Scientific Papers in SCI

Abstract

Combinations of perovskite-type oxides with transition and precious metals exhibit remarkable regenerating properties that can be exploited for catalytic applications. The objective of the present work was to study the structural changes experienced by LaCo_0.8Cu_0.2O₃ under reducing/oxidizing atmosphere (redox) and Preferential Oxidation of CO (PrOx, with high H₂ concentration) conditions and their reversibility. LaCo_0.8Cu_0.2O₃ was prepared by ultrasonic spray combustion and was characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Structural changes were followed by operando XRD and XAS. Metallic Co and Cu were segregated under both sets of reducing conditions and re-dissolved into the perovskite upon oxidation at 500 °C. Simultaneously, the perovskite-type oxide disappeared under reducing conditions and formed again upon high-temperature oxidation. The effects of this reversible reduction/dissolution of B-site metals on catalyst structure and activity were studied concerning the catalytic process of PrOx. The active phases of cobalt and copper oxides suffer a reduction during the PrOx reaction due to the high H₂ concentration; thus, the application of an intermediate oxidation treatment can regenerate the catalytic system and the perovskite can be used for several cycles of reaction and regeneration. In contrast, when this intermediate oxidation treatment is not applied, the catalytic performance decreases in successive activity cycles.

Abstract

Research on high-field magnetic resonance imaging (HF-MRI) has been increased in recent years, aiming to improve diagnosis accuracy by increasing the signal-to-noise ratio and hence image quality. Conventional contrast agents (CAs) have important limitations for HF-MRI, with the consequent need for the development of new CAs. Among them, the most promising alternatives are those based on Dy3+ or Ho3+ compounds. Notably, the high atomic number of lanthanide cations would bestow a high capability for X-ray attenuation to such Dy or Ho-based compounds, which would also allow them to be employed as CAs for X-ray computed tomography (CT). In this work, we have prepared uniform NaDy(WO4)(2) and NaHo(WO4)(2) nanoparticles (NPs), which were dispersible under conditions that mimic the physiological media and were nontoxic for cells, meeting the main requirements for their use in vivo. Both NPs exhibited satisfactory magnetic relaxivities at 9.4 T, thus making them a promising alternative to clinical CAs for HF-MRI. Furthermore, after their intravenous administration in tumor-bearing mice, both NPs exhibited significant accumulation inside the tumor at 24 h, attributable to passive targeting by the enhanced permeability and retention (EPR) effect. Therefore, our NPs are suitable for the detection of tumors through HF-MRI. Finally, NaDy(WO4)(2) NPs showed a superior X-ray attenuation capability than iohexol (commercial CT CA), which, along with their high r(2) value, makes them suitable as the dual-probe for both HF-MRI and CT imaging, as demonstrated by in vivo experiments conducted using healthy mice.

Abstract

Intraband carrier relaxation in quantum dots (QDs) has been a subject of extensive spectroscopic investigation for several decades, and have been used to optimize the efficiency of opto-electronic processes. In the past few years, metal halide perovskites-based QDs have been shown to exhibit slow hot-carrier cooling characteristics that are desirable for photo-energy harvesting technologies. While several mechanisms are proposed to rationalize the retardation of the cooling dynamics, including hot-phonon bottleneck and polaronic effects, the role of inter-particle connectivity in these dynamics is largely ignored. Here, an in-depth study of photo-excitation dynamics and carrier cooling on perovskite QD solids with varying degrees of inter-dot coupling is presented. It is observed that inter-particle connectivity has deterministic effects on the many-body interactions that are relevant for carrier cooling. These include carrier-carrier interactions that result in Auger-reheating of the carriers, and lattice characteristics that subsequently affect the phonon-assisted cooling dynamics. This spectroscopic study of ultrafast carrier dynamics in perovskite QD solids establishes inter-dot separation as a critical material design parameter for the optimization of photo-generated carrier temperature, which fundamentally determines the luminescence characteristics and thus the opto-electronic quality of the material.

The photo-excitation dynamics and carrier cooling in metal halide perovskite quantum dot solids are investigated here. Evidence for the deterministic role of inter-particle connectivity on the many-body interactions relevant to carrier cooling is discussed. These include carrier-carrier interactions that result in Auger-reheating of the carriers, and lattice coupling that subsequently affects the phonon-assisted cooling dynamics. image

Abstract

Carbon is a critical material for existing and emerging energy applications and there is considerable global effort in generating sustainable carbons. A particularly promising area is iron-catalyzed graphitization, which is the conversion of organic matter to graphitic carbon nanostructures by an iron catalyst. In this paper, it is reported that iron-catalyzed graphitization occurs via a new type of mechanism that is called homogeneous solid-state catalysis. Dark field in situ transmission electron microscopy is used to demonstrate that crystalline iron nanoparticles “burrow” through amorphous carbon to generate multiwalled graphitic nanotubes. The process is remarkably fast, particularly given the solid phase of the catalyst, and in situ synchrotron X-ray diffraction is used to demonstrate that graphitization is complete within a few minutes.

Abstract

This study presents a novel composite beads, AC@Alg-PANI, consisting of activated carbon (AC) derived from Crataegus monogyna, sodium alginate (Alg), and polyaniline (PANI), tested for the removal of methylene blue (MB). The physicochemical characteristics of the composite beads were analyzed using methods such as pHPZC, FTIR, TGA/DTA, SEM, and BET. Moreover, factors affecting the adsorption of MB, such as initial pH, dye concentration, adsorbent weight, ionic strength, and temperature, were also explored. A full factorial design was implemented to identify the optimum conditions for removal, which were found to be a pH of 6, an adsorbent amount of 100 mg, and a dye concentration of 100 mg/L. The isotherm data indicated that the adsorption of MB by AC@Alg-PANI follows the Langmuir model, with a maximum adsorption capacity of 774.6 mg/g. The adsorption kinetics followed the pseudo-first-order model, indicating that the adsorption process is physical in nature. The thermodynamic results suggest that MB adsorption on AC@Alg-PANI was favorable, spontaneous, and endothermic. Additionally, after five regeneration cycles, the composite beads demonstrated excellent recyclability for MB dye removal with high efficiency. Furthermore, molecular dynamics simulations (MDS) of the adsorption energy highlighted the physically spontaneous nature of the process, involving various weak interactions, including van der Waals forces, intermolecular interactions, hydrogen bonding, and π-electron interactions.

Abstract

The development of efficient strategies to tune the CO2RR selectivity of Cu-based catalytic interfaces, especially on specific domains, such as Cu (200) facets with high activity toward competitive hydrogenation evolution reaction (HER), remains a challenging task. In this work, Cu-based catalytic layers with thiocyanate (-SCN), cyanide (-CN), or ethylenediamine (-NH2R) coordination linkages are prepared on Cu nanocolumns arrays (Cu NCAs) with predominant (200) exposed facets. The coordination of these ligands induces more Cu+ species and inhibits the adsorption of H & lowast; on the Cu (200) facet, leading to enhanced CO2RR performance and substantially suppressing the competitive HER. The faradaic efficiency (FE) of Cu-SCN, Cu-CN, and Cu-NH2R NWAs for producing HCOOH, C2H4, and C1 mixture products (HCOOH and CO) reach to 66.5%, 21.1%, and 57.1%, respectively. In situ spectroscopic studies reveal Cu-SCN, Cu-CN, and Cu-NH2R exhibit more reasonable adsorption energy toward & lowast;OCHO, *CO, and *COOH intermediates, promoting the HCOOH, C2H4, and C1 mixture generation, respectively. This study might provide a new perspective for the development of high-performance Cu-based CO2RR catalytic electrodes based on the combination of various commercial free-standing Cu substrates and organic/inorganic ligands. (c) 2024 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Abstract

Herein, we demonstrate mechanically stable large-area thin films with a purely real refractive index (n) close to 1 in the optical range. At specific wavelengths, it can reach values as small as n = 1.02, the lowest reported for thin solid slabs. These are made of a random network of interwoven spherical silica shells, created by chemical vapour deposition of a thin layer of silica on the surface of randomly packed monodisperse polymer nanoparticles that form a film. Thermal processing of the composites results in highly porous silica-based transparent thin films. We demonstrate the potential of this approach by making novel photonic materials such as strong optical diffusers, built by integrating scattering centers within the ultralow n transparent films, or highly efficient light-emitting slabs, in which losses by total internal reflection are practically absent as a result of the almost null optical impedance at the film-air interface.

Abstract

Water quality and usability are global concerns due to microbial and chemical pollution resulting from anthropogenic activities. Therefore, strategies for eliminating contaminants are required. In this context, the removal and decrease in antibiotic activity (AA) associated with levofloxacin (LEV), using TiO₂ and Ag/TiO₂ catalysts, with and without sunlight and peroxydisulfate, was evaluated. Additionally, the disinfection capacity of catalytic systems was assessed. The catalysts were synthesized and characterized. Moreover, the effect of Ag doping on visible light absorption was determined. Then, the photocatalytic treatment of LEV in water was performed. The materials characterization and EPR analyses revealed that LEV degradation and AA decrease were ascribed to a combined action of solar light, sulfate radical, and photocatalytic activity of the TiO₂-based materials. Also, the primary byproducts were elucidated using theoretical analyses (predictions about moieties on LEV more susceptible to being attacked by the degrading species) and experimental techniques (LC-MS), which evidenced transformations on the piperazyl ring, carboxylic acid, and cyclic ether on LEV. Moreover, the AA decrease was linked to the antibiotic transformations. In addition, the combined system (i.e., light/catalyst/peroxydisulfate) was shown to be effective for E. coli inactivation, indicating the versatility of this system for decontamination and disinfection.

Abstract

In this piece, we explore the transformative potential of sustainable biofuel production as a solution to the energy crisis and a pivotal element in realizing the environmental and societal ambitions of Society 5.0. Through a critical examination of "bottom-up"and "topdown"strategies for converting bio-feedstocks sourced from anthropogenic activities into renewable fuels, the work underscores the need for innovation in catalysts and process intensification. By highlighting the advances and challenges in harnessing unconventional feedstocks and integrating renewable energy, this work points to a future where biofuels stand as a cornerstone of a sustainable energy landscape. The significance of this discussion extends beyond the technical realm, offering a vision for a circular economy that reduces dependence on fossil fuels, addresses climate change, and promotes global energy security. It calls for a united front among researchers, industry leaders, and policymakers to drive the biofuel sector toward efficiency, scalability, and widespread adoption.

Abstract

En este trabajo, la Titania se modificó por sulfatación o fluorización y platino en superficie, con el objetivo de mejorar la eficiencia en la reducción de Cr (VI) en comparación con el material TiO2 base sintetizado por el método sol-gel. Los materiales fueron caracterizados por DRX, SBET, UV-Vis DRS, FRX, TEM, FTIR y XPS. Las modificaciones permitieron obtener una mayor estabilidad en la fase Anatasa y en el área superficial del semiconductor. La adición de F y Pt en el TiO2 provocaron aumentos de absorción en la región visible del espectro electromagnético. Se observó una correlación entre las nuevas propiedades fisicoquímicas obtenidas tras la modificación del TiO2 y el rendimiento fotocatalítico del material. El mejor resultado en la reducción de cromo se obtuvo utilizando Pt-S-TiO2 como fotocatalizador, este material mostró una combinación adecuada de área superficial, alta absorción UV-Vis, alta hidroxilación y la existencia de nanopartículas de Pt en la superficie que favorecen un aumento de la vida media del par electrón-hueco. También se evaluaron parámetros de reacción que demostraron que el mejor desempeño fotocatalítico se obtuvo bajo atmósfera de N2, intensidad de luz de 120 W/m2 y 2 horas de tiempo total de reacción. Así mismo, se observó que aumentar el tiempo de reacción de 2 a 5 horas tuvo un efecto perjudicial sobre la eficiencia en la reducción de Cr (VI).

Abstract

This study focused on the development of vanadium-based catalysts for formic acid production from glucose. The influence of different vanadium precursors on the catalytic activity of titania supported catalysts was contemplated and compared to the performance of commercial and synthesized unsupported V2O5. The obtained results reveal a successful deposition of multiple vanadium species on TiO2 as confirmed by XRD, Raman, and UV-Vis measurements. Catalyst screening identifies V5+ species as main player indicating its important oxidizing potential. Afterwards, the key reaction conditions, as temperature, time, pressure and catalyst loading, were optimized as well as the state of the catalyst after the reaction characterized.

Abstract

The ability to control the porosity of thin oxide films is a key factor determining their properties. Despite the abundance of dry processes for synthesizing oxide porous layers, a high porosity range is typically achieved by spin-coating-based wet chemical methods. Besides, special techniques such as supercritical drying are required to replace the pore liquid with air while maintaining the porous network. In this study, we propose a new method for the fabrication of ultraporous titanium dioxide thin films at room or mild temperatures (T <= 120 degrees C) by a sequential process involving plasma deposition and etching. These films are conformal to the substrate topography even for high-aspect-ratio substrates and show percolated porosity values above 85% that are comparable to those of advanced aerogels. The films deposited at room temperature are amorphous. However, they become partly crystalline at slightly higher temperatures, presenting a distribution of anatase clusters embedded in the sponge-like open porous structure. Surprisingly, the porous structure remains after annealing the films at 450 degrees C in air, which increases the fraction of embedded anatase nanocrystals. The films are antireflective, omniphobic, and photoactive, becoming superhydrophilic when subjected to ultraviolet light irradiation. The supported, percolated, and nanoporous structure can be used as an electron-conducting electrode in perovskite solar cells. The properties of the cells depend on the aerogel-like film thickness, which reaches efficiencies close to those of commercial mesoporous anatase electrodes. This generic solvent-free synthesis is scalable and applicable to ultrahigh porous conformal oxides of different compositions, with potential applications in photonics, optoelectronics, energy storage, and controlled wetting.

Abstract

Next-generation light-emitting applications such as displays and opticalcommunications require judicious control over emitted light, includingintensity and angular dispersion. To date, this remains a challenge as con-ventional methods require cumbersome optics. Here, we report highly direc-tional and enhanced electroluminescence from a solution-processed quasi-2-dimensional halide perovskite light-emitting diode by building a devicearchitecture to exploit hybrid plasmonic-photonic Tamm plasmon modes. Byexploiting the processing and bandgap tunability of the halide perovskitedevice layers, we construct the device stack to optimise both optical andcharge-injection properties, leading to narrow forward electroluminescencewith an angular full-width half-maximum of 36.6° compared with the con-ventional isotropic control device of 143.9°, and narrow electroluminescencespectral full-width half-maximum of 12.1 nm. The device design is versatile andtunable to work with emission lines covering the visible spectrum with desireddirectionality, thus providing a promising route to modular, inexpensive, anddirectional operating light-emitting devices.

Abstract

Joule heating is generally acknowledged as the main driving force behind Flash Sintering. However, this view is challenged by the presence of athermal phenomena and the similarities between the flash process and dielectric breakdown. This work offers new insights into flash as an electrical runaway. Using current ramps to perform flash experiments on zinc oxide, two distinct stages within the process were revealed by electrical, thermal and microstructural measurements: a field-dominated regime where the flash event is triggered and a subsequent current-dominated regime associated with power dissipation. The contribution of each regime to the whole flash process was found to be determined by the initial resistivity of the sample. Furthermore, impedance spectroscopy data confirmed field-induced enhancement of conductivity at the flash-onset without significant Joule heating.

Abstract

In this work, the influence of the aspect ratio of graphene-based nanostructures (GBNs) and content on the mechanical properties of 3 mol% yttria tetragonal zirconia polycrystalline 3Y-TZP matrix composites was analysed. The influence of the dispersion method and sintering parameters on the flexural strength and elastic modulus of the composites was studied, and the fracture surfaces were characterized to determine the fracture mechanisms that occur. The results showed that small amounts of exfoliated graphene nanoplatelets, with reduced lateral size, and few layer graphene, up to 1.0 and 2.5 vol%, respectively, slightly increase the 3Y-TZP flexural strength. This has been attributed to the tortuosity of the crack propagation pathways and strengthening mechanisms. Higher contents cause a decrease in flexural strength and stiffness because of overlapped GBNs, which can promote the crack propagation. The pull-out of GBN was more significant in composites with non-exfoliated graphene nanoplatelets, where no increase on the flexural or biaxial strength was measured.

Abstract

The increasing anthropogenic emissions of greenhouse gases (GHG) is encouraging extensive research in CO₂ utilisation. Dry reforming of methane (DRM) depicts a viable strategy to convert both CO₂ and CH₄ into syngas, a worthwhile chemical intermediate. Among the different active phases for DRM, the use of nickel as catalyst is economically favourable, but typically deactivates due to sintering and carbon deposition. The stabilisation of Ni at different loadings in cerium zirconate inorganic complex structures is investigated in this work as strategy to develop robust Ni-based DRM catalysts. XRD and TPR-H₂ analyses confirmed the existence of different phases according to the Ni loading in these materials. Besides, superficial Ni is observed as well as the existence of a CeNiO₃ perovskite structure. The catalytic activity was tested, proving that 10 wt.% Ni loading is the optimum which maximises conversion. This catalyst was also tested in long-term stability experiments at 600 and 800°C in order to study the potential deactivation issues at two different temperatures. At 600°C, carbon formation is the main cause of catalytic deactivation, whereas a robust stability is shown at 800°C, observing no sintering of the active phase evidencing the success of this strategy rendering a new family of economically appealing CO₂ and biogas mixtures upgrading catalysts.

Abstract

Herein we study the economic performance of hydrochar and synthetic natural gas co-production from olive tree pruning. The process entails a combination of hydrothermal carbonization and methanation. In a previous work, we evidenced that standalone hydrochar production via HTC results unprofitable. Hence, we propose a step forward on the process design by implementing a methanation, adding value to the gas effluent in an attempt to boost the overall process techno-economic aspects. Three different plant capacities were analyzed (312.5, 625 and 1250 kg/hr). The baseline scenarios showed that, under the current circumstances, our circular economy strategy in unprofitable. An analysis of the revenues shows that hydrochar selling price have a high impact on NPV and subsidies for renewable coal production could help to boost the profitability of the process. On the contrary, the analysis for natural gas prices reveals that prices 8 times higher than the current ones in Spain must be achieved to reach profitability. This seems unlikely even under the presence of a strong subsidy scheme. The costs analysis suggests that a remarkable electricity cost reduction or electricity consumption of the HTC stage could be a potential strategy to reach profitability scenarios. Furthermore, significant reduction of green hydrogen production costs is deemed instrumental to improve the economic performance of the process. These results show the formidable techno-economic challenge that our society faces in the path towards circular economy societies.

Abstract

The impact derived from incorporating water into CH4/CO2 biogas stream for the generation of syngas was investigated over the Rh/MgAl2O4 catalyst using operando steady-state and transient DRIFT spectroscopy coupled with MS. The incorporation of steam resulted in improved CH4 conversion rates and attained syngas streams with higher H-2/CO ratios. It was demonstrated that in the presence of steam, the generation of CHxO species through the reaction of CO* with active *OH species is favored at the metal support surface. Besides, the enhanced resistance delivered by water molecules towards deactivating the coking phenomena was associated with easier carbonaceous decomposition and the exposition of the very active Rh (100) surfaces for methane decomposition. The Rh/MgAl2O4 catalyst was demonstrated to be an effective catalyst for the production of H-2-rich syngas streams. More importantly, the insights reported herein provide new evidences regarding the impact of steam on biogas reforming reactions.

Abstract

BiFeO3 is a promising multiferroic material for versatile device applications due to its co-existence of magnetic (i.e., antiferromagnetic) and ferroelectric ordering at room temperature. While its functional properties have been extensively investigated, the exploration of its mechanical behavior was limited mostly to the thin-film form of BiFeO3. In this work, we conducted in situ micropillar compression experiments to investigate the deformation behavior of La-doped BiFeO3 (La-BFO) samples processed by both conventional and flash sintering methods. The conventionally sintered La-BFO exhibited limited deformability at room temperature and 450 degrees C. In contrast, the deformability of the flash-sintered La-BFO specimens was substantially improved by nearly 100% at both testing temperatures. Detailed post-mortem studies suggest that preexisting dislocations and wide anti-phase boundaries introduced during flash sintering can toughen flash-sintered La-BFO by easing dislocation migration and ferroelastic domain switching. This study provides a fresh perspective to design an advanced multifunctional system with improved mechanical properties.

Abstract

Free-standing films have been obtained by drop-casting cellulose-glycerol mixtures (up to 50 wt% glycerol) dissolved in trifluoroacetic acid and trifluoroacetic anhydride (TFA:TFAA, 2:1, v:v). A comprehensive examination of the optical, structural, mechanical, thermal, hydrodynamic, barrier, migration, greaseproof, and biodegradation characteristics of the films was conducted. The resulting cellulose-glycerol blends exhibited an amorphous molecular structure and a reinforced H-bond network, as evidenced by X-ray diffraction analysis and infrared spectroscopy, respectively. The inclusion of glycerol exerted a plasticizing influence on the mechanical properties of the films, while keeping their transparency. Hydrodynamic and barrier properties were assessed through water uptake and water vapor/oxygen transmission rates, respectively, and obtained values were consistent with those of other cellulose-based materials. Furthermore, overall migration levels were below European regulation limits, as stated by using Tenax as a dry food simulant. In addition, these bioplastics demonstrated good greaseproof performance, particularly at high glycerol content, and potential as packaging materials for bakery products. Biodegradability assessments were carried out by measuring the biological oxygen demand in seawater and high biodegradation rates induced by glycerol were observed.

Abstract

This review presents an overview on the structures and electrical properties of B-site deficient hexagonal perovskite oxides, which have been receiving increasing attention as key components as dielectric resonators in microwave telecommunications, as well as solid-state oxide ion and proton conductors in solid oxide fuel cells. The structural evolution and stability, order-disorder of cation and anions, and mechanisms underlying the dielectric and ionic conduction behaviors for the B-site deficient hexagonal perovskites are summarized and the roles of the B-site deficiency on the structural stability and option, ion order-disorder and electrical performance are highlighted. This provides useful guidance for design of new hexagonal perovskite oxide materials and structural control to enhance their electrical properties and discover new functionality as dielectric resonators and solid-state ionic conductors.

Abstract

The electrification of heat necessitates the development of innovative domestic heat batteries to effectively balance energy demand with renewable power supply. Thermochemical heat storage systems show great promise in supporting the electrification of heating, thanks to their high thermal energy storage density and minimal thermal losses. Among these systems, salt hydrate-based thermochemical systems are particularly appealing. However, they do suffer from slow hydration kinetics in the presence of steam, which limits the achievable power density. Additionally, their relatively high dehydration temperature hinders their application in supporting heating systems. Furthermore, there are still challenges regarding the appropriate thermodynamic, physical, kinetic, chemical, and economic requirements for implementing these systems in heating applications. This study analyzes a proposal for thermochemical energy storage based on the direct hydration of sodium acetate with liquid water. The proposed scheme satisfies numerous requirements for heating applications. By directly adding liquid water to the salt, an unprecedented power density of 5.96 W/g is achieved, nearly two orders of magnitude higher than previously reported for other salt-based systems that utilize steam. Albeit the reactivity drops as a consequence of deliquescence and particle aggregation, it has been shown that this deactivation can be effectively mitigated by incorporating 10 % silica, achieving lower but stable energy and power density values. Furthermore, unlike other salts studied previously, sodium acetate can be fully dehydrated at temperatures within the ideal range for electrified heating systems such as heat pumps (40 °C – 60 °C). The performance of the proposed scheme in terms of dehydration, hydration, and multicyclic behavior is determined through experimental analysis.

Abstract

A bifunctional catalyst, comprising GaZr oxide and SAPO-34 zeolite, manifests enhanced catalytic activity in CO₂ hydrogenation to light olefins; nonetheless, the comprehensive analysis of the pivotal role played by the underlying structure of ZrO₂ in Ga-Zr oxide has not been investigated. Herein, different crystalline structures of ZrO₂ were prepared by the co-precipitation method and adopted as a support to deposit Ga to obtain ZrO₂ with different ratios of monoclinic ZrO₂ (m-ZrO₂) to tetragonal ZrO₂ (t-ZrO₂) in GaZr oxides for CO₂ hydrogenation to light olefins. Various characterizations demonstrated that the interface between Ga and the mixed phase of (m-t) ZrO₂ produces more oxygen vacancies which favors the adsorption and activation of CO₂, and the larger specific surface area and stronger H₂ adsorption and dissociation capacity promote CO₂ conversion. Interestingly, the GaZr oxide with high m-ZrO₂ content exhibits superior catalytic activity than the GaZr oxide with high content of t-ZrO₂. The highest light olefins yield (9.0%) and selectivity (77.9%) (CO free) with 27.9% CO₂ conversion was achieved. In-situ DRIFT spectra further elaborated that the GaZr oxides with different ZrO₂ crystalline phases follow the same reaction pathway to hydrogenate CO₂ first to HCOO* and then to CH₃O* on GaZr oxide surface. While compared with sole ZrO₂, the introduction of Ga significantly promotes the hydrogenation of HCOO* to CH₃O*, acting as a crucial reaction intermediate that subsequently diffuses into SAPO-34 pores to enhance the desired light olefins selectivity. 

Abstract

Photon upconversion via triplet-triplet annihilation (TTA-UC) provides a pathway to overcoming the thermodynamic efficiency limits in single-junction solar cells by allowing the harvesting of sub-bandgap photons. Here, we use mixed halide perovskite nanocrystals (CsPbX3, X = Br/I) as triplet sensitizers, with excitation transfer to 9,10-diphenylanthracene (DPA) and/or 9,10-bis[(triisopropylsilyl)ethynyl]anthracene (TIPS-An) which act as the triplet annihilators. We observe that the upconversion efficiency is five times higher with the combination of both annihilators in a composite system compared to the sum of the individual single-acceptor systems. Our work illustrates the importance of using a composite system of annihilators to enhance TTA upconversion, demonstrated in a perovskite-sensitized system, with promise for a range of potential applications in light-harvesting, biomedical imaging, biosensing, therapeutics, and photocatalysis.

Abstract

Bimodal medical imaging based on magnetic resonance imaging (MRI) and computed tomography (CT) is a well-known strategy to increase the diagnostic accuracy. The most recent advances in MRI and CT instrumentation are related to the use of ultra-high magnetic fields (UHF-MRI) and different working voltages (spectral CT), respectively. Such advances require the parallel development of bimodal contrast agents (CAs) that are efficient under new instrumental conditions. In this work, we have synthesized, through a precipitation reaction from a glycerol solution of the precursors, uniform barium dysprosium fluoride nanospheres with a cubic fluorite structure, whose size was found to depend on the Ba/(Ba + Dy) ratio of the starting solution. Moreover, irrespective of the starting Ba/(Ba + Dy) ratio, the experimental Ba/(Ba + Dy) values were always lower than those used in the starting solutions. This result was assigned to lower precipitation kinetics of barium fluoride compared to dysprosium fluoride, as inferred from the detailed analysis of the effect of reaction time on the chemical composition of the precipitates. A sample composed of 34 nm nanospheres with a Ba0.51Dy0.49F2.49 stoichiometry showed a transversal relaxivity (r(2)) value of 147.11 mM(-1)s(-1) at 9.4 T and gave a high negative contrast in the phantom image. Likewise, it produced high X-ray attenuation in a large range of working voltages (from 80 to 140 kVp), which can be attributed to the presence of different K-edge values and high Z elements (Ba and Dy) in the nanospheres. Finally, these nanospheres showed negligible cytotoxicity for different biocompatibility tests. Taken together, these results show that the reported nanoparticles are excellent candidates for UHF-MRI/spectral CT bimodal imaging CAs.

Abstract

The review provides an overview of the latest innovations, trends, and challenges in the field of 3D-printed metal and metal-ion batteries. It focuses on the materials used in the printing of batteries, including electrodes, electrolytes, and other electroactive components. Compared to other high-quality reviews on the topic, this review provides a broader selection of materials that are expected to gain attention in the next few years, such as redox-active polymers and metal-organic frameworks. This work gives an overview and insight into the latest trends in printing techniques as well as a statistical review of their uses and strengths. We have also gathered the latest works done for each of the material types, and we have taken the opportunity to put them in context and use them to exemplify in which direction is the field going. The review concludes with a critical view of the challenges ahead and a discussion of the direction that the field is taking as well as the external factors that might help to define its future. 

Abstract

The combustion in thermal explosion mode of reactive mixtures of Ti-Ni-graphite(carbides, borides, oxides), under load, was used to produce complex composite materials, densified and joined to a C55 carbon steel support. The ignition of the exothermic reaction, carried out thanks to the rapid high-frequency heating of a green compact up to 1573 K, was followed by an isothermal holding at 1373 K for 360 s. This procedure ensured a perfect mechanical assembly between the composite material and the steel substrate. SEM analysis and concentration profiles carried out at the interface testified to the interdiffusion of iron and titanium atoms between the two materials. The maximum combustion temperature (T-max.) exceeding 2200 K induced the appearance of a liquid phase that assisted densification and joining, and in which a part of the additions was dissolved before cooling. The starting chemical composition of reactive mixtures largely determined the microstructure, hardness and tribological behavior of the composites after the process. Thereby, the maximum hardness (1235 HV0.15) and the lowest wear rate (1.824 x 10(-6) mm(3).N-1.m(-1)) were obtained in the sample containing TiC, Al2O3 and TiB2 hard phases. The manufactured samples exhibit no deterioration of the composite by spalling, regardless of the starting composition.

Abstract

Hybrid organometal halide perovskites (HP) present exceptional optoelectronic properties, but their poor long-term stability is a major bottleneck for their commercialization. Herein, a solvent-free approach to growing single-crystal organic nanowires (ONW) is presented, along with nanoporous metal oxide scaffolds and HP, to form a core@multishell architecture. The synthesis is carried out under mild vacuum conditions employing thermal evaporation for the metal-free phthalocyanine (H₂Pc) nanowires, which are the core, plasma-enhanced chemical vapor deposition (PECVD) for the TiO₂ shell, and co-evaporation of lead iodide (PbI₂) and methylammonium iodide (CH₃NH₃I/MAI) for the CH₃NH₃PbI₃ (MAPbI₃/MAPI) perovskite shell. A detailed characterization of the nanostructures by electron microscopy, (S)-TEM, and X-ray diffraction, XRD, is presented, revealing a different crystallization of the HP depending on the template: while the growth on H₂Pc nanowires induces the typical MAPI tetragonal structure, a low-dimensional phase (LDP) is observed on the 1D-TiO₂ nanotubes. Such a combination yields an unprecedentedly stable photoluminescence emission over 20 h and over 300 h after encapsulation in polymethyl methacrylate (PMMA) under different atmospheres including N₂, air, and high moisture levels. Moreover, the unique 1D morphology of the system, together with the high refractive index, allows for a strong waveguiding effect along the HP nanowire length.

Abstract

We study the thermal properties of a bulk Ni₅₅Fe₁₉Ga₂₆ Heusler alloy in a conduction calorimeter. At slow heating and cooling rates (∼1Kh^-1), we compare as-cast and annealed samples. We report a smaller thermal hysteresis after the thermal treatment due to the stabilization of the 14 M modulated structure in the martensite phase. In ultraslow experiments (40mKh^-1), we detect and analyze the calorimetric avalanches associated with the direct and reverse martensitic transformation from cubic to 14 M phase. This reveals a distribution of events characterized by a power law with exponential cutoff p(u)∝u^-εexp(-u/ξ) where ε∼2 and damping energies ξ=370μJ (direct) and ξ=27μJ (reverse) that characterize the asymmetry of the transformation.