Iron–platinum nanoparticles (FePt NPs) are 3D

superlattices A superlattice is a periodic structure of layers of two (or more) materials. Typically, the thickness of one layer is several nanometers. It can also refer to a lower-dimensional structure such as an array of quantum dots or quantum wells. Di ...

composed of an approximately equal atomic ratio of Fe and Pt. Under standard conditions, FePt NPs exist in the

face-centered cubic In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of ...

phase but can change to a chemically ordered face-centered tetragonal phase as a result of

thermal annealing In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a materi ...

. Currently there are many synthetic methods such as water-in-oil

microemulsion Microemulsions are clear, thermodynamically stable isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be ...

, one-step thermal synthesis with metal precursors, and exchanged-coupled assembly for making FePt NPs.Hyie, K. M.(2010). “Synthesis of Iron-Platinum Nanoparticles in Water-in-Oil Microemulsions for High-Density Storage Media Application”. 1-9. 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 Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

/ CT scanning agents and a high-density recording material.

Properties

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 face-centered tetragonal. Iron-Platinum Nanoparticle Lattice

Plant viruses, such as Cowpea mosaic virus and

Tobacco mosaic virus ''Tobacco mosaic virus'' (TMV) is a positive-sense single-stranded RNA virus species in the genus ''Tobamovirus'' that infects a wide range of plants, especially tobacco and other members of the family Solanaceae. The infection causes characteri ...

, enlarge the average radius of the FePt NPs through direct mineralization. The virus acts as a natural template to monodisperse nanoparticles up to 30 nanometers in diameter. The size increase of the bimetallic nanoparticles enables a wider range of biological applications.

Synthesis

Platinum nanoparticles become more chemically stable when alloyed with iron,

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...

, or

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...

. The platinum

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...

s also have a better detection range and

catalytic Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

activity than platinum alone. These magnetic metal additions to platinum reduce the overall sensitivity to

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

while maintaining the desirable magnetic properties. Combined, FePt nanoparticles can be synthesized for medical 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 (III) acetylacetonate and platinum (II) acetylacetonate dissolved in methanol. The black

precipitates In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

are then washed and dried on

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

substrates to be characterized by

transmission electron microscopy Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a g ...

(TEM) and X-ray diffraction. Synthesis of Iron-Platinum Nanoparticles

An alternative method of synthesis involves the coreduction of

chloroplatinic acid Chloroplatinic acid (also known as hexachloroplatinic acid) is an inorganic compound with the formula 3Osub>2 tCl6H2O)''x'' (0 ≤ ''x'' ≤ 6). A red solid, it is an important commercial source of platinum, usually as an aqueous solution. Alth ...

(H₂PtCl₆) and iron (II) 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. For solid state applications FePt nanoparticles can be synthesised on a substrate by directly co-

sputtering In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and ca ...

Fe and Pt.

Applications

Magnetic storage

FePt NPs are promising materials for ultra-high density magnetic recording media due to their high

coercivity Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in ...

. Higher coercivity indicates the material cannot be demagnetized easily. After annealing at 700 °C, the film can have up to 14KOe

compared to common hard drives that have 5KOe coercivity. Nanoparticles have also been grown with coercivities up to 37 kOe.

Medicine

Due to their superparamagnetism and controllable shape, size, and surface, iron-platinum nanoparticles have great potential for advancing medicine in many fields, including imagining,

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

detection, and 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-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

s. FePt NPs also 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

ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elec ...

s 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

dipole In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system ...

s are used to detect the FePt NP-bacteria conjugate. By attaching

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. ...

s 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 A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane pr ...

’s intracellular environments breaks down the phospholipid bilayer. Fe catalyzed decomposition of

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

into ROSs results in membrane

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...

oxidation, damage to DNA and proteins, and tumor death. FePt-NP Antibody Application

References

* * * {{DEFAULTSORT:Iron-platinum nanoparticle Nanoparticles by composition Iron Platinum