Nano Technology - introduction, history, properties, classification, advantages and disadvantes.

Introduction to Nanotechnology, definition of nanotechnology, history of nanotechnology, unique properties of nanomaterials, classification of nanomaterials, advantages and disadvantages.

Definition of nanotechnology

• Nanotechnology is the term derived from the Greek word "nano'' meaning ''dwarf''.

• Applied in the principle of various science at a atomic, molecular or submicron level.

• Nanotechnology is science, engineering, and technology conducted at the nanoscale, which is about 1 to 100 nanometers.

• Nanotechnology are the study and application of very small things and can be used across all the other science fields, such as chemistry, biology, physics, materials science, and engineering etc.

• Nanotechnology refers to the branch of science and engineering involved in designing, producing, and using structures, devices, and systems by manipulating atoms and molecules at nanoscale, i.e. having one or more dimensions of the order of 100 nanometres or less.

• Many nano systems, which have been investigated in pharmacy that are liposomes, dendrimers, metallic nanoparticles etc.

• Nanoscience and nanotechnology involve the ability to see and control individual atoms and molecules

• Something smallest an atom is impossible to see with the naked eye. it’s impossible to see with the microscopes typically used in a high school science classes.

History of nanotechnology

• Nanoparticles and structures have been used by humans in fourth century AD, by the Roman, which demonstrated one of the most interesting examples of nanotechnology in the ancient world.

• In 1990, the scientists analysed the cup using a transmission electron microscopy (TEM) to explain the phenomenon of dichroism.

• During the 9th–17th centuries, glowing, glittering “luster” ceramic glazes used in the Islamic world, and later in Europe contained Ag or copper (Cu) or other nanoparticles.

• The Italians also employed nanoparticles in creating Renaissance pottery during 16th century.

• 1964, Liposome structure was published, sustained delivery of low molecular weight compounds using silicon polymer.

• 1976, First controlled release polymer system for ionic molecules and macromolecules.

• 1980, First targeted liposomes.

• 1986, Discovery of the EPR(Enhanced permeability and retention) effect.

• 1994, Long circulation PLGA-PEG nanoparticles FDA.

• 2004, PRINT technology developed.

• 2007, Polymeric micelle paclitaxel (Genexol – PM) marketed in Korea.

• 2008, First targeted siRNA polymeric nanoparticles entered clinical trials.

• 2011, First targeted controlled release polymeric nanoparticles entered clinical trials. Cell membrane coated nanoparticles developed to evade immune response

Unique properties of nanomaterials

• Large surface to Volume ratio

• High percentage of atoms/molecules on the surface

• Surface forces are very important while bulk forces are not as important.

• Metal nano particles have unique light scattering properties and exhibit plasma resonance.

• Semi conductor nano particles may exhibit confined energy states in their electric band structure

• Can have unique physical and chemical propertice.

Nano materials have some of major properties—

1. Mechanical properties

2. Physical properties

3. Thermal properties

4. Electrical properties

5. Magnetic properties

6. Catalytic properties

7. Melting point

8. Diffusivity

9. Optical properties

Mechanical properties

1. The unique mechanical properties of nanomaterials are because of the increased number of surface atoms and interfaces.

2. Which in turn leads to increased density of defects like grain boundaries, dislocations, triple junctions, etc. Nanomaterials exhibit the following mechanical properties as compared to bulk materials:

• Increased strength
• Increased toughness
• Increased hardness
• Increased ductility
• Decreased elasticity

Physical Properties

Physical properties of nanoparticles are depends on

• Size

• Shape

• Crystal structure

• Composition

• Surface ligand

Size

Molecules, nanoparticles and bulk materials can be distinguished by number of atoms comprising each type of material

• Nanoparticles exhibit unique properties due to their high surface area to volume ratio
• As surface cored to volume ratio increases, so does the percentage of atoms at the surface and surface forces becomes more dominant.
• As the percentage of atoms at the surface increases, the mechanical, optical, electrical, chemical and magnetic properties change melting point as a function of particle size.

Shape

Particles: May sinter together at lower than expected temperature

Rods: Can melt and form spherical droplets heated too high

Films: Thin films can form pin holes continued heating can lead to de-wetting behavior & island formation.

Electrical Properties

• Conductivity of a bulk or large material does not depend upon dimensions like diameter or area of cross section and twist in the conducting wire etc.

• It is also observed that conductivity also changes when some shear force is given to a nanotube.

• Conductivity of a multiwalled carbon nanotube is different than that of single nanotube of same dimensions.

• The carbon nanotubes can act as conductor or semiconductor in behavious but we all know that large carbon (graphite) is good conductor of electricity.

Classification of Nanomaterials

1. Classification based on composition

2. Classification based on dimension

1. Classification based on composition

a) Organic nanomaterials

• Composed of carbon

• The exists in different form

Eg. Carbon nanotube, Fullerenes, Graphene

• They are used in water purification process and as electrodes for solar cells.

b). Inorganic nanomaterials

• Composed of metal and metal-oxide nanomaterials

• They exists in different form

Eg. Silver nm, metal nm, Gold nanoparticle, iron nanoparticle

• The can be used as antibacterial agents, in fuel cells for medical diagnosis and testing

c). Hybrid nanomaterials

• They exists in combination like organic-organic, inorganic-organic, inorganic-inorganic nanoparticles.

Eg. Polymer, Liposome

• They can be used in dental fillings and coating.

2. Classification based on dimension

a). Zero dimensional

• In this all dimension reduced to nano range

• Movement of electrons restricted to all three dimensions i.e x,y,z direction.

Eg. Quantum dots nanoparticles

b). One dimensional

• In this, two dimensions reduced to nano range and one dimension remains large.

• Movement of electron is along this direction

Eg. Nanowires, nano rods

c). Two dimensional

• In this, one dimension is in nano range and two dimension remains large.

• Movement of electron is along these two directions

Eg. Nano wells, nano coatings, nano films.

d). Three dimensional

• In this, there is no confinement in nano range

• Movement of electrons is along all three directions

Eg. Bulk nano materials, nano powders

Advantages of nano technology

• Nanomedicines augment drug concentration in the site of action through passive targeting, which reduces drug concentration in normal tissues.

• Improves the solubility and doing stability.

• Protects drugs from being degraded in the before they reach their target

• Enhance the absorption of drugs into tumors and into the cancerous cells themselves.

• Allows for better control over the timing and distribution of drugs to the tissue, making it easier for oncologists to assess how well they work

• Prevent drugs from interacting with normal cells, then avoiding side effects

• Prolonged circulation time

• Biocompatibility

• Biodegradable

• Low cytotoxic potential

• Co-delivery of two or more phytomedicines. I

• injuries can be repaired cell by cell

• It may even become possible to heal genetic conditions by fixing the damaged genes

• Better imaging and diagnostic equipment

Disadvantages of nano technology

• Atomic weapons can now be more accessible and made to be more powerful destructive. There can be more accessible with nanotechnology

• Since these particles are very small, problems can be actually arise from the inhalation of these minute particles, much like the problems a person gets from inhaling particles.

• Presently nanotechnology is very expensive and it can cost you a lot of money.

• Environmental effects like ‘gray-goo scenario’

• Privacy and security

• Microscopic recording devices

• Nanotechnology could be weaponised

• Potential to cross blood brain barrier -- so toxic to humans.

• Nanoparticles can pass through mothers placenta

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