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The potentials of advanced transmission and scanning transmission electron microscopy in nanostructural studies of ceria-zirconia mixed oxides are overviewed. The crystallographic criteria that allow us to discriminate the different CeO-ZrO polymorphs and the nanocrystal size range within which they can be applied are discussed. The combined use of high resolution electron microscopy (HREM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) to detect disorder-order transitions in the cation sublattice of this family of oxides and the size limit down to which each of them can be used for that purpose are also analyzed. Criteria to discriminate, on the basis of HREM images, the oxygen arrangement of the so called κ-CeZrO phase from that of an oxidized pyrochlore CeZrO phase are presented and applied to the interpretation of experimental HREM images. HAADF-STEM tomography studies and detailed analysis of HAADF-STEM images establish both the crystallographic and compositional features of the surfaces of the mixed oxides that give enhanced redox activity. These findings allow deeper understanding of the influence of different thermal ageing pretreatments on the redox behavior of this family of mixed oxides. Novel characterization data do evidence that this model does not only fruitfully apply to binary ceria-zirconia oxides but also to more complex ternary oxides containing terbium. Advanced electron microscopies are systematically applied to the 2D and 3D structural and chemical characterization of ceria-zirconia systems of current interest in environmental catalysis. Relevant details concerning both the bulk and the surface of these materials are obtained, which allows us to establish a rational model to correlate redox properties, nanostructure, and thermochemical treatments. [ABSTRACT FROM AUTHOR]

A Pt catalyst has been designed to convert nitrocyclohexane into cyclohexanone oxime under mild hydrogenation conditions (4 bar of H2, 383 K, and solvent-free media). It has been found that the partial reduction of the nitro group to the oxime function is promoted by Pt nanoparticles decorated with TiO x species, being cyclohexanone the main undesired by-product. A reaction scheme has been proposed that explains the process and active sites involved with the formation of the different reaction products. Based on that, a further chemical modification of the catalyst with sodium cations has allowed to increase the selectivity to cyclohexanone oxime to ∼85% at 95% conversion. The final catalyst can be recycled and TON values of, at least, 13,000 can be obtained. [Copyright &y& Elsevier]

Accurate 3D nanometrology of catalysts with small nanometer-sized particles of light 3d or 4d metals supported on high-atomic-number oxides is crucial for understanding their functionality. However, performing quantitative 3D electron tomography analysis on systems involving metals like Pd, Ru, or Rh supported on heavy oxides (e.g., CeO 2 ) poses significant challenges. The low atomic number ( Z ) of the metal complicates discrimination, especially for very small nanoparticles (1-3 nm). Conventional reconstruction methods successful for catalysts with 5d metals (e.g., Au, Pt, or Ir) fail to detect 4d metal particles in electron tomography reconstructions, as their contrasts cannot be effectively separated from those of the underlying support crystallites. To address this complex 3D characterization challenge, we have developed a full deep learning (DL) pipeline that combines multiple neural networks, each one optimized for a specific image-processing task. In particular, single-image super-resolution (SR) techniques are used to intelligently denoise and enhance the quality of the tomographic tilt series. U-net generative adversarial network algorithms are employed for image restoration and correcting alignment-related artifacts in the tilt series. Finally, semantic segmentation, utilizing a U-net-based convolutional neural network, splits the 3D volumes into their components (metal and support). This approach enables the visualization of subnanometer-sized 4d metal particles and allows for the quantitative extraction of catalytically relevant structural information, such as particle size, sphericity, and truncation, from compressed sensing electron tomography volume reconstructions. We demonstrate the potential of this approach by characterizing nanoparticles of a metal widely used in catalysis, Pd ( Z = 46), supported on CeO 2 , a very high density (7.22 g/cm 3 ) oxide involving a quite high-atomic-number element, Ce ( Z = 58)., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The resistance of an ordered 3D-Bi 2 Te 3 nanowire nanonetwork was studied at low temperatures. Below 50 K the increase in resistance was found to be compatible with the Anderson model for localization, considering that conduction takes place in individual parallel channels across the whole sample. Angle-dependent magnetoresistance measurements showed a distinctive weak antilocalization characteristic with a double feature that we could associate with transport along two perpendicular directions, dictated by the spatial arrangement of the nanowires. The coherence length obtained from the Hikami-Larkin-Nagaoka model was about 700 nm across transversal nanowires, which corresponded to approximately 10 nanowire junctions. Along the individual nanowires, the coherence length was greatly reduced to about 100 nm. The observed localization effects could be the reason for the enhancement of the Seebeck coefficient observed in the 3D-Bi 2 Te 3 nanowire nanonetwork compared to individual nanowires.

Sub-nanometer metal clusters have special physical and chemical properties, significantly different from those of nanoparticles. However, there is a major concern about their thermal stability and susceptibility to oxidation. In situ X-ray Absorption spectroscopy and Near Ambient Pressure X-ray Photoelectron spectroscopy results reveal that supported Cu 5 clusters are resistant to irreversible oxidation at least up to 773 K, even in the presence of 0.15 mbar of oxygen. These experimental findings can be formally described by a theoretical model which combines dispersion-corrected DFT and first principles thermochemistry revealing that most of the adsorbed O 2 molecules are transformed into superoxo and peroxo species by an interplay of collective charge transfer within the network of Cu atoms and large amplitude "breathing" motions. A chemical phase diagram for Cu oxidation states of the Cu 5 -oxygen system is presented, clearly different from the already known bulk and nano-structured chemistry of Cu., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Gold-metallic nanofibrils were prepared from three different iso-apoferritin (APO) proteins with different Light/Heavy (L/H) subunit ratios (from 0% up to 100% L-subunits). We show that APO protein fibrils have the ability to in situ nucleate and grow gold nanoparticles (AuNPs) simultaneously assembled on opposite strands of the fibrils, forming hybrid inorganic-organic metallic nanowires. The AuNPs are arranged following the pitch of the helical APO protein fiber. The mean size of the AuNPs was similar in the three different APO protein fibrils studied in this work. The AuNPs retained their optical properties in these hybrid systems. Conductivity measurements showed ohmic behavior like that of a continuous metallic structure., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The oxygen stoichiometry of hollandite, KxMnO2-δ, nanorods has been accurately determined from a quantitative analysis of scanning-transmission electron microscopy (STEM) X-Ray Energy Dispersive Spectroscopy (XEDS) experiments carried out in chrono-spectroscopy mode. A methodology combining 3D reconstructions of high-angle annular dark field electron tomography experiments, using compressed-sensing algorithms, and quantification through the so-called ζ-factors method of XEDS spectra recorded on a high-sensitivity detector has been devised to determine the time evolution of the oxygen content of nanostructures of electron-beam sensitive oxides. Kinetic modeling of O-stoichiometry data provided K0.13MnO1.98 as overall composition for nanorods of the hollandite. The quantitative agreement, within a 1% mol error, observed with results obtained by macroscopic techniques (temperature-programmed reduction and neutron diffraction) validate the proposed methodology for the quantitative analysis, at the nanoscale, of light elements, as it is the case of oxygen, in the presence of heavy ones (K, Mn) in the highly compromised case of nanostructured materials which are prone to electron-beam reduction. Moreover, quantitative comparison of oxygen evolution data measured at macroscopic and nanoscopic levels allowed us to rationalize beam damage effects in structural terms and clarify the exact nature of the different steps involved in the reduction of these oxides with hydrogen., Competing Interests: Conflict of Interest The authors declare that they have no competing interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Microscopy Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Finding simple, easily controlled, and flexible synthetic routes for the preparation of ternary and hybrid nanostructured semiconductors is always highly desirable, especially to fulfill the requirements for mass production to enable application to many fields such as optoelectronics, thermoelectricity, and catalysis. Moreover, understanding the underlying reaction mechanisms is equally important, offering a starting point for its extrapolation from one system to another. In this work, we developed a new and more straightforward colloidal synthetic way to form hybrid Au-Ag 2 X (X = S, Se) nanoparticles under mild conditions through the reaction of Au and Ag 2 X nanostructured precursors in solution. At the solid-solid interface between metallic domains and the binary chalcogenide domains, a small fraction of a ternary AuAg 3 X 2 phase was observed to have grown as a consequence of a solid-state electrochemical reaction, as confirmed by computational studies. Thus, the formation of stable ternary phases drives the selective hetero-attachment of Au and Ag 2 X nanoparticles in solution, consolidates the interface between their domains, and stabilizes the whole hybrid Au-Ag 2 X systems., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Ligand-free sub-nanometer metal clusters (MCs) of Pt, Ir, Rh, Au and Cu, are prepared here in neat water and used as extremely active (nM) antitumoral agents for HeLa and A2870 cells. The preparation just consists of adding the biocompatible polymer ethylene-vinyl alcohol (EVOH) to an aqueous solution of the corresponding metal salt, to give liters of a MC solution after filtration of the polymer. Since the MC solution is composed of just neat metal atoms and water, the intrinsic antitumoral activity of the different sub-nanometer metal clusters can now fairly be evaluated. Pt clusters show an IC 50 of 0.48 μM for HeLa and A2870 cancer cells, 23 times higher than that of cisplatin and 1000 times higher than that of Pt NPs, and this extremely high cytotoxicity also occurs for cisplatin-resistant (A2870 cis) cells, with a resistance factor of 1.4 (IC 50 = 0.68 μM). Rh and Ir clusters showed an IC 50 ∼ 1 μM. Combined experimental and computational studies support an enhanced internalization and cytotoxic activation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Metal single-atom catalysts (SACs) promise great rewards in terms of metal atom efficiency. However, the requirement of particular conditions and supports for their synthesis, together with the need of solvents and additives for catalytic implementation, often precludes their use under industrially viable conditions. Here, we show that palladium single atoms are spontaneously formed after dissolving tiny amounts of palladium salts in neat benzyl alcohols, to catalyze their direct aerobic oxidation to benzoic acids without ligands, additives, or solvents. With this result in hand, the gram-scale preparation and stabilization of Pd SACs within the functional channels of a novel methyl-cysteine-based metal-organic framework (MOF) was accomplished, to give a robust and crystalline solid catalyst fully characterized with the help of single-crystal X-ray diffraction (SCXRD). These results illustrate the advantages of metal speciation in ligand-free homogeneous organic reactions and the translation into solid catalysts for potential industrial implementation.

Agrochemical encapsulation agents used up to now are commonly based on polymeric compounds or metal particles, but the employment of other natural products such as host structures has not been tackled in detail. In the work reported here, fully organic nanotubes composed of human bile acid (lithocholic acid) have been synthesized. These nanotubes were employed to encapsulate potential disulfide herbicide mimics that have previously shown relevant inhibitory activity against weeds. The three-dimensional chemical information from scanning transmission electron microscope analytical tomography with subnanometer scale resolution convincingly demonstrates for the first time the occurrence of efficient encapsulation within a fully organic nanotube of different organic molecules with activity as herbicides. The encapsulation was achieved in a one-pot synthesis, in an aqueous environment and under in situ conditions without using any marker or coating with contrast materials, which renders the process greener than those routinely used. The nanotubes allow complete water solubilization, with an encapsulation percentage of up to 78% in all of the herbicide compounds. Furthermore, nanotubes showed a flattened arrangement due to the host-guest interaction. The synthetic approach represents a step forward in solving the key problem of the quite limited solubility of natural agrochemicals in aqueous environments. In addition, the process presents a breakthrough in the use of natural products produced by the human body as encapsulating agents, which expands possible future applications. The preliminary docking approach clarifies that the 2o01 transmembrane transport protein seems to be the prior channel of the organic nanotube in the delivery process to vegetable cells. The etiolated wheat coleoptile bioassay demonstrated that the encapsulated herbicides have improved the bioactivity of free compounds, keeping 60% of inhibition of the weed at least for every disulfide, a requisite for their fruitful application as agrochemicals.

Ferritin, a soluble and highly robust protein with subunits packed into well-defined helices, is a key component of the iron regulatory system in the brain and thus is widely recognized as a crucial protein for iron metabolism, but may also bear possible implications in some neurodegenerative disorders. Here, we present evidence of how human recombinant apoferritin can convert into an unusual structure from its folded native state; that is, amyloid fibrils analogue to those found in pathological disorders such as Alzheimer's and Parkinson's diseases. An extensive combination of advanced microscopy, spectroscopy and scattering techniques concur to reveal that apoferritin fibrils possess a common double stranded twisted ribbon structure which can result in a mesoscopic right-handed chirality. We highlight a direct connection between the chirality and morphology of the resulting amyloid fibrils, and the initial protein subunits composition, advancing our understanding on the possible role of misfolding in some ferritin-related pathologies and posing new bases for the design of chiral 1D functional nanostructures.

The synthesis and reactivity of single metal atoms in a low-valence state bound to just water, rather than to organic ligands or surfaces, is a major experimental challenge. Herein, we show a gram-scale wet synthesis of Pt 1 1+ stabilized in a confined space by a crystallographically well-defined first water sphere, and with a second coordination sphere linked to a metal-organic framework (MOF) through electrostatic and H-bonding interactions. The role of the water cluster is not only isolating and stabilizing the Pt atoms, but also regulating the charge of the metal and the adsorption of reactants. This is shown for the low-temperature water-gas shift reaction (WGSR: CO + H 2 O → CO 2 + H 2 ), where both metal coordinated and H-bonded water molecules trigger a double water attack mechanism to CO and give CO 2 with both oxygen atoms coming from water. The stabilized Pt 1+ single sites allow performing the WGSR at temperatures as low as 50 °C., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt 0 2 clusters, homogenously distributed and densely packaged within the channels of a metal-organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO 2 methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less-dangerous industrial reactions., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanoencapsulation has proven to be an efficient route to increase significantly the solubility and bioavailability of organic compounds. This aspect of nanotechnology is illustrated for the case of phthalimide-lactone (PL), a recently synthesized strigolactone mimic whose very limited solubility in water, as a free chemical, precludes its practical use as an agrochemical in the fight against parasitic plants. Pluronic F-127 (P127) nanoparticles functionalized with PL have been synthesized and embedded in a polymeric matrix of poly(vinyl alcohol) (PVA). Low-voltage and medium voltage imaging and spectroscopic scanning electron microscopy (S(T)EM) techniques were combined to confirm the synthesis of multicore nanoparticles that were rich in nitrogen, a finding that is due to the successful encapsulation of PL. This PL@P127/PVA nanobiostimulator formulation has an impressive solubility in water, that is, 27 times higher than that of pure phthalimide-lactone. Also critical from the functional point of view, comparative bioassays clearly showed that the intrinsic stimulatory activity of this agrochemical is fully maintained in the nanoencapsulated formulation.

Using a method that combines experimental and simulated Aberration-Corrected High Resolution Electron Microscopy images with digital image processing and structure modeling, strain distribution maps within gold nanoparticles relevant to real powder type catalysts, i.e., smaller than 3 nm, and supported on a ceria-based mixed oxide have been determined. The influence of the reduction state of the support and particle size has been examined. In this respect, it has been proven that reduction even at low temperatures induces a much larger compressive strain on the first {111} planes at the interface. This increase in compression fully explains, in accordance with previous DFT calculations, the loss of CO adsorption capacity of the interface area previously reported for Au supported on ceria-based oxides.

Nano-structural and nano-analytical studies show that the dramatic difference in CO oxidation activity observed between two Au/Ce0.50Tb0.12Zr0.38O2-x samples prepared by deposition-precipitation with urea and further activated under oxidising or reducing conditions is due to the poisoning effect of a very thin layer of carbon grown on the pre-reduced catalyst.

A variety of advanced (scanning) transmission electron microscopy experiments, carried out in aberration-corrected equipment, provide direct evidence about subtle structural changes taking place at nanometer-sized Au||ceria oxide interfaces, which agrees with the occurrence of charge transfer effects between the reduced support and supported gold nanoparticles suggested by macroscopic techniques. Tighter binding of the gold nanoparticles onto the ceria oxide support when this is reduced is revealed by the structural analysis. This structural modification is accompanied by parallel deactivation of the CO chemisorption capacity of the gold nanoparticles, which is interpreted in exact quantitative terms as due to deactivation of the gold atoms at the perimeter of the Au||cerium oxide interface.

The influence of the highly dispersed gold phase on the CO-support interaction occurring in two 2.5 wt % Au/Ce(0.62)Zr(0.38)O(2) catalysts with medium (Au/CZ-MD) and high (Au/CZ-HD) metal dispersion is quantitatively assessed. For this purpose, we have followed an approach in which high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), computer modelling, volumetric adsorption and FTIR spectroscopy studies are combined. This approach has already been fruitfully applied to the investigation of the specific CO-metal adsorption in Au/ceria-zirconia catalysts. As deduced from the experimental studies reported herein, the presence of gold dramatically increases the amount of CO strongly chemisorbed on the support. Moreover, this amount is sensitive to the metal dispersion, thus suggesting the occurrence of a mechanism in which the CO molecules that are initially adsorbed on the gold nanoparticles are further transferred to the support by means of a spillover process. An annular model is proposed for the growth of the CO phase adsorbed on the ceria-zirconia mixed oxide in the presence of Au. By assuming this model, we have estimated the width of the annulus, Delta r, of the adsorbed CO grown around the Au nanoparticles in Au/CZ-MD and Au/CZ-HD catalysts. This value is found to be very close to Delta r approximately 2 nm in both cases, the coincidence lending some additional support to the model. To further confirm this proposal, we have investigated the influence of CO pre-adsorption on the D(2)-Au/CZ-MD interaction, at 298 K. As revealed by FTIR spectroscopy, the kinetics of the deuterium spillover is significantly disturbed by the pre-adsorbed CO, which is fully consistent with an annular model for the CO adsorption. We conclude from the global analysis of the results reported here and those already available on CO-Au adsorption that the appropriate combination of nanostructural, computer modelling and chemical techniques is a powerful tool allowing us to gain a comprehensive picture of the complex series of processes involved in the CO adsorption on this relevant family of gold catalysts.

Bimetallic CoNi nanoparticles have been prepared within the apoferritin cavity. The protein shell controls size, prevents aggregation, and makes nanoparticles water-soluble. The CoNi series prepared in this way were structurally and magnetically characterized, the resulting magnetic properties varying accordingly with composition (Co(75)/Ni(25), Co(50)/Ni(50), Co(25)/Ni(75)). Co and Ni metals were associated in each nanoparticle, as demonstrated by high-angle annular dark field scanning electron microscopy and electron energy loss spectroscopy (EELS). After intentional oxidation, the CoNi nanoparticles were characterized by EELS, X-ray absorption near edge structure (XANES), and SQUID measurements to evaluate the importance of the oxidation on magnetic properties.

CeO(2) nanotubes have been grown electrochemically using a porous alumina membrane as a template. The resulting material has been characterized by means of scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy, high-angle annular dark-field scanning transmission electron microscopy tomography, high-resolution electron microscopy (HREM), and electron energy loss spectroscopy. According to SEM, the outer diameter of the nanotubes corresponds to the pore size (200 nm) of the alumina membrane, and their length ranges between 30 and 40 microm. HREM images have revealed that the width of the nanotube walls is about 6 nm. The catalytic activity of these novel materials for the CO oxidation reaction is compared to that of a polycrystalline powder CeO(2) sample prepared by a conventional route. The activity of the CeO(2) nanotubes is shown to be in the order of 400 times higher per gram of oxide at 200 degrees C (77.2 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the nanotube-shaped CeO(2) and 0.16 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the powder CeO(2)).

An electrodeposition process is used to synthesize nanotubes of a lanthanum-containing phase, employing porous alumina membranes as templates. This method should lead to the formation of La(OH)(3) nanowires, according to the previous results presented by Bocchetta et al (2007 Electrochem. Commun. 9 683-8), which can be decomposed to La(2)O(3), as the latter shows more interest for different applications. The results obtained by means of different electron microscopy techniques indicate that this method leads to the formation of nanotubes of about 200 nm in diameter and 30-40 µm in length, instead of the nanowires proposed in the literature. Additionally, the chemical characterization demonstrates that the material synthesized is composed of lanthanum hydroxycarbonate. The presence of carbonates is found to be crucial in determining the conditions for the preparation of La(2)O(3) from the nanotubes here obtained.

Transmission Electron Microscopy (TEM), X-ray Absorption Near Edge Spectroscopy (XANES), Electron Energy-Loss Spectroscopy (EELS), Small-Angle X-ray Scattering (SAXS), and SQUID magnetic studies were performed in a batch of horse spleen ferritins from which iron had been gradually removed, yielding samples containing 2200, 1200, 500, and 200 iron atoms. Taken together, findings obtained demonstrate that the ferritin iron core consists of a polyphasic structure (ferrihydrite, magnetite, hematite) and that the proportion of phases is modified by iron removal. Thus, the relative amount of magnetite in ferritin containing 2200 to 200 iron atoms rose steadily from approximately 20% to approximately 70% whereas the percentage of ferrihydrite fell from approximately 60% to approximately 20%. These results indicate a ferrihydrite-magnetite core-shell structure. It was also found that the magnetite in the ferritin iron core is not a source of free toxic ferrous iron, as previously believed. Therefore, the presence of magnetite in the ferritin cores of patients with Alzheimer's disease is not a cause of their increased brain iron(II) concentration.