Synthesis of maghemite (γ-Fe2O3) nanoparticles by …
Due to their unique characteristics, magnetic nanoparticles have received much attention in recent year especially in various fields of application including electronic, mechanical engineering, aerospace, and environmental and bioengineering [–]. Iron oxide nanoparticles particularly magnetite (Fe3O4) and maghemite (γ-Fe2O3) are promising magnetic materials that are intensively explored due to their unique magnetic properties.
Synthesis and Magnetic Properties of Maghemite (γ …
Suspended maghemite nanoparticles in solvent creates new class of liquids called “magnetic fluids.” The uniqueness of these smart materials is because of their superparamagnetic property. The flow and energy transport of magnetic fluids can be controlled using external magnetic fields. Therefore, the magnetic fluids can be used effectively in thermal engineering applications .
Although many attempts have been made towards the synthesis of stable magnetic nanoparticles suspension, it still presents a big challenge. The most important parameter in the preparation of this materials is the stability of the magnetic nanoparticles suspension.
ThalesNano Nanotechology Inc - Publications
Hypoxia is regarded as a key feature of the tumor microenvironment that significantly influences tumor treatment response. An albumin-stabilized gold nanoparticle was synthesized for tumor hypoxia imaging (Figure a) . The nanoparticle was modified with hypoxia-sensitive nitroimidazole moiety, which was converted into amine groups in the presence of nitroreductase. Conversion from the nitro group of nitroimidazole to the amino group helped increase the zeta potential of the prepared nanoparticle, which thereby improved cell internalization for accumulation at the tumor . The designed nanoparticle displayed enhanced X-CT imaging for tumor hypoxia
International Journal of Nanomedicine - Dove Press
The magnetization curve of all samples is shown in . It is clear that the curves do not exhibit hysteresis and passes through the origin, which indicates that the samples are superparamagnetic. The saturation magnetization values of maghemite nanoparticles at room temperature for all samples are tabulated in . These values are lower than that of bulk maghemite (74emu/g) due to the fact that the crystallite size of maghemite particles is in nanosize range. This phenomenon is usually observed in nanoparticles interacting systems. Such a reduction of maximum magnetization can be ascribed to surface effects arising from broken symmetry and reduced coordination of atoms lying at the surface of maghemite nanoparticles and also to a high degree of interparticle interactions .
Iron oxides are chemical compounds composed of iron and oxygen
TGA curves of the maghemite nanoparticles at different nitric acid concentrations are shown in . It can be seen that the curves exhibit similar weight loss behavior and display two weight losses steps. The initial weight loss starts from the ambient temperature to 140°C and the final weight loss is within the temperature range of 140 to 400°C. The initial weight loss is associated with the evaporation of absorbed water and crystalline water from the sample. The final weight loss might be attributed to the volatilization of the remainder bonding water in the sample which will evaporate at water critical temperature of 374°C. No further significant weight loss or gain is found in the temperature range of 400 to 1000°C, indicating crystalline of maghemite has been formed completely. The temperature stability (Ts) for all samples when maghemite is completely formed is presented in . It can be seen that the temperature stability decreases with increasing concentration of nitric acid. This indicates that sample with the most concentrated nitric acid is stabilized earlier than other samples.
All together, there are sixteen known iron oxides and oxyhydroxides
On the basis of the high biocompatibility and long blood circulation half-life of albumin, many studies have been devoted to the development of albumin-stabilized nanoparticles for biomedical applications [-]. Albumin could be introduced during nanoparticle synthesis or stabilizer replacement [-].