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Layered TiS 2 intercalated with linear alkylamines has recently attracted significant interest as a model compound for flexible n -type thermoelectric applications, showing remarkably high power factors at room temperature. The thermal and, particularly, environmental stability of such materials is, however, a still an open challenge. In this paper, we show that amine-intercalated TiS 2 prepared by a simple mechanochemical process is prone to chemical decomposition through sulfur exsolution, and that the presence of molecular oxygen is likely to mediate the decomposition reaction. Through computational analysis of the possible reaction pathways, we propose that Ti-N adducts are formed as a consequence of amine groups substituting for S vacancies on the internal surfaces of the S-Ti-S layers. These findings provide insights for possible future applications of similar hybrid compounds as devices operating in ambient conditions, and suggest isolating them from atmospheric oxygen.

The structures of the disordered 1D (pseudo-)perovskites of general TMSO(Pb x Bi y )I 3 formulation [TMSO = (CH 3 ) 3 SO + ], obtained by doping the TMSOPbI 3 species with Bi 3+ ions, are investigated through the formulation of a statistical model of correlated disorder, which addresses the sequences of differently occupied BI 6 face-sharing octahedra (B = Pb, Bi or vacant site) within ideally infinite [(BI 3 ) - ] n chains. The x-ray diffraction patterns simulated on the basis of the model are matched to the experimental traces, which show many broad peaks with awkward (nearly trapezoidal) shapes, under the assumption that the charge balance is fully accomplished within each chain. The analysis allowed to establish a definite tendency of the metal species to cluster as pure Pb and Bi sequences. The application of the model is discussed critically, in particular as what concerns the possibility that further B-site neighbors beyond the second may influence the overall B-site occupancies., (© 2022 IOP Publishing Ltd.)

In this study, the structure and morphology, as well as time, ultraviolet radiation, and humidity stability of thin films based on newly developed 1D (PRSH)PbX 3 (X = Br, I) pseudo-perovskite materials, containing 1D chains of face-sharing haloplumbate octahedra, are investigated. All films are strongly crystalline already at room temperature, and annealing does not promote further crystallization or film reorganization. The film microstructure is found to be strongly influenced by the anion type and, to a lesser extent, by the DMF/DMSO solvent volume ratio used during film deposition by spin-coating. Comparison of specular X-ray diffraction and complementary grazing incidence X-ray diffraction analysis indicates that the use of DMF/DMSO mixed solvents promotes the strengthening of a dominant 100 or 210 texturing, as compared the case of pure DMF, and that the haloplumbate chains always lie in a plane parallel to the substrate. Under specific DMF/DMSO solvent volume ratios, the prepared films are found to be highly stable in time (up to seven months under fluxing N 2 and in the dark) and to highly moist conditions (up to 25 days at 78% relative humidity). Furthermore, for representative (PRSH)PbX 3 films, resistance against ultraviolet exposure (λ = 380 nm) is investigated, showing complete stability after irradiation for up to 15 h at a power density of 600 mW/cm 2 . These results make such thin films interesting for highly stable perovskite-based (opto)electronic devices.

This paper examines the production technology of Egyptian blue, an ancient artificial pigment, through the investigation of an unsuccessfully produced pellet derived from the Hellenistic production site of Kos (Dodecanese, Greece). This heterogeneous material was investigated by a combination of laboratory and synchrotron radiation-based (SR) techniques: scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, micro-Raman spectroscopy, high-resolution SR micro-X-ray fluorescence spectroscopy, and SR micro-X-ray absorption near-edge structure spectroscopy (XANES), at the ID21 beamline of the European Synchrotron Radiation Facility. Principal component analysis of a large dataset of 171 micro-XANES spectra acquired on the archaeological samples and on a series of reference copper compounds emphasizes high variations of XANES features due to different speciation and also orientation effects, as demonstrated by the simulated XANES spectra. The results indicate that, rather than inadequate firing temperatures that could have led to the reddish cuprite (Cu 2 O), unsuccessful production may occur due to the use of inappropriate starting materials, which contain an unusually high iron content. The contextual interpretation underlines the intertwined relationship between the production of Egyptian blue and metallurgy.

The literature concerning protonic ceramic devices is critically reviewed focusing the reader's attention on the structure, composition, and phenomena taking place at solid-solid interfaces. These interfaces play a crucial role in the overall device performance, and the relevance of understanding the phenomena taking place at the interfaces for the further improvement of electrochemical protonic ceramic devices is therefore stressed. The grain boundaries and heterostructures in electrolytic membranes, the electrode-electrolyte contacts, and the interfaces within composite anode and cathode materials are all considered, with specific concern to advanced techniques of characterization and to computational modeling by ab initio approaches. An outlook about future developments and improvements highlights the necessity of a deeper insight into the advanced analysis of what happens at the solid-solid interfaces and of in situ/operando investigations that are presently sporadic in the literature on protonic ceramic devices.

An R-space approach to the simulation and fitting of a structural model to the experimental pair distribution function is described, to investigate the structural disorder (distance distribution and stacking faults) in close-packed metals. This is carried out by transferring the Debye function analysis into R space and simulating the low-angle and high-angle truncation for the evaluation of the relevant Fourier transform. The strengths and weaknesses of the R-space approach with respect to the usual Q-space approach are discussed.

The modification of metal oxide surfaces with organic moieties has been widely studied as a method of preparing organic-inorganic hybrid materials for various applications. Among the inorganic oxides, ion-exchangeable layered perovskites are particularly interesting, because of their appealing electronic and reactive properties. In particular, their protonated interlayer surface can be easily functionalized with organic groups allowing the production of stable hybrid materials. As a further step in the design of new inorganic-organic hybrid proton conductors, a combined experimental and theoretical study of two intercalated compounds (propanol and imidazole) in HLaNb2O7 is presented here. A generally very good agreement with the available experimental data is found in reproducing both structural features and 13C-NMR chemical shifts, and marked differences between the two considered intercalated compounds are evidenced, with possible important outcomes for proton conduction. Notably, the free imidazole molecules are easily protonated by the acidic protons present in the interlayer spacing, thus inhibiting an efficient charge transport mechanism. In order to overcome this problem, a model system has been considered, where the imidazoles are bound to the end of a butyl chain, the whole being intercalated between two perovskite layers. The obtained theoretical data suggest that, in such a system, proton transfer between two adjacent imidazoles is a barrierless process. These results could then open new perspectives for such hybrid proton conductors.

Hypothesis: Nanostructured sorbents and, in particular, supramolecular gels are emerging as efficient materials for the removal of toxic contaminants from water, like industrial dyes. It is also known that ionic liquids can dissolve significant amounts of dyes. Consequently, supramolecular ionic liquids gels could be highly efficient sorbents for dyes removal. This would also contribute to overcome the drawbacks associated with dye removal by liquid-liquid extraction with neat ionic liquids which would require large volumes of extractant and a more difficult separation of the phases., Experiments: Herein we employed novel supramolecular ionic liquid gels based on diimidazolium salts bearing naturally occurring or biomass derived anions, to adsorb cationic and anionic dyes from wastewaters. We also carried out a detailed investigation of thermal, structural, morphological and rheological features of our gels to identify which of them are key in designing better sorbents for environmental remediation., Findings: The most effective gels showed fast and thorough removal of cationic dyes like Rhodamine B. These gels could also be reused up to 20 times without any loss in removal efficiency. Overall, our ionic gels outperform most of gel-based sorbents systems so far reported in literature., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The chemical compatibility between electrolytes and electrodes is an extremely important aspect governing the overall impedance of solid-oxide cells. Because these devices work at elevated temperatures, they are especially prone to cation interdiffusion between the cell components, possibly resulting in secondary insulating phases. In this work, we applied X-ray microspectroscopy to study the interface between a samarium-doped ceria (SDC) electrolyte and lanthanum ferrite cathodes (La 0.4 Sr 0.6 Fe 0.8 Cu 0.2 O 3 (LSFCu); La 0.9 Sr 0.1 Fe 0.85 Co 0.15 O 3 (LSCF)), at a submicrometric level. This technique allows to combine the information about the diffusion profiles of cations on the scale of several micrometers, together with the chemical information coming from space-resolved X-ray absorption spectroscopy. In SDC-LSCF bilayers, we find that the prolonged thermal treatments at 1150 °C bring about the segregation of samarium and iron in micrometer-sized perovskite domains. In both SDC-LSCF and SDC-LSFCu bilayers, cerium diffuses into the cathode perovskite lattice A-site as a reduced Ce 3+ cation, whereas La 3+ is easily incorporated in the ceria lattice, reaching 30 atom % in the ceria layer in contact with LSFCu.

Diimidazolium-based organic salts, bearing peptides or amino acids as anions have been synthesised and tested for their gelling ability in biocompatible solvents. These low molecular weight salts were successfully used as gelators in phosphate buffered saline (PBS) solution and ionic liquids. Then, the properties of the obtained soft materials were analysed in terms of melting temperature and gel strength as accounted for by rheological investigations. The gel-phase formation was studied by using UV/Vis and resonance light scattering measurements, whereas the morphology of the soft materials was analysed by using polarised optical microscopy and scanning electron microscopy. To get information about the organisation of the gelator in the gelatinous matrix, X-ray diffraction measurements were performed both on the neat gelators and their gels. The results collected show that the properties of the gel phases, like the thermal stability, the self-repairing ability, the resistance to flow as well as the morphology, are dependent on the nature of the anion. Furthermore, bioassays revealed that the obtained diimidazolium organic salts possessed antimicrobial activity, against gram-negative and gram-positive tester strains. In particular and noteworthy, the diimidazolium organic salts exert a bactericidal capability, which was retained even if they are included in the gel phase. Thus, a novel kind of bioactive soft material was obtained that could be fruitfully employed as a non-covalent coating exerting antibacterial capability., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A combined experimental and theoretical study of Mg-doped LaGaO 3 electrolyte was carried out, with the aim to unveil the interaction between oxygen vacancy (Vo) and perovskite B site cations. LaGaO 3 (LG) and LaGa 0.875 Mg 0.125 O 2.938 (LGM0125) samples were comprehensively characterized by X-ray absorption spectroscopy (XAS) and X-ray diffraction, in order to investigate short- and long-range structures of both undoped and Mg-doped materials. XAS analysis evidenced a preferential Ga-Vo interaction in LGM0125, confirmed by periodic hybrid density functional theory calculations, which were combined with a symmetry-independent classes (SICs) approach in order to (a) obtain a detailed picture of the different Mg and Vo configurations in the doped material and (b) characterize the structural features of the conducting sites. Among the 28 structures of LGM0125 considered in the SIC approach, the Ga-Vo-Ga and Ga-Vo-Mg axial configurations (oriented along the b crystallographic axis) were found to be the most stable. The relative stability of all vacancy configurations considered could be related to geometric distortions of the B-sites, possibly significantly affecting the oxygen-ion diffusion process in such electrolytes.

We describe the functionalization of the layered perovskite HLaNb 2 O 7 with n-propanol, n-decanol, 3-mercaptopropyl-trimethoxysilane, imidazole, n-decylamine, and histamine. The use of sonication is found to significantly improve the reaction yield and to reduce the reaction time, compared to conventional thermal treatment under reflux. The obtained intercalates are thoroughly characterized through the use of several complementary experimental techniques (scanning electron microscopy, IR spectroscopy, X-ray diffraction, thermogravimetric analysis, magic-angle spinning NMR), clarifying their structure and chemical bonding. The implications for the design of inorganic-organic composite materials are discussed.

Dion-Jacobson phases, like MLaNb2O7, are an interesting class of ion-exchangeable layered perovskites possessing electronic and photocatalytic properties. Their protonated and organo-modified homologues, in particular, have already been indicated as promising catalysts. However, the structural analysis of these highly tailorable materials is still incomplete, and both the intercalation process and thermal stability of the included organic moieties are far from being completely understood. In this study, we present a thorough solid-state NMR characterization of HLaNb2O7·xH2O intercalated with different amounts of octylamine, or with decylamine. Samples were analyzed as prepared, and after thermal treatment at different temperatures up to 220 °C. The substitution of pristine proton ions was followed via(1)H MAS NMR spectroscopy, whereas the alkyl chains were monitored through (13)C((1)H) CP MAS experiments. The interactions in the interlayer space were explored using (13)C((1)H) 2D heteronuclear correlation experiments. We demonstrate that some of the protons are involved in the functionalization reaction, and some of them are in close proximity to the alkyl ammonium chains. Heating of the hybrid materials leads first to a rearrangement of the alkyl chains and then to their degradation. The spatial arrangement of the chains, their interactions and the thermal behavior of the materials depend on the extent of the functionalization, and on the nature of the intercalated alkyl ammonium ions.

The structure of (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) reverse micelles, at various water-to-surfactant molar ratio (Rw, Rw = [water]/[DMEB]) and DMEB concentrations, has been investigated by small angle X-ray scattering (SAXS) and extended X-ray absorption fine structure spectroscopy (EXAFS). SAXS data of dry reverse micelles are consistent with a model of spherical hydrophilic core surrounded by DMEB alkyl chains whose polydispersity decreases significantly with surfactant concentration. By adding water, a sphere to cylinder transition occurs leading to a one-dimensional growth of reverse micellar cores with Rw and surfactant concentration. The observed behavior was taken as an indication that water molecules are confined in the core of DMEB reverse micelles, quite uniformly distributed among them and mainly located among surfactant head groups. EXAFS data allow to focus within the hydrophilic micellar core to solve the short range local environment around the Br(-) counterion and to follow its changing with surfactant concentration and Rw. Analysis of Fourier transform of the EXAFS spectra indicates the existence of a local order nearby the bromide ions; pointing toward a quite structured hydrophilic core of DMEB reverse micelles. However, as a consequence of the fluid nature of reverse micelles, such local order is lower than that found in the lamellar structure of solid DMEB. Water confinement within the reverse micellar cores induces an increase of the local disorder suggesting an enhancement of the micellar core dynamics.

A comprehensive theoretical investigation of the MLaNb2O7 (M = H, Li, Na, K, Rb, and Cs) series of ion-exchangeable layered perovskite is presented. These perovskites are in particular interesting in view of their potential applications as inorganic supports for the design of new hybrid inorganic-organic proton conductors. In particular, their structural and electronic properties have been investigated by periodic calculations in the framework of Density Functional Theory, using different exchange-correlation functionals. A general very good agreement with the available experimental (XRD, NPD, and EXAFS) data has been found. The structure of the protonated HLaNb2O7 form has also been further clarified and a new tetragonal space group is proposed for this compound, better reproducing the experimental cell parameters and yielding to a more realistic picture of the system. The electronic investigation highlighted that all the compounds considered are very similar to each other and that the interaction between interlayer cations and perovskite slabs is purely ionic, except for the proton that is, instead, covalently bound.

We present a thorough characterization of the interaction of novel nickel(II) (1), copper(II) (2) and zinc(II) (3) Schiff base complexes with native calf thymus DNA (ct-DNA), in buffered aqueous solution at pH 7.5. UV-vis absorption, circular dichroism (CD) and viscometry titrations provided clear evidence of the intercalative mechanism of the three square-planar metal complexes, allowing us to determine the intrinsic DNA-binding constants (K(b)), equal to 1.3 × 10(7), 2.9 × 10(6), and 6.2 × 10(5) M(-1) for 1, 2 and 3, respectively. Preferential affinity, of one order of magnitude, toward AT compared to GC base pair sequences was detected by UV-vis absorption titrations of 1 with [poly(dG-dC)]2 and [poly(dA-dT)]2. Structural details of the intercalation site of the three metal complexes within [dodeca(dA-dT)]2 were obtained by molecular dynamics (MD) simulations followed by density functional theory/molecular mechanics (DFT/MM) calculations. The calculations revealed that three major intermolecular interactions contribute to the strong affinity between DNA and the three metal complexes: (1) the electrostatic attraction between the two positively charged triethylammoniummethyl groups of the metal complexes and the negatively charged phosphate groups of the DNA backbone; (2) the intercalation of the naphthalene moiety within the four nitrogen bases of the intercalation site; (3) the metal coordination by exocyclic donor atoms of the bases, specifically the carbonyl oxygen and amine nitrogen atoms. Remarkably, the Gibbs formation free energy calculated for the intercalation complexes of 1, 2 and 3 with [dodeca(dA-dT)]2 in the implicit water solution is in agreement with the experimental Gibbs free energy values obtained from the DNA-binding constants as ΔG° = -RT ln(K(b)). In particular, the DNA-binding affinity trend, 1 > 2 > 3, is reproduced. Finally, the first shell coordination distances calculated for the intercalation complex 3/[dodeca(dA-dT)]2 are in excellent agreement with the experimental distances extracted from the extended X-ray absorption fine structure (EXAFS) spectrum of the corresponding 3/ct-DNA solutions. The latter results provided the first evidence of metal ion coordination by native DNA in aqueous solution.

The structure of small gold nanoclusters (around 2.5 nm) deposited on different silica-on-silicon (SiOx/Si) substrates is investigated using several characterization techniques (AFM, XRD, EXAFS and GISAXS). The grain morphology and the surface roughness of the deposited gold cluster layers are determined by AFM. The in-plane GISAXS intensity is modelled in order to obtain information about the cluster size and the characteristic length scale of the surface roughness. The surface morphology of the deposited clusters depends on whether the native defect-rich (n-SiOx/Si) or the defect-poor substrate obtained by thermal treatment (t-SiO2/Si) is used. Gold clusters show a stronger tendency to aggregate when deposited on n-SiOx/Si, resulting in films characterized by a larger grain dimension (around 20 nm) and by a higher surface roughness (up to 5 nm). The more noticeable cluster aggregation on n-SiOx/Si substrates is explained in terms of metal-support interaction mediated by the defects located on the surface of the native silica substrate. Evidence of metal-support interaction is provided by EXAFS, demonstrating the existence of an Au-O distance for clusters deposited on n-SiOx/Si that is not found on t-SiO2/Si.

Water-soluble gold nanorods (Au NRs) were synthesized using a silver-ion mediated photochemical route under UV irradiation. Extended X-ray Absorption Fine Structure (EXAFS) measurements on the Ag K-edge were performed on samples obtained at different Ag/Au ratios and at increasing irradiation times in order to investigate the fate of silver ions during the growth of Au NRs. EXAFS measurements allowed to probe the chemical state and the local environment of silver in the final product. Experimental data suggest that Ag atoms are placed on top of the Au particles as metallic Ag(0), while no significant contribution to the EXAFS spectra comes from AgBr or other Ag(+) based species. The reported results strongly support the deposition of Ag(0) islands on the (110) surfaces of the Au particles, thus driving the anisotropic growth via the (111) surfaces.

The microstructure of temperature-quenched solutions of reverse micelles formed by sodium, cobalt, ytterbium, and cobalt/ytterbium bis(2-ethylhexyl)sulfosuccinate in n-heptane has been investigated by SAXS and EXAFS. Some changes in the X-ray absorption spectra with respect to the same systems at room temperature have been observed. The analysis of the SAXS spectra leads to the hypothesis that at 77 K the closed spherical structure of reverse micelles is retained and that during the temperature quench they undergo a clustering process involving the transition from a quite random dispersion to the formation of more or less large clusters of strongly packed reverse micelles. This behavior is attributed to competitive effects caused by the temperature decrease. The prevalence of intermicellar attractive interactions with respect to Brownian motions leading to a collapse to more compact structure is in competition with the rapid decrease of reverse micelle diffusion rate involving a freezing of the local structures. In the case of cobalt, ytterbium, and cobalt/ytterbium bis(2-ethylhexyl)sulfosuccinate reverse micelles, further information from EXAFS measurements indicates that within the reverse micelle core exists a quite ordered nanosized domain composed of water, surfactant counterions, and oxygen atoms of the SO3- head groups. The conservation of local order and inverse structure during the clustering phenomenon that results from the fast freezing with liquid nitrogen of solutions of reverse micelles could have biological implications, i.e., the preservation of tissue samples at cryogenic temperatures.

The catalyst Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is studied by CO-temperature programmed reduction (CO-TPR), isothermal oxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt L(III) edge, and in situ X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidation by ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is compared to that of bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and the maximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia. XAS analysis allows one to evidence the formation of a platinum-cerium alloy in redox-aged samples and the stability of the metal particles toward oxidation and sintering during high-temperature treatments. Under CO flux at 773 K, bare ceria-zirconia shows a continuous drift of diffraction peaks toward smaller Bragg angles, due to a progressive increase of Ce(III) content. Under the same treatment, the structural rearrangement of Pt-supported ceria-zirconia starts after an induction time and takes place with an abrupt change of the lattice constant. The experimental evidence points to the role of supported Pt in modifying the redox properties of ceria-zirconia with respect to the bare support. It is proposed that the much faster bulk reduction observed by in situ XRD for redox-aged Pt/ceria-zirconia can be attributed to an easier release of reacted CO(2), producing a more effective turnover of reactants at the catalyst surface.

An in situ cell for reductive and oxidative treatments at different temperatures that allows the possibility of recording data as a function of temperature has been designed and constructed for X-ray absorption experiments at the GILDA beamline BM08 of ESRF. The cell is linked to a mass quadrupole spectrometer providing control of the reaction gases and monitoring of the products. The apparatus allows measurements to be performed both in transmission and fluorescence geometry. The cell was tested by studying the CO oxidation reaction promoted by a Pt/ceria-zirconia-supported catalyst. The CO(2) yield is correlated with the structural results confirming the existence of a strong metal-support interaction between the Pt metal clusters and the ceria-zirconia support.