Characterizationof Nano Particles and Applications

BY:Wajeeha Yusra

Introduction pro

Outline

Nanoparticles (these are materials of which at least one dimension is nanometric, i.e. 10-9 m) consist of several tens or hundreds of atoms or molecules and may have a variety of sizes and morphologies (amorphous, crystalline, spherical, needles, etc.).

Such nanoparticles are creating a new category of materials, which is different either from conventional bulk materials or from atoms, the smallest units of matter.

Nanoscale materials are used in electronic, magnetic and optoelectronic, biomedical, pharmaceutical, cosmetic, energy, catalytic and materials applications.

Relative sizes of physical bodies

Nanoparticles are small clusters of atoms about 1 to 100 nanometers long.

'Nano' derives from the Greek word "nanos", which means dwarf or extremely small. It can be used as a prefix for any unit like a second or a liter to mean a billionth of that unit. A nanosecond is a billionth of a second. A nanoliter is a billionth of a liter. And therefore a nanometer is a billionth of a meter or 10-9 m.

In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size: in terms of diameter, fine particles cover a range between 100 and 2500 nanometers. On the other hand, ultrafine particles are sized between 1 and 100 nanometers. Similar to ultrafine particles, nanoparticles are sized between 1 and 100 nanometers. The reason for this double name of the same object is that, during the 1970-80's, when the first large-scale projects were running with "nanoparticles" in the USA [1] and Japan,[2] they were called "ultrafine particles" (UFP). However, during the 1990s before the National Nanotechnology Initiative was launched in the USA, the new name, "nanoparticle" had become fashionabl

High surface area is critical factor in performance of catalysis and structures such as electrodes allowing imporvement in such technologies as fuel cells or batteries.

The large surface area of nano particles also results in a lot of interactions between the intermixed materials in nano composites leading to special properties such as increased strength and increased chemical or heat resistance.

Nanoparticles are often defined as particles of less than 100nm in diameter

There is an increase in ratio of surface area to volume.

The increase in surface are to volume ratio which is the gradual progression as the particle get smaller leads to an increase dominance of the behaviour of atoms on the surface of particles over that those in the interior of the particles

Nanoparticles

Thay have dimensionsbelow the critical wavelength of light which makes them transparent. A property which makes them very useful in use in packaging, cosmetics and coatings.

Nanoparticles are the smallest identifiable pieces of a material or substance. These particles can be taken from any material, however the size of any one particle cannot exceed one nanometer in size. Their size is indicated in the "nano" prefix, meaning one billionth so one nanometer is approximately one billionth of a meter. Something this small is not visible to the human eye, so high-powered microscopes are required to work with these materials. Their unusually small size opens up a whole new world of science and discovery.

Read more: An Introduction to Nanoparticles | eHow.com http://www.ehow.com/about_5386877_introduction-nanoparticles.html#ixzz1PcQSChIG

They have been used for very long time. Probably the early use being in glazesfor

early dynasty chinese porcelain. A roman cup called the Lycurgus cup, used

nanosized gold clusters to create different colors depending on whether It as illuminated from the frot or back.

The cause of the effect was not known to those who exploited this.

History

Carbon black is the most famous exmaple of nanoparticle which has been produced in huge quantitiy for decades.

Roughly 1.5 billion tons are poduced every year.

Nano paticles are currently made up of many materials. The most common is ceramics which are best split in to metal oxides ceramices such as titanum, aluminium, zinc, metal

Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures.

A bulk material should have constant physical properties regardless of its size, but at the nano-scale size-dependent properties are often observed.

Thus, the properties of materials change as their size approaches the nanoscale and as the percentage of atoms at the surface of a material becomes significant.

For bulk materials larger than one micrometer (or micron), the percentage of atoms at the surface is insignificant in relation to the number of atoms in the bulk of the material.

The interesting and sometimes unexpected properties of nanoparticles are therefore largely due to the large surface area of the material, which dominates the contributions made by the small bulk of the material.

For examp5le, nanoparticles of usually yellow gold and gray silicon are red in color; gold nanoparticlesmelt at much lower temperatures (~300 °C for 2.5 nm size) than the gold slabs (1064 °C); and absorption of solar radiation in photovoltaic cells is much higher in materials composed ofnanoparticles than it is in thin films of continuous sheets of material – the smaller the particles, the greater the solar absorption.

Other size-dependent property changes include quantum confinement in semiconductor particles, surface plasmon resonance in some metal particles and superparamagnetism in magnetic materials. Ironically, the changes in physical properties are not always desirable.

Ferroelectric materials smaller than 10 nm can switch their magnetisation direction using room temperature thermal energy, thus making them unsuitable for memory storage.

Suspensions of nanoparticles are possible since the interaction of the particle surface with the solvent is strong enough to overcome density differences, which otherwise usually result in a material either sinking or floating in a liquid.

Nanoparticles also often possess unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. For example gold nanoparticles appear deep red to black in solution.

The high surface area to volume ratio of nanoparticles provides a tremendous driving force for diffusion, especially at elevated temperatures.

Sintering can take place at lower temperatures, over shorter time scales than for larger particles. This theoretically does not affect the density of the final product, though flow difficulties and the tendency of nanoparticles to agglomerate complicates matters. Moreover, nanoparticles have been found to impart some extra properties to various day to day products.

For example 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 oxide particles have been found to have superior UV blocking properties compared to its bulk substitute. This is one of the reasons why it is often used in the preparation of sunscreen lotions., and is completely photostable.

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). Nanoparticleshave 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 quantization of electronic energy levels occurs. Such nanoscale particles are used in biomedical applications as drug carriers or imaging agents.

Semi-solid and soft nanoparticles have been manufactured. A prototype nanoparticle of semi-solid nature is the liposome. Various types of liposome nanoparticles are currently used clinically as delivery systems for anticancer drugs and vaccines.

There are variety of techniques for producing nanoparticles.

They fall in to three categories Condensation from a vapor Chemical synthesis Solid sate processes such as milling Particels then can be coated with

hydrophilic substances or hydrophobic substnaces depending on desired use.

Production techniques

Used to make metallic and metal oxide ceramic nano particles.

It involves evaporatio of solid metal followed by condensation of to form naano sized clusters that settles in the form of a powder

Various approaches to vaporize the metal can be used. And variation of jte medium in which in to which the vapor is to released affects the nature and size of the particles.

Inert gases are used to avoid oxidation when creating metal nano partiles.

whereas reactive oxygen atmosphere is used to produce metal oxide ceramic nanoparticles.

The main advantage of this technique is low contamination. Final particle size can be controlled by varitation in tmeeprature, gas enviroenmnt and evaporation rate.

1

Most widely used chemical synthesis technique consist essentially of growing nanoparticles in a liquid medium containing various reactants. This is typified by sol gel approach and is also used to create this echnique is better than the condensatiob tehnique for controlling the final shape of the nano partiles.

These tehniques are usually low cost and high volume but contamination from precursor chemical can be a problem.

Chemical synthesis

Grinding and milling can be used to create nano partilce

The milling material, milling time and atmospheric material affects resultant nano particles.

This approach is used to make nanoparticles from material that don’t readily lend them with previous two techniques.

Contmaination from the parent material can be ann issue.

Solid state processes

Nanoparticle characterization is necessary to establish understanding and control of nanoparticlesynthesis and applications. Characterization is done by using a variety of different techniques, mainly drawn from materials science.

Common techniques are electron microscopy (TEM, SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), x-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF), ultraviolet-visible spectroscopy, dual polarisation interferometry and nuclear magnetic resonance (NMR).

Whilst the theory has been known for over a century (see Robert Brown), the technology forNanoparticle tracking analysis (NTA) allows direct tracking of the Brownian motion and this method therefore allows the sizing of individual nanoparticles in solution.

Characterization

Nanoparticle research is currently an area of intense scientific research, due to a wide variety of potential applications in biomedical, optical, and electronic fields. Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures

Applications

Iron oxide nanoparticles can used to improve MRI images of cancer tumors. The nanoparticle is coated with a peptide that binds to a cancer tumor, once the nanoparticles are attached to the tumor the magnetic property of the iron oxide enhances the images from the Magnetic Resonance Imagining scan.

Using gold nanoparticles embedded in a porous manganese oxide as a room temperature catalyst to breakdown volatile organic compounds in air.

Nanoparticles coated with proteins that attach to damaged portions of arteries. This could allow delivery of drugs to the damaged regions of arteries to fight cardiovascular disease.

Magnetic nanoparticles that attach to cancer cells in the blood stream may allow the cancer cells to be removed before they establish new tumors.

A layer of closely spaced palladium nanoparticles that detect hydrogen. When hydrogen is absorbed the palladium nanoparticles swell, causing shorts between nanoparticles which lowers the resistance of the palladium layer.

Quantum Dots (crystalline nanoparticles) that identify the location of cancer cells in the body.

Combining gold nanoparticles with organic molecules to create a transistor known as a NOMFET (Nanoparticle Organic Memory Field-Effect Transistor).

Nanoparticles that deliver chemotherapy drugs directly to cancer cells.

Iron nanoparticles used to clean up carbon tetrachloride pollution in ground water.

Silicon nanoparticles coating anodes of lithium-ion batteries to increase battery power and reduce recharge time.

Gold nanoparticles that allow heat from infrared lasers to be targeted on cancer tumors.

Silicate nanoparticles used to provide a barrier to gasses (for example oxygen), or moisture in a plastic film used for packaging. This could reduce the possibly of food spoiling or drying out.

Zinc oxide nanoparticles dispersed in industrial coatings to protect wood, plastic and textiles from exposure to UV rays.

Silicon dioxide crystalline nanoparticles filling gaps between carbon fibers strengthen tennis racquets.

Silver nanoparticles in fabric that kills bacteria making clothing odor-resistant.

Porous silica nanoparticles used to deliver chemotherapy drugs to cancer cells.

Semiconductor nanoparticlesapplied in a low temperature printing process that results in low cost solar cells.

Nanoparticles, when activated by x-rays, that generate electrons that cause the destruction of cancer cells to which they have attached themselves. This is intended to be used in place radiation therapy with much less damage to healthy tissue.

Iron oxide nanoparticles used to clean arsenic from water wells.

A  nanoparticle cream that releases nitric oxide gas to fight staph infections.

Nanoparticles are now being used in the manufacture of scratchproof eyeglasses, crack- resistant paints, anti-graffiti coatings for walls, transparent sunscreens, stain-repellent fabrics, self-cleaning windows and ceramic coatings for solar cells. Nanoparticles can contribute to stronger, lighter, cleaner and “smarter” surfaces and systems. At the nanoscale, the properties of particles may change in unpredictable ways. Nanoparticles of titanium oxide used in sunscreens, for example, have the same chemical composition as the larger white titanium oxide particles used in conventional products for decades, but nanoscale titanium oxide is transparent. Antimony - tin oxide provides another example since nanoparticles of this oxide are incorporated into a coating to provide scratch- resistance and offer transparent protection from ultra-violet radiation, not seen with larger size particles.

In chemical terms, nanoparticles have different properties from their "big brothers and sisters": they have a large surface area in relation to their tiny mass and at the same time a small number of atoms. This can produce quantum effects that lead to altered material properties. Ceramics made of nanomaterials can suddenly become bendy, for instance, or a gold nugget is gold-coloured while a nanosliver of it is reddish. Up to now, very little research has been carried out on the effects of these altered properties on living organisms. Only recently, a study caused quite a stir by suggesting that nanoparticles like titanium oxide in toothpaste or sun cream have a similar effect on the human lung as asbestos

http://www.sciencedaily.com/articles/n/nanoparticle.htm

http://www.understandingnano.com/nanoparticles.html

http://www.chm.bris.ac.uk/webprojects2002/etan/Webpages/introduction2.htm

http://ec.europa.eu/health/opinions2/en/nanotechnologies/l-3/5-nanoparticles-consumer-products.htm

http://www.nanowerk.com/news/newsid=20223.php

http://www.anekadownload.com/ebook-viewer.php?url=http://frontpage.okstate.edu/nanotech/Reports/2007/Presentations/Brian%20Morrow.ppt

http://www.anekadownload.com/ebook-viewer.php?url=http://nanoparticles.org/pdf/Scalf-West.pdf

Refrences

The atomic force microscope (AFM) is ideally suited for characterizing nanoparticles. It offers the capability of 3D

visualization and both qualitative and quantitative information on many physical properties including size, morphology, surface texture and roughness. Statistical information, including size, surface area, and volume distributions,

can be determined as well. A wide range of particle sizes can be characterized in the same scan, from 1 nanometer

to 8 micrometers. In addition, the AFM can characterize nanoparticles in multiple mediums including ambient air,

controlled environments, and even liquid dispersions

AFM can be performed in liquid or gas mediums. This capability can be very advantageous for nanoparticle characterization. For example, with combustion-generated nanoparticles, a major component of the particles are volatile components that are only present in ambient conditions.

Small particle chemistry: Reasons for differences and related conceptual challenges

Nanoparticle characterization using light scattering technologies Susana Frasés, PhD Albert Einstein College of Medicine New York