Procedimiento para modular las propiedades eléctricas de óxidos con estructura tipo perovskita derivados del niobato de sodio mediante la creación de vacantes catiónicas

Procedimiento para modular las propiedades eléctricas de óxidos con estructura tipo perovskita derivados del niobato de sodio mediante la creación de vacantes catiónicas. La presente invención se refiere a un procedimiento para modificar controladamente las propiedades eléctricas del óxido NaNbO3 mediante la creación de vacantes catiónicas en la subred A de la estructura tipo perovskita. La introducción progresiva de vacantes en la subred A al dopar con un ión alcalinotérreo como por ejemplo Sr2+ o con un ión de tierra rara como por ejemplo La3+ permite la estabilización de un material ferroeléctrico, y el cambio continuo de comportamiento ferroeléctrico a ferroeléctrico-relaxor característico de las disoluciones sólidas tipo perovskita sin plomo. La presente invención incluye el procedimiento para la obtención de los óxidos que, en función de sus propiedades, pueden ser usados en dispositivos electrónicos como materiales piezoeléctricos y piroeléctricos en sensores y actuadores.Universidad Complutense de Madrid, Consejo Superior de Investigaciones Científicas (España)A1 Solicitud de patentes con informe sobre el estado de la técnic

Morphology and magnetic properties of W-capped Co nanoparticles

3 páginas, 3 figuras, 2 tablas.-- et al.Co–W nanoparticles formed by sequential sputtering of Co on amorphous alumina substrate and subsequent W capping are studied by high resolution and by scanning transmission electron microscopies, and by superconducting quantum interference device magnetometry. The analysis is focused on W nominal thickness dependence. Results suggest the formation of amorphous Co–W alloy nanoparticles, whose magnetic moment per Co atom is systematically reduced as the nominal thickness of W capping layer increases. The Co–W nanoparticles show superparamagnetic behavior. The activation energy for moment reversal and the effective anisotropy are obtained.The financial support of MAT08/1077 is acknowledged. A. I. Figueroa acknowledges a JAE-Predoc grant.Peer reviewe

Hybrid Enzyme-Polymeric Capsules/Mesoporous Silica Nanodevice for In Situ Cytotoxic Agent Generation

A novel nanocarrier based on functionalized mesoporous silica nanoparticles able to transport a non-toxic pro-drug and the enzyme responsible for its activation is presented. This nanodevice is able to generate in situ cytotoxic species once accumulated in the tumoral cell. Enzymes are sensitive macromolecules which can suffer denaturalization in biological media due to the presence of proteases or other aggressive agents. Moreover, the direct attachment of enzymes to the silica surface can reduce their activity by conformational changes or active site blockage. For these reasons, in order to create a robust system able to work in living organisms, the enzymes are previously coated with a protective polymeric shell which allows the attachment on the silica surface preserving their activity. The efficacy of this hybrid nanodevice for antitumoral purposes is tested against several human tumoral cells as neuroblastoma and leukemia showing significant efficacy. It converts this device in a promising candidate for further in vivo studies for oncology therapy

Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

Under the terms of the Creative Commons Attribution license.-- et al.Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by COPD alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3d-4d bands associated to the Co and Pd chemical arrangement in a L10 structure type.The financial support of the Spanish Ministerio de Economía MAT2014-53921-R and Aragonese DGA-IMANA E34 projects is acknowledged.Peer Reviewe

Structural and magnetic properties of granular CoPd multilayers

Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk.The financial support of the Spanish MINECO MAT2011-23791, MAT2014-53921-R and Aragonese DGA-IMANA E34 projects is acknowledged.Peer Reviewe

Magnetism and structure of amorphous Co-W alloyed nanoparticles

Resumen del póster presentado al American Physical Society March Meeting celebrado en Boston (US) del 27 de febrero al 2 de marzo de 2012.-- et al.W-capped Co nanoparticles dispersed in an alumina matrix are studied by means of high-resolution transmission electron microscopy, extended x-ray absorption fine structure, SQUID-based magnetic measurements, ac magnetic susceptibility, and x-ray magnetic circular dichroism. Results show the formation of amorphous Co-W alloy nanoparticles, the magnetic properties of which are modified by the amount of W or Co present in the samples. The average Co magnetic moment depends on the number of W atoms surrounding it. Co-W particles show superparamagnetic behavior and are described as an array of noninteracting particles with random anisotropy axes and an average moment per particle proportional to the particle volume and to the average Co moment for each alloy composition. Values of the magnetic anisotropy constant of the particles are on the order of 10 6 erg/cm 3 , higher than that of bulk Co. Evidence of short-range ordering within each amorphous particle is found that provides insight of the origin of their magnetic anisotropy.Peer reviewe

Bone Mass and the CAG and GGN Androgen Receptor Polymorphisms in Young Men

BACKGROUND: To determine whether androgen receptor (AR) CAG (polyglutamine) and GGN (polyglycine) polymorphisms influence bone mineral density (BMD), osteocalcin and free serum testosterone concentration in young men. METHODOLOGY/PRINCIPAL FINDINGS: Whole body, lumbar spine and femoral bone mineral content (BMC) and BMD, Dual X-ray Absorptiometry (DXA), AR repeat polymorphisms (PCR), osteocalcin and free testosterone (ELISA) were determined in 282 healthy men (28.6+/-7.6 years). Individuals were grouped as CAG short (CAG(S)) if harboring repeat lengths of < or = 21 or CAG long (CAG(L)) if CAG > 21, and GGN was considered short (GGN(S)) or long (GGN(L)) if GGN < or = 23 or > 23. There was an inverse association between logarithm of CAG and GGN length and Ward's Triangle BMC (r = -0.15 and -0.15, P<0.05, age and height adjusted). No associations between CAG or GGN repeat length and regional BMC or BMD were observed after adjusting for age. Whole body and regional BMC and BMD values were similar in men harboring CAG(S), CAG(L), GGN(S) or GGN(L) AR repeat polymorphisms. Men harboring the combination CAG(L)+GGN(L) had 6.3 and 4.4% higher lumbar spine BMC and BMD than men with the haplotype CAG(S)+GGN(S) (both P<0.05). Femoral neck BMD was 4.8% higher in the CAG(S)+GGN(S) compared with the CAG(L)+GGN(S) men (P<0.05). CAG(S), CAG(L), GGN(S), GGN(L) men had similar osteocalcin concentration as well as the four CAG-GGN haplotypes studied. CONCLUSION: AR polymorphisms have an influence on BMC and BMD in healthy adult humans, which cannot be explained through effects in osteoblastic activity

Evidence of intrinsic magnetism in capped ZnO nanoparticles

We present here direct experimental evidence of the magnetic polarization of Zn atoms in ZnO nanoparticles capped with different materials by means of x-ray magnetic circular dichroism (XMCD). Our results demonstrate that the magnetism in this material is intrinsic and relays in the ZnO conduction band. The analysis of both x-ray absorption spectroscopy and XMCD signals points out the formation of a well-defined interface between ZnO and the capping molecule in which the exotic magnetism arises at the hybridized band formed among Zn and the bonding atom of the molecule. The magnetic properties of these systems should critically depend on the details of this interface which may offer a new insight into the different observations for seemingly identical materials