods where externally controlled tools are used to cut, mill, and shape materials into the desired shape and order.
• It includes Micropatterning techniques, such as photolithography and inkjet printing 

Top Down approach

• These methods use macroscopic materials which are reduced to nanoscale after a sequence of operations.
• These methods are expensive as they require large installations.
• Growth process is slow, hence not suitable for large scale production.
• Devices used to shape objects are stiff and hard , so these methods are not suitable for soft samples.

TOP –UP APPROACHES

• Physical Vapour Deposition
• Chemical Vapour Deposition
• Metal-organic Chemical Vapour Deposition(mocvd)
• Ion Implantation
• Electron Beam Lithography/ X-ray Lithography

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Bottom Up Approach

• Bottom-up approaches seek to have smaller components built up into more complex assemblies, while top-down approaches seek to create nanoscale devices by using larger, externally controlled ones to direct their assembly.
• It uses the chemical properties of single molecules to cause single-molecule components to
• (a) self-organize or self-assemble into some useful conformation,
• (b) rely on positional assembly.

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Bottom up approaches

• Ball milling
• Sol-Gel Process
• Electrodeposition
• Self-Assembly

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General Applications of Nanotechnology

Nano-Technology and Environment

THANKS