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Complex permittivity spectra of the multiwalled carbon nanotube (MWNT)-epoxy composites with mass concentrations up to 25.9% were measured from 10 MHz to 20 GHz. The composites exhibit high real and imaginary relative permittivities over broad bandwidth, showing strong dependence on the MWNT loading. It is observed that distinct resonance takes place at ∼1.5 GHz, with the corresponding resonant frequency shifts downward as the MWNT concentration increases. The origin of the dielectric properties is explained in terms of the dielectric relaxation/resonance and electrical conduction behavior of the nanotube composites, substantiated by the agreement between simulation and experimental data.

We report the efficiency of genomic DNA extraction as a function of particle size and quantity. For DNA extraction, we synthesized magnetic nanoclusters of various sizes and coated the surface of these magnetic nanoclusters with meso-2,3-dimercaptosuccinic acid. We showed that the nanoclusters had a tight particle size distribution and high crystallinity. Furthermore, we observed that the three types of magnetic nanoclusters studied exhibited ferrimagnetic behavior and that larger nanoclusters showed larger saturation magnetization values. The resultant efficiency of DNA extraction is inversely proportional to particle size in the range of nanoclusters tested, due to the fact that the surface-to-volume ratio decreases as particle size increases.

We report the synthesis and characterization of monosized Eu-doped ZnO nanocrystals via a nanoemulsion process as a function of the doping ratio. The structure, optical, and magnetic properties of the nanocrystals are investigated by XRD, TEM, PL spectrometry, and physical property measurement system. The nanocrystals as prepared show high crystallinity and tight particle size distributions with the diameters of ∼ 10 nm. The doped samples clearly exhibit the 5D0→7FJ transition emission due to the presence of the Eu3+ ions. Meanwhile, the magnetic responses demonstrate the temperature dependence and change with dopant concentration.

NiFe/Au barcode nanowires were synthesized by pulsed electrodeposition using anodic aluminum oxide nanotemplate, comprising magnetic, catalytic, and optical segments, respectively. The self-powered motion of the BNWs due to the catalytic reaction was observed in aqueous H2O2. The approach demonstrates how sophistication in barcode nanoarchitecture can be used to synthesize a wide range of hybrid materials.

Interparticle interactions in magnetic nanoparticles are studied by dc and ac magnetization measurements. For non-interacting nanoparticles, while the anisotropy constant of the nanoparticles Keff = 1.6 × 105 erg/cm3 is accurately determined by fitting zero-field-cooled and field-cooled measurements, we show that Keff values deduced only from time relaxation measurements must require simultaneous adjustments of the complex susceptibility by taking into account the size distribution of nanoparticles. This leads to Keff = 1.7 × 105 erg/cm3 in agreement with dc measurements. For interacting nanoparticles, comparisons with theoretical models show that energies due to magnetic dipolar interactions can only be predicted for weak and moderate interactions.

This work investigates the intrinsic cell labeling efficiency of the Fe3O4 nanoparticles prepared by a modified thermal decomposition method using nontoxic precursors and a biocompatible polymer surfactant. This method eliminates the current need for additional step of surface modification. The structural analysis reveals the highly crystalline feature of the nanoparticles, while the magnetic measurement shows their superparamagnetic behavior at room temperature. Fe3O4 nanoparticles were efficiently incorporated into the murine macrophage cells (RAW264.7) without visible cytotoxicity. Cell labeling efficiency was found to be over 90% as measured by magnetically activated cell sorting and physical property measurement system. Therefore, such Fe3O4 nanoparticles could provide a useful magnetic cell labeling tool for macrophage cells using their phagocytic/endocytic activity and further apply to the other relevant biomedical applications.

We report the nonaqueous synthesis and magnetic properties of narrowly size distributed ZnFe2O4 nanocrystals of two different particle sizes by nanoemulsion, of which structure and properties were investigated by transmission electron microscopy, x-ray diffraction, vibrating sample magnetometry, and physical property measurement system. The morphological and structural characterization show the high crystallinity and excellent particle size distribution of the ZnFe2O4 nanocrystals in the diameters of 5.37 ± 0.68 nm and 6.44 ± 0.95 nm, separately. Meantime, the corresponding magnetic measurements reveal the strong size dependence and well-defined nanomagnetism of the nanocrystals.

We present the synthesis and magnetic properties of multifunctional CoPtAu alloy nanoparticles of three compositions, Co0.33Pt0.33Au0.33, Co0.2Pt0.2Au0.6, and Co0.4Pt0.4Au0.2, by a modified polyol process. The x-ray diffraction and transmission electron microscopy analyses confirm the formation of the alloy nanostructure comprising Au-rich and Pt-rich nanophases, with a narrow distribution of particle sizes and provides the detailed structural arrangements. The magnetic study shows the composition dependence of the magnetic properties of the nanoparticles, from superparamagnetic for both Co0.33Pt0.33Au0.33 and Co0.4Pt0.4Au0.2 to soft ferromagnetic for Co0.2Pt0.2Au0.6.

We report the preparation and characterization of multifunctional AuFe alloy nanoparticles of three compositions, Au0.25Fe0.75, Au0.5Fe0.5, and Au0.75Fe0.25, by a polyol process. It is found that the fusion of the two elements into one nanostructure entity retains the optical and magnetic properties of the individual components. The x-ray diffraction and transmission electron microscopy analyses confirm the formation of the alloy nanostructure with a narrow distribution of particle sizes and provides the detailed structural arrangements. The magnetic investigation shows the superparamagnetic or soft ferromagnetic behavior of the nanoparticles at room temperature, whereas the UV-visible measurements display the variation of the absorption bands at ∼560nm. The AuFe nanoparticles are rendered water soluble after thiolation.

We studied the effects of copper doping on the microstructure and magnetic properties of CoPt nanowires fabricated in anodized aluminium oxide (AAO) nanotemplates by electrodeposition. The morphological observation indicates well-formed CoPt and CoPtCu nanowires, while the structural analysis shows that fcc-Co3Pt phase exists prior to annealing and is retained in the doped nanowires, with minor hcp-CoPt phase postannealing. The doping causes shrinkage of the lattice spacing prior to annealing due to the insertion of smaller copper atoms. Compared to the undoped CoPt nanowires, the magnetic measurements reveal significant enhancement in the magnetic properties of the CoPtCu nanowire postannealing, resulting in the more rapid increase in the coercivity with annealing temperature.

The effect of substrates on the microstructure and magnetic properties of electrodeposited Co nanowire arrays in porous anodic aluminum oxide membrane was investigated. It is found that the nanowires possess dominant (002) and (110) textures on the Co-coated nanocrystalline Finemet™ and Au substrates, respectively. Magnetic measurements show that the easy axis of the nanowire arrays switches from perpendicular to the wire axis on Au to parallel to the wire axis on the Co-coated nanocrystalline Finemet™ substrate.

We have investigated the effect of external magnetic field exercised during the fabrication of the Co and Co∕Cu multilayer nanowires in anodic aluminum oxide (AAO) templates using pulse electrodeposition. It is found that the effect becomes significant when the pore size is small. Deterioration occurs in the magnetic properties for the Co nanowires studied, whereas a distinct enhancement in the magnetic properties for the Cu∕Co multilayer nanowires is achieved by applying an external magnetic field during nanowire growth using the AAO template comprising pores of 50nm diameter.