Layered hydroxide salts: Synthesis, properties and potential applications

Surface-enhanced Raman scattering (SERS)-active nanomaterials have extended from noble metals and transition metals to semiconductor materials, since the first discovery of SERS in the mid-1970s. In comparison with metal substrates and transition metals, semiconductor materials have additional optical and electrical properties besides SERS enhancement ability, which enable them to display remarkable charge-transfer enhancement and catalytic ability. Moreover, their superior biocompatibility allows these nanomaterials to have great potential applications in bioscience. Herein we highlight the fast growing research field focusing on SERS-active semiconductor nanomaterials and semiconductor-other material heterostructures developed in our group as well as in other related research studies. The material size, morphology and assembly-dependent SERS enhancement have been discussed in detail. Furthermore, a variety of promising applications of semiconductor-enhanced Raman scattering in photoelectric characterization, redox biochemistry, sensing, and the catalytic degradation of organic pollutants are introduced.

Semiconductor-enhanced Raman scattering: active nanomaterials and applications.

Nickel nanoparticles obtained by a modified polyol process: synthesis, characterization, and magnetic properties.

Kinetics of thermite reaction in Al-Fe2O3 system

Current trends in the miniaturization of microwave devices have prompted considerable interest in studying electromagnetic transport in nanoscale systems. Understanding the effect of physical structure and the role of interfaces is critical for gaining insight into the electromagnetic and magnetic properties of nanostructures and their behavior in microwave devices such as circulators and isolators. Previously, we have described the electromagnetic characteristics at microwave frequencies and the static magnetic properties of γ–Fe2O3∕ZnO micro- and nanocomposites fabricated via powder processing. Here we present systematic effective permeability measurements of magnetically structured granular systems composed of magnetic grains embedded in a nonmagnetic matrix using broadband microwave spectroscopy. Using the transmission∕reflection waveguide method, the effective complex permeability was measured in the frequency range of 0.01–10GHz. The results were compared for composites consisting of micrometer-size...

Effective magnetic permeability of Ni and Co micro- and nanoparticles embedded in a ZnO matrix

The structural and magnetic properties of powdered composites consisting of nanosized Fe and Co particles embedded in alumina grains have been investigated. The composites were synthesized by a novel and simple method using co-precipitation from a hybrid gel solution containing layered double hydroxide and aluminium hydroxide. After a vacuum annealing procedure, the Fe composites have a negligible number of Fe+3 ions and a high concentration of crystalline α-Fe nanoparticles having truncated polyhedron shapes with an average diameter of 20 nm that are physically well separated from each other. Magnetization measurements as a function of temperature revealed a superparamagnetic-like behavior characteristic of an assembly of fine particles. A spurious ferromagnetism related to surface interaction between magnetic particles from different powder grains and the formation mechanism of the composites are also discussed.

Structural and magnetic properties of Fe and Co nanoparticles embedded in powdered Al2O3.

Potentiostatic electrodeposition methods have been used to grow polycrystalline ZnSe and ZnSe-Fe granular thin films on stainless steel substrates from aqueous solutions. These films were characterized by x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy and Raman spectroscopy.

http://www.scielo.br/pdf/bjp/v32n2a/a38v322a.pdf

Structural and chemical properties of ZnSe-Fe electrodeposited granular films

We provide evidence for the existence of an antiferromagnetic coupling between iron epilayers separated by a wedge-like ZnSe crystalline semiconductor by magnetometric and ferromagnetic resonance experiments. The coupling strength of 46 mu J m(-2) for t(ZnSe) = 25 angstrom is strongly reduced as the barrier thickness is increased. The coupling increases linearly with temperature from 5 to 300 K, with a 5.5 x 10(-9) J m(-2) K-1 rate. Thermally induced effective exchange coupling mediated by spin-dependent tunnelling of electrons via localized mid-gap defect states in the ZnSe spacer layer appears to be the most plausible mechanism to induce the antiferromagnetic coupling.

Thermal enhancement of the antiferromagnetic exchange coupling between Fe epilayers separated by a crystalline ZnSe spacer

Micro-Raman spectroscopy has been carried out on hybrid systems consisting of magnetic Fe and Co nanoclusters immersed in a semiconductor ZnSe host. The experimental results clearly reveal surface-enhanced Raman scattering for the ZnSe matrix phonon modes. The intensity enhancement correlates with the Fe content and sample morphology. Enhancement factors of up to about one order were achieved, as compared to the pure ZnSe sample.

Surface-enhanced Raman scattering for magnetic semiconductor ZnSe:Fe hybrid structures

ZnSe-Fe and ZnSe-Co granular films have been successfully obtained by electrodeposition under potentiostatic conditions. Cyclic voltammograms of the solutions containing all precursors of the systems are consistent with anomalous codeposition of the zinc and iron-group metals. Electron microscopy analyses reveal a network of Fe and Co particles dispersed in polycrystalline ZnSe without evidence of intermediate compound formation.

http://esl.ecsdl.org/content/5/1/C11.full.pdf

D. H. Mosca

Papers

Structural and magnetic properties of Fe and Co nanoparticles embedded in powdered Al2O3.

Structural and chemical properties of ZnSe-Fe electrodeposited granular films

Thermal enhancement of the antiferromagnetic exchange coupling between Fe epilayers separated by a crystalline ZnSe spacer

Surface-enhanced Raman scattering for magnetic semiconductor ZnSe:Fe hybrid structures

Electrodeposition of ZnSe-Fe and ZnSe-Co Granular Films