Papers by Keyword: Magnetic Nanoparticle

Abstract: The Wheatstone bridge-giant magnetoresistance (GMR) sensor with single and double spin valve thin film was successfully developed for potential biomolecular detection. The GMR sensor with spin valves structure of [Ta (2nm)/IrMn (10nm)/CoFe (3nm)/Cu (2,2nm)/CoFeB (10nm)/Ta (5nm)] was fabricated using DC Magnetic Sputtering method. The Fe₃O₄ magnetic nanoparticles were synthesized by the co-precipitation method as a magnetic label. The magnetic properties of the Fe₃O₄ nanoparticles measured are the saturation magnetization (Ms) of 77.7 emu/g, remanence magnetization (Mr) of 7.7 emu/g, and coercivity (Hc) of 49 Oe. The X-ray diffraction pattern showed the inverse cubic spinel structure with an average crystal size of about 20.1 nm. Fe₃O₄ magnetic nanoparticles with various concentrations were used to be detected using a GMR sensor. The output voltage of the GMR sensor with the single and double spin-valve increased from 1.7 to 3.9 mV and 2.9 to 5.3 mV with the increase of the Fe₃O₄ concentration from 0 to 20 mg/mL, respectively.

Abstract: In the work reported here the magnetic properties of nanocomposite system composed of polystyrene (PS) latex polymer and superparamagnetic nanoparticles (MNPs), is presented. A series of mixtures were prepared by mixing of PS latex dispersion with different amount of MNPs and drop casting on glass substrates at room temperature. After drying, film samples were annealed at 250 °C for 10 min. Morphological changes of the films were examined by scanning electron microscopy (SEM) and magnetic properties studied using vibrating sample magnetometer (VSM) as a function of MNPs content. The saturation magnetization (M_s) of composites increased as MNPs content increased. M_s showed two maxima at 50 wt% and 85 wt% MNPs contents with M_s values of 0.014 emu and 0.020 emu, respectively. The morphological changes of PS/MNPs composite films were also found consistent with these results indicating that magnetic properties these composites can be readily tuned by varying MNPs content.

Abstract: Zinc ferrites (ZnFe₂O₄) nanoparticles were successfully prepared by the simple co-precipitation method. The effects of calcination temperature and the amount of surfactant on the microstructure of zinc ferrite products were studied. The products were characterized with X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectroscopy (DRS). The XRD results confirmed the formation of a cubic spinel structure in all samples. The SEM results revealed that surfactant molecules play a crucial role to control the microstructure of the samples. All samples showed extended absorptions in the visible region. The photocatalytic results indicated that ZnFe₂O₄ enhanced the photocatalytic activity with increased calcination temperature. In addition, the ZnFe₂O₄ prepared by addition of high concentrations of surfactant gave the highest photocatalytic activity. The synthesized ZnFe₂O₄ can be recovered by applying an external magnetic field.

Abstract: The effects of NiF₂ addition on the superconducting and transport properties of Bi_1.4Pb_0.6Sr₂Ca₂Cu₃O_10+δ (Bi-2223) were studied. Bi-2223 superconductor samples were prepared via conventional nitrate coprecipitation method, and 0.01 wt% - 0.05 wt% of NiF₂ nanoparticles with average size of 20 nm were added into the samples. The critical temperature (T_c) of each sample was measured by using the four-point probe method. Furthermore, phase formation and the microstructure of the samples were identified using x-ray diffraction method (XRD) and scanning electron microscope (SEM) respectively. The optimum T_c was observed for the sample with 0.04 wt% addition of NiF₂. Results of electrical transport measurement are presented.

Abstract: Many types of electrochemical biosensors employ magnetic nanoparticles which have been surface functionalized to recognize specific molecular targets. Here the paper emphatically introduced the operation principle of biosensing magnetic nanoparticles, the overall strategy for fabricating magnetic nanoparticles-based biosensor and the latest application progress in detecting lignocellulase activity and gene expression by electrochemical biosensors.

Abstract: The nanosize magnetic particles were synthesized by thermal decomposition method with size distribution in the range of 10 ~ 30 nm. Different category and quantity of surfactants were used modifying the surface of the synthesized nanoparticles to control the particles’ shape and size. Multi-shapes, such as uniformity cubic, mixture of spherical and cubic, and the similar chick footmarks, were acquired in our experiment by different surfactants. It indicates the surfactant is a key factor for the size and shape of particles. The surfactants of PVP and oleylamine made the particle shape be uniformity cubic; However, the particle partly behaved as spherical shape in the case of using PVP and oleic acid as surfactants.

Abstract: Among the proposed techniques for delivering drugs to specific locations within the human body, magnetic drug targeting (MDT) surpasses because of its noninvasive character and its high targeting efficiency. In this study, two novel arrangements of permanent magnets, Halbach array and spin-Halbach, were introduced to improve the magnetic force acting on a magnetic micro/nanoparticle. Then an approach of design and evaluate the MDT magnets was developed, which was based on three performances proposed in the paper, force parameter, evaluation variable, and transverse inhomogeneity. Corresponding parameters for Halbach-Like arrays at distance of 3 cm of application from magnetic field source were calculated and compared with the other two simple magnet arrays. According to the results, the values of performances for the Halbach-Like magnet arrays were improved obviously.

Abstract: The graphene layer-encapsulated iron nanoparticles were modified by pre-treatment of Ar plasma and post-treatment of NH3 plasma using an inductively coupled RF plasma. Analysis of XPS spectra have been carried out to study the effect of the plasma treatment on the improvement of enrichment of nitrogen-containing groups. The morphology of nanoparticles has been also analyzed by using a Scanning Transmission Electron Microscope (STEM) together with Energy Dispersive X-Ray Spectroscopy (EDS) elemental mapping to observe the distribution of elements.

Abstract: MnAlC nanoparticles were synthesized by plasma arc-discharge method. Heat treatment of these nanoparticles at temperature from 400 to 600 °C resulted in the formation of the ferromagnetic τ-phase. Most of the nanoparticles had nearly spherical shape, smooth surface and core/shell structure. The shells of the nanoparticles mainly consisted of Al2O3 and a small amount of Mn oxides. Though the saturation magnetization of MnAlC nanoparticles was lower than that of bulk samples due to the effect of nonmagnetic phases (β, γ2 and Mn3AlC) and the oxide shell, the highest coercivity, up to 5.6 kOe in the MnAlC magnets, was achieved when annealed at 500 °C for 30 min.

Abstract: The composite magnetic nanoparticles of coated SiO nano film with about 8 nm size can be dispersed in various liquid media, widely known as magnetic fluids or ferrofluids with both magnetic and liquid properties. In this paper, a bio-medicine coating technology on surface of magnetic nanoparticles and the optimum fabrication condition and the magnetism of composed bio-nanoparticles are investigated. Through observation of micro-structure of the bio-nanopaticles on coating surface, and evaluation of magnetic property and safety to apply to biomaterials, we know the bio-medicine coated on surface of magnetic nanoparticles is suitable of bio-solutions into surface of biomaterials.