Reorientation kinetics of superparamagnetic nanostructured rods

The attractive interactions between oppositely charged species (colloids, macromolecules etc) dispersed in water are strong, and the direct mixing of solutions containing such species generally yields to a precipitation, or to a phase separation. We have recently developed means to control the electrostatically-driven attractions between nanoparticles and polymers in water, and at the same time to preserve the stability of the dispersions. We give here an account of the formation of supracolloidal aggregates obtained by co-assembly of 7 nm particles with copolymers. Nanostructured rods of length comprised between 5 and 50 microns and diameter 500 nm were investigated. By application of a magnetic field, the rods were found to reorient along with the magnetic field lines. The kinetics of reorientation was investigated using step changes of the magnetic field of amplitude 90 degrees. From the various results obtained, among which an exponential decay of the tangent of the angle made between the rod and the field, we concluded that the rods are superparamagnetic.Comment: 12 pages - 452kB 7 - figures - 1 Table will be published in Journal of Physics : Condensed Matte

Optimization of the transmitter setup for a molecular communication link based on superparamagnetic iron nanoparticles

The search for innovative applications in the fields of biomedicine and nanotechnology benefit the further advance in molecular communication research. Nevertheless, a fullyfunctional artificial molecular system is not yet a reality. Institute for Electronics Engineering from FAU has developed an experimental molecular communication testbed based on magnetic nanoparticles, which has demonstrated to be effective in the transmission of bit sequences encoded by SPIONs. As part of this work, an optimization of the transmitter of this setup is implemented and tested. This optimization is based on the steering of SPIONs through a desired path after a splitting by use of the magnetic force generated by an electromagnet, which is located tactically in the proximity of the tubes where the nanoparticles flow. The electromagnet size has been selected in proportion to the tubes size of the system. Also, an electronic control circuit to switch automatically the electromagnet has been designed and mounted on a protoboard. Measuring of magnetic particles amount in the tubes of the system is accomplished using a susceptometer coil, an electronic device where the magnetic particles move through and generate an electrical signal. Experimental results for magnetic susceptibility changes in both channels after the Yconnector are presented. They have not been as expected, thus, recommendations in order to acquire more reliable measurements and further advancing in the presented research work are given.Outgoin

The effect of core-shell engineering on the energy product of magnetic nanometals.

Solution-based growth of magnetic FePt-FeCo (core-shell) nanoparticles with a controllable shell thickness has been demonstrated. The transition from spin canting to exchange coupling of FePt-FeCo core-shell nanostructures leads to a 28% increase in the coercivity (12.8 KOe) and a two-fold enhancement in the energy product (9.11 MGOe)

Cell bystander effect induced by radiofrequency electromagnetic fields and magnetic nanoparticles

Induced effects by direct exposure to ionizing radiation (IR) are a central issue in many fields like radiation protection, clinic diagnosis and oncological therapies. Direct irradiation at certain doses induce cell death, but similar effects can also occur in cells no directly exposed to IR, a mechanism known as bystander effect. Non-IR (radiofrequency waves) can induce the death of cells loaded with MNPs in a focused oncological therapy known as magnetic hyperthermia. Indirect mechanisms are also able to induce the death of unloaded MNPs cells. Using in vitro cell models, we found that colocalization of the MNPs at the lysosomes and the non-increase of the temperature induces bystander effect under non-IR. Our results provide a landscape in which bystander effects are a more general mechanism, up to now only observed and clinically used in the field of radiotherapy.Comment: 16 pages, 4 figures, submitted to International Journal of Radiation Biolog

Magnetic nanocomposites at microwave frequencies

Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small. Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table

Formation of octapod MnO nanoparticles with enhanced magnetic properties through kinetically-controlled thermal decomposition of polynuclear manganese complexes

Polynuclear manganese complexes are used as precursors for the synthesis of manganese oxide nanoparticles (MnO NPs). Altering the thermal decomposition conditions can shift the nanoparticle product from spherical, thermodynamically-driven NPs to unusual, kinetically-controlled octapod structures. The resulting increased surface area profoundly alters the NP's surface-dependent magnetism and may have applications in nanomedicine

Diameter dependence of ferromagnetic spin moment in Au nanocrystals

Au nanoparticles exhibit ferromagnetic spin polarization and show diameter dependence in magnetization. The magnetic moment per Au atom in the particle attains its maximum value at a diameter of about 3 nanometer (nm) in the Magnetization-Diameter curve. Because Au metal is a typical diamagnetic material, its ferromagnetic polarization mechanism is thought to be quite different from the ferromagnetism observed in transition metals. The size effect strongly suggests the existence of some spin correlation effect at the nanoscale. The so-called ``Fermi hole effect'' is the most probable one given in the free electron gas system. Ferromagnetism in Au nanoparticles is discussed using this model.Comment: 5 pages, 6 figures, to appear in Phys. Rev.

Multiscale Biofluidic and Nanobiotechnology Approaches for Treating Sepsis in Extracorporeal Circuits

Infectious diseases and their pandemics periodically attract public interests due to difficulty in treating the patients and the consequent high mortality. Sepsis caused by an imbalanced systemic inflammatory response to infection often leads to organ failure and death. The current therapeutic intervention mainly includes "the sepsis bundles," antibiotics (antibacterial, antiviral, and antifungal), intravenous fluids for resuscitation, and surgery, which have significantly improved the clinical outcomes in past decades; however, the patients with fulminant sepsis are still in desperate need of alternative therapeutic approaches. One of the potential supportive therapies, extracorporeal blood treatment, has emerged and been developed for improving the current therapeutic efficacy. Here, I overview how the treatment of infectious diseases has been assisted with the extracorporeal adjuvant therapy and the potential utility of various nanobiotechnology and microfluidic approaches for developing new auxiliary therapeutic methods