Study Of Magnetic Nanostructured Wires Made From Superparamagnetic Nanoparticles

The one-dimensional magnetic nanostructured wires have attracted more and more attentions due to its potential application in cell manipulation,microfluidics and micro-mechanics, Therefore, it is emerging to find a simple and effective methodology to sythesis wires and to study the corresponding assembly mechanism. In this study, we use the electrostatic complexation to synthesis the one-dimensional magnetic nanostructured wires. The structure of the wires were controlled by tunning the charge ratio Z between the γ-Fe2O3 nanoparticles and cationic polyelectrolyte polymer and the temperature T during the synthesis.Here, the γ-Fe2O3 nanoparticles made by co-precipitation were characterized by using XRD, VSM, TEM and DLS, indicating that the γ-Fe2O3 nanoparticles have a typical superparamagnetic properties, relatively uniform particle size, and a small polydispersity. The bare nanoparticles were coated by an anionic polymer in order to improve its colloidal stability and further fonctionality. DLS study shows that the organic coating thickness is about 5 nm. The coated nanoparticles was found to have remarkable colloid stability in aqueous with high concentration of salt and complicated bioligical environment. Around the surface of coated nanoparticles, there exist numerous free carboxyl functional groups,which is an excellent precursor for further biomedical functionalization, which could be widely used in MRI contrast agents, targeted drug delivery and heat treatment.Moreover, one-dimensional magnetic nanostructured wires were obtained by electrostatic complexation. Wires structure can be controlled by tunning the temperature and charges ratio in the process of assembly. We have established a simple, efficient and general approach for moderating the turbulent electrostatic interaction between colloidal nanoparticles and widespread homopolyelectrolytes.The growth of spherical precursors of 250 nm and second as either random link and accretion of precursors into coral-like clusters; or unidimensional link and accretion of precursors into rod-like wires with “bundle” structures in the presence of an externalnal magnetic field. Using this approach, mixing ofoppositely charged species in dispersion generates aggregates with controlled size and morphology with minimum restriction of specific assembly devices,nature of the polycations, and charge ratio between species, which promises great potential for application.