File Name: nanomaterials properties and applications .zip
Nanomaterials NMs have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts.
A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and nanometres nm in diameter. For the same reason, dispersions of nanoparticles in transparent media can be transparent,  whereas suspensions of larger particles usually scatter some or all visible light incident on them. Nanoparticles also easily pass through common filters , such as common ceramic candles ,  so that separation from liquids requires special nanofiltration techniques.
The properties of nanoparticles often differ markedly from those of larger particles of the same substance. Since the typical diameter of an atom is between 0. Therefore, the properties of that surface layer may dominate over those of the bulk material. This effect is particularly strong for nanoparticles dispersed in a medium of different composition since the interactions between the two materials at their interface also becomes significant. Nanoparticles occur widely in nature and are objects of study in many sciences such as chemistry , physics , geology and biology.
Being at the transition between bulk materials and atomic or molecular structures, they often exhibit phenomena that are not observed at either scale. They are an important component of atmospheric pollution , and key ingredients in many industrialized products such as paints , plastics , metals , ceramics , and magnetic articles.
The production of nanoparticles with specific properties is an important branch of nanotechnology. In general, the small size of nanoparticles leads to a lower concentration of point defects compared to their bulk counterparts,  but they do support a variety of dislocations that can be visualized using high-resolution electron microscopes.
Anisotropy in a nanoparticle leads to a lot of changes in the properties of the nanoparticles. Non-spherical nanoparticles of gold, silver, and platinum due to their fascinating optical properties are finding diverse applications and are of great interest in the field of research.
Non-spherical geometries of nanoprisms give rise to high effective cross-sections and deeper colors of the colloidal solutions. Anisotropic nanoparticles display a specific absorption behavior and stochastic particle orientation under unpolarized light, showing a distinct resonance mode for each excitable axis. This property can be explained based on the fact that on a daily basis there are new developments being made in the field of synthesis of these nanoparticles for preparing them in high yield.
According to the International Standards Organization ISO technical specification , a nanoparticle is an object with all three external dimensions in the nanoscale, whose longest and shortest axes do not differ significantly, with a significant difference typically being a factor of at least 3. For some properties, like transparency or turbidity , ultrafiltration , stable dispersion, etc.
Therefore, the term is sometimes extended to that size range. Nanoclusters are agglomerates of nanoparticles with at least one dimension between 1 and 10 nanometers and a narrow size distribution.
Nanopowders  are agglomerates of ultrafine particles, nanoparticles, or nanoclusters. Nanometer-sized single crystals , or single-domain ultrafine particles, are often referred to as nanocrystals. The terms colloid and nanoparticle are not interchangeable. A colloid is a mixture which has particles of one phase dispersed or suspended within an other phase. Nanoparticles are naturally produced by many cosmological ,  geological,   meteorological , and biological processes.
A significant fraction by number, if not by mass of interplanetary dust , that is still falling on the Earth at the rate of thousands of tons per year, is in the nanoparticle range;   and the same is true of atmospheric dust particles. Many viruses have diameters in the nanoparticle range. Nanoparticles were used by artisans since prehistory, albeit without knowledge of their nature.
They were used by glassmakers and potters in Classical Antiquity , as exemplified by the Roman Lycurgus cup of dichroic glass 4th century CE and the lusterware pottery of Mesopotamia 9th century CE. Michael Faraday provided the first description, in scientific terms, of the optical properties of nanometer-scale metals in his classic paper.
The result is that white light is now freely transmitted, reflection is correspondingly diminished, while the electrical resistivity is enormously increased.
During the s and 80s, when the first thorough fundamental studies with nanoparticles were underway in the United States by Granqvist and Buhrman  and Japan within an ERATO Project ,  researchers used the term ultrafine particles. However, during the s, before the National Nanotechnology Initiative was launched in the United States, the term nanoparticle had become more common for example, see the same senior author's paper 20 years later addressing the same issue, lognormal distribution of sizes .
Nanoparticles occur in a great variety of shapes, which have been given many informal names such as nanospheres,  nanorods , nanochains ,  nanostars, nanoflowers, nanoreefs,  nanowhiskers, nanofibers, and nanoboxes. The shapes of nanoparticles may be determined by the intrinsic crystal habit of the material, or by the influence of the environment around their creation, such as the inhibition of crystal growth on certain faces by coating additives, the shape of emulsion droplets and micelles in the precursor preparation, or the shape of pores in a surrounding solid matrix.
The study of fine particles is called micromeritics. Semi-solid and soft nanoparticles have been produced. 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.
The breakdown of biopolymers into their nanoscale building blocks is considered a potential route to produce nanoparticles with enhanced biocompatibility and biodegradability. The most common example is the production of nanocellulose from wood pulp.
Nanoparticles with one half hydrophilic and the other half hydrophobic are termed Janus particles and are particularly effective for stabilizing emulsions. Hydrogel nanoparticles made of N-isopropylacrylamide hydrogel core shell can be dyed with affinity baits, internally. The properties of a material in nanoparticle form are usually very different from those of the bulk material even when divided into micrometer-size particles.
A bulk material should have constant physical properties such as thermal and electrical conductivity , stiffness , density , and viscosity regardless of its size. However, in a nanoparticle, the volume of the surface layer the material that is within a few atomic diameters of the surface becomes a significant fraction of the particle's volume; whereas that fraction is insignificant for particles with diameter of one micrometer or more.
For nanoparticles dispersed in a medium of different composition, the interfacial layer — formed by ions and molecules from the medium that are within a few atomic diameters of the surface of each particle — can mask or change its chemical and physical properties. Indeed, that layer can be considered an integral part of each nanoparticle.
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 often develop or receive coatings of other substances, distinct from both the particle's material and of the surrounding medium. Even when only a single molecule thick, these coatings can radically change the particles' properties, such as and chemical reactivity, catalytic activity, and stability in suspension.
The high surface area of a material in nanoparticle form allows heat, molecules, and ions to diffuse into or out of the particles at very large rates. The small particle diameter, on the other hand, allows the whole material to reach homogeneous equilibrium with respect to diffusion in a very short time. Thus many processes that depend on diffusion, such as sintering can take place at lower temperatures and over shorter time scales.
The small size of nanoparticles affects their magnetic and electric properties. The reduced vacancy concentration in nanocrystals can negatively affect the motion of dislocations , since dislocation climb requires vacancy migration.
In addition, there exists a very high internal pressure due to the surface stress present in small nanoparticles with high radii of curvature. In particular, this affects the nature of the dislocation source and allows the dislocations to escape the particle before they can multiply, reducing the dislocation density and thus the extent of plastic deformation.
There are unique challenges associated with the measurement of mechanical properties on the nanoscale, as conventional means such as the universal testing machine cannot be employed. As a result, new techniques such as nanoindentation have been developed that complement existing electron microscope and scanning probe methods. A material may have lower melting point in nanoparticle form than in the bulk form.
For example, 2. Quantum mechanics effects become noticeable for nanoscale objects. Quantum effects are responsible for the deep-red to black color of gold or silicon nanopowders and nanoparticle suspensions. In both solar PV and solar thermal applications, by controlling the size, shape, and material of the particles, it is possible to control solar absorption. Core-shell nanoparticles can support simultaneously both electric and magnetic resonances, demonstrating entirely new properties when compared with bare metallic nanoparticles if the resonances are properly engineered.
By introducing a dielectric layer, plasmonic core metal -shell dielectric nanoparticles enhance light absorption by increasing scattering. Recently, the metal core-dielectric shell nanoparticle has demonstrated a zero backward scattering with enhanced forward scattering on a silicon substrate when surface plasmon is located in front of a solar cell. Nanoparticles of sufficiently uniform size may spontaneously settle into regular arrangements, forming a colloidal crystal.
These arrangements may exhibit original physical properties, such as observed in photonic crystals  . Artificial nanoparticles can be created from any solid or liquid material, including metals , dielectrics , and semiconductors. They may be internally homogeneous or heterogenous, e.
There are several methods for creating nanoparticles, including gas condensation , attrition , chemical precipitation ,  ion implantation , pyrolysis and hydrothermal synthesis. Friable macro- or micro-scale solid particles can be ground in a ball mill , a planetary ball mill , or other size-reducing mechanism until enough of them are in the nanoscale size range.
The resulting powder can be air classified to extract the nanoparticles. Biopolymers like cellulose , lignin , chitin , or starch may be broken down into their individual nanoscale building blocks, obtaining anisotropic fiber- or needle-like nanoparticles. The biopolymers are disintegrated mechanically in combination with chemical oxidation or enzymatic treatment to promote breakup, or hydrolysed using acid.
Another method to create nanoparticles is to turn a suitable precursor substance, such as a gas or aerosol , into solid particles by combustion or pyrolysis. This is a generalization of the burning of hydrocarbons or other organic vapors to generate soot.
Traditional pyrolysis often results in aggregates and agglomerates rather than single primary particles. This inconvenience can be avoided by ultrasonic nozzle spray pyrolysis, in which the precursor liquid is forced through an orifice at high pressure. Nanoparticles of refractory materials, such as silica and other oxides , carbides , and nitrides , can be created by vaporizing the solid with a thermal plasma , which can reach temperatures of 10, kelvin , and then condensing the vapor by expansion or quenching in a suitable gas or liquid.
The plasma can be produced by dc jet , electric arc , or radio frequency RF induction. Metal wires can be vaporized by the exploding wire method. In RF induction plasma torches, energy coupling to the plasma is accomplished through the electromagnetic field generated by the induction coil. The plasma gas does not come in contact with electrodes, thus eliminating possible sources of contamination and allowing the operation of such plasma torches with a wide range of gases including inert, reducing, oxidizing, and other corrosive atmospheres.
As the residence time of the injected feed droplets in the plasma is very short, it is important that the droplet sizes are small enough in order to obtain complete evaporation. Inert-gas condensation is frequently used to produce metallic nanoparticles. The metal is evaporated in a vacuum chamber containing a reduced atmosphere of an inert gas. Early studies were based on thermal evaporation. The use of sequential growth schemes, where the particles travel through a second metallic vapor, results in growth of core-shell CS structures.
Nanoparticles can also be formed using radiation chemistry. Radiolysis from gamma rays can create strongly active free radicals in solution. This relatively simple technique uses a minimum number of chemicals.
These including water, a soluble metallic salt, a radical scavenger often a secondary alcohol , and a surfactant organic capping agent. High gamma doses on the order of 10 4 Gray are required. In this process, reducing radicals will drop metallic ions down to the zero-valence state.
A scavenger chemical will preferentially interact with oxidizing radicals to prevent the re-oxidation of the metal.
The rapidly growing area of information technology constantly demands higher storage densities. Creating ever smaller magnetic structures is an important issue and the magic Terabits per square inch density an ambitious goal. This has led to a dramatically enhanced interest in magnetic nanoparticles and their behavior with a view to being able to design and control their properties to make them suitable for information storage. The toolbox for preparing such particles includes both physical and chemical related approaches with top down and bottom up preparation methods. Preparation, however, has to be accompanied by strict quality control including the arrangements of particles, their shape, structure and magnetic properties. The close interrelation between preparation, properties and control of these particles is emphasized in this Thematic Series.
A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and nanometres nm in diameter. For the same reason, dispersions of nanoparticles in transparent media can be transparent,  whereas suspensions of larger particles usually scatter some or all visible light incident on them. Nanoparticles also easily pass through common filters , such as common ceramic candles ,  so that separation from liquids requires special nanofiltration techniques. The properties of nanoparticles often differ markedly from those of larger particles of the same substance. Since the typical diameter of an atom is between 0.
Nanomaterials can be defined as materials possessing, at minimum, one external dimension measuring nm. The definition given by the European Commission states that the particle size of at least half of the particles in the number size distribution must measure nm or below. Nanomaterials can occur naturally, be created as the by-products of combustion reactions, or be produced purposefully through engineering to perform a specialised function. These materials can have different physical and chemical properties to their bulk-form counterparts. Due to the ability to generate the materials in a particular way to play a specific role, the use of nanomaterials spans across various industries, from healthcare and cosmetics to environmental preservation and air purification.
Nanomaterials research takes a materials science -based approach to nanotechnology , leveraging advances in materials metrology and synthesis which have been developed in support of microfabrication research. Materials with structure at the nanoscale often have unique optical, electronic, thermo-physical or mechanical properties. Nanomaterials are slowly becoming commercialized  and beginning to emerge as commodities. This includes both nano-objects , which are discrete pieces of material, and nanostructured materials , which have internal or surface structure on the nanoscale; a nanomaterial may be a member of both these categories.
In recent years, researchers used many scientific studies to improve modern technologies in the field of reducing the phenomenon of pollution resulting from them. In this chapter, methods to prepare nanomaterials are described, and the main properties such as mechanical, electrical, and optical properties and their relations are determined. The investigation of nanomaterials needed high technologies that depend on a range of nanomaterials from 1 to nm; these are scanning electron microscopy SEM , transmission electron microscopy TEM , and X-ray diffractions XRD. The applications of nanomaterials in environmental improvement are different from one another depending on the type of devices used, for example, solar cells for producing clean energy, nanotechnologies in coatings for building exterior surfaces, and sonochemical decolorization of dyes by the effect of nanocomposite. Nanotechnology and the Environment. The term nanotechnology is the creation of functional material devices and systems through the control of matter in the range of 1— nm and the ability to work at the molecular level, atom by atom to create large structures with fundamentally new molecular organization.
Nanoscience and nanotechnology are among the most widely used terms in the modern scientific and technological literature.Reply