Iron–platinum nanoparticles are 3D superlattices composed of an equal atomic ratio of Fe and Pt. Under standard conditions, FePt NPs exist in the face centered cubic phase but can change to a chemically ordered face centered tetragonal phase as a result of thermal annealing. There are many synthetic methods such as water-in-oil microemulsion, one-step thermal synthesis with metal precursors, exchanged-coupled assembly for making FePt NPs. An important property of FePt NPs is their superparamagnetic character below 10 nanometers; the superparamagnetism of FePt NPs has made them attractive candidates to be used as MRI/CT scanning agents and a high-density recording material. The various properties of iron-platinum nanoparticles allow them to function in multiple ways. In standard conditions, FePt NPs exist in the face centered cubic phase with a 3 to 10 nanometer diameter. However, once heat is added the structure becomes a face centered superparamagnetic; the nanoparticles become superparamagnetic because the addition of heat makes the particle smaller and iron rich, since it removes any impurities in the particles.
As a result, the nanoparticles are used in MRI scans. Plant viruses, known as Cowpea mosaic virus and Tobacco mosaic virus, enlarge the average radius of the FePt NPs through direct mineralization; the virus template acts as a natural and benign method to monodisperse the nanoparticles up to 30 nanometers in diameter. The size increase of the bimetallic nanoparticles entitles it to a wider range of biological applications. Platinum nanoparticles have a stronger chemical stability with the addition of iron, cobalt, or nickel; the platinum alloys have a better detection range and catalytic activity than their counterpart. These magnetic metal additions to platinum reduce the overall sensitivity to oxidation while maintaining the desirable magnetic properties. Combined, FePt nanoparticles are synthesized for medicinal applications. One method of synthesis uses incident laser technology to irradiate solutions containing iron and platinum to combine the two alloys. A laser beam is emitted onto a 4:1 mixture of iron acetylacetonate and platinum acetylacetonate dissolved in methanol.
The black precipitates are washed and dried on silicon substrates to be characterized by transmission electron microscopy and X-ray diffraction. An alternative method of synthesis involves the coreduction of chloroplatinic acid and iron chloride in water-in-oil microemulsions. In this process, the normal face-centered cubic structure is transformed to a face-centered tetragonal configuration, offering a higher density product useful for many storage media applications. FePt NPs are promising materials for ultra-high density magnetic recording media due to their high coercivity. Higher coercivity indicates. After annealing at 700 °C, the film can have up to 14KOe coercivity compared to common hard drives that have 5KOe coercivity. Due to their superparamagnetism and controllable shape and surface, iron-platinum nanoparticles have great potential for advancing medicine in many fields, including imagining, pathogen detection, targeted cancer therapy; the NPs can be conjugated with antibodies for tissue-specific delivery, providing a systematic way to customize for either technology.
FePt NPs are compatible for CT scans because of their strong ability to absorb x-rays. FePt NPs provide a non-toxic, more persistent alternative to iodinated molecules that are harmful to the kidney and survive in the body for only a short time; the superparamagnetic properties of the nanoparticles and the systematic method for conjugating ligands to the FePt surface makes them viable vehicles for detection of pathogens such as gram-positive bacteria. Antibodies for the bacteria conjugated to the FePt NP bind to the bacteria and magnetic dipoles are used to detect the FePt NP-bacteria conjugate. By attaching peptides to the surface of the face centered cubic FePt NPs, cytotoxic iron can be delivered to specific locations and taken up with high selectivity. A phospholipid coating of the FCC-FePt prevents Fe release. Once in the cell, the low pH of lysosome’s intracellular environments breaks down the phospholipid bilayer. Fe catalyzed decomposition of hydrogen peroxide into ROSs results in membrane lipid oxidation, damage to DNA and proteins, tumor death
A nanotextured surface is a surface, covered with nano-sized structures. Such surfaces have one dimension on the nanoscale, i.e. only the thickness of the surface of an object is between 0.1 and 100 nm. They are gaining popularity because of their special applications due to their unique physical properties. Nanotextured surfaces are in various forms like columns, or fibers; these are water, ice and microorganism repellent, superamphiphobic, anti-icing, antifouling and thus self-cleaning. They are anti-reflective and transparent, hence they are termed smart surfaces. In research published online October 21, 2013, in Advanced Materials, of a group of scientists at the U. S. Department of Energy's Brookhaven National Laboratory, led by BNL physicist and lead author Antonio Checco, proposed that nanotexturing surfaces in the form of cones produces water-repellent surfaces; these nano-cone textures are super-water-hating. Cyril R. A. John Chelliah, Cyril R. A. John Chelliah, Rajesh Swaminathan, Rajesh Swaminathan, "Pulsed laser deposited hexagonal wurzite ZnO thin-film nanostructures/nanotextures for nanophotonics applications," Journal of Nanophotonics 12, 016013.
Silver nanoparticles are nanoparticles of silver of between 1 nm and 100 nm in size. While described as being'silver' some are composed of a large percentage of silver oxide due to their large ratio of surface-to-bulk silver atoms. Numerous shapes of nanoparticles can be constructed depending on the application at hand. Used are spherical silver nanoparticles but diamond and thin sheets are popular, their large surface area permits the coordination of a vast number of ligands. The properties of silver nanoparticles applicable to human treatments are under investigation in laboratory and animal studies, assessing potential efficacy and costs; the most common methods for nanoparticle synthesis fall under the category of wet chemistry, or the nucleation of particles within a solution. This nucleation occurs when a silver ion complex AgNO3 or AgClO4, is reduced to colloidal silver in the presence of a reducing agent; when the concentration increases enough, dissolved metallic silver ions bind together to form a stable surface.
The surface is energetically unfavorable when the cluster is small, because the energy gained by decreasing the concentration of dissolved particles is not as high as the energy lost from creating a new surface. When the cluster reaches a certain size, known as the critical radius, it becomes energetically favorable, thus stable enough to continue to grow; this nucleus remains in the system and grows as more silver atoms diffuse through the solution and attach to the surface When the dissolved concentration of atomic silver decreases enough, it is no longer possible for enough atoms to bind together to form a stable nucleus. At this nucleation threshold, new nanoparticles stop being formed, the remaining dissolved silver is absorbed by diffusion into the growing nanoparticles in the solution; as the particles grow, other molecules in the solution attach to the surface. This process stabilizes the surface energy of the particle and blocks new silver ions from reaching the surface; the attachment of these capping/stabilizing agents slows and stops the growth of the particle.
The most common capping ligands are trisodium citrate and polyvinylpyrrolidone, but many others are used in varying conditions to synthesize particles with particular sizes and surface properties. There are many different wet synthesis methods, including the use of reducing sugars, citrate reduction, reduction via sodium borohydride, the silver mirror reaction, the polyol process, seed-mediated growth, light-mediated growth; each of these methods, or a combination of methods, will offer differing degrees of control over the size distribution as well as distributions of geometric arrangements of the nanoparticle. A new promising wet-chemical technique was found by Elsupikhe et al.. They have developed a green ultrasonically-assisted synthesis. Under ultrasound treatment, silver nanoparticles are synthesized with κ-carrageenan as a natural stabilizer; the reaction is performed at ambient temperature and produces silver nanoparticles with fcc crystal structure without impurities. The concentration of κ-carrageenan is used to influence particle size distribution of the AgNPs.
There are many ways. This includes glucose, maltose, etc. but not sucrose. It is a simple method to reduce silver ions back to silver nanoparticles as it involves a one-step process. There have been methods that indicated that these reducing sugars are essential to the formation of silver nanoparticles. Many studies indicated that this method of green synthesis using Cacumen platycladi extract, enabled the reduction of silver. Additionally, the size of the nanoparticle could be controlled depending on the concentration of the extract; the studies indicate that the higher concentrations correlated to an increased number of nanoparticles. Smaller nanoparticles were formed at high pH levels due to the concentration of the monosaccharides. Another method of silver nanoparticle synthesis includes the use of reducing sugars with alkali starch and silver nitrate; the reducing sugars have free aldehyde and ketone groups, which enable them to be oxidized into gluconate. The monosaccharide must have a free ketone group because in order to act as a reducing agent it first undergoes tautomerization.
In addition, if the aldehydes are bound, it will be stuck in cyclic form and cannot act as a reducing agent. For example, glucose has an aldehyde functional group, able to reduce silver cations to silver atoms and is oxidized to gluconic acid; the reaction for the sugars to be oxidized occurs in aqueous solutions. The capping agent is not present when heated. An early, common, method for synthesizing silver nanoparticles is citrate reduction; this method was first recorded by M. C. Lea, who produced a citrate-stabilized silver colloid in 1889. Citrate reduction involves the reduction of a silver source particle AgNO3 or AgClO4, to colloidal silver using trisodium citrate, Na3C6H5O7; the synthesis is performed at an elevated temperature to maximize the monodispersity of the particle. In this method, the citrate ion traditionally acts as both the reducing agent and the capping ligand, making it a useful process for AgNP production due to its relative ease and short reaction time. However, the silver particles formed may exhibit broad size distributions and form several different particle geometries simultaneously.
The addition of stronger reducing agents to the reaction is used to synthesize particles of a more uniform size and shape. The synthesis of silver na
A copper nanoparticle is a copper based particle 1 to 100 nm in size. Like many other forms of nanoparticles, a copper nanoparticle can be formed by natural processes or through chemical synthesis; these nanoparticles are of particular interest due to their historical application as coloring agents and their modern-day biomedical ones. One of the earliest uses of copper nanoparticles was to color glass and ceramics during the ninth century in Mesopotamia; this was done by applying it to clay pottery. When the pottery was baked at high temperatures in reducing conditions, the metal ions migrated to the outer part of the glaze and were reduced to metals; the end result was a double layer of metal nanoparticles with a small amount of glaze in between them. When the finished pottery was exposed to light, the light would penetrate and reflect off the first layer; the light penetrating the first layer would reflect off the second layer of nanoparticles and cause interference effects with light reflecting off the first layer, creating a luster effect that results from both constructive and destructive interference.
Various methods have been described to chemically synthesize copper nanoparticles. An older method involves the reduction of copper hydrazine carboxylate in an aqueous solution using reflux or by heating through ultrasound under an inert argon atmosphere; this results in a combination of copper oxide and pure copper nanoparticle clusters, depending on the method used. A more modern synthesis utilizes copper chloride in a room temperature reaction with sodium citrate or myristic acid in an aqueous solution containisodium formaldehyde sulfoxylate]] to obtain a pure copper nanoparticle powder. While these syntheses generate consistent copper nanoparticles, the possibility of controlling the sizes and shapes of copper nanoparticles has been reported; the reduction of copper acetylacetonate in organic solvent with oleyl amine and oleic acid causes the formation of rod and cube-shaped nanoparticles while variations in reaction temperature affect the size of the synthesized particles. Another method of synthesis involves using copper hydrazine carboxylate salt with ultrasound or heat in water to generate a radical reaction, as shown in the figure to the right.
Copper nanoparticles can be synthesized using green chemistry to reduce the environmental impact of the reaction. Copper chloride can be reduced using only L-ascorbic acid in a heated aqueous solution to produce stable copper nanoparticles. Copper nanoparticles display unique characteristics including catalytic and antifungal/antibacterial activities that are not observed in commercial copper. First of all, copper nanoparticles demonstrate a strong catalytic activity, a property that can be attributed to their large catalytic surface area. With the small size and great porosity, the nanoparticles are able to achieve a higher reaction yield and a shorter reaction time when utilized as reagents in organic and organometallic synthesis. In fact, copper nanoparticles that are used in a condensation reaction of iodobenzene attained about 88% conversion to biphenyl, while the commercial copper exhibited only a conversion of 43%. Copper nanoparticles that are small and have a high surface to volume ratio can serve as antifungal/antibacterial agents.
The antimicrobial activity is induced by their close interaction with microbial membranes and their metal ions released in solutions. As the nanoparticles oxidize in solutions, cupric ions are released from them and they can create toxic hydroxyl free radicals when the lipid membrane is nearby; the free radicals disassemble lipids in cell membranes through oxidation to degenerate the membranes. As a result, the intracellular substances seep out of cells through the destructed membranes. In the end, all these alterations inside of the cell caused by the free radicals lead to cell death. Copper nanoparticles with great catalytic activities can be applied to biosensors and electrochemical sensors. Redox reactions utilized in those sensors are irreversible and require high overpotentials to run. In fact, the nanoparticles have the ability to make the redox reactions reversible and to lower the overpotentials when applied to the sensors. One of the examples is a glucose sensor. With the use of copper nanoparticles, the sensor does not require any enzyme and therefore has no need to deal with enzyme degradation and denaturation.
As described in Figure 3, depending on the level of glucose, the nanoparticles in the sensor diffract the incident light at a different angle. The resulting diffracted light gives a different color based on the level of glucose. In fact, the nanoparticles enable the sensor to be more stable at high temperatures and varying pH, more resistant to toxic chemicals. Moreover, using nanoparticles, native amino acids can be detected. A copper nanoparticle-plated screen-printed carbon electrode functions as a stable and effective sensing system for all 20 amino acid detection
An icosahedral twin is a nanostructure appearing for atomic clusters. The these clusters are twenty-faced, made of ten interlinked dual-tetrahedron crystals joined along triangular faces having three-fold symmetry. One can think of their formation as a kind of atom-scale self-assembly. A variety of nanostructures assume icosahedral form on size scales where surface forces eclipse those from the bulk. A twinned form of these nanostructures is sometimes found to occur e.g. in face-centered-cubic metal-atom clusters. This may occur when the building blocks beneath each of the 20 facets of an icosahedral cluster "make the case" for conversion to a translationally symmetric crystalline form When interatom bonding does not have strong directional preferences, it is not unusual for atoms to gravitate toward a kissing number of 12 nearest neighbors; the three most symmetric ways to do this are by icosahedral clustering, or by crystalline face-centered-cubic and/or hexagonal close packing. Icosahedral arrangements because of their smaller surface area, may be preferred for small clusters e.g. noble gas and metal atoms in condensed phases.
However, the Achilles heel for icosahedral clustering about a single point is that it cannot fill space over large distances in a way, translationally ordered. Hence bulk atoms revert to one of the crystalline close-packing configurations instead. In other words, when icosahedral clusters get sufficiently large, the bulk-atom vote wins out over the surface-atom vote, the atoms beneath each of the 20 facets adopt a face-centered-cubic pyramidal arrangement with tetrahedral facets, thus icosahedral twins are born, with a certain amount of strain along the interfacial planes. Icosahedral twinning has been seen in face-centered-cubic metal nanoparticles that have nucleated: by evaporation onto surfaces, out of solution, by reduction in a polymer matrix. Quasicrystals are un-twinned structures with long range rotational but not translational periodicity, that some tried to explain away as icosahedral twinning. Quasi-crystals let. However, they form only when the compositional makeup serves as an antagonist to formation of one of the more common close-packed space-filling but twinned crystalline forms.
Face-centered-cubic noble metal atomic clusters are important nano-catalysts for chemical reactions. One example of this is the platinum used in automobile catalytic converters. Icosahedral twinning makes it possible to cover the entire surface of a nanoparticle with facets, in cases where those particular atomic-facets show favorable catalytic activity. Electron diffraction and high-resolution transmission electron microscopy imaging are two methods for identifying the icosahedral-twin structure of individual clusters. Digital dark field analysis of lattice-fringe images shows promise for recognition of icosahedral twinning from most of the randomly oriented clusters in a microscope-image field of view. Nanotechnology Nanomaterial based catalyst Crystal twinning Self-assembly of nanoparticles Icosahedron Quasicrystals Dark field microscopy
Colloidal gold is a sol or colloidal suspension of nanoparticles of gold in a fluid water. The colloid is either an intense red colour or blue/purple. Due to their optical and molecular-recognition properties, gold nanoparticles are the subject of substantial research, with many potential or promised applications in a wide variety of areas, including electron microscopy, nanotechnology, materials science, biomedicine; the properties of colloidal gold nanoparticles, thus their potential applications, depend upon their size and shape. For example, rodlike particles have both transverse and longitudinal absorption peak, anisotropy of the shape affects their self-assembly. Used since ancient times as a method of staining glass colloidal gold was used in the 4th-century Lycurgus Cup, which changes color depending on the location of light source. During the Middle Ages, soluble gold, a solution containing gold salt, had a reputation for its curative property for various diseases. In 1618, Francis Anthony, a philosopher and member of the medical profession, published a book called Panacea Aurea, sive tractatus duo de ipsius Auro Potabili.
The book introduces information on the formation of its medical uses. About half a century English botanist Nicholas Culpepper published book in 1656, Treatise of Aurum Potabile discussing the medical uses of colloidal gold. In 1676, Johann Kunckel, a German chemist, published a book on the manufacture of stained glass. In his book Valuable Observations or Remarks About the Fixed and Volatile Salts-Auro and Argento Potabile, Spiritu Mundi and the Like, Kunckel assumed that the pink color of Aurum Potabile came from small particles of metallic gold, not visible to human eyes. In 1842, John Herschel invented a photographic process called chrysotype that used colloidal gold to record images on paper. Modern scientific evaluation of colloidal gold did not begin until Michael Faraday's work in the 1850s. In 1856, in a basement laboratory of Royal Institution, Faraday accidentally created a ruby red solution while mounting pieces of gold leaf onto microscope slides. Since he was interested in the properties of light and matter, Faraday further investigated the optical properties of the colloidal gold.
He prepared the first pure sample of colloidal gold, which he called'activated gold', in 1857. He used phosphorus to reduce a solution of gold chloride; the colloidal gold Faraday made 150 years ago is still optically active. For a long time, the composition of the'ruby' gold was unclear. Several chemists suspected it to be a gold tin compound, due to its preparation. Faraday recognized that the color was due to the miniature size of the gold particles, he noted the light scattering properties of suspended gold microparticles, now called Faraday-Tyndall effect. In 1898, Richard Adolf Zsigmondy prepared the first colloidal gold in diluted solution. Apart from Zsigmondy, Theodor Svedberg, who invented ultracentrifugation, Gustav Mie, who provided the theory for scattering and absorption by spherical particles, were interested in the synthesis and properties of colloidal gold. With advances in various analytical technologies in the 20th century, studies on gold nanoparticles has accelerated. Advanced microscopy methods, such as atomic force microscopy and electron microscopy, have contributed the most to nanoparticle research.
Due to their comparably easy synthesis and high stability, various gold particles have been studied for their practical uses. Different types of gold nanoparticle are used in many industries, such as medicine and electronics. For example, several FDA-approved nanoparticles are used in drug delivery. Colloidal gold has been used by artists for centuries because of the nanoparticle’s interactions with visible light. Gold nanoparticles absorb and scatter light resulting in colours ranging from vibrant reds to blues to black and to clear and colorless, depending on particle size, local refractive index, aggregation state; these colors occur because of a phenomenon called Localized Surface Plasmon Resonance, in which conduction electrons on the surface of the nanoparticle oscillate in resonance with incident light. As a general rule, the wavelength of light absorbed increases as a function of increasing nano particle size. For example, pseudo-spherical gold nanoparticles with diameters ~ 30 nm have a peak LSPR absorption at ~530 nm.
Changes in the apparent color of a gold nanoparticle solution can be caused by the environment in which the colloidal gold is suspended The optical properties of gold nanoparticles depends on the refractive index near the nanoparticle surface, therefore both the molecules directly attached to the nanoparticle surface and/or the nanoparticle solvent both may influence observed optical features. As the refractive index near the gold surface increases, the NP LSPR will shift to longer wavelengths In addition to solvent environment, the extinction peak can be tuned by coating the nanoparticles with non-conducting shells such as silica, bio molecules, or aluminium oxide; when gold nano particles aggregate, the optical properties of the particle change, because the effective particle size and dielectric environment all change. Colloidal gold and various derivatives have long been among the most used labels for antigens in biological electron microscopy. Colloidal gold particles can be attached to many traditional biological probes such as antibodies, superantigens, nucleic acids, receptors.
Particles of diff
Microstructure is the small scale structure of a material, defined as the structure of a prepared surface of material as revealed by a microscope above 25× magnification. The microstructure of a material can influence physical properties such as strength, ductility, corrosion resistance, high/low temperature behaviour or wear resistance; these properties in turn govern the application of these materials in industrial practice. Microstructure at scales smaller than can be viewed with optical microscopes is called nanostructure, while the structure in which individual atoms are arranged is known as crystal structure; the nanostructure of biological specimens is referred to as ultrastructure. A microstructure’s influence on the mechanical and physical properties of a material is governed by the different defects present or absent of the structure; these defects can take many forms but the primary ones are the pores. If those pores play a important role in the definition of the characteristics of a material, so does its composition.
In fact, for many materials, different phases can exist at the same time. These phases have different properties and if managed can prevent the fracture of the material; the atoms and molecules comprising minerals and living matter are bound by six types of bonds with different intensities and properties. Examples include metallic bonds, covalent bonds, ionic bonds, weak bonds. Among the weak bonds, there is a distinction between polar bonds or hydrophilic bonds and nonpolar or hydrophobic bonds. From these properties will come the spatial form of the associated atoms and the molecules and at a larger scale, of the crystal, of the organism as a whole. Metallic bonds are formed by the sharing of electrons in the outer layer of the atom in an electron cloud, where they are free and delocalized; this free-electron gas ensures the cohesion of the remaining cations and enables electrical conduction in metals and alloys. Covalent bonds are formed by the sharing of pairs of valence electrons in order to fill the outer electron shells of each atom.
They are strong bonds that are found in non-metals such as semiconductors, certain ceramics and biological materials. Ionic bonds are formed by the transfer of an electron from one atom to the other, they are strong bonds that appear, for example, between a metal atom that has released an electron and a non-metal atom that has captured the free electron. After bonding, both atoms become charged; these bonds are found in minerals, biological materials, certain polymers. Weak polar bonds are electrostatic and correspond to simple attractions between dipoles in compounds or molecules with inhomogeneous or polarizable charges, they act with less intensity than strong bonds. Among them, for example, are van der Waals bonds between molecules and hydrogen bonds between water molecules in liquid water and ice; these bonds are found in all biological materials, certain hydrated minerals and some mixed–composite materials. Weak nonpolar bonds or hydrophobic bonds are formed by repulsion. In a polar liquid, the molecules try to establish a maximum number of bonds between each other.
If nonpolar molecules are added to the solution, their presence disrupts the formation of this network of bonds, they will be rejected. Uniquely nonpolar molecules are rare for the most part are found in hydrocarbons. Fatty acids are amphiphilic molecules, containing a nonpolar end; these molecules will form complex structures, with the polar end on the outside in contact with the water and the nonpolar end on the inside isolated from the water. Depending on the nature of the molecule, these structures will either be small globules called micelles or be membranes; these bonds are found in all biological materials. The concept of microstructure is observable in macrostructural features in commonplace objects. Galvanized steel, such as the casing of a lamp post or road divider, exhibits a non-uniformly colored patchwork of interlocking polygons of different shades of grey or silver; each polygon is a single crystal of zinc adhering to the surface of the steel beneath. Zinc and lead are two common metals.
The atoms in each grain are organized into one of seven 3d stacking arrangements or crystal lattices. The direction of alignment of the matrices differ between adjacent crystals, leading to variance in the reflectivity of each presented face of the interlocked grains on the galvanized surface; the average grain size can be controlled by processing conditions and composition, most alloys consist of much smaller grains not visible to the naked eye. This is to increase the strength of the material. To quantify microstructural features, both morphological and material property must be characterized. Image processing is a robust technique for determination of morphological features such as volume fraction, inclusion morphology and crystal orientations. To acquire micrographs, optical as well as electron microscopy are used. To determine material property, Nanoindentation is a robust technique for determination of properties in micron and submicron level for which conventional testing are not feasible.
Conventional mechanical testing such as tensile testing or dynamic mechanical analysis can only return macroscopic properties without any indication of microstructural properties. However, nanoindentation can be used for determination of local microstructural pr