$\mathrm{Fe_3O_4}$ (Iron oxide) is one of the easily synthesized compounds occurring in nature are iron oxides. The iron oxides are better known as magnetic oxides have been in use by humans for ages now. A very common example of magnetic oxides being used are the nanoparticles of iron oxide (IONPS). For around 50 years, they have been used for diagnosis conducted in vitro as a contrast agent. Iron oxides have the formula as $\mathrm{Fe_3O_4}$. They are also simply seen as rust.
Laboratory-easy synthesized compounds, also commonly found in nature are Iron oxides. The iron oxides existing in nature are 16 in number. They include;
Oxides of iron
Hydroxides of iron
Hydroxy-Oxides of iron
They are usually found to have formed as a result of reactions. These reactions are usually aqueous. They show variability in pH levels and redox levels. The oxides have a common basic composition. It includes; Fe (Iron), O (Oxygen) or OH (Hydroxide). They are differentiated among themselves by varying valency and crystal structure. The common examples of iron oxides are; Hematite, Akaganeite, Magnetite, Lepidocrocite, and Goethite.
Iron Oxide (II, III) has the chemical formula $\mathrm{Fe_3O_4}$. Mineral name for $\mathrm{Fe_3O_4}$ is magnetite. This is the most commonly found iron oxides found in nature. The name of iron oxide is usually followed with (II, III) because they have been found containing $\mathrm{Fe^{+3}}$ as well as $\mathrm{Fe^{+2}}$ ions. This explains $\mathrm{Fe_3O_4}$'s attraction to even the smallest magnetic field (external).
Figure 1: Magnetite (Fe3O4)
James St. John, Magnetite-pyrite-actinolite rock (Jurassic, 156-162 Ma; Mina 5, Marcona Magnetite Deposit, Ica Department, Peru) 1, CC BY 2.0
Following are the relevant properties of $\mathrm{Fe_3O_4}$,
The colour $\mathrm{Fe_3O_4}$ appears in is dark color most commonly black appearing.
231.531 g/mol is the molar mass of $\mathrm{Fe_3O_4}$.
$\mathrm{Fe_3O_4}$ has a melting point of 1597°C.
2623°C is the melting point for $\mathrm{Fe_3O_4}$.
It is found as an odorless and solid black powder when observed under room temperature.
The structure of $\mathrm{Fe_3O_4}$ commonly found is cubical and inverse spinel.
$\mathrm{Fe_3O_4}$ has a good electrical conductance. It is 106 times the conductivity of $\mathrm{Fe_2O_3}$.
Proper induction in a magnetic field helps the $\mathrm{Fe_3O_4}$ particles to act magnetic, resembling tiny magnets.
The compound has also been called Mars Black, a black pigment.
The Harber process is catalysed using $\mathrm{Fe_3O_4}$ as the catalyst. It helps produce Ammonia.
MRI scanning is facilitated with the use of $\mathrm{Fe_3O_4}$ - nanoparticles. They play the role of contrast agent.
Like any other metal oxide in nature, iron oxide too has significant uses. They have been mentioned below,
Black iron oxide (ordinary) is utilised for inks used in die stamping and copperplate.
Among different components used for plastic, pharmaceuticals, inks, and paint industry products, the most common is iron oxide.
Salts of copper oxide are very often used in wastewater treatment, fertilizers, dying of textiles and production of additives for feed.
Copper oxide also is very popular as a polishing material in the jewellery industry.
The nanoparticles like; maghemite and magnetite are utilised very often in colloidal suspension preparation. They are now synthesised using solution combustion. The process in concluded in the following steps;
A flask with a round bottom is taken.
The flask is used to store a solution of,
$\mathrm{Fe(NO_3)_39H_2O}$
fuel utilised in magnetite synthesis $\mathrm{(C_6H_8O_7H_2O)}$ and
fuel utilised in maghemite synthesis $\mathrm{(D-(+)-C_6H_{12}O_6)}$
Heat the solution to 400°C without the presence of air.
Water evaporates, resulting in a combustion reaction (smouldering), as a result a black powder is left behind.
Black powder is now treated with distilled water after crushing.
This washed black powder is exposed to 80°C and dried.
This powder is finally treated with H2O2 and any carbon remaining as a residue (as a result of the earlier combustion reaction) on the surface is removed.
The nanoparticles are obtained.
Figure 2: Preparation of Iron Oxide Nanoparticles
Figure 3: Iron Oxide Nanoparticles
Erik Wetterskog et al., Self-assembly of iron oxide nanocrystals, CC BY 3.0
Some important points about Iron Oxide Nanoparticles are,
They are usually a product of $\mathrm{Fe_2O_3}$ (Maghemite) or $\mathrm{Fe_3O_4}$ (Magnetite) nanoparticles.
The diameter for these nanoparticles lies in a range of 1 to 100 nanometers.
The use of these nanoparticles is mostly found in drug delivery, data storage (magnetic), Biosensing, etc.
There is a significant increase seen in the ratio of the area to volume of these nanoparticles. Therefore, in turn increasing their binding capacity significantly higher. They also show an excellent dispersion rate in a solution.
Another one of their qualities is supermagnetism. This can be seen in NPs with sizes ranging from 2 to 20 nanometers. This indicates towards; zero magnetism when they are found outside the presence of an external magnetic source or field. This makes Nanoparticles highly stable in solutions.
The chemical compounds made of both iron and oxygen as its constituents are called Iron oxides. There are 16 iron oxides/oxyhydroxides known to men at present. The most common among the iron oxides is rust. They are very easily available in nature. With being easily accessible in nature, they can also be with-ease synthesised within a laboratory.
The magnetite $\mathrm{(Fe_3O_4)}$ and maghemite nanoparticles using synthesis named solution combustion use iron oxides as an important component of that solution. These Nanoparticles later help to prepare colloidal suspensions.
Ordinarily available black iron oxide also helps in preparing, copperplate and inks (die stamping). The most common industries that popularly utilize iron oxides are; cosmetic, paint, plastic, ink, and pharmaceuticals.
Q1. What is the role of magnetite in iron oxide nanoparticles formation?
Ans. Magnetite plays the role of an important component of the solution undergoing combustion to form iron oxide nanoparticles.
Q2. What is understood by iron oxides?
Ans. Iron oxides are the oxides of transition metals. They can vary on the basis of stoichiometry and crystals. Among some very common iron oxides are Fe2O3 (Maghemite) and Fe3O4 (Magnetite).
Q3. What are some industrial uses of magnetite ($\mathrm{(Fe_3O_4)}$)?
Ans. The industrial uses of iron oxides are in the field of; paint, ink, pharmaceuticals, cosmetics, etc. They are also utilized in preparation of IONPs.
Q4. What are some commonly known properties of iron oxide nanoparticles?
Ans. The properties of iron oxide NPs are,
Are highly stable in solutions as they show super magnetism.
Have a higher binding capacity.
Help in storage of magnetic data.
Have a higher dispersion rate in a solution.
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