Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials,...

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

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Sliding Friction-Physical Principles and Applications

The oxides of copper (CuxO) are fascinating materials due to their remarkable optical, electrical, thermal and magnetic properties. Nanostructuring of CuxO can further enhance the performance of this important functional material and provide it with unique properties that do not exist in its bulk form. Three distinctly different phases of CuxO, mainly CuO, Cu2O and Cu4O3, can be prepared by numerous synthesis techniques including, vapour deposition and liquid phase chemical methods. In this article, we present a review of nanostructured CuxO focusing on their material properties, methods of synthesis and an overview of various applications that have been associated with nanostructured CuxO.

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Nanostructured copper oxide semiconductors: a perspective on materials, synthesis methods and applications

Enzymes are highly efficient catalysts extensively employed in biotechnology. Among the many challenging aspects in this area, enzymes are yet difficult to obtain and purify, which makes them extremely expensive. Therefore, the industrial use of such expensive biocatalysts suffers from a critical point, which is the lack of efficient recovery processes. As a very promising strategy, superparamagnetic nanoparticles based on magnetite (Fe3O4) and maghemite (γ-Fe2O3) have been recently employed as supporting materials for enzymes, exhibiting striking characteristics, such as large surface area, mobility and high mass transference. More than that, they can be easily recovered by applying an external magnetic field. In addition to their excellent environmental compatibility, the use of such superparamagnetic nanoparticles represents an effective green chemistry approach, since it prolongs, through the successive recovery cycles, the useful lifetime of the biocatalyst. Several enzymes and biomolecules, including antibodies, albumin, α-chymotrypsin, aminopeptidase, acetylcholine esterase, amylase, amyloglucosidase, celullase, epoxide hydrolases, esterase, lipase, lysozyme, pectinases, phosphatase, pyruvate phosphate dikinase, trypsin, subtilisin, urease, chitosanase, haloalkane dehalogenase, RNA polymerase, lactate dehydrogenase, alcohol dehydrogenase, galactosidase, catalase, cholesterol oxidase, d -amino acid oxidase, cathecol dioxygenase, fructosyl amino acid oxidase, l -lactate dehydrogenase, xanthine oxidase, glucose oxidase, glucosidase, laccase, peroxidases, tyrosinase and so on, have been successfully immobilized onto magnetic nanoparticles, and the recent progress in this area is focused on this review.

Superparamagnetic nanoparticles as versatile carriers and supporting materials for enzymes

We report a crystallographic and magnetic characterization of the Sr2FeMnO6 novel polycrystalline complex manganite produced by the ceramic method. This material was mixed in volume percentages from 0% to 100% with the granular high temperature superconductor YBa2Cu3O7−δ to conform Sr2FeMnO6/YBa2Cu3O7−δ composites. Studies of chemical stability reveal that the Sr2FeMnO6 does not react with the YBa2Cu3O7−δ superconductor. X-ray results show an excellent coupling between the respective lattice parameters. DC susceptibility measurements indicate that the superconductivity of the YBa2Cu3O7−δ and the exotic magnetic properties of the Sr2FeMnO6 coexist up to 80% volume of this material in the composite. These characteristics permit to infer that these compounds would be utilized to the production of antiferromagnetic-superconductor multi-layer devices.

Coexistence of superconductivity and magnetism, crystallographic coupling and chemical stability in Sr2FeMnO6/YBa2Cu3O7−δ composites

The results of structure, superconductivity and normal state, i.e. above T c , magnetism of the CaLaBaCu 3− n Fe x O 7 superconductor, obtained using powder X-ray diffraction and a SQUID (superconducting quantum interface device) magnetometer have been presented. The critical temperature ( T c ) of the pristine sample determined from ac susceptibility measurements decreases with Fe concentration. The normal state high field (5 kOe) dc magnetism of these samples infers a nearly temperature independent and relatively small molar susceptibility for the x = 0.0 sample, while for the Fe doped samples the same follows a Curie-Weiss temperature dependence, in terms of a localized moment presumably on doped Fe ions. The effective paramagnetic moment on Fe in the doped samples appears to be less than known Fe 2+ /Fe 3+ moments. Namely it is 5.09, 4.53 2.79 and 3.37 μ B respectively for x = 0.03, 0.06, 0.12 and 0.24 samples. The reduced moment of Fe is probably due to the presence of crystal field effects in these systems, which has an increasing trend with an increase in Fe concentration.

Structure, superconductivity and normal state magnetism of CaLaBaCu3−xFexO7 superconductor, 0.0 ⩽ x ⩽ 0.24

This work presents some results of the synthesis and structural, microstructural, and magnetic characterization of fucan coated cobalt ferrite nanoparticles prepared by using a modified coprecipitation method. Aqueous suspensions of magnetic particles were prepared by coprecipitation of Fe(III) and Co(II) in the presence of NaOH, acid oleic and fucan polymer. The samples were characterized by X-ray diffraction (XRD), electron scanning microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), accelerated surface area, and porosimetry (ASAP/BET-Brunauer-Emmet-Teller) determination and magnetization measurements. Our results reveal that both uncoated and fucan polysaccharide coated CoFe2O4 nanoparticles were successfully obtained. The nanoparticles present sizes between 7 to 20 nm and saturation magnetization of the order of 40 emu/g. The nanoparticles thus obtained are suitable for future applications as a solid support for enzymes immobilization and other biotechnology applications.

Synthesis and Characterization of Fucan-Coated Cobalt Ferrite Nanoparticles

We have synthesized and studied the characteristics of Ba2HoNbO6 (BHNO) substrates for the fabrication of LaBaCaCu3O7-δ (LBCCO) superconducting films BHNO has an A2BB'O6 complex cubic perovskite structure with lattice constant a = 8, 439 A Energy-dispersive X-ray (EDX) analysis shows that BHNO is free from impurity traces and scanning electron micrographs reveal that it has uniform surface morphology and particle size distribution Based on the doubling of the ABO3 cubic perovskite unit cell, (1/2)a = 4, 220 A, BHNO has fairly good lattice matching (lattice mismatch ~ 9%) with LBCCO superconductors X-ray diffractometry, back-scattered scanning electron microscopy and magnetic measurements effectuated on BHNO/LBCCO composites show that BHNO is chemically and physically compatible and it could be used as a potential substrate material for the growth of LBCCO superconducting films

J. Albino Aguiar

Papers

Coexistence of superconductivity and magnetism, crystallographic coupling and chemical stability in Sr2FeMnO6/YBa2Cu3O7−δ composites

Structure, superconductivity and normal state magnetism of CaLaBaCu3−xFexO7 superconductor, 0.0 ⩽ x ⩽ 0.24

Synthesis and Characterization of Fucan-Coated Cobalt Ferrite Nanoparticles

SUBSTRATE CHARACTERISTICS OF Ba2HoNbO6 FOR THE FABRICATION OF LaBaCaCu3O7-δ SUPERCONDUCTING FILMS

Site-bond-correlated D-vector model on the Bethe lattice.