Nickel nanowire arrays with high aspect ratio and large packing densities have been grown in thin nanochannel glass templates by an electrochemical deposition method. The templates were polished and etched for enough time to obtain parallel, uniform, hollow channels. One of surfaces of templates was then deposited with copper to provide an electrode. The pH value of NiSO4 aqueous solution was 1 to 2 and the deposition potential was chosen to be –1.2 V versus the saturated Calomel electrode. Obtained nickel wires were circular, each approximately 80 – 160 nm in diameter and 150 μm long, depending on the diameter of nanochannel. Finally, scanning electron microscopy has been used to characterize the nanostructures. Magnetic properties of the nickel wire arrays have been also investigated by using a superconducting quantum interference device magnetometer (SQUID).

Co-Au Core-shell nanoparticles are synthesized by slowly reducing an organo-gold compound on pre-made cobalt seeds with a weak reducer at mild condition. For the first time, these coreshell nanoparticles are generated in non-polar solvent in a controlled manner. The formation theory of core-shell structure, especially the seed size effect, is addressed as well. These coreshell structures are confirmed with a wide range of transmission electron microscopy (TEM) methods, which includes routine TEM images, high resolution TEM, and z-contrast imaging.

Nd40Fe30Co15Al10B5 bulk amorphous prepared by high energy milling shows a coercivity of 8.1 kOe with a Curie temperature of 645 K. The controlled nanocrystallization enhances the coercivity to 20 kOe and the remanence ratio is equal to 0.59. The coexistence of two crystalline magnetic phases, ferromagnetic Nd2(Fe,Co,Al)14B and antiferromagnetic Nd6(Fe,Co,Al)14 are revealed by x-ray diffraction, high-resolution transmission electron microscopy, magnetization measurements, and Mössbauer spectrometry. The grain size for optimal magnetic properties is around 30 nm. The nucleation process may play a leading role in the high magnetic behavior.

The aberration-corrected STEM allows nanostructures to be investigated with greater resolution and sensitivity than ever before. Single atom sensitivity is achieved both in imaging and also for spectroscopy, for atoms on surfaces or within the bulk. Nanocrystal size, shape, surface termination, 3D structure and the presence of any defects can be seen with unprecedented ease. The improved sensitivity provides improved input for theory, allowing new insights into nanostructure properties and the origin of their unique functionality. Furthermore, the larger aperture available with aberration-corrected STEM improves the depth resolution dramatically. Nanometer depth resolution can be achieved by simply taking a focal series of images, which may then be reconstructed into a 3D rendering of the material in the same manner as with confocal optical microscopy but maintaining sensitivity to individual atoms.

Cobalt nickel nanoparticles with an oxide shell were prepared by polyol reduction syntheses with varying heating rates, reflux times, surfactants, and reagent concentrations. Differences in particle formation temperature, as evidenced by the reaction medium changing color from violet to black, the UV-Vis absorption spectra of aliquots of reaction media extracted throughout the synthesis reaction, and the colloidal stability of the particle dispersions were observed when the surfactant was changed between otherwise identical reactions. These changes in the reaction kinetics, and therefore the particle sizes of the different samples, also resulted in varying magnetic properties and air stabilities of the samples. Particles with diameters of 15 nm, synthesized using oleic acid, displayed exchange biasing and enhanced coercivity below 50 K, with Hex = 650 Oe and an increase in Hc from 570 Oe to 910 Oe after cooling in field to 2 K. These particles were stable in air over a period of at least five months, showing no change in magnetic moment. Smaller (6 nm) particles synthesized with the same surfactant did not exhibit exchange biasing after field cooling and experienced degradation of their magnetic properties upon exposure to air for one month. Particles synthesized with trioctylphosphine and mixtures of trioctylphosphine and oleic acid were 5 nm and formed the most stable dispersions, but oxidized upon drying in air to non-ferromagnetic phases.

A novel method of dynamically and selectively controlling the diffusion of molecules using aggregation of ferrofluid is proposed. This method can be used to mask specific locations on a surface for combinatorial chemistry or to restrict diffusion of molecules in selected areas in a microfluidic device. This method works by using the controlled aggregation of stabilized 10nm diameter iron oxide particles (ferrofluid) to slow the diffusion of molecules in a similar manner as to how a porous media restricts diffusion. Dynamic aggregate formation is controlled by a magnetic pattern on a substrate in conjunction with an external field. The external magnetic field bias applied to the system causes ferrofluid to aggregate only in designated areas around the magnetic patterns thereby slowing diffusion through the areas where the aggregate clouds have formed.

The paper describes the surface roughness and dilution effects on the magnetic behavior of nanocrystalline nickel ferrites studied by SQUID magnetometer. Two different kinds of measurements were performed: (a) zero-field cooling (ZFC) and field cooling (FC) magnetization versus temperature and (b) magnetization as a function of the applied field. The analysis of magnetic measurements indicate that while the superparamagnetic behavior is retained by nanocrystalline ferrites of different surface roughness (0.8-1.8 nm) at 300K, the hysteresis loop at 2K becomes non-squared and the coercivity increases with increase in surface roughness. This behavior is discussed in terms of broken bonds and degree of surface spin disorder. In diluted dispersion systems containing 10-40% nickel ferrite in a polyethylene matrix, the interparticle attractions continue to be dominant even when the concentration of nickel ferrite is 10 wt.% in the diluted system. The general magnetic behavior of diluted dispersion system is similar to the undiluted system; however, coercivity, remanence, and saturation magnetization are altered. These changes in the magnetic data are ascribed to magnetization interactions that encourage flux closure configuration.

The research described here investigates the hypothesis that nanoarchitecture contained in a nanowire array is capable of attenuating the adverse host response, biofouling, generated when medical devices, such as sensors, are implanted in the body. This adverse host response generates an avascular fibrous mass transfer barrier between the device and the analyte of interest, disabling the sensor. Numerous studies have indicated that surface chemistry and architecture modulated the host response. These findings lead us to hypothesize that nanostructured surfaces will significantly inhibit the formation of an avascular fibrous capsule. We are investigating whether vibrating magnetostrictive nanowires, formed in nanowire arrays, can prevent protein and cell adhesion. Magnetostrictive nanowires are fabricated by electroplating a ferromagnetic metal alloy into the pores of a nanoporous alumina template. The ferromagnetic nanowires are made to vibrate by altering the magnetic field surrounding the wires. Enzyme-linked immunosorbent assay (ELISA) and other protein assays were used to study protein adhesion on the nanowire arrays. These results display a reduced protein adhesion per surface area of static nanowires. The vibrating nanowires show a further reduction in protein adhesion, compared to static wires. Studies were also preformed to investigate the effects of nanoarchitecture have on cell adhesion. These studies were performed with both static and vibrating nanowires. Preliminary protein adhesion studies have shown that a nanowire arrays modulate protein adhesion in vitro.