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Magnetic Fe 3 O 4 nanoparticles "decorated" by LAPONITE® nanodisks have been materialized utilizing the Schikorr reaction following a facile approach and tested as mediators of heat for localized magnetic hyperthermia (MH) and as magnetic resonance imaging (MRI) agents. The synthetic protocol involves the interaction between two layered inorganic compounds, ferrous hydroxide, Fe(OH) 2 , and the synthetic smectite LAPONITE® clay Na 0.7 + [(Si 8 Mg 5.5 Li 0.3 )O 20 (OH) 4 ] 0.7 - nanoparticles, which are well decorated by the diamagnetic clay nanodisks. The latter imparts high negative 3 O 4 nanoparticles, which are well decorated by the diamagnetic clay nanodisks. The latter imparts high negative ζ -potential values (up to -34.1 mV) to the particles, which provide stability against flocculation and precipitation, resulting in stable water dispersions. The obtained LAPONITE®-"decorated" Fe 3 O 4 nanohybrids were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, dynamic light scattering (DLS) and vibrating sample magnetometry (VSM) at room temperature, revealing superior magnetic hyperthermia performance with specific absorption rate (SAR) values reaching 540 W g Fe -1 (28 kA m -1 , 150 kHz) for the hybrid material with a magnetic loading of 50 wt% Fe 3 O 4 /LAPONITE®. Toxicity studies were also performed with human glioblastoma (GBM) cells and human foreskin fibroblasts (HFF), which show negligible to no toxicity. Furthermore, T 2 -weighted imaging, allowing for imaging of the magnetic nanoparticles.3 O 4 nanohybrids predominantly affected the transverse T 2 relaxation time of tissue water, which resulted in a signal drop on the MRI T 2 -weighted imaging, allowing for imaging of the magnetic nanoparticles.

By means of high-resolution ac calorimetry and polarizing optical microscopy, it is demonstrated that surface-functionalized spherical CdSSe nanoparticles induce a twist-grain boundary phase when dispersed in a chiral liquid crystal. These nanoparticles can effectively stabilize the one-dimensional lattice of screw dislocations, thus establishing the twist-grain boundary order between the cholesteric and the smectic-A phases. A Landau-de Gennes-Ginzburg model is used to analyze the impact of nanoparticles on widening the temperature range of molecular organizations possessing a lattice of screw dislocations. We show that in addition to the defect-core-replacement mechanism, the saddle-splay elasticity may also play a significant role.

In this paper, a general method for making nanoscale Au–Fe3O4 clusters in an oil-in-water emulsion is reported, which involves thermolytic decomposition of Fe(acac)3 and reduction of AuCl3 in a hot oleyl amine–oleic acid mixture. A detailed investigation by transmission electron microscopy (TEM), X-ray diffraction, UV-vis, and vibrating-sample magnetometry was done in order to study the morphology and properties of the hybrid nanoparticulate clusters (NPCs). The NPCs are all spherical and their building blocks are individual Au and Fe3O4 nanoparticles (NPs) with an average diameter of 9.6 and 7.1 nm, respectively. TEM images show that these clusters have a flower-like morphology with controllable size. It is found that the cetyltrimethylammonium bromide concentration, the time, and the temperature of reaction are three important parameters that significantly affect the shape, size, and magnetic properties of these clusters. Magnetic measurements reveal the superparamagnetic behavior of individual NPs of Fe3O4 with a blocking $T_{\mathrm {B}}= 80.2$ K. The blocking temperature is significantly shifted to higher temperatures in the case of the clusters. The Au–Fe3O4 NPCs show a plasmonic peak at 530 nm and have a much higher magnetization than the individual NPs, making them better suited for biomedical applications. [ABSTRACT FROM AUTHOR]

Metallic iron nanoparticles with a crystalline iron oxide shell were synthesized by the thermal decomposition of iron pentacarbonyl [Fe(CO)5] in octadecene in the presence of oleic acid and oleylamine. The effect of different synthetic parameters was investigated in details including the refluxing time and temperature, the injection temperature of iron precursor and the surfactant concentrations. The particles size can be tuned by controlling the injection temperature of iron precursor. Particle composition was adjusted by controlling the refluxing time. Both XRD diffraction and magnetic measurements indicated that these particles are very stable against oxidation which was further evidenced by microstructure analysis. [ABSTRACT FROM AUTHOR]

The stabilization of liquid-crystalline blue phases is recently attracting considerable interest because of the envisioned applications in fast optical displays and tunable photonic crystals. We report on the effect of surface-functionalized graphene nanosheets on the blue phase range of a chiral liquid crystal. Calorimetric and optical measurements, reproducible on heating and cooling, demonstrate that the resulting soft nanocomposite exhibits an increased blue phase temperature stability range for a minute concentration of dispersed graphene. The impact is stronger on the ordered, cubic structured blue phase I. These findings suggest that anisotropic nanoparticles may be of great usefulness for stabilizing blue phases. [ABSTRACT FROM AUTHOR]

The existence of an indirect magnetoelectricity in a soft composite material prepared as a mixture of magnetite ferromagnetic nanoparticles (NPs) and the ferroelectric liquid crystal (FLC) Felix 015/100 was verified by using a SQUID-based magnetometer. It was observed that the orientation of nanoparticles is directly coupled to the liquid crystal director field. Such a coupling allows the possibility of indirect coupling between the magnetic and ferroelectric order. This gifts the mixtures of FLC and magnetic nanoparticles (MNPs) with a great potential for soft indirect magnetoelectrics. [ABSTRACT FROM AUTHOR]

The impact of the surface–functionalised CdSe nanoparticles on various phase transitions of the two liquid crystals, 8CB and CE8, has been examined by means of high-resolution calorimetry. The addition of nanoparticles results in suppression of phase transitions and change in heat capacity anomalies. In contrast to silica aerosils CdSe nanoparticles do not form a rigid network. As a consequence, the impact of CdSe impurities on phase transitions resembles so called floppy phase regime, which exists at low concentrations of aerosils mixtures. [ABSTRACT FROM PUBLISHER]

Multiwall carbon nanotubes (MWNTs) decorated with CoO nanocrystals were synthesized by in-situ thermal decomposition of Co(acac)2 in oleyl amine under reflux conditions open in the air. The CoO/MWNTs composite material can be easily converted to metallic Co/MWNTs through annealing under reducing atmosphere (4% H2) at 500°C without any significant sintering effect. The composite materials characterized by X-ray diffraction, transmission electron microscopy, and Nuclear Magnetic Resonance (NMR) spectroscopy. The structural and morphological characterization shows that the CoO has cubic face (fcc) and the particles deposited uniformly on the external surface of the carbon nanotubes. In the annealed materials, the NMR shows that the fcc and hcp metallic Co phases coexist with a significant percentage of stacking faults. The magnetic measurements indicated that the CoO/MWNTs composite is largely composed of CoO nanoparticles with uncompensated surface spins. The fluctuations of spins persist in partially reduced CoO grains as shown by nuclear spin-lattice relaxation measurements. [ABSTRACT FROM AUTHOR]

Facile methods for the selective preparation of capped iron oxide nanoparticles (γ-Fe2O3, Fe3O4) are described. The magnetic oxides are obtained via oxidative transformation of an iron hydroxide gel using H2O2 or (NH4)2S2O8 solutions as oxidants. Capping with oleic or other aliphatic acids is established simultaneously in one step by adding a toluene solution of the capping agent and refluxing the resulting biphase system. The method is simple, soft and affords nanoparticles of γ-Fe2O3 or Fe3O4 of controlled size depending on the reaction conditions. The capped nanoparticles are readily soluble in organic or aqueous media according to the nature of the sheath surrounding the surface of the particles, providing stable and high concentration ferrofluids. [ABSTRACT FROM AUTHOR]

Nanoparticulate FeCo alloys have been synthesized by Fe(CO)5 and Co2(CO)8 thermal decomposition in paraffin oil in the presence of oleic acid and oleyl amine. The crystal structure and morphology of the nanoparticles were confirmed by powder x-ray diffraction and transmission electron microscopy. The size and crystallinity of the particles was found to depend on the reaction conditions such as the precursors concentration, reaction time, and carbonyls injection temperature. Also the Fe/Co ratio can be easily controlled by controlling the Fe and Co carbonyls ratio. The as-made nanoparticles were annealed at 500 °C under CH4 stream in order to be protected from future oxidation. This treatment leads to the formation of a graphitic shell around the particles which also protects them from sintering. Additionally, these particles can be functionalized with 1-pyrenebutiric acid in order to be soluble in various solvents. [ABSTRACT FROM AUTHOR]

Abstract: FePt is a very interesting magnetic material and many attempts have been made towards the lowering of its ordering temperature. Addition of Au and Ag seems to be a satisfying solution, since it can reduce the annealing temperature by 100–150°C. In the present work, FePtAu and FePtAg nanoparticles have been synthesized via a modification of the polyol method in different compositions. The ideal percentage of the third metal was chosen in order to study its effect on the transformation to the phase. Some attempts have been made to study the ordering kinetics and the role of the third metal. [Copyright &y& Elsevier]