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2010


Gallium Arsenide Infiltration of Nanoporous Multi layers: A Route to High-Dielectric-Contrast One-Dimensional Photonic Crystals


Sanchez-Sobrado, O; Thomas, K; Povey, I; Pemble, ME; Miguez, H
Small, 6 (2010) 1283-1287
Materiales Ópticos Multifuncionales

ABSTRACT

Periodic multilayers of wide photonic bandgap and high reflectance in the visible and near infrared regions are fabricated. Optical properties show that reflectance intensities close to 90% are reached for stacks of only six layers, as well as gap-to-midgap ratios of 50%. The optical response of the hybrid ensemble can be accurately tuned through the number of infiltration cycles performed.


Junio, 2010 | DOI: 10.1002/smll.200902190

Environmentally responsive nanoparticle-based luminescent optical resonators


Sanchez-Sobrado, O; Calvo, ME; Nunez, N; Ocana, M; Lozano, G; Miguez, H
Nanoscale, 2 (2010) 936-941
Materiales Coloidales, Materiales Ópticos Multifuncionales

ABSTRACT

In this work, we demonstrate that optical resonators built using all-nanoparticle-based porous building blocks provide a responsive multifunctional matrix, totally different emission spectra being attained from the same embedded luminescent nanophosphors under varying environmental conditions. We show a clear correlation between modifications in the ambient surroundings, the induced changes of the resonant modes, and the resulting variations in the emission response. The method is versatile and allows nanophosphors of arbitrary shape to be integrated in the cavity. By precise control of the spectral features of the optical resonances, luminescence is strongly modulated in selected and tuneable wavelength ranges. Applications in the fields of sensing and detection are foreseen for these materials.


Junio, 2010 | DOI: 10.1039/b9nr00338j

Murillo's paintings revealed by spectroscopic techniques and dedicated laboratory-made micro X-ray diffraction


Duran, A; Siguenza, MB; Franquelo, ML; de Haro, MCJ; Justo, A; Perez-Rodriguez, JL
Analytica Chimica Acta, 671 (2010) 1-8

ABSTRACT

This paper describes one of the first case studies using micro-diffraction laboratory-made systems to analyse painting cross-sections. Pigments, such as lead white, vermilion, red ochre, red lac, lapis lazuli, smalt, lead tin yellow type I, massicot, ivory black, lamp black and malachite, were detected in cross-sections prepared from six Bartolome Esteban Murillo paintings by micro-Raman and micro-XRD combined with complementary techniques (optical microscopy, SEM-EDS, and FT-IR). The use of micro-XRD was necessary due to the poor results obtained with conventional XRD. In some cases, pigment identification was only possible by combining results from the different analytical techniques utilised in this study.


Junio, 2010 | DOI: 10.1016/j.aca.2010.05.004

Microstructural characterization of ceramic-intermetallic composites using TEM related techniques


Sayagues, MJ; Aviles, MA; Cordoba, JM; Alcala, MD; Gotor, FJ
Journal of the European Ceramic Society, 30 (2010) 1765-1774
Reactividad de Sólidos

ABSTRACT

TiCxVy/Ni and TiCxNy/Ti-Co composites formed by ceramic and intermetallic binder phases were produced by pressureless sintering at 1400 degrees C from powders synthesized by a mechanically induced self-sustaining reaction (MSR) process. Four different composites were characterized using high-resolution electron microscopic techniques, in both scanning (SEM, HRSEM) and transmission (TEM, HRTEM, ED, EDS and EELS) modes and using an energy filtered technique (EFTEM) associated with electron energy loss spectroscopy (EELS). The microcharacterization showed that the ceramic phase with an fcc-cubic structure displayed a short-range order in many crystals detected by diffuse scattering in the ED patterns. This was possibly due to a sequence of C, N, and vacancies of both atoms along certain directions in the structure. On the other hand, even though the binder phase was introduced as metal in the reaction process, it was formed by Ni-Ti or Co-Ti known intermetallic compounds (NiTi2, Ni3Ti, and Co3Ti). An unknown Ni-Ti intermetallic structure with a Ni:Ti ratio close to 2:1 was only found in one of the synthesized composites and displayed a cubic structure with a lattice parameter, a, of about 8.7 angstrom.


Junio, 2010 | DOI: 10.1016/j.jeurceramsoc.2010.01.039

Permanent magnetism in phosphine- and chlorine-capped gold: from clusters to nanoparticles


Munoz-Marquez, MA; Guerrero, E; Fernandez, A; Crespo, P; Hernando, A; Lucena, R; Conesa, JC
Journal of Nanoparticle Research, 12 (2010) 1307-1318
Materiales Nanoestructurados y Microestructura

ABSTRACT

Magnetometry results have shown that gold NPs (similar to 2 nm in size) protected with phosphine and chlorine ligands exhibit permanent magnetism. When the NPs size decreases down to the subnanometric size range, e.g. undecagold atom clusters, the permanent magnetism disappears. The near edge structure of the X-ray absorption spectroscopy data points out that charge transfer between gold and the capping system occurs in both cases. These results strongly suggest that nearly metallic Au bonds are also required for the induction of a magnetic response. Electron paramagnetic resonance observations indicate that the contribution to magnetism from eventual iron impurities can be disregarded.


Mayo, 2010 | DOI: 10.1007/s11051-010-9862-0

Identification of cellulose fibres belonging to Spanish cultural heritage using synchrotron high resolution X-ray diffraction


Herrera, LK; Justo, A; Duran, A; de Haro, MCJ; Franquelo, M; Rodriguez, JLP
Applied Physics A-Materials Science & Processing, 99 (2010) 391-398

ABSTRACT

A complete characterisation of fibres used in Spanish artwork is necessary to provide a complete knowledge of these natural fibres and their stage of degradation. Textile samples employed as painting supports on canvas and one sample of unprocessed plant material were chosen for this study. All the samples were investigated by synchrotron radiation X-ray diffraction (SR-XRD). Flax and cotton have the Cellulose I structure. The values of the crystalline index (CI) were calculated for both types of fibres. The structure of Cellulose IV was associated with the unprocessed plant material. The information obtained by SR-XRD was confirmed by laboratory techniques including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).


Mayo, 2010 | DOI: 10.1007/s00339-010-5626-z

On the microstructure of single wall carbon nanotubes reinforced ceramic matrix composites


Zapata-Solvas, E; Gomez-Garcia, D; Dominguez-Rodriguez, A
Journal of Materials Science, 45 (2010) 2258-2263
Propiedades Mecánicas de Sólidos

ABSTRACT

A microstructural modelling of the microstructure in single wall carbon nanotubes reinforced alumina ceramics has been developed. The model accounts for the main microstructural features, being quite useful to describe the carbon nanotube distribution along the ceramic matrix. The microstructural analysis derived from this model is found to give a deeper insight into the high-temperature creep of these composites.


Mayo, 2010 | DOI: 10.1007/s10853-009-4126-z

The Effect of Water on Particle Size, Porosity and the Rate of Drug Release From Implanted Titania Reservoirs


Lopez, T; Ortiz, E; Alexander-Katz, R; Odriozola, JA; Quintana, P; Gonzalez, RD; Lottici, PP; Marino, LG
Journal of Biomedical Materials Research Part-B Applied Biomaterials, 93B (2010) 401-406
Química de Superficies y Catálisis

ABSTRACT

The implantation of controlled drug release devices represents a new strategy in the treatment of neurodegenerative disorders Sol-gel titania implants filled with valproic acid, have been used for this purpose to treat induced epilepsy in rats The kinetics of the drug release depend on. (a) porosity, (b) chemical interactions between valproic acid and surface hydroxyl groups of titania, (c) particle size, and (d) particle size agglomerates The concentration of water used in the hydrolysis reaction is an important variable in the degree of porosity, hydroxylation, and structural defects of the nanostructured titanium oxide reservoir The titanium n-butoxide/water ratio was systematically varied during the sol-gel synthesis, while maintaining the amount of valproic acid constant. Characterization studies were performed using DTA-TGA, FTIR, Raman, TEM, SEM, BET, and in vitro release kinetic measurements The particle agglomerate size and porosity were found to depend on the amount of water used in the sol-gel reactio.


Mayo, 2010 | DOI: 10.1002/jbm.b.31595

SiOxNy thin films with variable refraction index: Microstructural, chemical and mechanical properties


Godinho, V; de Haro, MCJ; Garcia-Lopez, J; Goossens, V; Terryn, H; Delplancke-Ogletree, MP; Fernandez, A
Applied Surface Science, 256 (2010) 4548-4553
Materiales Nanoestructurados y Microestructura

ABSTRACT

In this work amorphous silicon oxynitride films with similar composition (ca. Si0.40N0.45O0.10) were deposited by reactive magnetron sputtering from a pure Si target under different N-2-Ar mixtures. Rutherford backscattering (RBS) studies revealed that the coatings presented similar composition but different density. The mechanical properties evaluated by nanoindentation show also a dependence on the deposition conditions that does not correlate with a change in composition. An increase in nitrogen content in the gas phase results in a decrease of hardness and Young's modulus. The microstructural study by high resolution scanning electron microscopy (SEM-FEG) on non-metalized samples allowed the detection of a close porosity in the form of nano-voids (3-15 nm in size), particularly in the coatings prepared under pure N-2 gas. It has been shown how the presence of the close porosity allows tuning the refraction index of the films in a wide range of values without modifying significantly the chemical, thermal and mechanical stability of the film.


Mayo, 2010 | DOI: 10.1016/j.apsusc.2010.02.045

A new model for the kinetic analysis of thermal degradation of polymers driven by random scission


Sanchez-Jimenez, PE; Perez-Maqueda, LA; Perejon, A; Criado, JM
Polymer Degradation and Stability, 95 (2010) 733-739
Reactividad de Sólidos

ABSTRACT

In this paper, a series of f(alpha) kinetic equations able to describe the random scission degradation of polymers is formulated in such a way that the reaction rate of the thermal degradation of polymers that go through a random scission mechanism can be directly related to the reacted fraction. The proposed equations are validated by a study of the thermal degradation of poly(butylene terephthalate) (PBT). The combined kinetic analysis of thermal degradation curves of this polymer obtained under different thermal pathways have shown that the proposed equation fits all these curves while other conventional models used in literature do not.


Mayo, 2010 | DOI: 10.1016/j.polymdegradstab.2010.02.017

Excitation transfer mechanism along the visible to the Near-IR in rhodamine J-heteroaggregates


Sanchez-Valencia, JR; Toudert, J; Gonzalez-Garcia, L; Gonzalez-Elipe, AR; Barranco, A
Chemical Communications, 46 (2010) 4372-4374
Nanotecnología en Superficies y Plasma

ABSTRACT

An enhanced fluorescent emission of the dye Rhodamine 800 in the Near-IR is observed in the presence of other xanthene dye molecules (RhX) when they are hosted in different matrices due to the formation of a new type of fluorescent J-heteroaggregates.

This enhanced emission of the acceptor occurs despite the low spectral overlapping and the low quantum yield of Rh800.


Mayo, 2010 | DOI: 10.1039/c0cc00087f

N- and/or W-(co)doped TiO2-anatase catalysts: Effect of the calcination treatment on photoactivity


Kubacka, A; Colon, G; Fernandez-Garcia, M
Applied Catalysis B-Environmental, 95 (2010) 238-244
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

A series of nanosized W,N-codoped and single-doped N- and W-anatase-TiO2 catalysts have been prepared by a microemulsion method and calcined at different temperatures. The activity in the sunlight selective photo-oxidation of toluene and styrene has been correlated with structural, electronic, and surface examinations of the catalysts done with the help of XRD-Rietveld, N-2 physisorption, X-ray photoelectron, infrared, electron paramagnetic resonance (EPR) and UV-vis spectroscopies. Irrespective of the reaction, W,N-codoped nanocatalysts showed an enhanced photoactivity with respect to bare anatase and single-doped N-TiO2 and W-TiO2 materials. A strong W-N synergistic interaction appears to play a decisive role in driving the excellent photoactivity performance of W,N-codoped materials by affecting (i) electronic properties, particularly maximizing the anatase band gap decrease and enhancing the subsequent visible light photon absorption, and (ii) surface properties, in turn related to the formation of OH radicals upon light excitation. The maximum photoactivity is reached by calcination at 450 degrees C and is concomitantly observed with a near complete selectivity to partial oxidation products. Higher calcination temperatures yielded solids with significantly inferior photocatalytic performance. The properties of the W-N interaction are discussed as a function of the calcination temperature.


Abril, 2010 | DOI: 10.1016/j.apcatb.2009.12.028

Gas phase photocatalytic oxidation of toluene using highly active Pt doped TiO2


Colon, G; Maicu, M; Hidalgo, MC; Navio, JA; Kubacka, A; Fernandez-Garcia, M
Journal of Molecular Catalysis A-Chemical, 320 (2010) 14-18
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

Platinum doped TiO2 materials were studied for the gas phase photocatalytic degradation of toluene. Platinum deposition was achieved by photodeposition method over TiO2 prepared by means of a sol-gel route. The effect of sulphuric acid pretreatment on the further platinisation process has been extensively studied. From the wide structural and surface analysis of the catalysts an interesting synergetic effect has been demonstrated. The previous sulphate treatment over TiO2 leads to improved dispersion of the Pt which presents a lower aggregation and homogeneous cluster size. This fact, together with the adequate control of anatase structural and surface parameter due to the sulphate treatment, renders a good photocatalytic performance for toluene oxidation reaction. The highest reaction rates and CO2 selectivities have been obtained for Pt-S-TiO2 samples.


Abril, 2010 | DOI: 10.1016/j.molcata.2009.12.009

Non-destructive depth compositional profiles by XPS peak-shape analysis


Lopez-Santos, MC; Yubero, F; Espinos, JP; Gonzalez-Elipe, AR
Analytical and Bioanalytical Chemistry, 396 (2010) 2757-2768
Nanotecnología en Superficies y Plasma

ABSTRACT

The measured peak shape and intensity of the photoemitted signal in X-ray photoelectron spectroscopy (XPS) experiments (elastic and inelastic parts included) are strongly correlated, through electron-transport theory, with the depth distribution of photoelectron emitters within the analyzed surface. This is the basis of so-called XPS peak-shape analysis (also known as the Tougaard method) for non-destructive determination of compositional in-depth (up to 6-8 nm) profiles. This review describes the theoretical basis and reliability of this procedure for quantifying amounts and distributions of material within a surface. The possibilities of this kind of analysis are illustrated with several case examples related to the study of the initial steps of thin-film growth and the modifications induced in polymer surfaces after plasma treatments.


Abril, 2010 | DOI: 10.1007/s00216-009-3312-9

Surface Functionalization, Oxygen Depth Profiles, and Wetting Behavior of PET Treated with Different Nitrogen Plasmas


Lopez-Santos, C; Yubero, F; Cotrino, J; Gonzalez-Elipe, AR
ACS Applied Materials & Interfaces, 2 (2010) 980-990
Nanotecnología en Superficies y Plasma

ABSTRACT

Polyethylene terephthalate (PET) plates have been exposed to different nitrogen containing plasmas with the purpose of incorporating nitrogen functional groups on its surface. Results with a dielectric barrier discharge (DBD) at atmospheric pressure and a microwave discharge (MW) at reduced pressure and those using an atom source working under ultrahigh vacuum conditions have been compared for N-2 and mixtures Ar + NH3 as plasma gases. The functional groups have been monitored by X-ray Photoemission Spectroscopy (XPS). Nondestructive oxygen and carbon depth profiles for the plasma treated and one month aged samples have been determined by means of the nondestructive Tougaard's method of XPS background analysis. The surface topography of the treated samples has been examined by Atomic Force Microscopy (AFM), while the surface tension has been determined by measuring the static contact angles of water and iodomethane. It has been found that the DBD with a mixture of Ar+NH3 is the most efficient treatment for nitrogen and amine group functionalization as determined by derivatization by reaction with chlorobenzaldehyde. It is also realized that the nitrogen functional groups do not contribute significantly to the observed increase in surface tension of plasma treated PET.


Abril, 2010 | DOI: 10.1021/am100052w

Physical and geotechnical properties of clay phyllites


Garzon, E; Sanchez-Soto, PJ; Romero, E
Applied Clay Science, 48 (2010) 307-318
Materiales Avanzados

ABSTRACT

An experimental programme is presented with the aim of characterising - from physical, microstructural and geotechnical perspectives - the main properties of compacted clay phyllites. These clay phyllites are widely used as waterproofing material for roofs in the Alpujarra (Andalusia, Spain), as sealing liners in irrigation ponds, and as core material of small earthen zoned dams. An exhaustive physical-characterisation programme on the powder fraction has been followed using X-ray fluorescence (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), chemical analysis by energy dispersive X-ray spectroscopy (EDX), thermal analysis, particle-size distribution analysis, consistency limits, and density of solid particles. From a microstructural standpoint, mercury intrusion porosimetry (MIP) tests, as well as nitrogen-adsorption tests, were carried out to characterise the pore network and surface area of the material in both natural and compacted states. The geotechnical characterisation programme on the compacted material was focused on the water-permeability and water-retention properties, the volume change on soaking (swelling or collapse), the compressibility on loading, the shear-strength properties, and the mechanical-penetration properties. In this way, an important physical and hydro-mechanical data base is provided, which could help in evaluating the suitability for using this material in a wide range of earthen constructions (liners, road subgrades, embankments, core material in zoned dams). It has been found that the material contains illite, chlorite and quartz as the main components, and feldspar, iron oxide and interstratified illite-smectite as minor ones. Despite the presence of active clay minerals, the compacted material did not display an important swelling on soaking at low stresses, as a consequence of its low specific surface and low water-retention ability. The material exhibited good compaction properties and, consequently, low water permeability plus a stiff response on loading. Nevertheless, despite the low porosity attained on the dry-side compaction, the material underwent some collapse on soaking at stresses greater than 100 kPa.


Abril, 2010 | DOI: 10.1016/j.clay.2009.12.022

Catalytic nanomedicine: Functionalisation of nanostructured cryptomelane


Lopez, T; Ortiz, E; Alvarez, M; Manjarrez, J; Montes, M; Navarro, P; Odriozola, JA
Materials Chemistry and Physics, 120 (2010) 518-525
Química de Superficies y Catálisis

ABSTRACT

Nanostructured cryptomelanes (KMn8O16) were synthesized from manganese sulphate and manganese acetate precursors by the reflux method. The respectively obtained samples, CRYSO4 and CRYAc, were functionalised with hydroxyl, ammonium, sulphate and phosphate groups in order to modify the biocompatibility and surface properties of cryptomelane. Characterization by FTIR and XRD confirmed bond formation of CRY-NH, CRY=S=O, CRY-NH, and CRY=PO4. In both functionalise samples (CRYSO4-F and CRYAc-F), IR bands occurred at 1399 cm(-1), corresponding to the sulphate species, and 1106 cm(-1), related to phosphate vibrations; along with the OH and NH characteristic vibration bands in the high energy region. Biocompatibility of functionalised samples was tested by implantation of cryptomelane reservoir in the basolateral amygdala and caudal nucleus of Wistar rats using stereotactic surgery. The brains of the rats were processed in order to evaluate any damage associated with the implant. The results showed that functionalised cryptomelanes did not cause tissue damage or inflammation while not functionalised cryptomelanes caused cell death.


Abril, 2010 | DOI: 10.1016/j.matchemphys.2009.11.049

One-Step Dry Method for the Synthesis of Supported Single-Crystalline Organic Nanowires Formed by pi-Conjugated Molecules


Borras, A; Groning, O; Aguirre, M; Gramm, F; Groning, P
Langmuir, 26 (2010) 5763-5771
Nanotecnología en Superficies y Plasma

ABSTRACT

We present for the first time a general vacuum process for the growth of supported organic nanowires formed by pi-conjugated molecules, including metalloporphyrins, metallophthalocyanines, and perylenes. This methodology consists on a one-step physical vapor deposition of the pi-conjugated molecules. The synthesis is carried out at controlled temperature on substrates with tailor morphology which allows the growth or organic nanowires in the form of squared nanofibers and nanobelts. The study of the nanowires by electron diffraction and HRTEM combining with the results of a theoretical analysis of the possible arrangement of the pi-conjugated molecules along the nanowires reveals that the nanowires show a columnar structure along the fiber axis consisting of pi-stacked molecules having a herringbone-like arrangement. The formation of these nanowires on different substrates demonstrates that the growth mechanism is independent of the substrate chemical composition. An in-depth phenomenological study of the Formation of the nanowires drives us to propose a growth mechanism based on a crystallization process. Furthermore, the growth method allows the fabrication of two particular ID heterostructures: binary and open core@shell organic nanofibers.


Abril, 2010 | DOI: 10.1021/la1003758

Determination of pigments and binders in Pompeian wall paintings using synchrotron radiation - High-resolution X-ray powder diffraction and conventional spectroscopy-chromatography


Duran, A; De Haro, MCJ; Perez-Rodriguez, JL; Franquelo, ML; Herrera, LK; Justo, A
Archaeometry, 52 (2010) 286-307

ABSTRACT

The employment of synchrotron techniques complemented by conventional laboratory systems has allowed us to deepen and improve our knowledge of Roman wall painting procedures. The palette identified in wall paintings from Pompeii and Herculaneum from the second century bc includes goethite, hematite, cinnabar, glauconite, Egyptian blue, and other components such as calcite and aragonite. Proof of the use of organic binders is provided by FTIR and PY-GC/MS. Therefore, the possibility of the use of 'a secco' techniques cannot be ruled out. Pigments in wall paintings are usually found in small percentages and conventional X-ray diffractometers do not detect them. Synchrotron radiation - high-resolution X-ray powder diffraction has allowed identification with only a few micrograms of sample.


Abril, 2010 | DOI: 10.1111/j.1475-4754.2009.00478.x

A thermal study approach to roman age wall painting mortars


Duran, A; Perez-Maqueda, LA; Poyato, J; Perez-Rodriguez, JL
Journal of Thermal Analysis and Calorimetry, 99 (2010) 803-809

ABSTRACT

Roman ancient mortars have been widely studied, in connection with both diagnosis and application required for restoring. Thermoanalytical experiments performed on mortars from Pompeii and Herculaneum provided a very good understanding of the technology employed. The mortars from Pompeii were obtained by the proper mixing of lime and marble grains while mortars of Herculaneum by lime and silicates compounds. The position of the endothermic peak of calcite decomposition showed important variations in the different samples studied, which was assigned to the different crystallinity and particle sizes. Experiments under CO2 flow confirmed the presence of magnesium calcium carbonates.


Marzo, 2010 | DOI: 10.1007/s10973-009-0667-2

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