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2021


Enhanced UV and visible light photocatalytic properties of synthesized AgBr/SnO2 composites


Puga, F.; Navío, J.A.; Hidalgo, M.C.
Separation and Purification Tecnology, 257 (2021) 117948
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

Composites (AgBr/SnO2) comprised of AgBr and SnO2 with different molar % of bare SnO2, have been synthesized by simple precipitation methods; the bare SnO2 used, was synthesized by hydrothermal procedure. Samples have been characterized by X-ray diffraction (XRD), N2-adsorption, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the as-prepared photocatalysts was evaluated through photocatalytic degradation of rhodamine B (RhB) and caffeic acid (CAFA) under UV and Visible illumination. In photocatalytic degradation studies, for both substrates, conversion rates of around 95% were found in 45 min of both UV-illumination and 85% under visible lighting. These conversion rates were superior than the conversion rates of pure parental components, AgBr and SnO2 under the same experimental conditions. At least, for RhB no loss of photocatalytic activity has been observed after five recycles although the mineralization degree progressively diminished along the recycles. The enhanced photocatalytic degradation of AgBr/SnO2 compounds was attributed, in part, to a synergistic increase in adsorption viability, as well as to the effective separation of photoinduced load carriers that resulted from the formation of a heterojunction according to the type II junction. Radical scavengers’ experiments indicated that active oxidant species as O2.−, ·OH and h+ all are involved in this photocatalytic system, although it seems that O2.− played the major role in the photocatalytic degrading of RhB by AgBr/SnO2 composites. In summary, coupling AgBr with SnO2 remarkably improves the photocatalytic activity under both UV and visible-illumination with respect to the parental components. These features open the route to future applications of this material in the field of environmental remediation.


Febrero, 2021 | DOI: 10.1016/j.seppur.2020.117948

Guaiacol hydrodeoxygenation in hydrothermal conditions using N-doped reduced graphene oxide (RGO) supported Pt and Ni catalysts: Seeking for economically viable biomass upgrading alternatives


Parrilla-Lahoz, S; Jin, W; Pastor-Perez, L; Carrales-Alvarado, D; Odriozola, JA; Dongil, AB; Reina, TR
Applied Catalysis A-General, 611 (2021) 117977
Química de Superficies y Catálisis

ABSTRACT

Herein we present an innovative route for model biomass compounds upgrading via “H2-free” hydrodeoxygenation (HDO) reactions. The underlaying idea is to implement a multifunctional catalyst able to activate water and subsequently use in-situ generated hydrogen for the HDO process. In this sense we have developed a series of effective Ni and Pt based catalysts supported on N-promoted graphene decorated with ceria. The catalyst reached commendable conversion levels and selectivity to mono-oxygenated compounds considering the very challenging reaction conditions. Pt outperforms Ni when the samples are tested as-prepared. However, Ni performance is remarkably boosted upon applying a pre-conditioning reductive treatment. Indeed, our NiCeO2/GOr-N present the best activity/selectivity balance and it is deemed as a promising catalyst to conduct the H2-free HDO reaction. Overall, this “proof-concept” showcases an economically appealing route for bio-compounds upgrading evidencing the key role of advanced catalysts for a low carbon future.


Febrero, 2021 | DOI: 10.1016/j.apcata.2020.117977

Photocatalytic oxidation of pollutants in gas-phase via Ag3PO4-based semiconductor photocatalysts: Recent progress, new trends, and future perspectives


Y. Naciri; A. Hsini; A. Bouziani; R. Djellabi; Z. Ajmal; M. Laabd; J.A. Navío; A. Mills; C.L. Bianchi; H.Li; B. Bakiz; A. Albourine
Critical Reviews in Environmental Science and Technology,
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

Air pollution has become a significant challenge for both developing and developed nations. due to its close association with numerous fatal diseases such as cancer, respiratory, heart attack, and brain stroke. Over recent years, heterogeneous semiconductor photocatalysis has emerged as an effective approach to air remediation due to the ease of scale-up, ready application in the field, use of solar light and ready availability of a number of different effective photocatalysts. To date, most work in this area has been conducted using UV-absorbing photocatalysts, such as TiO2 and ZnO; However, recent studies have revealed Ag3PO4 as an attractive, visible-light-absorbing alternative, with a bandgap of 2.43 eV. In particular, this material has been shown to be an excellent photocatalyst for the removal of many types of pollutants in the gas phase. However, the widespread application of Ag3PO4 is restricted due to its tendency to undergo photoanodic corrosion and the poor reducing power of its photogenerated conductance band electrons, which are unable to reduce O2 to superoxide •O2 −. These limitations are critically evaluated in this review. In addition, recent studies on the modification of Ag3PO4 via combination with the conventional heterojunctions or Z-scheme junctions, as well as the photocatalytic mechanistic pathways for enhanced gas-pollutants removal, are summarized and discussed. Finally, an overview is given on the future developments that are required in order to overcome these challenges and so stimulate further research into this promising field.


Febrero, 2021 | DOI: 10.1080/10643389.2021.1877977

Patterning and control of the nanostructure in plasma thin films with acoustic waves: mechanical vs. electrical polarization effects


García-Valenzuela, A.; Fakhouri, A.; Oliva-Ramírez, M.; Rico-Gavira, V.; Rojas, T.C.; Alvarez, R.; Menzel, S.B.; Palmero, A.; Winkler, A.; González-Elipe, A.R.
Materials Horizons, 8 (2021) 515-524
Nanotecnología en Superficies y Plasma - Tribología y Protección de Superficies

ABSTRACT

Nanostructuration and 2D patterning of thin films are common strategies to fabricate biomimetic surfaces and components for microfluidic, microelectronic or photonic applications. This work presents the fundamentals of a surface nanotechnology procedure for laterally tailoring the nanostructure and crystalline structure of thin films that are plasma deposited onto acoustically excited piezoelectric substrates. Using magnetron sputtering as plasma technique and TiO2 as case example, it is demonstrated that the deposited films depict a sub-millimetre 2D pattern that, characterized by large lateral differences in nanostructure, density (up to 50%), thickness, and physical properties between porous and dense zones, reproduces the wave features distribution of the generated acoustic waves (AW). Simulation modelling of the AW propagation and deposition experiments carried out without plasma and under alternative experimental conditions reveal that patterning is not driven by the collision of ad-species with mechanically excited lattice atoms of the substrate, but emerges from their interaction with plasma sheath ions locally accelerated by the AW-induced electrical polarization field developed at the substrate surface and growing film. The possibilities of the AW activation as a general approach for the tailored control of nanostructure, pattern size, and properties of thin films are demonstrated through the systematic variation of deposition conditions and the adjustment of AW operating parameters.


Febrero, 2021 | DOI: 10.1039/D0MH01540G

Long-term low friction maintenance and wear reduction on the ventral scales in snakes


Sanchez-Lopez, JC; Schaber, CF; Gorb, SN
Materials Letters, 285 (2021) 129011
Tribología y Protección de Superficies

ABSTRACT

Snake skins evolved to withstand permanent friction and wear during sliding. Here, the microstructure of ventral scales of the snake Lampropeltis getula californiae was analyzed using scanning electron microscopy, and the long-term dynamic friction behavior was investigated by reciprocating sliding friction tests. A smooth epoxy resin with similar elasticity modulus and hardness was used for comparison purposes. Strong differences in frictional and wear mechanisms between the two materials were revealed in spite of similar mechanical properties. Snake skin showed a considerably lower frictional coefficient that kept stable over several thousands of sliding cycles. A reduction of the stick-slip behavior was also denoted by analyzing the variation of the friction coefficient in the forward and reverse motion influencing the wear mechanism. This frictional behavior can be explained by three different but complementary mechanisms: fibrous layered composite material of the skin with a gradient of material properties, surface microstructure, and the presence of ordered layers of lipid molecules at the skin surface.


Febrero, 2021 | DOI: 10.1016/j.matlet.2020.129011

Impact of Tb4+ and morphology on the thermal evolution of Tb-doped TiO2 nanostructured hollow spheres and nanoparticles


Colomer, MT; Rodriguez, E; Moran-Pedroso, M; Vattier, F; de Andres, A
Journal of Alloys and Compounds, 853 (2021) 156973
Materiales Ópticos Multifuncionales

ABSTRACT

Tb-doped TiO2 hollow spheres (HSs) in the range 0.0-2.0 at.% have been synthesized by the first time to the best of our knowledge. The HSs are compared with nanoparticles (NPs) to evaluate the impact of morphology on their physicochemical and photoluminescence (PL) behavior upon increasing calcination temperature. After calcination at 550 degrees C, the particles are anatase with a primary average size of 10.0 +/- 0.2 nm for the NPs and 12.0 +/- 0.2 nm for those that form the micron sized hollow spheres of 1.8 +/- 0.2 mu m diameter and ca. 64 nm shell thickness. The temperature of the anataseerutile transition is found to be strongly dependent on the presence of Tb as well as on morphology. Contrarily to the usual stabilization of anatase when doping with trivalent rare-earth ions, the transition temperature is reduced when doping with Tb. The rutile phase is further favored for the HSs compared to the NPs probably related to the low density of the HSs and/or a more efficient packing density and/or a bigger crystal size of the nanoparticles that form those spheres with respect to the packing and the size of the NPs and/or the crystal size of the nanoparticles of the HSs with respect to the size of the NPs. Only a slight unit-cell volume increase for the anatase structure is observed upon Tb doping, in both the NPs and in the HSs, contrary to the expected increment due to the larger ionic radius of Tb3+ compared to Ti4+. In addition, the intensity of the characteristic f-f Tb3+ emission bands is extremely weak both in the anatase and rutile phases. The transition is accompanied with the emergence of an infrared emission band centered at 810 nm related to the formation of defects during the structural transformation providing deep levels in the gap that partly quench the f-f emissions in the rutile phase. The results are consistent with the presence of Tb in both +3 and +4 valence states. XPS measurements confirmed the presence of Tb3+ as well as of Tb4+ in both HSs and NPs. The large fraction of Tb4+ present in the samples originates the weak f-f emission intensity, an only slight increase of the cell parameters and the destabilization of the anatase phase. 


Febrero, 2021 | DOI: 10.1016/j.jallcom.2020.156973

Insights into the role of the layer architecture of Cr-Ti-N based coatings in long-term high temperature oxidation experiments in steam atmosphere


Mato, S; Sanchez-Lopez, JC; Barriga, J; Perez, FJ; Alcala, G
Ceramics International, 47 (2021) 4257-4266
Tribología y Protección de Superficies

ABSTRACT

Knowledge on hard coatings has been applied in the energy field extending their use as protecting coatings of steam power generation plants components. The role of the layer architecture of Cr-Ti-N based coatings deposited by reactive cathodic arc evaporation on P92 steel substrates was studied with the focus on their oxidation resistance at 650 degrees C in 100% steam atmosphere up to 2000 h. Characterization of the coatings was performed by gravimetry, scanning electron microscopy, electron probe microanalysis, glow discharge optical emission spectroscopy, X-ray diffraction, thermodynamic simulations using the CALPHAD method, Rockwell C indentation and nanoindentation. The layered arrangement improves the oxidation resistance of TiN under the working conditions of steam power plants, as well as the mechanical properties of CrN. The produced architectures performance under the described working conditions boosts the understanding of the processes taking place at high temperature, making possible the design of optimal coatings combining the best behavior of both nitrides for each specific application, reaching a corrosion protection at high temperature in water vapor comparable to that of CrN and a hardness and Young's modulus as high as those of TiN.


Febrero, 2021 | DOI: 10.1016/j.ceramint.2020.10.003

Active sites and optimization of mixed copper-cobalt oxide anodes for anion exchange membrane water electrolysis


Lopez-Fernandez, E; Gil-Rostra, J; Escudero, C; Villar-Garcia, IJ; Yubero, F; Consuegra, AD; Gonzalez-Elipe, AR
Journal of Power Sources, 485 (2021) 229217
Nanotecnología en Superficies y Plasma

ABSTRACT

The optimization of the catalysts incorporated to the electrodes for anion exchange membrane water electmlysers is a key issue to maximize their performance through the improvement of the oxygen evolution reaction (OER) yield. In this work, we show that the modification of the microstructure and the chemical properties of a mixed copper-cobalt oxide anode may contribute to increase the activity of this reaction. For this purpose, the OER has been systematically studied, either in a half cell or in a membrane electrode assembly configuration, as a function of the load and agglomeration degree of the catalysts used as electrodes, as prepared on a carbon paper support by magnetron sputtering deposition in an oblique angle configuration. Chemical analysis by X-ray absorption spectroscopy and electrochemical analysis by cyclic voltammetry and impedance spectroscopy have shown that cobalt-copper mixed oxide catalysts with a 1.8 Co/Cu atomic ratio and about one micron equivalent thickness maximizes the cell performance. The chemical, structural and microstructural factors controlling the final behaviour of these anodes and accounting for this maximization of the reaction yield are discussed on the basis of these characterization results and as a function of preparation variables of the electrodes and operating conditions of the cell.


Febrero, 2021 | DOI: 10.1016/j.jpowsour.2020.229217

The Possible Detriment of Oxygen in Creep of Alumina and Zirconia Ceramic Composites Reinforced with Graphene


Cano-Crespo, R; Rivero-Antunez, P; Gomez-Garcia, D; Moreno, R; Dominguez-Rodriguez, A
Materials, 14 (2021) 984
Propiedades mecánicas, modelización y caracterización de cerámicos avanzados

ABSTRACT

This paper aims to give an answer to the following question: is the oxidation of graphene a critical issue for high-temperature plasticity in graphene-reinforced ceramics? To give a convincing reply, we will focus on two very different graphene-based ceramic composites: reduced graphene oxide (rGO)-reinforced alumina (alpha-Al2O3) and reduced graphene oxide (rGO)-reinforced yttria tetragonal zirconia (t-ZrO2). The processing of the powders has been made using a colloidal route, and after that, a spark plasma sintering process was performed in order to densify the samples. Creep tests were performed at temperatures between 1200-1250 degrees C in an argon atmosphere. The microstructure obtained by SEM of the sintered and tested specimens was characterized quantitatively to elucidate the deformation mechanism. Raman spectroscopy was carried out to check the integrity of the graphene. The average grain size was in the order of 1 mu m and the shape factor was 0.7 for all the studied materials. The integrity of the graphene was checked before and after the creep experiments. The careful analysis of the creep tests shows that graphene oxide or its reduced version are not efficient phases for creep resistance improvement in general, contrary to what is reported elsewhere. However, the results permit the suggestion of a creep improvement in nanocomposites at a very high temperature regime due to an enhanced reactivity of oxygen between carbon and alumina interfaces. In the case of zirconia, the results give us the conclusion that the oxidation of graphene is a highly detrimental issue regarding the improvement of high-temperature plasticity.


Febrero, 2021 | DOI: 10.3390/ma14040984

Influence of Successive Chemical and Thermochemical Treatments on Surface Features of Ti6Al4V Samples Manufactured by SLM


Gonzalez, JE; de Armas, G; Negrin, J; Beltran, AM; Trueba, P; Gotor, FJ; Peon, E; Torres, Y
Metals, 11 (2021) 313
Reactividad de Sólidos

ABSTRACT

Ti6Al4V samples, obtained by selective laser melting (SLM), were subjected to successive treatments: acid etching, chemical oxidation in hydrogen peroxide solution and thermochemical processing. The effect of temperature and time of acid etching on the surface roughness, morphology, topography and chemical and phase composition after the thermochemical treatment was studied. The surfaces were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and contact profilometry. The temperature used in the acid etching had a greater influence on the surface features of the samples than the time. Acid etching provided the original SLM surface with a new topography prior to oxidation and thermochemical treatments. A nanostructure was observed on the surfaces after the full process, both on their protrusions and pores previously formed during the acid etching. After the thermochemical treatment, the samples etched at 40 °C showed macrostructures with additional submicro and nanoscale topographies. When a temperature of 80 °C was used, the presence of micropores and a thicker anatase layer, detectable by X-ray diffraction, were also observed. These surfaces are expected to generate greater levels of bioactivity and high biomechanics fixation of implants as well as better resistance to fatigue.


Febrero, 2021 | DOI: 10.3390/met11020313

A Novel, Simple and Highly Efficient Route to Obtain PrBaMn2O5+δ Double Perovskite: Mechanochemical Synthesis


Garcia-Garcia, FJ; Sayagues, MJ; Gotor, FJ
Nanomaterials, 11 (2021) 380
Reactividad de Sólidos

ABSTRACT

In this work, a mechanochemical route was proposed for the synthesis of the PrBaMn2O5+δ (PMBO) double layered perovskite phase. The mechanochemical reaction between Pr6O11, BaO2, and MnO powders with cationic stoichiometric ratios of 1/1/2 for Pr/Ba/Mn was performed using high-energy milling conditions in air. After 150 min of milling, a new phase with perovskite structure and cubic symmetry consistent with the A-site disordered Pr0.5Ba0.5MnO3 phase was formed. When this new phase was subsequently annealed at a high temperature in an inert Ar atmosphere, the layered PrBaMn2O5+δ phase was obtained without needing to use a reducing atmosphere. At 1100 °C, the fully reduced layered PrBaMn2O5 phase was achieved. A weight gain was observed in the 200–300 °C temperature range when this fully reduced phase was annealed in air, which was consistent with the transformation into the fully oxidized PrBaMn2O6 phase. The microstructural characterization by SEM, TEM, and HRTEM ascertained the formation of the intended PrBaMn2O5+δ phase. Electrical characterization shows very high electrical conductivity of layered PBMO in a reducing atmosphere and suitable in an oxidizing atmosphere, becoming, therefore, excellent candidates as solid oxide fuel cell (SOFC electrodes).


Febrero, 2021 | DOI: 10.3390/nano11020380

Critical Influence of the Processing Route on the Mechanical Properties of Zirconia Composites with Graphene Nanoplatelets


Gallardo-Lopez, A; Munoz-Ferreiro, C; Lopez-Pernia, C; Jimenez-Pique, E; Gutierrez-Mora, F; Morales-Rodriguez, A; Poyato, R
Materials, 14 (2021) 108
Reactividad de Sólidos

ABSTRACT

Graphene-based nanostructures, used as potential reinforcement in ceramic composites, have a great tendency to agglomerate. This requires the use of homogenization techniques during the powder processing, posing the need to evaluate how these techniques affect the microstructure and the mechanical properties of the resulting composites. The influence of the processing route on the properties of 3YTZP (3 mol % yttria tetragonal zirconia polycrystals) ceramic composites with 10 vol % cost-effective GNP (graphene nanoplatelets) has been addressed. Four different powder processing routines combining ultrasonic powder agitation (UA) and planetary ball milling (PBM) in wet and dry media have been used and all the composites were densified by spark plasma sintering (SPS). The mechanical properties at room temperature in the macroscale have been assessed by Vickers indentations, four-point bending tests and the impulse-echo technique, while instrumented indentation was used to measure the hardness and Young’s modulus at the nanoscale. The application of dry-PBM enhances greatly the mechanical and electrical isotropy of the composites, slightly increases the hardness and lowers the elastic modulus, independently of the application of UA. The combination of UA and dry-PBM enhances the flexure strength by 50%, which is desirable for structural applications.


Enero, 2021 | DOI: 10.3390/ma14010108

Sol-gel synthesis of ZnWO4-(ZnO) composite materials. Characterization and photocatalytic properties


Jaramillo-Páez, C., Navío, J.A., Puga, F., Hidalgo, M.C.
Journal of Photochemistry & Photobiology, A: Chemistry, 404 (2021) 112962
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

ZnWO4 based powder photocatalyst have been successfully prepared by calcining a co-precipitated precursor (ZnWO) obtained from aqueous Zn2+ and WO4 2− solutions at pH = 7, without surfactants addition. The as-formed sample was characterized by XRD, N2-absorption, SEM, TEM, DRS and XPS. Both techniques, XRD and XPS results showed that prepared sample corresponds to a crystalline, Zn-enriched composition, ZnWO4 indicating the formation of a ZnWO4-(ZnO) composite, whit ca. 10 wt.-% of ZnO confirmed by XRF analysis. Photocatalytic activities towards degradation of Rhodamine B (RhB), Methyl Orange (MO) and Phenol, under UV-illumination, was investigated not only by monitoring the percentages of conversion of substrates, but also by estimating the corresponding percentages of mineralization that accompany the photocatalytic process. Comparative substrateconversion rates estimated per surface area unit of catalyst, showed that the activity for ZnWO4-(ZnO) composite is similar to that for TiO2(P25), at least for MO and RhB, and even higher that for TiO2(P25) in respect to phenol conversion. By adding TEA to the synthesis procedure, a composite named as ZnWO4-ZnO-(pH = 10)-600 is generated, which has a higher proportion of ZnO (ca. 39 %) and superior specific surface area than the so-called ZnWO4-(ZnO) sample. Furthermore, the photocatalytic degradation of MO using the former material indicates that it is superior to ZnWO4-(ZnO) and even that TiO2(P25) itself under the same operational conditions. 


Enero, 2021 | DOI: 10.1016/j.jphotochem.2020.112962

Physicochemical surface analysis and germination at different irrigation conditions of DBD plasma‐treated wheat seeds


Molina, R; Lalueza, A; Lopez-Santos, C; Ghobeira, R; Cools, P; Morent, R; de Geyter, N; Gonzalez-Elipe, AR
Plasma Processes and Polymers, 18 (2021) e2000086
Nanotecnología en Superficies y Plasma

ABSTRACT

Plasma treatment is increasingly being explored as an effective presowing treatment improving seed germination. This study examines the synergetic effect of the irrigation condition and the physicochemical surface properties of wheat seeds subjected to atmospheric dielectric barrier discharge plasma activation on their water uptake and germination. Extensive surface analysis revealed a remarkably enhanced wettability of plasma-treated seeds due to the insertion of oxygen-containing functionalities on their surface. However, long plasma exposures damaged the outermost layers of the pericarp due to a pronounced oxidative etching effect. Although the seed germination capacity was not affected by the plasma treatments, short plasma exposures were shown to enhance water uptake and accelerate seed germination, especially under water-scarcity conditions.


Enero, 2021 | DOI: 10.1002/ppap.202000086

Anisotropic Resistivity Surfaces Produced in ITO Films by Laser-Induced Nanoscale Self-organization


Lopez-Santos, C; Puerto, D; Siegel, J; Macias-Montero, M; Florian, C; Gil-Rostra, J; Lopez-Flores, V; Borras, A; Gonzalez-Elipe, AR; Solis, J
Advanced Optical Materials, 9 (2021) 2001086
Nanotecnología en Superficies y Plasma

ABSTRACT

Highly anisotropic resistivity surfaces are produced in indium tin oxide (ITO) films by nanoscale self-organization upon irradiation with a fs-laser beam operating at 1030 nm. Anisotropy is caused by the formation of laser-induced periodic surface structures (LIPSS) extended over cm-sized regions. Two types of optimized structures are observed. At high fluence, nearly complete ablation at the valleys of the LIPSS and strong ablation at their ridges lead to an insulating structure in the direction transverse to the LIPSS and conductive in the longitudinal one. A strong diminution of In content in the remaining material is then observed, leading to a longitudinal resistivity rho(L) approximate to 1.0 omega center dot cm. At a lower fluence, the material at the LIPSS ridges remains essentially unmodified while partial ablation is observed at the valleys. The structures show a longitudinal conductivity two times higher than the transverse one, and a resistivity similar to that of the pristine ITO film (rho approximate to 5 x 10(-4) omega center dot cm). A thorough characterization of these transparent structures is presented and discussed. The compositional changes induced as laser pulses accumulate, condition the LIPSS evolution and thus the result of the structuring process. Strategies to further improve the achieved anisotropic resistivity results are also provided.


Enero, 2021 | DOI: 10.1002/adom.202001086

Sponge-like processed D-periodic self-assembled atelocollagen supports bone formation in vivo


Borrego-Gonzalez, S; Rico-Llanos, G; Becerra, J; Diaz-Cuenca, A; Visser, R
Materials Science & Engineering C-Materials for Biological Applications, 120 (2021) art.111679
Materiales para Bioingeniería y Regeneración Tisular

ABSTRACT

Fibrous biopolymeric collagen extracted from animal tissues has been widely used for fabricating matrices for bone tissue engineering (BTE). However, animal extracted collagens can trigger immune reactions when implanted in vivo and the presence of native crosslinks leads to batch-to-batch variability. Atelocollagen, a monomeric form of collagen, is free of telopeptides, which are mainly responsible for the immunogenicity of collagen, and can self-assemble in vitro to obtain fibrils with the characteristic D-periodic staining pattern of native collagen. However, atelocollagen-based biomaterials have not extensively been studied and, hence, their suitability for BTE remains relatively unexplored. Besides, to stabilize collagen biomaterials, chemical and physical crosslinking are used, although chemical agents are cytotoxic while the physical methods yield a less effective crosslinking. A combination of physical and chemical crosslinking is a suitable alternative that has rarely been tested in BTE programs. In this work, a sponge-like biomaterial (DCol-S) was processed from D-periodic self-assembled atelocollagen and its stabilization was studied using the combination of a dehydrothermal treatment (DHT) and minimal glutaraldehyde (GTA) exposition crosslinking, to increase the resistance to degradation of the scaffold without a major effect on the biomaterial structure. The microstructural features of the final sponges were characterised and compared to a commercial biomaterial processed from native bovine collagen (Helistat (R), Integra Lifesciences, NJ, USA), demonstrating that a D-periodic nanostructure was obtained and maintained after processing of the sponges. MC3T3-E1 preosteoblast adhesion, proliferation and differentiation assays in vitro showed that DCol-S is biocompatible. Furthermore, intramuscular implantation of the biomaterials loaded with rhBMP-2 revealed that the double-crosslinked sponges were able to support ectopic bone formation, while sponges stabilised only with the DHT treatment were not. Altogether, these findings show that atelocollagen-based sponges stabilised with a DHT treatment followed by a mild GTA crosslinking are a suitable alternative to polymeric extracted collagen for BTE applications.


Enero, 2021 | DOI: 10.1016/j.msec.2020.111679

Photocatalytic activity of ZnO nanoparticles and the role of the synthesis method on their physical and chemical properties


Uribe-Lopez, MC; Hidalgo-Lopez, MC; Lopez-Gonzalez, R; Frias-Marquez, DM; Nunez-Nogueira, G; Hernandez-Castillo, D; Alvarez-Lemus, MA
Journal of Photochemistry & Photobiology, A: Chemistry, 404 (2021) 112866
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

In the present study, we report on the effect of the synthesis method in the photoactivity of ZnO-NPs. The nanoparticles were prepared by precipitation and sol-gel procedures using zinc nitrate and zinc (II) acetylacetonate as ZnO precursors, respectively. The obtained samples were named as ZnO-PP (precipitation method) and ZnO-SG (sol-gel method). The powders were calcined at 500 degrees C and further characterized by Fourier Transform Infrared spectroscopy, X-ray Powder Diffraction, N-2 adsorption, thermal analysis, Diffuse Reflectance UV-Vis spectroscopy, and Electron Microscopy. Both methods of synthesis lead to formation of pure ZnO with hexagonal-wurtzite crystalline structures with average crystallite sizes similar to 30 nm. The specific surface area was affected by the synthesis method, since SBET values were 5 m(2)/g and 13 m(2)/g for sol-gel and precipitation method, respectively. The electron microscopy revealed significant changes in morphology for the obtained nanoparticles, as sol-gel directed the hexagonal rod-like geometries (similar to 50 nm in diameter) while quasi-spherical nanoparticles (similar to 100 nm in diameter) were formed using precipitation method. Photocatalytic activity was estimated by degrading phenol (50 ppm) as probe molecule under UVA irradiation (lambda = 356 nm), the results demonstrated that ZnO-PP reached 100 % of degradation after 120 min and 90 % of the pollutant was mineralized, whereas for ZnO-SG the results were 80 % and 48 % respectively. Fluorescence test using terephthalic acid (TA) demonstrated higher formation of OH center dot radicals for ZnO synthesized by precipitation method, which could explain the higher photodegradation and mineralization observed. These results support that even slight differences in physical and chemical properties of ZnO, have a significant impact on the photocatalytic performance of such nanoparticles.


Enero, 2021 | DOI: 10.1016/j.jphotochem.2020.112866

Elucidating the Promotional Effect of Cerium in the Dry Reforming of Methane


Rodriguez-Gomez, A; Lopez-Martin, A; Ramirez, A; Gascon, J; Caballero, A
Chemcatchem, 13 (2021) 553-563
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

ABSTRACT

A series of Ni-Ce catalysts supported on SBA-15 has been prepared by co-impregnation, extensively characterized and evaluated in the carbon dioxide reforming of methane (DRM). The characterization by TEM, XRD and TPR has allowed us to determine the effect of metal loading on metal dispersion. Cerium was found to improve nickel location inside the mesopores of SBA-15 and to suppress coke formation during the DRM reaction. The analysis by XPS allowed us to associate the high cerium dispersion with the presence of low-coordinated Ce3+ sites, being main responsible for its promotional effect. A combination of XAS and XPS has permitted us to determine the physicochemical properties of metals under reduction conditions. The low nickel coordination number determined by XAS in N-Ce doped systems after reduction suggests the generation of very small nickel particles which showed greater catalytic activity and stability in the reaction, and a remarkable resistance to coke formation.


Enero, 2021 | DOI: 10.1002/cctc.202001527

Dysprosium and Holmium Vanadate Nanoprobes as High-Performance Contrast Agents for High-Field Magnetic Resonance and Computed Tomography Imaging


Gomez-Gonzalez, E; Nunez, NO; Caro, C; Garcia-Martin, ML; Fernandez-Afonso, Y; de la Fuente, JM; Balcerzyk, M; Ocana, M
Inorganic Chemistry, 60 (2021) 152-160
Materiales Coloidales

ABSTRACT

We describe a wet chemical method for the synthesis of uniform and well-dispersed dysprosium vanadate (DyVO4) and holmium vanadate (HoVO4) nanoparticles with an almost spherical shape and a mean size of ∼60 nm and their functionalization with poly(acrylic acid). The transverse magnetic relaxivity of both systems at 9.4 T is analyzed on the basis of magnetic susceptibility and magnetization measurements in order to evaluate their potential for application as high-field MRI contrast agents. In addition, the X-ray attenuation properties of these systems are also studied to determine their capabilities as computed tomography contrast agent. Finally, the colloidal stability under physiological pH conditions and the cytotoxicity of the functionalized NPs are also addressed to assess their suitability for bioimaging applications.


Enero, 2021 | DOI: 10.1021/acs.inorgchem.0c02601

Enhanced Directional Light Extraction from Patterned Rare-Earth Phosphor Films


Cabello-Olmo, E; Molet, P; Mihi, A; Lozano, G; Miguez, H
Advanced Optical Materials, 9 (2021) 2001611
Materiales Ópticos Multifuncionales

ABSTRACT

The combination of light‐emitting diodes (LEDs) and rare earth (RE) phosphors as color‐converting layers comprises the basis of solid‐state lighting. Indeed, most LED lamps include a photoluminescent coating made of phosphor material, i.e., crystalline matrix suitably doped with RE elements, to produce white light from a blue or ultraviolet LED chip. Transparent phosphor‐based films constitute starting materials for new refined emitters that allow different photonic designs to be implemented. Among the different photonic strategies typically employed to tune or enhance emission, surface texturing has proved its versatility and feasibility in a wide range of materials and devices. However, most of the nanofabrication techniques cannot be applied to RE phosphors directly because of their chemical stability or because of their cost. The first monolithic patterned structure of down‐shifting nanophosphors with square arrays of nanoholes with different lattice parameters is reported in this study. It is shown that a low‐cost soft‐nanolithography procedure can be applied to red‐emitting nanophosphors (GdVO4:Eu3+ nanocrystals) to tune their emission properties, attaining a twofold directional enhancement of the emitted light at predesigned emission wavelengths in specific directions.


Enero, 2021 | DOI: 10.1002/adom.202001611

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