EuS Nanocrystals Research Articles

Self-aggregation of magnetic semiconductor EuS nanocrystals

Controlled formation of aggregates having organized structure of cube-shaped EuS nanocrystals is reported. The EuS aggregates in liquid media (methanol) were obtained by means of van der Waals interaction between EuS nanocrystals. The packing structure of the EuS aggregates is characterized with transmission electron microscopy (TEM) and small angle X-ray scattering measurements (SAXS). TEM image indicates the EuS nanocrystals form self-aggregated 2D orthogonal lattice structure. The diffraction peak of (111) of SAXS profile shows that the cube-shaped EuS form 3D cubic superlattice. We successfully demonstrated that the aggregates of cube-shaped EuS nanocrystals formed cubic stacking structure.

Electrophoretic Deposition of Star Polymer-Europium Chalcogenide Nanocomposite Films

The electrophoretic deposition of polystyrene/divinylbenzene (PS/DVB) star polymer-europium sulphide (EuS) nanocomposite films from a colloidal suspension is reported. Liquid suspension, containing both the PS/DVB star polymer and EuS nanocrystals were prepared by separately injecting dichloromethane (DCM) based solutions of EuS nanocrystals and of the star polymers, respectively, into a stratified liquid combination of hexane and DCM. Scanning electron microscopy illustrates images of the dependence of surface morphology on nanocrystal concentration of the PS/DVB-EuS star polymer film. These polymer-encased nanocrystal films may be a more practical option for the fabrication of magneto-optical thin film devices, such as optical switches, optical isolators, and optical memories.

Enhanced Faraday rotation of cube-shaped EuS nanocrystals with a magnetic coercive field

Enhanced Faraday effect of cube-shaped EuS nanocrystals (average crystal size = 12 nm) with a coercive field is demonstrated for the fast time. The coercive field and the remanent magnetization of cube-shaped EuS nanocrystals were found to be 0.011 T and 0.05 μB, respectively, using a SQUID (superconducting quantum interface device). Consideration of the volume percentages of cube-shaped EuS nanocrystals in polymer thin film gives a large Verdet constant (0.071 deg/cm Oe), which is 3.7 times larger than that of the polymer thin films containing sphere-shaped EuS nanocrystals (average crystal size = 14 nm). Cube-shaped EuS nanocrystals with a coercive field are expected to be used as active magneto-optical materials.

Demonstration of Bulk Semiconductor Optical Properties in Processable Ag2S and EuS Nanocrystalline Systems

EuS and Ag2S colloidal semiconductor nanocrystals are observed to display optical properties characteristic of the corresponding bulk materials, yet have the desirable processing properties of colloidal nanocrystals. We envision that bulk nanoparticles will play a complementary role to quantum-confined structures as another building block for the development of new technologies.

Polymer encapsulation effects on the magnetism of EuS nanocrystals

Surface mediated phenomena are important in controlling the magnetism of nanocrystals. Here, we provide a versatile chemical method which allows the formation of EuS nanocrystals encapsulated in poly(styrene) (PS). These materials are the first example of a polymer based EuS nanocomposite prepared in situ. Besides their practical interest, these materials are of general relevance because they allow fundamental knowledge on the magnetism of EuS, which is commonly used as a model of an insulating ferromagnet, to be acquired. Comparatively to the starting powders of EuS nanocrystals (8 nm), in the final nanocomposites there is a decrease of the blocking temperature TB and a change in the shape of the field-cooled susceptibility curve, indicating that the intensity of dipolar interactions decreases when the nanoparticles are incorporated into PS. Differences in the magnetic properties of the EuS nanocrystals and the EuS/PS nanocomposites are also due to the appearance of a peak in the susceptibility at 60 K, in the latter sample, ascribed to surface phenomena occurring in EuS nanocrystals dispersed in the polymer matrix.

The first observation of the magnetic circular dichroism in EuS nanocrystals

EuS nanocrystals were prepared by the liquid ammonia method. The size effect of EuS nanocrystals was observed in the magnetic measurements, the absorption spectra and the MCD spectra.

Single-Source Precursor Route for the Synthesis of EuS Nanocrystals

A single-source precursor synthetic route for the preparation of colloidal EuS nanocrystals is reported. By varying the decomposition conditions of the lanthanide complex, cube-, sphere-, or polygon-shaped nanocrystals with good colloidal stability are prepared. Size control is not achieved. It is demonstrated that chelating ligands incorporated into the precursor, for example, 1,10-phenanthroline and 2,2‘-bipyridine, are integrated, together with the stabilizing ligands trioctylphosphine and oleylamine, onto the nanocrystal surface.

A Novel Method for Synthesizing EuS Nanocrystals from a Single‐Source Precursor under White LED Irradiation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Magnetic properties of EuS nanoparticles synthesized by thermal decomposition of molecular precursors

Europium(II) sulfide nanoparticles with an average particle size of 5.5 nm and a narrow size distribution were synthesized by the direct and facile thermal decomposition of a molecular precursor Eu(Phen)(Ddtc)3 (Phen = 1,10-phenanthroline, Ddtc = diethyldithiocarbamate) at the relatively low temperature of 200 °C. Compared with EuS samples of 50–120 nm in size, which show bulk ferromagnetic ordering, the EuS nanocrystals of 5–6 nm in size show a cluster glass-like behavior. Moreover, a quasi-ferrimagnetic behavior was observed in the smallest EuS sample upon oxidation of the surface.

A novel method for synthesizing EuS nanocrystals from a single-source precursor under white LED irradiation

EuS nanocrystals, with an average diameter of 9 nm, have been synthesized by the photolysis of Na[Eu(S2CEt2)4].3.5H2O; the first quantum confined particles of EuS to be reported.

Size Selective Synthesis of Surface-modified EuS Nanocrystals Using Pyridine and Their Physical Properties

Abstract The particle size of EuS nanocrystals was gradually increased by addition of pyridine to the reaction mixture of europium metal and hydrogen sulfide in liquid ammonia. The size effect of EuS nanocrystals was found in the absorption spectra for the first time. The size effect on the magnetic properties of the nanocrystals was also observed.

Liquid‐Phase Synthesis of EuS Nanocrystals and Their Physical Properties.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Liquid-Phase Synthesis of EuS Nanocrystals and Their Physical Properties

The first EuS nanocrystals were prepared by the reaction of europium metal and H2S in liquid ammonia. X-ray diffraction (XRD) patterns and TEM images supported the formation of nanoscaled EuS crystals with average size of 20.4 nm. The nanocrystals showed blue shift compared with previously reported EuS films. The Curie point of EuS nanocrystals (16.6 K) was the same as that of the corresponding bulk compound, but a decreasing of magnetic moment was found because of the specific surface condition of the nanocrystals.