Folate-conjugated Fe_3O_4 nanoparticles for in vivo tumor labeling

Highly biocompatible superparamagnetic Fe3O4 nanoparticles were synthesized by amide of folic acid （FA） ligands and the NH2-group onto the surface of Fe3O4 nanoparticles. The as-synthesized folate-conjugated Fe3O4 nanoparticles were characterized by X-ray diffraction diffractometer, transmission electron microscope, FT-IR spectrometer, vibrating sample magnetometer, and dynamic light scattering instrument. The in vivo labeling effect of folate-conjugated Fe3O4 nanoparticles on the hepatoma cells was investigated in tumor-bearing rat. The results demonstrate that the as-prepared nanoparticles have cubic structure of Fe3O4 with a particle size of about 8 nm and hydrated diameter of 25.7 nm at a saturation magnetization of 51 A·m2/kg. These nanoparticles possess good physiological stability, low cytotoxicity on human skin fibroblasts and negligible effect on Wistar rats at the concentration as high as 3 mg/kg body mass. The folate-conjugated Fe3O4 nanoparticles could be effectively mediated into the human hepatoma Bel 7402 cells through the binding of folate and folic acid receptor, enhancing the signal contrast of tumor tissue and surrounding normal tissue in MRI imaging. It is in favor of the tumor cells labeling, tracing, magnetic resonance imaging （MRI） target detection and magnetic hyperthermia.

Substrate temperature dependence of chemical state and magnetoresistance characteristics of Co–TiO2 nanocomposite films

Co−TiO2 nanocomposite films were prepared via magnetron sputtering at various substrate temperatures.The films comprise Co particles dispersed in an amorphous TiO2 matrix and exhibit coexisting ferromagnetic and superparamagnetic properties.When the substrate temperature increases from room temperature to 400℃,Co particles gradually grow,and the degree of Co oxidation significantly decreases.Consequently,the saturation magnetization increases from 0.13 to 0.43 T at the same Co content by increasing the substrate temperature from room temperature to 400℃.At a high substrate temperature,conductive pathways form among some of the clustered Co particles.Thus,resistivity rapidly declines from 1600 to 76μΩ·m.The magnetoresistive characteristic of Co−TiO2 films is achieved even at resistivity of as low as 76μΩ·m.These results reveal that the obtained nanocomposite films have low Co oxidation,high magnetization and magnetoresistance at room temperature.

Preparation and property characterization of PAA/Fe_(3)O_(4) nanocomposite

PAA/Fe_(3)O_(4) nanocomposites were prepared by mixing nano-Fe_(3)O_(4) and polyacrylic acid(PAA)ethanol solution and then evaporating the solvent.The materials were characterized by transmission electron microscope(TEM),Fourier transform infrared spectroscope(FTIR),thermogra-vimetry analysis(TGA),dynamic ultra-micro hardness tester(DUMHT)and superconducting quantum interference device(SQUID)magnetometer.Results showed that PAA coordi-nated with nano-Fe_(3)O_(4) to form a cross-linking structure.The presence of nano-Fe_(3)O_(4) enhanced the thermal stability of the nanocomposite.The elasticity and hardness of the nanocomposite increased,and the indentation depth reduced with the increase of Fe_(3)O_(4) content in the composites.The nanocomposites showed superparamagnetic properties at 300 K.

Enhanced Cryogenic Magnetocaloric Effect Induced by Small Size GdNi_5 Nanoparticles

GdNi5 nanoparticles and GdNis/Gd2O3 nanocapsules （with GdNi5 core and Gd2O3 shell） were prepared by arcdischarge technique under different hydrogen partial pressure. The GdNi5 nanoparticles show irregular spherical shape and have a size distribution of 10-50 nm with an average diameter of 15 nm. In comparison, the GdNi5/Gd2O3 nanocapsules present spherical morphology and show a size distribution of 10-100 nm with an average diameter of 60 nm. Under a magnetic field change of 50 kOe, the maximum magnetic entropy change of GdNi5 nanoparticles is 13.5 J/（kg K） at 5 K, while the corresponding value of the GdNis/Gd2O3 nanocapsuels is only 5.7 J/（kg K） at 31 K. The origin of the large magnetic entropy change of GdNi5 nanoparticles is ascribed to its high atomic moments and small anisotropy energy barrier induced by its small particle size.

Highly Ordered Superlattices from Self-assembly of Fe3O4 Nanocrystals

The nano materials often exhibit very interesting electrical, optical, magnetic, and chemical properties, which can not be achieved by their bulk counterparts. The development of uniform nanometer sized particles has been intensively pursued because of their technological and fundamental scientific importance. It is significant that nanostructured materials can be controllably assembled into the required geometry onto substrates, becoming the basis of the next generation of components and devices. The development of new methods and strategies for organizing the nanoparticle basic building blocks into the desired structures is required. Superlattices made from these building blocks give us the opportunity to study not only the properties of the individual building blocks, but also collective effects. The superparamagnetic iron oxide nanocrystals（NCs） have been used in the fields of bio-medicine, ferrofluids, refrigeration system, catalysis,

A new scale for optimized cryogenic magnetocaloric effect in ErAl_2@Al_2O_3 nanocapsules

The Er Al2@Al2O3 nanocapsules with Er Al2core and Al2O3 shell were synthesized by modified arc-charge technique.The typical core-shell structure of the nanocapsules was confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy.Transmission electron microscopy analysis shows the irregular sphere of the nanocapules with an average diameter of 26 nm.Magnetic investigation revealed the Curie temperature of Er Al2@Al2O3 nanocapsules at 20 K and the typical superparamagnetic behavior between blocking temperature and Curie temperature.Based on the blocking temperature and average diameter,the magnetocrystalline anisotropy constant of Er Al2@Al2O3nanocapsules was estimated to illustrate the magnetic contribution to the-SM.The large-SMof 14.25 J/（kg K）was obtained under 50 k Oe at 5 K.A vital parameter β was introduced in the present work to scale the optimized magnetic characteristics and the optimized mechanism was discussed in detail according to classical superparamagnetic theory.The results demonstrate that the optimal-SMwill be obtained when the magnetic parameter β is close to the theoretical coefficient.