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Living organisms control the formation of mineral skeletons and other structures through biomineralization. Major phylogenetic groups usually consistently follow a single biomineralization pathway. Foraminifera, which are very efficient marine calcifiers, making a substantial contribution to global carbonate production and global carbon sequestration, are regarded as an exception. This phylum has been commonly thought to follow two contrasting models of either in situ 'mineralization of extracellular matrix' attributed to hyaline rotaliid shells, or 'mineralization within intracellular vesicles' attributed to porcelaneous miliolid shells. Our previous results on rotaliids along with those on miliolids in this paper question such a wide divergence of biomineralization pathways within the same phylum of Foraminifera. We have found under a high-resolution scanning electron microscopy (SEM) that precipitation of high-Mg calcitic mesocrystals in porcelaneous shells takes place in situ and form a dense, chaotic meshwork of needle-like crystallites. We have not observed calcified needles that already precipitated in the transported vesicles, what challenges the previous model of miliolid mineralization. Hence, Foraminifera probably utilize less divergent calcification pathways, following the recently discovered biomineralization principles. Mesocrystalline chamber walls in both models are therefore most likely created by intravesicular accumulation of pre-formed liquid amorphous mineral phase deposited and crystallized within the extracellular organic matrix enclosed in a biologically controlled privileged space by active pseudopodial structures. Both calcification pathways evolved independently in the Paleozoic and are well conserved in two clades that represent different chamber formation modes.

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Mesocrystals (MCs) with high-index facets may have superior catalytic properties to those with low-index facets and their nanocrystal counterparts. However, synthesizing such mesocrystal materials is still very challenging because of the metastability of MCs and energetic high-index crystal facets. This work reports a successful solvothermal method followed by calcination for synthesizing copper oxide-based MCs possessing a core-shell structure (denoted as Cu2 O@CuO HIMCs). Furthermore, these MCs are predominantly bounded by the high-index facets such as {311} or {312} with a high-density of stepped atoms. When used as catalysts in Si hydrochlorination to produce trichlorosilane (TCS, the primary feedstock of high-purity crystalline Si), Cu2 O@CuO HIMCs exhibit significantly enhanced Si conversion and TCS selectivity compared to those with flat surfaces and their nanostructured counterparts. Theoretical calculations reveal that both the core-shell structure and the high-index surface contribute to the increased electron density of Cu sites in Cu2 O@CuO HIMCs, promoting the adsorption and dissociation of HCl and stabilizing the dissociated Cl* intermediate. This work provides a simple method for synthesizing high-index faceted MCs and offers a feasible strategy to enhance the catalytic performance of MCs.

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Magnetic iron oxide mesocrystals have been reported to exhibit collective magnetic properties and consequently enhanced heating capabilities under alternating magnetic fields. However, there is no universal mechanism to fully explain the formation pathway that determines the particle diameter, crystal size, and shape of these mesocrystals and their evolution along with the reaction. In this work, we have analyzed the formation of cubic magnetic iron oxide mesocrystals by thermal decomposition in organic media. We have observed that a nonclassical pathway leads to mesocrystals via the attachment of crystallographically aligned primary cubic particles and grows through sintering with time to achieve a sizable single crystal. In this case, the solvent 1-octadecene and the surfactant agent biphenyl-4-carboxylic acid seem to be the key parameters to form cubic mesocrystals as intermediates of the reaction in the presence of oleic acid. Interestingly, the magnetic properties and hyperthermia efficiency of the aqueous suspensions strongly depend on the degree of aggregation of the cores forming the final particle. The highest saturation magnetization and specific absorption rate values were found for the less aggregated mesocrystals. Thus, these cubic magnetic iron oxide mesocrystals stand out as an excellent alternative for biomedical applications with their enhanced magnetic properties.

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Electron-transporting materials (ETMs) with higher carrier mobility and a suitable band gap structure play a significant role in determining the photovoltaic performance of perovskite solar cells (PSCs). Herein, cube-like mesoporous single-crystal anatase TiO2 (Meso-TiO2) nanoparticles synthesized by using a facile hydrothermal method were utilized as an efficient ETM for PSCs. The superior semiconducting properties of the Meso-TiO2 based ETM enabled the best power conversion efficiency (PCE) of 20.05% for a PSC. Moreover, the device retained 80% of its initial PCE after being stored in ambient conditions for 20 days under 25 ± 5% relative humidity. In contrast to the commercial TiO2 ETM, the Meso-TiO2 ETM based PSC showed a distinguished interface with better interfacial conditions and improved carrier extraction originating from the cube-like mesoporous single-crystal anatase TiO2 ETM.

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Piezoelectric mesocrystals as defective materials have been demonstrated to possess adsorptive and catalytic properties in redox reactions. However, there is still a lack of research on the quantitative relationship between the defect concentration and the piezocatalytic performance in piezoelectric mesocrystals. Herein, twin-hierarchical structure ZnO piezoelectric mesocrystals are taken with different oxygen-vacancies (OVs) concentrations to quantitatively investigate the effect of defect content on the peroxymonosulfate (PMS) piezo-activation in water purification. The ZnO piezoelectric mesocrystal with moderate OVs concentration exhibits a rapid antibiotic ornidazole (ORZ) pollutants degradation rate (0.034 min-1 ) and achieves a high PMS utilization efficiency (0.162) that exceeds the most state-of-the-art catalytic processes, while excessive OVs suppressed the piezocatalytic performance. Through calculations of electron property and reactants affinity, a quantitative relationship between OVs concentration and piezocatalytic properties is established. The ZnO mesocrystal with moderate OVs concentration realized increased electron delocalization, reduced charge transfer barrier, and enhanced reactants affinity, thus accelerating the kinetics of PMS activation. This work provides theoretical guidance for the application of defect engineering in mesocrystal to realize enhanced piezocatalytic performance.

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Mesocrystals are a class of nanostructured material, where a multiple-length-scale structure is a prerequisite of many interesting phenomena. Resolving the mesocrystal structure is quite challenging due to their structuration on different length scales. The combination of small- and wide-angle X-ray scattering (SAXS and WAXS) techniques offers the possibility of non-destructively probing mesocrystalline structures simultaneously, over multiple length scales to reveal their microscopic structure. This work describes how high dynamical range of modern detectors sheds light on the weak features of scattering, significantly increasing the information content. The detailed analysis of X-ray diffraction (XRD) from the magnetite mesocrystals with different particle sizes and shapes is described, in tandem with electron microscopy. The revealed features provide valuable input to the models of mesocrystal growth and the choice of structural motif; the impact on magnetic properties is discussed.

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Y0.8-xGdxF3:Yb/Er mesocrystals with a biocompatible surface and diverse morphological characteristics were successfully synthesized using chitosan-assisted solvothermal processing. Their structural properties, studied using X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy and energy dispersive X-ray analysis, were further correlated with the up-conversion emission (λexc = 976 nm) recorded in function of temperature. Based on the change in the visible green emissions originating from the thermally coupled 2H11/2 and 4S3/2 levels of Er3+, the corresponding LIR was acquired in the physiologically relevant range of temperatures (25-50 °C). The detected absolute sensitivity of about 0.0042 °C-1, along with the low cytotoxicity toward both normal human lung fibroblasts (MRC-5) and cancerous lung epithelial (A549) cells, indicate a potential for use in temperature sensing in biomedicine. Additionally, their enhanced internalization in cells, without suppression of cell viability, enabled in vitro labeling of cancer and healthy cells upon 976 nm laser irradiation.

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Tuning the electronic structures of mesocrystals at the atomic level is an effective approach to obtaining unprecedented properties. Here, a lattice-confined strategy to obtain isolated single-site Sn atoms in CuO mesocrystals to improve catalytic performance is reported. The Sn/CuO mesocrystal composite (Sn/CuO MC) has ordered Sn-O-Cu atomic interfaces originated from the long-range ordering of the CuO mesocrystal itself. X-ray absorption fine structure measurements confirm that the positively charged Sn atoms can tune the electronic structure of the Cu atoms to some extent in Sn/CuO MC, quite different from that in the conventional single-atom Sn-modified CuO nanoparticles and nanoparticulate SnO2 -modified CuO mesocrystal catalysts. When tested for the Si hydrochlorination reaction to produce trichlorosilane, Sn/CuO MC exhibits significantly better performances than the above two catalysts. Theoretical calculations further reveal the electronic modification to the active Cu component and the induced improvement in HCl adsorption, and thus enhance the catalytic performance. This work demonstrates how to design efficient metal oxide mesocrystal catalysts through an electronic structure modification approach.

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Cu2 O is an ideal p-type material for photo-electrochemical (PEC) hydrogen evolution, although serious electron-hole recombination and photocorrosion restrict its further improvement for PEC activity. In this work, CeO2 nanoparticles (NPs) self-assemble on the surface of Cu2 O octahedra, thus successfully forming a Cu2 O/CeO2 structure in which p-n heterojunctions and micro-mesocrystals (m-MCs) work together. The optimum Cu2 O/CeO2 composite, without the use of any cocatalyst, exhibits a fivefold higher photocurrent density (4.63 mA cm-2 at 0 V vs. the reversible hydrogen electrode) than that of Cu2 O octahedra, which is better than most Cu2 O-based photocathodes without cocatalyst and even comparable with advanced Cu2 O-based photocathodes. The hydrogen production of the optimal Cu2 O/CeO2 (Faradaic efficiency of ∼100 %) is 17.5 times higher than that of pure Cu2 O octahedra, and the photocurrent shows almost no decay under the 12 h stability test. The delicately designed Cu2 O/CeO2 structure in this work provides reference and inspiration for the design of cathodes materials.

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Poriferous monocrystal-like nanostructures are contributing to fabricate long-distance charge transfer pathways and rapid diffusions of the degraded products, and attracts wide attentions. In this work, layered and poriferous (Al,C)-Ta2O5 mesocrystals were fabricated by topotactic transformation strategy with Ta4AlC3 MAX as starting materials for visible-light photocatalytic antibiotic degradation. The prepared sample exhibited enhanced visible-light absorption and visible-light photocatalytic performance, far superior to those of commercial Ta2O5 and Ta4AlC3 MAX, which was mainly because of the elemental doping in the samples. The experimental results also indicated that continuous attacks of the photo-generated holes and ·O2- species efficiently induced efficient visible-light photodegradation of tetracycline. Current work also indicates a new and potential tantalum-based semiconductors for high-performance environmental photocatalysis.

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Elucidation of reaction mechanisms in forming nanostructures is relevant to obtain robust and affordable protocols that can lead to materials with enhanced properties and good reproducibility. Here, the formation of magnetic iron oxide monocrystalline nanoflowers in polyol solvents using N-methyldiethanolamine (NMDEA) as co-solvent has been shown to occur through a non-classical crystallization pathway. This pathway involves intermediate mesocrystals that, in addition, can be transformed into large single colloidal nanocrystals. Interestingly, the crossover of a non-classical crystallization pathway to a classical crystallization pathway can be induced by merely changing the NMDEA concentration. The key is the stability of a green rust-like intermediate complex that modulates the nucleation rate and growth of magnetite nanocrystals. The crossover separates two crystallization domains (classical and non-classical) and three basic configurations (mesocrystals, large and small colloidal nanocrystals). The above finding facilitated the synthesis of magnetic materials with different configurations to suit various engineering applications. Consequently, the effect of the single and multicore configurations of magnetic iron oxide on the biomedical (magnetic hyperthermia and enzyme immobilization) and catalytic activity (Fenton-like reactions and photo-Fenton-like processes driven by visible light irradiation) has been experimentally demonstrated.

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Here we report a successful one-step synthesis of vanadium-doped anatase mesocrystals by reactive annealing of NH4TiOF3/PEG2000 mesocrystal precursors with NH4VO3. The formation solid solution Ti1-xVxO2with vanadium content up tox = 25 at% inheriting the structure of mesocrystals is observed for the first time. The doping mechanism via vapor phase transport of vanadium is proposed. The Ti1-xVxO2mesocrystals exhibit improved specific capacity of 175 mAh g-1(compared to 150 mAh g-1for pure anatase phase) and decreased potential gap between charge and discharge processes.

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The tetramethylammonium hydroxide (TMAH)-controlled alkaline etching of nickel hexacyanoferrate (NiHCF) mesocrystals is explored. The alkaline etching enables the formation of hollow framework structures with an increased surface area, the exposure of active Ni and Fe sites and the retention of morphology. The ambient reaction conditions enable the establishment of a sustainable production. Our work reveals novel perspectives on the eco-friendly synthesis of hollow and colloidal superstructures for the efficient degradation of the organic contaminants rhodamine-B and bisphenol-A. In the case of peroxomonosulfate (PMS)-mediated bisphenol-A degradation, the rate constant of the etched mesoframes was 10,000 times higher indicating their significant catalytic activity.

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The unique InVO4 mesocrystal superstructure, particularly with cubical skeleton and hollow interior, which consists of numerous nanocube building blocks, closely stacking by stacking, aligning by aligning, and sharing the same crystallographic orientations, is successfully fabricated. The synergy of a reaction-limited aggregation and an Ostwald ripening process is reasonably proposed for the growth of this unique superstructure. Both single-particle surface photovoltage and confocal fluorescence spectroscopy measurements demonstrate that the long-range ordered mesocrystal superstructures can significantly retard the recombination of electron-hole pairs through the creation of a new pathway for anisotropic electron flow along the inter-nanocubes. This promising charge mobility feature of the superstructure greatly contributes to the pronounced photocatalytic performance of the InVO4 mesocrystal toward fixation of N2 into NH3 with the quantum yield of 0.50% at wavelength of 385 nm.

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Mesocrystals are types of fascinating multifunctional materials in fabricating rapid charge transport pathways, and surface engineering could be considered as a significant influencing factor in boosting charge separation for efficient photocatalytic application. In this work, surface engineered Ta2O5-x mesocrystals were synthesized by facile alkali treatment strategy for enhanced visible light photocatalytic tetracycline degradation. The highly enhanced photocatalytic activity could be attributed to the highly increased surface areas and surface hydroxyl groups to compare with those of commercial Ta2O5 and pristine Ta2O5-x mesocrystals, which could provide more surface reactive sites and high electron density center for trapping photo-generated holes. Besides, possible tetracycline transformation pathways over surface engineered Ta2O5-x mesocrystals and visible light photocatalytic mechanism were also proposed in this work. Current work also provides a facile strategy for regulating surface property of ultrawide bandgaps semiconductors for enhanced visible light photocatalytic performance.

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Diclofenac (DCF), a non-steroidal anti-inflammatory drug, is considered one of the most widespread emerging contaminants. Its incidence in water can favor the growth of drug-resistant bacteria and harm aquatic organisms endangering both the human health and the ecosystem. Advanced oxidation processes (AOPs) based on the action of reactive oxygen species are very effective technologies for the removal of this contaminant from water. In this context, ZnO is one of the most studied semiconductors for photocatalytic water treatment. In this work, the photocatalytic activity of fluorine-doped ZnO nano- and meso-crystals synthesized by a hydrothermal approach is reported, exploring the role of a low F atomic concentration (0.25, 0.5 and 1 at. %) on the degradation of DCF in comparison with bare ZnO. All doped samples show high rates of DCF degradation and mineralization, which were realized primarily thanks to their high efficiency in the generation of hydroxyl radicals (OH). The property-structure-function relationships of the materials are investigated by complementary techniques, such as SEM, XRD, EPR, UV-vis DRS and PL, with the aim to evaluate the role of fluorine in determining their morphological, electronic and optical properties.

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TiO2 is the most widely used material for preparing the electron-transporting layer (ETL) in perovskite solar cells (PSCs). However, it requires a high-temperature sintering process. Moreover, the intrinsic defects and low electron mobility of TiO2 ETLs cause instability and hysteresis effects in PSCs. In this study, a mesoporous film composed of anatase TiO2 mesocrystals was facilely fabricated by a low-temperature route and then used as an ETL in PSCs for the first time. A satisfactory efficiency of 20.26 % can be achieved through delicate control of the entire device fabrication procedure. The optimal device, with an area of 1 cm2 , achieves an efficiency of 17.07 %. In comparison to the common TiO2 ETLs, those composed of TiO2 mesocrystals show the enhanced electron extraction and suppression of charge accumulation at the perovskite/ETL interface, resulting in improved photovoltaic performance and reduced hysteresis.

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Oriented attachment (OA) has become a well-recognized mechanism for the growth of metal, ceramic, and biomineral crystals. While many computational and experimental studies of OA have shown that particles can attach with some misorientation then rotate to remove adjoining grain boundaries, the underlying atomistic pathways for this "imperfect OA" process remain the subject of debate. In this study, molecular dynamics and in situ transmission electron microscopy (TEM) are used to probe the crystallographic evolution of up to 30 gold nanoparticles during aggregation. It is found that Imperfect OA occurs because 1) grain boundaries become quantized when their size is comparable to the separation between constituent dislocations and 2) kinetic barriers associated with the glide of grain boundary dislocations are small. In support of these findings, TEM experiments show the formation of a single crystal aggregate after annealing nine initially misoriented, agglomerated particles with evidence of dislocation activity and twin formation during particle/grain alignment. These observations motivate future work on assembled nanocrystals with tailored defects and call for a revision of Read-Shockley models for grain boundary energies in nanocrystalline materials.

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Applications in the fields of materials science and nanotechnology increasingly demand monodisperse nanoparticles in size and shape. Up to now, no general purification procedure exists to thoroughly narrow the size and shape distributions of nanoparticles. Here, we show by analytical ultracentrifugation (AUC) as an absolute and quantitative high-resolution method that multiple recrystallizations of nanocrystals to mesocrystals is a very efficient tool to generate nanocrystals with an excellent and so-far unsurpassed size-distribution (PDIc =1.0001) and shape. Similar to the crystallization of molecular building blocks, nonclassical recrystallization removes "colloidal" impurities (i.e., nanoparticles, which are different in shape and size from the majority) by assembling them into a mesocrystal. In the case of nanocrystals, this assembly can be size- and shape-selective, since mesocrystals show both long-range packing ordering and preferable crystallographic orientation of nanocrystals. Besides the generation of highly monodisperse nanoparticles, these findings provide highly relevant insights into the crystallization of mesocrystals.

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A self-enhanced electrochemiluminescent ratiometric immunoassay for zearalenone is described. A system composed of N-aminobutyl-N-ethylisoluminol (ABEI) and glutathione (GSH) produces a strong electrochemiluminescence (ECL) at an applied potential of 0.8 V, probably because of short electron transfer distance and reduced energy loss. The method also uses octahedral anatase mesocrystals (OAM) with a large specific surface facilitating immobilization of ABEI and GSH. Helical carbon nanotubes, possessing a large specific surface, superior mechanical stability, and excellent electrical conductivity which serve as a solid support, greatly enhanced the loading capacity for g-C3N4 nanosheets and horseradish peroxidase-labeled anti-antibody. The peroxidase accelerates the decomposition of H2O2 to produce reactive oxygen species (ROSs), amplifying the blue ECL of ABEI and the green ECL of g-C3N4. The ratiometric sandwich immunoassay (performed by the ratio of ECL intensity at - 1.3 V and 0.8 V) allows for sensitive and reliable determination of ZEN in a wide linear range from 1.0 × 10-4 ng/mL to 10 ng/mL. The method was successfully applied to the analysis of corn hazelnut samples for ZEN. Graphical abstract Schematic presentation of a self-enhanced electrochemiluminescent ratiometric immunosensor based on octahedral anatase mesocrystals (OAM) supported ABEI-glutathione (GSH) and g-C3N4 functionalized helical carbon nanotubes (HCNT) for zearalenone (ZEN) determination.