Tuneable magnetic properties of hydrothermally synthesised core/shell CoFe2O4/NiFe2O4 and NiFe2O4/CoFe2O4 nanoparticles

The aim of this study was to prepare a novel targeting nano drug delivery system of 2-methoxyestradiol (2-ME) based on the folic acid-modified bovine serum albumin, in order to improve the clinical application disadvantages and antitumor effect of 2-ME. In this study, 2-methoxyestradiol-loaded albumin nanoparticles (2-ME-BSANPs) were prepared by desolvation method, and then the activated folic acid was conjugated to 2-ME-BSANPs by covalent attachment (2-ME-FA-BSANPs). The size and zeta potential of 2-ME-FA-BSANPs were about 208.8 ± 5.1 nm and ?32.70 ± 1.01 mV, respectively. 2-ME loading efficiency and loading amount of the nanoparticles were 80.49 ± 3.80 and 10.25 ± 1.59 %, respectively. SEM images indicated that 2-ME-FA-BSANPs were of a round shape, similar uniform size, and smooth surface. Studies on drug release indicated that 2-ME-FA-BSANPs had the properties of sustained and controlled release, which provided them with the ability to fight continually against cancer cells. Internalization analysis demonstrated that 2-ME-FA-BSANPs-targeting drug delivery system could get efficiently transferred into the cells through the folic acid-mediated endocytosis, leading to higher apoptosis and affording higher antitumor efficacy against SMMC-7721 cells in vitro compared with 2-ME alone. Furthermore, the cell-cycle arrest of 2-ME-FA-BSANPs on the SMMC-7721 cells occurred at G2/M phase, and 2-ME-FA-BSANPs did not change the inhibition of the tumor mechanisms of 2-ME. Based on these results, it was concluded that albumin nanoparticles could be the promising nano carrier for 2-ME, and 2-ME-FA-BSANPs-targeting drug delivery system may be promising candidate for providing high treatment efficacy with minimal side effects in future cancer therapy.     

Sonocatalytic degradation of tetracycline hydrochloride with CoFe2O4/g-C3N4 composite

In this work, different mass percent ratios of CoFe₂O₄ coupled g-C₃N₄ (w%-CoFe₂O₄/g-C₃N₄, CFO/CN) nanocomposites were integrated through a hydrothermal process for the sonocatalytic eradication of tetracycline hydrochloride (TCH) from aqueous media. The prepared sonocatalysts were subjected to various techniques to investigate their morphology, crystallinity, ultrasound wave capturing activity and charge conductivity. From the investigated activity of the composite materials, it has been registered that the best sonocatalytic degradation efficiency of 26.71 % in 10 min was delivered when the amount of CoFe₂O₄ was 25% in the nanocomposite. The delivered efficiency was higher than that of bare CoFe₂O₄ and g-C₃N₄. This enriched sonocatalytic efficiency was credited to the accelerated charge transfer and separation of e⁻-h⁺ pair through the S-scheme heterojunctional interface. The trapping experiments confirmed that all the three species i.e. ^•OH, h⁺ and ^•O₂⁻ were involved in the eradication of antibiotics. A strong interaction was shown up between CoFe₂O₄ and g-C₃N₄ in the FTIR study to support charge transfer as confirmed from the photoluminescence and photocurrent analysis of the samples. This work will provide an easy approach for fabricating highly efficient low-cost magnetic sonocatalysts for the eradication of hazardous materials present in our environment.     

Preparation and characterization of multiferroic CoFe2O4/Bi0.97Ce0.03FeO3 coaxial nanotubes

Multiferroic CoFe₂O₄ (CFO)/Bi_0.97Ce_0.03FeO₃ (BCFO) coaxial nanotubes were prepared by a sol-gel template method. Transmission electron microscopy revealed that the coaxial nanotubes featured with inner CFO and outer BCFO nanotubes. Selected area electron diffraction confirmed the coexistence of spinel CFO and perovskite BCFO phases in the coaxial nanotubes. Vibrating sample magnetometer measurements showed that the saturated magnetization of the coaxial nanotubes was 3.3?emu/g, smaller than that of CFO nanotubes. The P–E hysteresis loop of the coaxial nanotubes was of poor shape due to possible high conductivity in the inner CFO nanotubes. Dielectric measurements exhibited that the dielectric constant of the coaxial nanotubes decreased while the dielectric loss increased due probably to the small dielectric constant and high conductivity in the inner CFO nanotube. Ferroelectric and magnetic properties were simultaneously demonstrated in the CFO/BCFO coaxial nanotubes.     

CoFe2O4/空心微球复合体的制备与吸波性能

采用化学共沉淀法,在空心微球上包覆一层CoFe2O4,得到一种低密度的空心磁性微球．磁测量结果表明,磁场下退火制备的CoFe2O4样品反位缺陷减少,从而导致饱和磁化强度随退火磁场的增强而增大．吸波性能测试结果表明,包覆结构的CoFe2O4/空心球样品是一种轻质的微波吸收材料.     

CoFe_2O_4/空心微球复合体的制备与吸波性能

采用化学共沉淀法,在空心微球上包覆一层CoFe2O4,得到一种低密度的空心磁性微球.磁测量结果表明,磁场下退火制备的CoFe2O4样品反位缺陷减少,从而导致饱和磁化强度随退火磁场的增强而增大.吸波性能测试结果表明,包覆结构的CoFe2O4/空心球样品是一种轻质的微波吸收材料.     

CoFe2O4和MnFe2O4纳米复合介质的制备及其磁性研究

采用热分解法制备了分散程度高且平均晶粒尺寸为20 nm的CoFe₂O₄和MnFe₂O₄复合介质.低温磁化曲线测量显示,制备的复合介质具有软-硬磁交换弹性耦合效应,且合成温度以及软磁和硬磁相的成分比例对磁交换弹性耦合的强度有很大的影响.变温磁测量显示,温度为20K时,复合纳米介质的表面自旋冻结效应导致饱和磁化强度显著增加.Henkel测量显示,对分散的CoFe₂O₄和MnFe₂O₄复合介质,磁偶极相互作用占主导作用.     

Thermal conductivity of Zn doped CoFe2O4 ferrites

A series of samples of the type Co_1-xZn_xFe₂O₄ (x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0) was prepared as ceramics. The existence of a single phase was confirmed by x-ray studies. The thermal conductivity and specific heat were measured at temperatures ranging from 100°C to 200°C. The thermal conductivity had a minimum value at x = 0.4, caused by maximum scattering of thermal phonons which arose from the change of crystal size and excess of lattice vacancies. The phonon frequency was estimated to have an optimum value at x = 0.4, resulting from maximum porosity which disturbs the propagation of the thermal waves.     

Synthesis and characterization of composite Au/TiO2 nanoparticles by laser irradiation

Composite Au/TiO₂ nanoparticles were synthesized by laser ablation of gold plate in TiO₂ sol. The nanoparticles were characterized by UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction, and atomic force microscopy. The peak of surface plasmon is at 550 nm with a red shift of 30 nm compared with that of Au nanoparticles in water. Monolayers of composite Au/TiO₂ nanoparticles were obtained by dip-coating technique. The XRD pattern of Au/TiO₂ powders resembles a mixture of anatase TiO₂ and gold.     

Mechanical stability of ferrimagnetic CoFe2O4 flexible thin films

We fabricated high-quality ferrimagnetic CoFe₂O₄ (CFO) thin films on a mica substrate using a pulsed laser deposition technique. High-resolution X-ray diffraction and transmission electron microscopy revealed that the film grew epitaxially with the relationships of CFO <1-10> || Mica [010] and CFO [111] || Mica [001]. The films were highly flexible in terms of both inward and outward bending, and exhibited clear ferrimagnetic hysteresis with weak anisotropy in both the in-plane and out-of-plane directions. We observed that the magnetization of CFO films was robust against mechanical stimuli without microcracks. The remnant magnetization and coercive field were within 8% and 11% over a strain of ±0.54%. As the number of bending cycles increased, the magnetic easy axis became more closely aligned to the out-of-plane direction, without any noticeable change in domain size.     

Preparation and characterization of antibacterial Au/C core-shell composite

An environment-friendly oxidation-reduction method was used to prepare Au/C core-shell composite using carbon as core and gold as shell. The chemical structures and morphologies of Au/C core-shell composite and carbon sphere were characterized by X-ray diffraction, transmission electron microscope, energy dispersion X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The antibacterial properties of the Au/C core-shell composite against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) were examined by the disk diffusion assay and minimal inhibition concentration (MIC) methods. In addition, antibacterial ability of Au/C core-shell composite was observed by atomic force microscope. Results demonstrated that gold homogeneously supported on the surface of carbon spheres without aggregation and showed efficient antibacterial abilities.     

Polarisation resistance of the O2, Au/O2− and H2-H2O, Au/O2− electrode systems

Gold electrodes with known contact geometries were studied using impedance spectroscopy. From these data it was possible to determine the specific polarisation conductivity per unit length of three-phase boundary (TPB). The values were found to be (3÷22)×10⁻⁴ S·cm⁻¹ dependent on the electrode history in pure oxygen at 977 °C and 2×10⁻⁶ S·cm⁻¹ at 977 °C in “pure” hydrogen (P_O2=10⁻²⁰ atm at 1001 °C). The results are compared with previous data obtained for platinum electrodes.     

Cationic distribution and spin canting in CoFe2O4 nanoparticles

CoFe(2)O(4) nanoparticles (D(NPD) ~6 nm), prepared by a thermal decomposition technique, have been investigated through the combined use of dc magnetization measurements, neutron diffraction, and (57)Fe M?ssbauer spectrometry under high applied magnetic field. Despite the small particle size, the value of saturation magnetization at 300 K (M(s) ?= 70 A m(2) kg(-1)) and at 5 K (M(s) ?= 100 A m(2) kg(-1)) are rather close to the bulk values, making the samples prepared with this method attractive for biomedical applications. Neutron diffraction measurements indicate the typical ferrimagnetic structure of the ferrites, showing an inversion degree (γ(NPD) = 0.74) that is in very good agreement with cationic distribution established from low temperature (10 K) M?ssbauer measurements in high magnetic field (γ(moss) = 0.76). In addition, the in-field M?ssbauer spectrum shows the presence of a non-collinear spin structure in both A and B sublattices. The results allow us to explain the high value of saturation magnetization and provide a better insight into the complex interplay between cationic distribution and magnetic disorder in ferrimagnetic nanoparticles.     

Bi-functional Au/FeS (Au/Co3O4) composite for in situ SERS monitoring and degradation of organic pollutants

Journal of Nanoparticle Research - Magnetic particles (MPs) are known to respond to a magnetic field and can be moved by magnetic force, which make them good carriers in bioengineering and...     

Investigation of nanocrystalline CoFe 2 O 4 by positron annihilation lifetime spectroscopy

Nanoparticles of cobalt ferrite prepared by the co-precipitation method with crystallite size varying from 4.7 to 41 nm have been characterized by positron annihilation lifetime spectroscopy. Three lifetime components are fitted to the lifetime data. The shortest lifetime component is attributed to the delocalized positron lifetime shortened by defect trapping. The intermediate lifetime is assigned to the positron annihilation in diffuse vacancy clusters or microvoids at the grain boundaries and at the grain-boundary triple points. The longest component corresponds to the pick-off annihilation of ortho-positronium formed at the larger voids. The variations in these lifetimes and their relative intensities with annealing temperature and crystallite size have been studied in detail.     

Electrochemical deposition and characterization of Cu2O nanowires

Cu₂O nanowires were successfully synthesized by an electrochemical method using an alumina membrane as template through precise control of the pH value of the electrolyte. The deposition process was monitored by the time–current curve. Characterization was performed by means of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The growth directions of the Cu₂O nanowires were determined and the possible growth mechanism is discussed. PACS 68.37.Lp; 81.07.-b; 81.16.Be     

Magnetic properties of polycrystalline films of CoCr2O4 and CoFe0.5Cr1.5O4 multiferroics

This paper reports on the first study of the magnetic properties of polycrystalline films of CoCr₂O₄ and CoFe_0.5Cr_1.5O₄ multiferroics. The study covered, in particular, magnetization reversal curves and temperature dependences of the magnetization at temperatures ranging from 4.2 to 300 K in magnetic fields of up to 10 kOe. It has been shown that the Curie temperature and the pattern of the temperature dependence of the magnetization depend on the cation composition of the multiferroic. The temperature dependence of the magnetization of polycrystalline CoCr₂O₄ films has revealed an anomaly in the temperature range 10–70 K.     

Size-dependent magnetic properties of CoFe2O4 nanoparticles prepared in polyol

Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe M?ssbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles.     

Influence of domain wall density on interlayer coupling in CoFe/Au/Co/Au multilayers

We measure magnetization reversal and giant magnetoresistance of CoFe/Au/Co/Au multilayers and use micromagnetic simulations to model them. We characterize the system by perpendicular and easy-plane effective anisotropy of Co and CoFe layers, respectively. We show that minor hystereses of magnetoresistance can be reasonably well described by the model. The simulations show that the variation of resistance with the field depends on the field strength at which the sweep reverses, and is correlated with the number of stripe domains present in the Co layers.     

Low temperature measurements by infrared spectroscopy in CoFe2O4 ceramic

This paper presents results of new far-infrared and middle-infrared measurements (wavenumber range of 4000?C100 cm^?1) of the CoFe₂O₄ ceramic in the temperature range from 300 K to 8 K. The band positions and their shapes remain constant across the wide temperature range. The quality of the sample was investigated by X-ray, EDS and EPMA studies. The CoFe₂O₄ retains the cubic structure (Fd - 3m) across the temperature range from 85 K to 360 K without any traces of distortion. Based on current knowledge the polycrystalline CoFe₂O₄ does not exhibit any phase transitions across the temperature range from 8 K to 300 K.