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Artículos SCI

2017


Titulo: A Promising approach to the kinetics of crystallization processes: The sample controlled thermal analysis
Autores: Perejon, A; Sanchez-Jimenez, PE; Criado, JM; Perez-Maqueda, LA
Revista: Journal of the American Ceramic Society, 100 (2017) 1125-1133
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Constant Rate Thermal Analysis (CRTA) method implies controlling the temperature in such a way that the reaction rate is maintained constant all over the process. This method allows determining simultaneously both the kinetic parameters and the kinetic model from a single experiment as the shape of the CRTA -T curves strongly depends on the kinetic model. CRTA method has been developed in the market only for thermogravimetric and thermodilatometric systems and, therefore, its use has been limited until now to the kinetic study of processes involving changes in mass or size of the samples, respectively. To overcome this obstacle, a method has been developed in this work for using the DSC signal for controlling the process rate in such a way that CRTA would be applied to the kinetic analysis of either phase transformations or crystallizations. The advantages of CRTA for performing the kinetics of crystallization processes have been here successfully demonstrated for the first time after selecting the crystallization of zirconia gel as test reaction.

Marzo, 2017 | DOI: 10.1111/jace.14604

Titulo: Antibacterial response of titanium oxide coatings doped by nitrogen plasma immersion ion implantation
Autores: Esparza, J; Fuentes, GF; Bueno, R; Rodriguez, R; Garcia, JA; Vitas, AI; Rico, V; Gonzalez-Elipe, AR
Revista: Surface and Coatings Technology, 314 (2017) 67-71
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Plasma immersion ion implantation technology has been utilized to enhance the photocatalytic activity of the anatase phase of TiO2 thin films deposited by cathodic arc evaporation PVD. The main objective of this study is to shift the light absorbance of the titania in order to obtain antibacterial activity under visible light irradiation. TiO2 thin films, deposited on polished stainless steel AISI 304 and silicon wafers, were implanted with nitrogen ions (N+/N2+) at 20 kV energy and different temperatures between 250 and 350 °C. The antibacterial activity of nitrogen implanted titania coatings has been monitored for Escherichia coli under visible light irradiation. Additionally ultra violet/visible spectrophotometry tests have been carried out to measure the changes in the light absorbance of the doped films. Further characterization has been performed, including X-ray photoelectron spectroscopy, X-ray diffraction and glow discharge optical emission spectrometry. As a result of Nitrogen implantation, the light absorption peak shifted from ultra violet region (UV-A) to visible wavelength range, which led to an increase of the antibacterial efficacy under visible light irradiation.

Marzo, 2017 | DOI: 10.1016/j.surfcoat.2016.11.002

Titulo: On the effect of wall slip on the determination of the yield stress of magnetorheological fluids
Autores: Caballero-Hernandez, J; Gomez-Ramirez, A; Duran, JDG; Gonzalez-Caballero, F; Zubarev, AY; Lopez-Lopez, MT
Revista: Applied Rheology, 27 (2017) 15001 (8 pages)
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We study the effect of wall slip on the measured values of the yield stress of magnetorheological (MR) fluids. For this aim we used a rheometer provided with parallel-plate geometries of two types, distinguished by having smooth or rough surfaces. We found that wall slip led to the underestimation of the yield stress when measuring geometries with smooth surfaces were used, and that this underestimation was more pronounced for the static than for the dynamic yield stress. Furthermore, we analysed the effect that both irreversible particle aggregation due to colloidal interactions and reversible magnetic fieldinduced particle aggregation had on the underestimation provoked by wall slip. We found that the higher the degree of aggregation the stronger the underestimation of the yield stress. At low intensity of the applied magnetic field irreversible particle aggregation was dominant and, thus, the underestimation of the yield stress was almost negligible for well-dispersed MR fluids, whereas it was rather pronounced for MR fluids suffering from irreversible aggregation. As the magnetic field was increased the underestimation of the yield stress became significant even for the best dispersed MR fluid.

Marzo, 2017 | DOI: 10.3933/ApplRheol-27-15001

Titulo: Reliability of new poly (lactic-co-glycolic acid) membranes treated with oxygen plasma plus silicon dioxide layers for pre-prosthetic guided bone regeneration processes
Autores: Castillo-Dali, G; Castillo-Oyague, R; Batista-Cruzado, A; Lopez-Santos, C; Rodriguez-Gonzalez-Elipe, A; Saffar, JL; Lynch, CD; Gutierrez-Perez, JL; Torres-Lagares, D
Revista: Medicina Oral Patología Oral y Cirugia Oral, 22 (2017) E242-E250
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Background: The use of cold plasmas may improve the surface roughness of poly(lactic-co-glycolic) acid (PLGA) membranes, which may stimulate the adhesion of osteogenic mediators and cells, thus accelerating the biodegradation of the barriers. Moreover, the incorporation of metallic-oxide particles to the surface of these membranes may enhance their osteoinductive capacity. Therefore, the aim of this paper was to evaluate the reliability of a new PLGA membrane after being treated with oxygen plasma (PO2) plus silicon dioxide (SiO2) layers for guided bone regeneration (GBR) processes. 
Material and Methods: Circumferential bone defects (diameter: 11 mm; depth: 3 mm) were created on the top of eight experimentation rabbits' skulls and were randomly covered with: (1) PLGA membranes (control), or (2) PLGA/ PO2/SiO2 barriers. The animals were euthanized two months afterwards. A micromorphologic study was then performed using ROI (region of interest) colour analysis. Percentage of new bone formation, length of mineralised bone, concentration of osteoclasts, and intensity of ostheosynthetic activity were assessed and compared with those of the original bone tissue. The Kruskal-Wallis test was applied for between-group com asignificance level of a=0.05 was considered. 
Results: The PLGA/ PO2/SiO2 membranes achieved the significantly highest new bone formation, length of miner-alised bone, concentration of osteoclasts, and ostheosynthetic activity. The percentage of regenerated bone supplied by the new membranes was similar to that of the original bone tissue. Unlike what happened in the control group, PLGA/PO2/SiO2 membranes predominantly showed bone layers in advanced stages of formation. Conclusions: The addition of SiO2 layers to PLGA membranes pre-treated with PO2 improves their bone-regeneration potential. Although further research is necessary to corroborate these conclusions in humans, this could be a promising strategy to rebuild the bone architecture prior to rehabilitate edentulous areas.

Marzo, 2017 | DOI: 10.4317/medoral.21512

Titulo: High vacuum synthesis and ambient stability of bottom-up graphene nanoribbons
Autores: Fairbrother, A; Sanchez-Valencia, JR; Lauber, B; Shorubalko, I; Ruffieux, P; Hintermann, T; Fasel, R
Revista: Nanoscale, 9 (2017) 2785-2792
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Carbon-based nanomaterials such as graphene are at a crucial point in application development, and their promising potential, which has been demonstrated at the laboratory scale, must be translated to an industrial setting for commercialization. Graphene nanoribbons in particular overcome one limitation of graphene in some electronic applications because they exhibit a sizeable bandgap. However, synthesis of bottom-up graphene nanoribbons is most commonly performed under ultra-high vacuum conditions, which are costly and difficult to maintain in a manufacturing environment. Additionally, little is known about the stability of graphene nanoribbons under ambient conditions or during transfer to technologically relevant substrates and subsequent device processing. This work addresses some of these challenges, first by synthesizing bottom-up graphene nanoribbons under easily obtained high vacuum conditions and identifying water and oxygen as the residual gases responsible for interfering with proper coupling during the polymerization step. And second, by using Raman spectroscopy to probe the stability of nanoribbons during storage under ambient conditions, after transfer to arbitrary substrates, and after fabrication of field-effect transistor devices, which shows structurally intact nanoribbons even several months after synthesis. These findings demonstrate the potential of graphene nanoribbon technologies by addressing some limitations which might arise in their commercialization.

Febrero, 2017 | DOI: 10.1039/C6NR08975E

Titulo: Cholesterol biosensing with a polydopamine-modified nanostructured platinum electrode prepared by oblique angle physical vacuum deposition
Autores: Martin, M; Salazar, P; Alvarez, R; Palmero, A; Lopez-Santos, C; Gonzalez-Mora, JL; Gonzalez-Elipe, AR
Revista: Sensors and Actuators B-Chemical, 240 (2017) 37-45
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This paper reports a novel cholesterol biosensor based on nanostructured platinum (Pt) thin films prepared by Magnetron Sputtering (MS) in an oblique angle (OAD) configuration. Pt thin films were deposited onto a gold screen-printed electrode and characterized using Rutherford Back Scattering (RBS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Cyclic Voltammetry (CV), X-ray Photo-electron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and wetting analysis. Our results confirmed that the film is highly porous and formed by tilted nanocolumns, with an inclination of around 40 degrees and a total thickness of 280 nm. XRD and CV analysis confirmed the polycrystalline nature of the Pt thin film. Cholesterol oxidase (ChOx) was covalently immobilized using a bioinspired polymer, polydopamine (PDA), via Schiff base formation and Michael-type addition. After being immobilized, ChOx displayed apparent activation energy of 34.09 kJ mol(-1) and Michaelis constant (K-M) values of 34.09 kJ mol(-1) and 3.65 mM, respectively, confirming the high affinity between ChOx and cholesterol and the excellent ability of the PDA film for immobilizing biological material without degradation. Under optimized working conditions the developed biosensor presented a sensitivity of 14.3 mA M(-1)cm(-2) (R-2:0.999) with a linear range up to 0.5 mM and a limit of detection of 10.5 mu M (S/N= 3). Furthermore, the biosensor exhibited a fast response (<8 s), good anti-interference properties and high stability after relatively long-term storage (2 months). 

Febrero, 2017 | DOI: 10.1016/j.snb.2016.08.092

Titulo: Comprehensive and Systematic Analysis of the Immunocompatibility of Polyelectrolyte Capsules
Autores: Zyuzin, MV; Diez, P; Goldsmith, M; Carregal-Romero, S; Teodosio, C; Rejman, J; Feliu, N; Escudero, A; Almendral, MJ; Linne, U; Peer, D; Fuentes, M; Parak, WJ
Revista: Bioconjugate Chemistry, 28 (2017) 556-564
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The immunocompability of polyelectrolyte capsules synthesized by layer-by-layer deposition has been investigated. Capsules of different architecture and composed of either non-degradable or biodegradable polymers, with either positively or negatively charged outer surface, and with micrometer size, have been used, and the capsule uptake by different cell lines has been studied and quantified. Immunocompatibility studies were performed with peripheral blood mononuclear cells (PBMCs). Data demonstrate that incubation with capsules, at concentrations relevant for practical applications, did not result in a reduced viability of cells, as it did not show an increased apoptosis. Presence of capsules also did not result in an increased expression of TNF-α, as detected with antibody staining, as well as at mRNA level. It also did not result in increased expression of IL-6, as detected at mRNA level. These results indicate that the polyelectrolyte capsules used in this study are immunocompatible.

Febrero, 2017 | DOI: 10.1021/acs.bioconjchem.6b00657

Titulo: Preparation of ytterbium substituted BiFeO3 multiferroics by mechanical activation
Autores: Gil-Gonzalez, E; Perejon, A; Sanchez-Jimenez, PE; Hayward, MA; Perez-Maqueda, LA
Revista: Journal of the European Ceramic Society, 37 (2017) 945-954
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Samples in the system Bi1-xYbxFeO3 (0.02 <= x <= 0.07) have for the first time been prepared by mechanical activation followed by sintering. XRD and DSC measurements show that the solubility limit of ytterbium in the R3c Bi1-xYbxFeO3 system is reached at x similar to 0.03. Higher ytterbium contents lead to a two-phase mixture of a main R3c phase of approximate composition Bi0.97Yb0.03FeO3 and ytterbium enriched secondary phases that cannot be readily indexed or quantified due to their small amount. DSC and temperature-dependent XRD showed that while the magnetic ordering temperature, T-N, was unaffected by Yb substitution, the ferroelectric ordering, T-C, declined. Temperature-dependent XRD patterns show that all samples exhibit rhombohedral R3c to orthorrhombic Pnma phase transitions. Diffuse reflectance spectroscopy suggests the potential use of the samples in photocatalytic applications due to their low band gap energy. Impedance spectroscopy and magnetic measurements show that samples are electrically homogenous and highly insulating, exhibiting antiferromagnetic behaviour at room temperature. 

Febrero, 2017 | DOI: 10.1016/j.jeurceramsoc.2016.09.014

Titulo: Fabrication of black-gold coatings by glancing angle deposition with sputtering
Autores: Vitrey, A; Alvarez, R; Palmero, A; Gonzalez, MU; Garcia-Martin, JM
Revista: Beilstein Journal of Nanotechnology, 8 (2017) 434–439
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The fabrication of black-gold coatings using sputtering is reported here. Glancing angle deposition with a rotating substrate is needed to obtain vertical nanostructures. Enhanced light absorption is obtained in the samples prepared in the ballistic regime with high tilt angles. Under these conditions the diameter distribution of the nanostructures is centered at about 60 nm and the standard deviation is large enough to obtain black-metal behavior in the visible range.

Febrero, 2017 | DOI: 10.3762/bjnano.8.46

Titulo: Identification of Outer and Inner Nickel Particles in a Mesoporous Support: How the Channels Modify the Reducibility of Ni/SBA-15 Catalysts
Autores: Rodriguez-Gomez, A; Caballero, A
Revista: Chemnanomat, 3 (2017) 94-97
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Two different nickel supported on SBA-15 catalytic systems have been prepared by means of impregnation (Ni/SBA-15-ImU) and deposition-precipitation (Ni/SBA-15-DP) methodologies. Upon calcination, Ni/SBA-15DP presents a well-developed nickel phyllosilicate phase, which after reduction gives rise to a dispersed and homogeneous metallic phase, mainly located inside the 5 nm in diameter mesoporous structure of the support. On the contrary, as evidenced by XRD and a double temperature programmed reduction (TPR) peak, the Ni/SBA-15-ImU catalyst presents two different NiO phases, which after reduction in hydrogen generate nickel particles in a wide range of sizes. In situ XAS and XPS have unambiguously showed that the distinct TPR profiles obtained for each system are related with particles located in and out the mesoporous structure of the SBA-15 channels. The particles inside the porous are more difficult to reduce, clearly showing a kind of confinement effect of the SBA-15 mesostructure, modifying the reducibility of the NiO phase.

Febrero, 2017 | DOI: 10.1002/cnma.201600297

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