Materials Science Institute of Barcelona
Recent publications
The use of adequate thermal energy storage (TES) systems has shown the potential to increase energy efficiency in many fields, such as the building sector. Shape-stabilized phase change materials (SS-PCMs) have attracted attention to address one of the key barriers of phase change materials (PCMs), the leakage during the liquid state, that nowadays limits its applicability. However, SS-PCMs still have drawbacks to overcome, such as poor fire reaction and thermal stability. In the present study, polymeric SS-PCMs are nano-enhanced with layered silicates to overcome these drawbacks. The new shape-stabilized nano-enhanced phase change material (SS-NEPCM) is based on ethylene propylene diene monomer (EPDM) as a polymeric matrix, palmitic acid (PA) as PCM and montmorillonite (MMT) as the layered silicate. An innovative method based on a Banbury mixer was used to prepare it, which is an industrially scalable fabrication method. To evaluate the effect of each component, eight different formulations were prepared: pure EPDM, EPDM with MMT additions (1 wt%, 3 wt% and 5 wt%), EPDM with PA additions (5 wt% and 10 wt%) and EPDM with MMT (3 wt%) and PA additions (5 wt% and 10 wt%). The composite materials obtained were not degraded by processing as FT-IR results show. The results obtained by X-ray diffraction showed that an ordered intercalated morphology is formed between EPDM chains and MMT. Thermogravimetric experimental results revealed an increase in the thermal stability of SS-NEPCM as a result of the barrier effect provided by MMT. Moreover, SS-NEPCM fire resistance was improved with a great reduction or avoidance of the dripping phenomenon.
Soft-tissue replacements are challenging due to the stringent compliance requirements for the implanted materials in terms of biocompatibility, durability, high wear resistance, low friction, and water content. Acrylate hydrogels are worth considering as soft tissue implants as they can be photocurable and sustain customized shapes through 3D bioprinting. However, acrylate-based hydrogels present weak mechanical properties and significant dimensional changes when immersed in liquids. To address these obstacles, we fabricated double network (DN) hydrogels composed of polyacrylic acid (PAA) and bacterial cellulose nanofibers (BCNFs) by one fast UV photopolymerization step. BCNFs/PAA hydrogels with a 0.5 wt% BCNFs content present an increased stiffness and a lower, non-pH-dependent swelling than PAA hydrogels or PAA hydrogels with cellulose nanocrystals. Besides, BCNFs/PAA hydrogels are biocompatible and can be frozen/thawed. Those characteristics endorse these hybrid hydrogels as potential candidates for vascular and cartilage tissue implants.
This work aims to assess the potential reactivity of a mechanically activated kaolin for its use as an alternative cement precursor. The mechanical activation was successfully achieved by grinding at different rotation speeds (250, 300, and 350 rpm) and times (60, 90, and 120 min), obtaining a highly amorphous and reactive material. The amorphization was monitored through XRD with amorphous content estimation and FTIR deconvolution. The potential reactivity was evaluated through chemical attacks, obtaining SiO2 and Al2O3 availabilities up to 95 wt% and 93 wt% of total SiO2 and Al2O3 content. XRD and FTIR also allowed the identification of the non-reactive phases on the insoluble residue after chemical attacks. NMR analysis revealed that part of the aluminium was in IV coordination, limiting the reactivity in the alkali activation process. This work demonstrated the effectiveness of mechanical activation as a greener treatment than thermal dehydroxylation to increase the raw kaolin's reactivity.
Electrolyte effects play an important role on the activity of the oxygen reduction reaction (ORR) of Pt-based electrodes. Herein, we combine a computational model and rotating disk electrode measurements to investigate the effects from phosphate anion poisoning for the ORR on well-defined extended Pt surfaces. We construct a model including the poisoning effect from phosphate species on Pt(111) and Cu/Pt(111) based on density functional theory simulations. We have investigated the effect of adsorbed phosphate species at low overpotentials when tuning *OH binding energies. Our work shows that, regardless of the surface site blockage from phosphate, the trend in catalytic oxygen reduction activity is predominately governed by the *OH binding.
The photoconversion of a norbornadiene (NBD) derivative was studied under high-intensity mono- and polychromatic light conditions at high concentrations. The photoisomerization quantum yield (ϕNBD→QC), proceeding from NBD to its quadricyclane (QC) isomer, was determined using a tunable OPO laser and a solar simulator light source. The solar simulator was designed to mimic the AM1.5G solar spectrum between 300 and 900 nm. Using the OPO laser, ϕNBD→QC was measured at discrete values between 310 and 350 nm in steps of 10 nm, and a variation between 0.81 and 0.96 was observed. Weighting these values of ϕNBD→QC with the spectral profile of the solar simulator, an averaged value of 0.87 ± 0.03 was obtained. Determination of ϕNBD→QC was also performed directly in the solar simulator providing a value of 0.97 ± 0.14, in good agreement with the weighted values from the OPO. Photoisomerization quantum yields were found to decrease slightly at higher concentrations. At high concentrations, we found that correcting for the presence of QC was important due to similar absorption coefficients of the NBD and QC isomers at the absorption tail. Cyclability of the forward and backward NBD/QC conversion was studied over several cycles. The NBD/QC couple exhibited excellent thermal stability, but a slight photodegradation per cycle was observed, increasing with the concentration of the sample. This result indicates that the molecules undergo some intermolecular reactions.
Magneto-ionics is an emerging actuation mechanism to control the magnetic properties of materials via voltage-driven ion motion. This effect largely relies on the strength and penetration of the induced electric field into the target material, the amount of generated ion transport pathways, and the ionic mobility inside the magnetic media. Optimizing all these factors in a simple way is a huge challenge, although highly desirable for technological applications. Here, we demonstrate that the introduction of suitable transition-metal elements to binary nitride compounds can drastically boost magneto-ionics. More specifically, we show that the attained magneto-ionic effects in CoN films (i.e., saturation magnetization, toggling speeds, and cyclability) can be drastically enhanced through 10% substitution of Co by Mn in the thin-film composition. Incorporation of Mn leads to transformation from nanocrystalline into amorphous-like structures, as well as from metallic to semiconducting behaviors, resulting in an increase of N-ion transport channels. Ab initio calculations reveal a lower energy barrier for CoMn-N compared to Co-N that provides a fundamental understanding of the crucial role of Mn addition in the voltage-driven magnetic effects. These results constitute an important step forward toward enhanced voltage control of magnetism via electric field-driven ion motion.
We demonstrate the key role of charge-transfer complexes in surface doping as a successful methodology for improving channel field-effect mobility and reducing the threshold voltage in organic field-effect transistors (OFETs), as well as raising the film conductivity. Demonstrated here for 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) doped with 2,2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6TCNNQ), channel doping by sequential deposition is consistently rationalized by the development of a cocrystalline structure that forms and evolves from the surface of the organic semiconductor film without trading the thin-film structure integrity. This scenario brings higher benefits for the device operation than doping by codeposition, where a decrease in the field-effect mobility of the device, even for a dopant content of only 1 mol %, makes codeposition less suitable. Insight into the structural and electronic properties of the interface satisfactorily explains the improved performance of OFETs upon the incorporation of the dopant and provides an understanding of the mechanism of doping in this system.
Transient liquid assisted growth (TLAG) is an ultrafast non‐equilibrium growth process mainly governed by kinetic parameters, which are only accessible through fast in situ characterizations. In situ synchrotron X‐ray diffraction (XRD) analysis and in situ electrical resistivity measurements are used to derive kinetic diagrams of YBa2Cu3O7−x (YBCO) superconducting films prepared via TLAG and to reveal the unique peculiarities of the process. In particular, diagrams for the phase evolution and the YBCO growth rates have been built for the two TLAG routes. It is shown that TLAG transient liquids can be obtained upon the melting of two barium cuprate phases (and not just one), differentiated by their copper oxidation state. This knowledge serves as a guide to determine the processing conditions to reach high performance films at high growth rates. With proper control of these kinetic parameters, films with critical current densities of 2–2.6 MA cm⁻² at 77 K and growth rates between 100–2000 nm s⁻¹ are reached. These growth rates are 1.5–3 orders of magnitude higher than those of conventional methods.
Bimetallic single–atom catalysts (b–SACs) have recently gained prominence by virtue of the unique catalytic cooperative interactions they can exhibit, intertwining electronic and geometric effects. To date, research efforts have exclusively focused on direct mechanisms such as electron density transfer or sequential reactivity. Herein, the first study on indirect, coordination–induced catalytic synergies in carbon‐supported RuPt SACs is conducted. To this end, a holistic approach is developed, combining i) precision synthesis, ii) advanced characterization, iii) exploration of single–site adsorption properties via the hydrogen evolution reaction, and iv) modeling through density functional theory. Despite the lack of both intermetallic coordination in the first or second shell and charge redistribution effects, the RuPt SACs exhibit a H2 formation rate enhanced up to 15–fold compared with their monometallic counterparts. To unfold the origin of the intermetallic cooperativity, modifications of the structural and catalytic properties induced by the integration of a second metal species are investigated. Thus, Pt atoms are found to selectively occupy the most energeticallyfavorable cavities in the support, prompting Ru atoms to assume a distinct, more active, configuration. This contribution unveils a novel principle of bimetallic cooperativity, demonstrating the key role of integrative experimental and computational analyses in studying b–SACs.
Catalyst activity can depend distinctly on nanoparticle size and shape. Therefore, understanding the structure sensitivity of catalytic reactions is of fundamental and technical importance. Experiments with single-particle resolution, where ensemble-averaging is eliminated, are required to study it. Here, we implement the selective trapping of individual spherical, cubic, and octahedral colloidal Au nanocrystals in 100 parallel nanofluidic channels to determine their activity for fluorescein reduction by sodium borohydride using fluorescence microscopy. As the main result, we identify distinct structure sensitivity of the rate-limiting borohydride oxidation step originating from different edge site abundance on the three particle types, as confirmed by first-principles calculations. This advertises nanofluidic reactors for the study of structure-function correlations in catalysis and identifies nanoparticle shape as a key factor in borohydride-mediated catalytic reactions.
The fabrication of efficient organic photovoltaic (OPV) modules via high throughput methods is a crucial milestone to facilitate their commercialization. The achievement of reliable printing and coating processes for large-scale modules has, however, been challenging thus far. Indeed, the performance gap is large between cells produced at lab-scale and those resulting from industrial methods. Therefore, understanding the critical steps in the upscaling process is decisive to address the research efforts towards decreasing the aforementioned gap. In this contribution, we analyze the efficiency losses associated with several of the main steps involved in the up-scaling pathway of the OPV devices, from lab-scale blade coating to pre-industrial slot die roll-to-roll coating. We show that when using materials in the active layer for which the performance is tolerant to thickness/microstructure variations, the critical steps are related to the charge carrier blocking layers, as well as potential losses due to parasitic absorption in the semitransparent electrodes.
Tailoring the magnetic features of cobalt ferrite nanoparticles (NPs) has been achieved via varying the doping percent of nickel. The nickel-substituted cobalt ferrite NPs Ni x Co 1-x Fe 2 O 4 (0 ≤ x ≤ 1.0) are constructed by the eco-friendly coprecipitation method. The formation of a nearly cubic single-phase spinel frame is assured by the analysis of XRD data. Moreover, the Rietveld analysis based on structure refinement is implemented in this study to precisely determine the microstructural parameters and estimate the cation distribution. A linear drop-in lattice constant with boosting the Ni ²⁺ ion percent is acclaimed, in regard to Vegard's law. The creation of nanoparticles that are nearly spherical along with polyhedron shape and have a diameter of (about 39–45 nm) has been affirmed by utilizing high-resolution transmission electron microscopy (HRTEM). Also, the crystalline essence of the formed nanoparticles has been declared by selective area electron diffraction (SAED). The magnetic properties have been collected from the hysteresis loops and FC–ZFC curves. These curves have been tweaked as a function of low-temperature from 5 K up to 300 K and in the existence of an external magnetic field (± 70KOe). The magnetization curves revealed that CoFe 2 O 4 (NPs) correspond to the hard ferrimagnetic material, whereas NiFe 2 O 4 (NPs) matched well with identical soft ferrimagnetic material. Also, the divergence betwixt the theoretical and experimental values of the magnetic moment is well explained by the model of "Random Canting of Spins, (RCS)". In addition, a remarkable reduction is found in the recorded values of magnetic parameters by increasing Ni ²⁺ content and decreasing the temperature towards 5 K. These findings imply the potential of Ni ²⁺ ions doping in enhancing the magnetic properties of cobalt ferrite for vast magnetic applications.
Lysosomal storage disorders (LSD) are a group of rare life-threatening diseases caused by a lysosomal dysfunction, usually due to the lack of a single enzyme required for the metabolism of macromolecules, which leads to a lysosomal accumulation of specific substrates, resulting in severe disease manifestations and early death. There is currently no definitive cure for LSD, and despite the approval of certain therapies, their effectiveness is limited. Therefore, an appropriate nanocarrier could help improve the efficacy of some of these therapies. Liposomes show excellent properties as drug carriers, because they can entrap active therapeutic compounds offering protection, biocompatibility, and selectivity. Here, we discuss the potential of liposomes for LSD treatment and conduct a detailed analysis of promising liposomal formulations still in the preclinical development stage from various perspectives, including treatment strategy, manufacturing, characterization, and future directions for implementing liposomal formulations for LSD.
Rare earth activated nitridosilicates have important applications as phosphor components in white light emitting diodes. (Oxy)nitridosilicates with β-K2SO4 structure doped with Eu²⁺ are luminescent materials with emission wavelengths ranging from green to red under excitation with blue-UV light. Here we report the synthesis of isostructural NdEuSiO3N and the new oxynitridosilicate NdSrSiO3N by solid state reaction between Nd2O3, NdN, Eu2O3 or SrO and Si3N4 under N2/H2 gas at temperatures of 1300 °C and 1500 °C respectively. These compounds are the limiting compositions of the solid solution NdSr1-xEuxO3N crystallizing in the space group Pmnb with cell parameters a = 5.62293(1), b = 7.02285(1), c = 9.64784(2) Å for NdEuSiO3N, and a = 5.63074(9), b = 7.01658(10), c = 9.65765(15) Å for NdSrSiO3N. The Nd³⁺and Eu²⁺ cations in NdEuSiO3N or Nd³⁺ and Sr²⁺ in NdSrSiO3N show partial order in the two available crystallographic sites of coordination numbers 10 (M1) and 9 (M2), with strongly preferred occupancy of the larger divalent cations Eu²⁺ (77%) and Sr²⁺ (78%) for the M1 site, whereas the M2 site is preferred by Nd³⁺. Magnetic susceptibility measurements down to 2 K show that NdEuSiO3N is ferromagnetic with Tc = 3 K, in contrast to NdSrSiO3N that shows antiferromagnetic interactions at low temperatures. The band gaps of NdEuSiO3N and NdSrSiO3N determined from diffuse reflection spectroscopy are 2.37 and 3.72 eV respectively. NdEuSiO3N and the members of the solid solution NdSr0.98Eu0.02SiO3N and NdSr0.5Eu0.5SiO3N are orange-red light emitting luminescent materials, showing a broad emission band centered between 605 and 639 nm under excitation at 405 nm. These compounds are new phosphor materials with emission wavelengths shifted to the red with respect to the isostructural oxysilicates, which is induced by the introduction of nitride.
Due to their complex formulation, conductive nanoparticle inks for inkjet printing are limited in terms of the types of metals and substrates that can be utilized. A new and simplified class of inks called metal salt decomposition (MSD) inks has the potential to introduce a multitude of metals of which can be printed directly onto a wide range of substrates. Here, we demonstrate the use of atmospheric oxygen plasma to develop polycrystalline Au and Pt films at processing temperatures near room temperature (⁓33 ºC) with excellent conductivities up to 105 S m‐1. The conformal nature of the ink allows metal films to be printed onto a broad range of temperature sensitive substrates including polymers, papers, and fabric. The Au ink is then used to build a simple LED circuit showing both its flexibility, durability and long term stability as deposited thin metal films. Additionally, such inks cost less than 1/3rd the price of similar nanoparticle inks highlighting its overall affordability and good stability. This article is protected by copyright. All rights reserved.
Piezoelectric force microscopy (PFM) has demonstrated to be a powerful tool to characterize ferroelectric materials. However, extrinsic effects, most notably, those resulting from surface charges, often mask or mirror genuine piezoelectric response, challenging PFM data understanding. The contribution of surface charges to PFM signal is commonly compensated by using appropriate external bias voltage, which is ad-hoc selected and sample dependent. Here, we determine the compensating voltage in thin films of different ferroelectric materials and we compare with the corresponding I-V characteristics recorded using suitable electrodes. It turns out that the sign and magnitude of the bias voltage required to compensate the surface charges are related to the asymmetry of the I-V characteristics. We propose that this relation results from the fact that the semiconducting properties of the material determine both the I-V dependence, and the sign of charged adsorbates. We show how to make use of this correlation to predict the required compensation voltage of a non-ferroelectric material and we show that spurious piezoelectric-like contributions are largely cancelled. The results provide guidelines to mitigate common extrinsic contributions in PFM imaging.
Bread waste is a major part of food wastage which could be upcycled to produce functional materials, following the principles of the circular bioeconomy. This work shows that bread waste can be recycled and valorized to produce a composite conductive material with excellent properties for chemical sensor applications. Here, dry bread is impregnated with an aqueous solution of a silver precursor and pyrolyzed to produce a porous carbon matrix containing Ag nanoparticles with diameters ranging from 20 to 40 nm. These particles perform as catalytic redox centers for the electrochemical detection of halide ions (Cl-, Br-, and I-) and organohalide target molecules such as sucralose and trichloroacetic acid. A thorough analytical characterization is carried out to show the potential application of the developed material for the manufacturing of electrochemical sensor approaches. The material preparation is sustainable, low-cost, simple, and upscalable. These are ideal features for the large-scale manufacturing by screen-printing technologies of single-use electrochemical sensors for the rapid analysis of halogenated organic pollutants in waters.
Understanding how reaction conditions affect metal-support interactions in catalytic materials is one of the most challenging tasks in heterogeneous catalysis research. Metal nanoparticles and their supports often undergo changes in structure and oxidation state when exposed to reactants, hindering a straightforward understanding of the structure-activity relations using only ex situ or ultrahigh vacuum techniques. Overcoming these limitations, we explored the metal-support interaction between gold nanoparticles and ceria supports in ultrahigh vacuum and after exposure to CO. A combination of in situ methods (on powder and model Au/CeO2 samples) and theoretical calculations was applied to investigate the gold/ceria interface and its reactivity toward CO exposure. X-ray photoelectron spectroscopy measurements rationalized by first-principles calculations reveal a distinctly inhomogeneous charge distribution, with Au+ atoms in contact with the ceria substrate and neutral Au0 atoms at the surface of the Au nanoparticles. Exposure to CO partially reduces the ceria substrate, leading to electron transfer to the supported Au nanoparticles. Transferred electrons can delocalize among the neutral Au atoms of the particle or contribute to forming inert Auδ- atoms near oxygen vacancies at the ceria surface. This charge redistribution is consistent with the evolution of the vibrational frequencies of CO adsorbed on Au particles obtained using diffuse reflectance infrared Fourier transform spectroscopy.
This work aims to highlight the beneficial effect of annealing of Cu2ZnSn(S,Se)4 (CZTSSe) nanoparticles (NPs) on the properties of the obtained films by RF-magnetron sputtering at room temperature (RT) and at 200 °C. The CZTSSe targets used for the deposition are obtained using nanoparticles synthesized by solvothermal technique. It is denoted that the elemental composition of thin films becomes independent of the growth temperature in the case of annealed CZTSSe NPs. The optical investigation gives that the gap energy is ranging between 1.26 and 1.40 eV with an Urbach’s energy between 100 and 200 meV. By using the Wemple and Didominico model to analyze the refractive index spectra, we have identified common oscillator energy for all CZTSSe thin films and dispersion energy ranging from 2.63 to 5.81 eV. CZTSSe thin films obtained by means of annealed NPs exhibit higher dielectric constant and refractive index. The dispersion of different parameters with experimental conditions is analyzed via a common relationship that illustrates the linear dependence of n0, Ed, εs, and εL on the square of the valence difference (ΔZ). The conductivity spectra are deduced, and a theoretical model was identified to fit the permittivity spectra. The obtained results are promising for solar cell applications.
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175 members
Alexander Edström
  • Theory and simulation
Joffre Gutierrez Royo
  • Nanostructured Materials
Xabier Mikel Turrillas
  • Department of Advanced Crystallography & Functional Materials
Elies Molins
  • Department of Crystallography
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Barcelona, Spain