Super paramagnetic iron oxide nanoparticles with appropriate surface moiety have recently attracted a great deal of attention due to their potential biological applications.
Synthesis
The super paramagnetic nanocrystals asynthesized by the chemical co-precipitation of ferrous and ferric salts in a basic aqueous solution with humic acid as coating agents. The as synthesized products are highly soluble in water.
Uses
The humic acid coated super paramagnetic Fe3O4 nanocrystals with large numbers of functional groups have potential applications in biological and environmental science. Super paramagnetic iron oxide nanoparticles can be used for bio separation, as biosensor, biocatalysts, hyperthermia, MRI image contrasting, wastewater treatment, for specific cell labeling and tracking and as adsorbents for removal of cationic organic dye Methylene blue (MB) from neutral water. The magnetic properties of these unique nanostructures have been measured and their applications in medicine, information storage and processing and sensing are being developed.
Colloidal magnetic nanocrystals
There has been a tremendous research effort in the past few years in colloidal magnetic nanocrystals. New synthetic methods have been developed that enable a wide variety of magnetic materials to be synthesized in nanocrystal form, including ferromagnetic transition metals, intermetallics and metal oxides. These nanocrystals can be obtained with controlled size, shape and composition.
Fluorescent-magnetic nanocrystals
A fluorescent-magnetic YPxV1−xO4:Eu@GdPO4 core/shell nanostructure can be prepared by Chinese researchers in a two-step method. The YPxV1−xO4:Eu core can be synthesized using a hydrothermal method, and it exhibits strong photoluminescence with the effective doping of phosphorus (P) and europium (Eu) into a YVO4 matrix. The hydrothermal process provides a hydrophilic and fresh surface for coating GdPO4 shell. As YPxV1−xO4:Eu and GdPO4 have the similar unit cell parameters, YPxV1−xO4:Eu nanoparticles (NPs) afavorably coated by an epitaxial growth of GdPO4 shell in aqueous phase. These optical and magnetic properties promise outstanding fluorescent-magnetic bifunctional nanomaterials.
Magnetic nanocrystals in organisms
According to literature, ferrimagnetic nanocrystals are present in virtually every organism. They are used by bacteria, algae, mollusks, insects, and vertebrates either for navigating in the geomagnetic field or for hardening their tissues. Advanced transmission electron microscopy techniques, including electron holography, reveal the complex interplay between the physical and magnetic properties and biological functions of ferrimagnetic nanocrystals in bacteria. Although some information is now available about magnetic sensory systems in more complex organisms, much further research is required to understand fully the origin and function of biomagnetism.
Iron oxide magnetic nanocrystals
The properties of a metamaterial depend on the characteristics and interactions of the different nanocrystals used to make it. Metamaterials with improved magnetic, optical, electrical and mechanical properties could be used in applications as diverse as electric drives, motors and generators. Magnetic nanocrystals and semiconductor quantum dots can self-assemble into ‘metamaterials’ that could be useful in a range of applications.