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Chiroptical activity in luminescent all-inorganic cesium copper bromide produced via a ligand-assisted reprecipitation method in the presence of arginine.

Chiral semiconductor quantum dots have recently received broad attention due to their promising application in several fields such as sensing and photonics. The extensive work in the last few years was focused on the observation of the chiroptical properties in binary Cd based systems. Herein, we report on the first evidence of ligand-induced chirality in silver indium sulfide semiconductor quantum dots. Ternary disulfide quantum dots are of great interest due to their remarkable optical properties and low toxicity. Non-stoichiometric silver indium sulfide quantum dots were produced

The use of readily prepared bisphosphonic acids obtained in few steps through a thio-Michael addition of commercially available thiols on tetraethyl vinylidenebisphosphonate enables the straightforward surface modification of amorphous mesoporous zirconia nanoparticles. Simple stirring of the zirconia nanoparticles in a buffered aqueous solution of the proper bisphosphonic acid leads to the surface functionalization of the nanoparticles with different kinds of functional groups, charge and hydrophobic properties. Formation of both chemisorbed and physisorbed layers of the bisphosphonic acid take place, observing after extensive washing a grafting density of 1.1 molecules/nm2 with negligible release in neutral or acidic pH conditions, demonstrating stronger loading compared to monophosphonate derivatives. The modified nanoparticles were characterized by IR, XPS, ζ-potential analysis to investigate the loading of the bisphosphonic acid, FE-SEM to investigate the size and morphologies of the nanoparticles and 31 P and 1 H MAS NMR to investigate the coordination motif of the phosphonate units on the surface. All these analytical techniques demonstrated the strong affinity of the bisphosphonic moiety for the Zr(IV) metal centers. The functionalization with bisphosphonic acids represents a straightforward covalent approach for tailoring the superficial properties of zirconia nanoparticles, much straightforward compared the classic use of trisalkoxysilane or trichlorosilane reagents typically employed for the functionalization of silica and metal oxide nanoparticles. Extension of the use of bisphosphonates to other metal oxide nanoparticles is advisable.

A new instrumental neutron activation analysis (INAA) for the simultaneous determination of titanium (TiO

We report on a Cu(ii) catalyzed process for the production of cysteine based chiral carbon dots; the process does not require any thermal treatment and the carbon dot formation is driven by the production of reactive radical species that are generated in the reaction media by the catalytic role played by the multivalent transition metal. The nanomaterial presents a well-defined chirality and the enantioselectivity of the synthesis is proved by the isolation of both the carbon dot enantiomers. We focused our attention on the processes that take place during the carbon dot formation and the relationship with the structure of the organic starting material. Thanks to the comparison of reactions conducted with different organic substrates whose thiyl radical chemistry is known, we recognized a non-trivial role of the radical hydrogen abstraction reactions in the carbon dot formation process. The reported process allows access to a large variety of analyses to monitor the reaction mixtures during the reaction course. Finally, we report a detailed analysis on the evolution of optical chirality during the synthesis and related this feature with the formation mechanism of the nanomaterial revealing significant evidence on the chirality origin and structure of chiral carbon dots.

Background: TiO2 nanoparticles (TiO2 NPs) are the nanomaterial most produced as an ultraviolet (UV) filter. However, TiO2 is a semiconductor and, in nanoparticle size, is a strong photocatalyst, raising concerns about photomutagenesis. Mesoporous silica nanoparticles (MSN) were synthetized incorporating TiO2 NPs (TiO2@MSN) to develop a cosmetic UV filter. The aim of this study was to assess the toxicity of TiO2@MSN, compared with bare MSN and commercial TiO2 NPs, based on several biomarkers. Materials and Methods: Human peripheral blood mononuclear cells (PBMC) were exposed to TiO2@MSN, bare MSN (network) or commercial TiO2 NPs for comparison. Exposed PBMC were characterized for cell viability/apoptosis, reactive oxygen species (ROS), nuclear morphology, and cytokines secretion. Results: All the nanoparticles induced apoptosis, but only TiO2 NPs (alone or assembled into MSN) led to ROS and micronuclei. However, TiO2@MSN showed lower ROS and cytotoxicity with respect to the P25. Exposure to TiO2@MSN induced Th2-skewed and pro-fibrotic responses. Conclusions: Geno-cytotoxicity data indicate that TiO2@MSN are safer than P25 and MSN. Cytokine responses induced by TiO2@MSN are imputable to both the TiO2 NPs and MSN, and, therefore, considered of low immunotoxicological relevance. This analytical assessment might provide hints for NPs modification and deep purification to reduce the risk of health effects in the settings of their large-scale manufacturing and everyday usage by consumers.

We report a microwave assisted synthesis of NaNbO3 perovskite mesocrystals with a hierarchical morphology formed by the self-assembly of nanoparticles in particle clusters. The synthesis method combines non-aqueous sol–gel synthesis and microwave heating in a single step process that allows us to isolate crystalline single phase NaNbO3 in few minutes. A detailed investigation of the effect of the reaction temperature on the crystallinity and morphology of the product was conducted. The synthesis stabilizes the unusual orthorhombic phase Pmma, a property that can be ascribed to the crystal size (24 nm). TEM and SAED analyses show that the hierarchical polycrystalline particles behave as single crystals, a feature related to a non-classical crystallization mechanism. Moreover, the optical bandgap of this NaNbO3 phase was estimated for the first time. The results suggest the potential of this synthetic procedure for the fast production of high quality tertiary oxide nanocrystals.

[Image: see text] There is the need for reproducible, simple, high-yielding synthetic protocols aimed at obtaining carbon dots (CDs) with controlled fluorescence, photothermal and photochemical behavior, surface properties, biocompatibility, tumor targeting ability, drug absorption biodistribution, and tumor uptake. This Letter describes a systematic study on the effect of glucose, fructose, and ascorbic acid as starting materials for the preparation of highly luminescent CDs, characterized by a blue emission. Their composition and morphology are investigated by titration of OH surface groups, spectroscopic techniques, and high-resolution transmission electron microscopy (HR-TEM), and their toxicity was tested toward HeLa cells. CDs made using fructose were toxic, while those made from glucose and ascorbic acid showed good biocompatibility. The reproducible and simple synthetic procedure yields luminescent biomass-derived CDs for combined cancer therapy and diagnostics. Their doxorubicin (DOX) drug uptake was measured by spectrofluorimetry, indicating a crucial role of the morphologies of the CDs in controlling DOX loading. The glucose derived CDs showed up to 28% w/w of DOX loading.

Some crystallographic considerations on the novel orthorhombic ZrO2 (o-ZrO2) stabilized at ambient conditions by Ta substitutional doping are presented. Specifically, how the Ta-doped o-ZrO2 was observed for the first time by conventional X-ray diffractometry (XRD) is reported, after which the ab initio and non-ab initio procedures used to resolve its crystal structure are detailed. The crystal structure is then explicitly reported (i.e., space group and cell parameters, as well as atomic positions of the asymmetric unit). It is also shown that this novel Ta-doped o-ZrO2 has a crystal structure similar, but not identical, to the high-pressure o-ZrO2. Additionally, given that the crystal structure of the Ta-doped o-ZrO2 is identified as being a symmetry-breaking distortion of the typical tetragonal ZrO2 (t-ZrO2) stabilized with the commonest dopants, a complete analysis is also made of the structural distortions relating both the Ta-doped o-ZrO2 and the high-pressure o-ZrO2 to the t-ZrO2. Finally, a justification for the apparent greater immunity of the Ta-doped o-ZrO2 to aging is provided.

A novel fine-grained orthorhombic ZrO2 ceramic stabilized with 12 mol% Ta doping was fabricated by spark-plasma sintering from home-made powders, and its high-temperature mechanical properties evaluated for the first time by compressive creep tests in both Ar and air. It was found that the high-temperature plasticity of the ceramic deformed in Ar, under which the Ta-doped orthorhombic ZrO2 is a black suboxide with abundant oxygen vacancies in its crystal structure, is controlled by grain boundary sliding (stress exponent ∼2, and activation energy ∼780–800 kJ/mol). However, the high-temperature plasticity of the ceramic deformed in air, under which the Ta-doped orthorhombic ZrO2 is a white oxide due to the elimination in situ of oxygen vacancies, is controlled by recovery creep (stress exponent ∼3, and activation energy ∼750 kJ/mol). It was also observed that black Ta-doped orthorhombic ZrO2 is more creep resistant than its white counterpart with the same grain size, and that the former deforms as the more conventional Y2O3-stabilized ZrO2 does., This work was supported by the Junta de Andalucía under Grant nº P12-FQM-1079 and by the Junta de Extremadura under Grant nº GR15078, co-financed with FEDER Funds. Financial support from the Ministerio de Economía y Competitividad (Government of Spain) and FEDER Funds under Grants nº MAT2015-71411-R and MAT2016-76638-R is gratefully acknowledged as well.

Background: TiO2 nanoparticles (TiO2 NPs) are the nanomaterial most produced as an ultraviolet (UV) filter. However, TiO2 is a semiconductor and, in nanoparticle size, is a strong photocatalyst, raising concerns about photomutagenesis. Mesoporous silica nanoparticles (MSN) were synthetized incorporating TiO2 NPs (TiO2@MSN) to develop a cosmetic UV filter. The aim of this study was to assess the toxicity of TiO2@MSN, compared with bare MSN and commercial TiO2 NPs, based on several biomarkers. Materials and Methods: Human peripheral blood mononuclear cells (PBMC) were exposed to TiO2@MSN, bare MSN (network) or commercial TiO2 NPs for comparison. Exposed PBMC were characterized for cell viability/apoptosis, reactive oxygen species (ROS), nuclear morphology, and cytokines secretion. Results: All the nanoparticles induced apoptosis, but only TiO2 NPs (alone or assembled into MSN) led to ROS and micronuclei. However, TiO2@MSN showed lower ROS and cytotoxicity with respect to the P25. Exposure to TiO2@MSN induced Th2-skewed and pro-fibrotic responses. Conclusions: Geno-cytotoxicity data indicate that TiO2@MSN are safer than P25 and MSN. Cytokine responses induced by TiO2@MSN are imputable to both the TiO2 NPs and MSN, and, therefore, considered of low immunotoxicological relevance. This analytical assessment might provide hints for NPs modification and deep purification to reduce the risk of health effects in the settings of their large-scale manufacturing and everyday usage by consumers.

In this study, an aqueous sol–gel chemistry route based on phosphoric acid as the phosphorus precursor, calcium acetate monohydrate and lanthanide (III) oxides as source of calcium and lanthanide ions, respectively, have been used to prepare europium- and thulium-substituted calcium hydroxyapatite (CHAp:Ln3+) powders. The ethylenediaminetetraacetic acid was used as complexing agent in the sol–gel processing. The final products were obtained by calcination of the dry precursor gels for 5 h at 1000 °C. The phase transformations, composition, and structural changes in the polycrystalline samples were studied by infrared spectroscopy, X-ray powder diffraction analysis, scanning electron microscopy and photoluminescence measurements. It was demonstrated, however, that the substitution of calcium by Eu or Tm proceeds in the CHAp at low concentration of lanthanide ion. Excitation and emission of Tm3+ in CHAp:Tm3+ spectra.

Core-shell systems have attracted increasing interest among the research community in recent years due to their unique properties and structural features, and the development of new synthetic strategies is still a challenge. In this work, we have investigated lanthanide-doped Bi2SiO5 nanocrystal formation inside mesoporous silica nanoparticles (MSNs). The role of both synthesis temperature and concentration of the bismuth precursor impregnated into the MSNs is discussed, showing an unprecedented strategy for the simultaneous stabilization of a crystalline core and a glassy shell. Temperature dependent synchrotron radiation X-ray powder diffraction (SR-XRPD) and high resolution transmission electron microscopy (HR-TEM) analyses allow one to follow the crystalline core growth. A mechanism for the formation of a Bi2SiO5@g-SiO2 core-shell nanosystem is proposed. In addition, the easy tunability of the color output of the upconverting system is demonstrated by means of suitable doping lanthanide ions with potential applications in several fields.

Five new luminescent ionic liquids (LILs) derived from tryptophan (Trp), phenylalanine (Phe) and the dipeptide Gly-Gly functionalized with a dansyl chromophore moiety, were synthesized by an original protocol involving both green reagents/solvents such as non-toxic dimethyl carbonate (DMC: MeOCO2Me) and 2-propanol, and reaction conditions. In particular, DMC was used for: (i) the synthesis of methyltrioctyl methylcarbonate onium salts [Q1mmn][MeOCO2] (Q = N, m = 1, n = 8; Q = P, n = m = 4, 8) by P- and N-methylation of trioctylphosphine and trioctylamine, respectively, and (ii) acid-catalyzed esterifications of Trp and Phe to produce the corresponding methyl esters (Trp-OMe and Phe-OMe). Both reactions proceeded with >90% isolated yields and a mass index (esterifications) as low as 4.5. 2-propanol was used as the solvent for N-dansylation reactions where Trp-OMe and Gly-Glyethyl ester hydrochloride (Gly-Gly-OEt) were coupled to dansyl chloride (DNS-Cl) as a luminescent precursor. A final anion metathesis step between methylcarbonate onium salts and N-dansyl amino acid derivatives gave desired LILs of general formula [Q1mmn][DNS-X] (X = Trp, Phe, and Gly-Gly) in quantitative yields and with by-products minimization. Upon excitation (λex = 340 nm) in MeCN, all LILs exhibited green luminescence with emission quantum yields in the range of 33–41% and monoexponential emission lifetimes of 12.6 ± 0.5 ns. Moreover, each compound showed a remarkable hypsochromic shift in the peak emission wavelength when dissolved in solvents of decreasing polarity (from water to MeCN, toluene and CH2Cl2, respectively). A photostability test by a 350 nm continuous excitation on thin films of LILs proved that, after 10 min, the GlyGly derivative fully retained its PL intensity, while this (intensity) decreased from 10 to 25% for other LILs.

Natural hydraulic lime-based mortars are recommended for retrofitting operations in historical buildings, primarily because of their high chemical, physical and mechanical compatibility with the existing ones; moreover, their autogenous and engineering self-healing capacities make them a more suitable material for the aforementioned interventions. This work proposes a methodology to quantify the autogenous self-healing in terms of recovery of the compression strength and ultrasonic pulse velocity in samples made of natural hydraulic lime mortars; specimens were pre-cracked at different ages (14–84 days) and levels of damage (70% of the compression strength in pre-peak regime; 90% of the compression strength in post-peak regime), and then cured under water up to 28 days. The capacity of healing after two loading/healing cycles has been also investigated. An interdisciplinary approach has been pursued characterising the mechanical aspects of the healing and the chemical nature of the products via SEM/EDS analyses. The results provide useful indication about the dependence of the self-healing capacity on the aforementioned variables.

A route for europium (III) tris-pyrazolyl borate complex [Eu(Tp)3] formation inside the pores of mesoporous silica nanoparticles (MSNs) has been established to yield a highly luminescent nanostructured hybrid. Two different in situ chemical precipitation techniques have been explored for the nanoencapsulation of the Eu3+ complex [Eu(Tp)3] inside the pore channels of mesoporous silica nanoparticles, by varying the sequence order of precursor impregnation. In the first method, the Eu salt is introduced into the pores by wet impregnation and removal of the solvent, followed by wet impregnation of the ligand. In the second approach, the addition sequence is reversed. The importance of the addition sequence was demonstrated by the successful formation of the europium (III) tris-pyrazolyl borate complex in the pore network by following the first approach. The observed pyrazol-1-yl borate (Tp) to Eu3+ intramolecular energy transfer, i.e., the antenna effect, verified the formation of the complex. Photoluminescence spectroscopy, X-ray diffraction, N2 adsorption, FTIR spectroscopy, and TEM were used to characterize the material.

In this work, we demonstrate that the martensitic t -> m phase transformation of ZrO2 powder stabilized with Eu3+ and Eu3+/Y3+ ions, can be effectively monitored by photoluminescence (PL) spectroscopy. As the luminescent properties of Eu3+ from within a host lattice are strongly influenced by the coordination geometry of the ion, we used the emission spectrum to monitor structural changes of ZrO2. We synthesized Eu3+-doped and Eu3+/Y3+-codoped samples via the coprecipitation method, followed by calcination. We promoted the martensitic transformation by applying mechanical compression cycles with an increasing pressure, and deduced the consequential structural changes from the relative intensities of the 5D0 -> 7F2 hypersensitive transitions, centered, respectively, at 606 and 613 nm whether the Eu3+ is in the eightfold coordinated site of the tetragonal phase or in the sevenfold coordinated site of the monoclinic phase. We suggest that the unique emission profile for Eu3+ ions in different symmetry sites can be exploited as a simple analytical tool for remote testing of mechanical components that are already mounted and in use. The structural changes observed by PL spectroscopy were corroborated by Xray powder diffraction (XRPD), with the phase compositions and volume fractions being determined by Rietveld analysis.

In this work we synthesized rare earth-doped yttria nanocrystals via the Pechini method. We used Ce(3+), Yb(3+) and Er(3+) as dopant ions and studied their behavior when they are simultaneously embedded in the yttrium oxide lattice. The tri-doped system exhibits both downshifting and up-converting properties, due to the presence of, respectively, cerium-erbium and ytterbium-erbium couples. Efforts were put into determination of the effects of the presence of increasing content of cerium. We synthesized a series of samples having the general formula (Y0.88-xCexYb0.1Er0.02)2O3, where x = 0.01, 0.02, 0.10, 0.20, and 0.40. The structural properties of the samples were analyzed by the X-ray powder diffraction (XRPD) technique and the morphological features were disclosed using transmission electron microscope (TEM) observations. Photoluminescence properties were tested by carrying out photoluminescence (PL) emission, photoluminescence excitation (PLE) and lifetime (LT) measurements.

The application of nanosized inorganic UV filters in cosmetic field is limited by their high photocatalytic properties that could induce the degradation or dangerous transformation of the organic molecules in sunscreen formulations. To overcome this problem and simultaneously enlarge the window of filter’s absorption, we propose the growth of bismuth titanates BixTiyOz into mesoporous silica nanoparticles (MSN). We investigated the chemical-physical properties by means of XRPD, TEM, UV–vis spectroscopy, N2 physisorption, XPS, and SF-ICP-MS analysis, while the influence on the environment was evaluated through photocatalytic tests. The growing process of this new nanosystem is discussed underlining the key role of the Bi3+ ion that, acting as a low-melting point agent for the silica framework, led to a self-sealing mechanism. The excellent UV shielding properties combined with a radical suppression of the photocatalytic activity make the proposed nanosystem a perfect candidate for the development of the ne...

A synthesis of variably functionalized thiol-protected palladium nanoparticles (Pd-NPs) is presented. The nanoparticle syntheses are performed in acetone/water or tetrahydrofuranwater solutions, without making use of either phase-transfer agents or complex purification procedures of the as-synthesized nanoparticles. Small and mostly monodisperse thiol-protected Pd nanoparticles (Pd-NPs ~ 2 nm) have been prepared with 11-mercaptoundecanoic acid (MUA), 9-mercapto-1-nonanol (MN), 1-dodecanethiol (DT), or mixtures thereof, and a simple scale-up synthesis is also proposed. The role of PdII-thiolate species as metal precursors in the stage of nanoparticle synthesis and the influence of the reaction parameters on the final Pd-NPs size and size distribution are discussed. The formation of mixed-monolayer protected nanoparticles is achieved, with the final monolayer composition dictated by the thiols, initial molar ratio. Overall, the procedure presented here allows the preparation of functionalized nanoparticles with a high density of functional groups at the edge of the monolayer, with no need of place-exchange reactions. Specific postfunctionalization procedures conducted at the acid groups of the MUA-Pd monolayer are reported so as to widen the potential applicability of these amphiphilic nanoparticle precursors with respect to different applications in the field of material science. Finally, the successful use and the easy recycling/reuse of the Pd-NPs in a model Suzuki cross-coupling reaction are presented.

Manila clam Ruditapes philippinarum represents an important economic resource of Italian aquaculture. However, especially for Venice lagoon, health and environmental risks should be evaluated. A multidisciplinary approach was used. In particular, local production chain analysis and end-user requirements were investigated to assess manila clam safety and traceability in Northern Adriatic Sea. Moreover, the molecular and biochemical techniques demonstrated a good quality of the investigated farming sites, due to the absence of biotoxins. Molecular markers provided informations on the population genetics and specific genetic traits of Ruditapes philippinarum in Northern Adriatic Sea, which was investigated for the first time. The complexity of all these informations was simplified in a single useful tool: a database containing all the informations about the seafood product.

Polymer encapsulation of submicrometer-sized silica particles by synthesis of the polymer shell, poly(methyl methacrylate) under static conditions in a reaction medium free of surfactants and stabilizing agents is described. The Stöber method, a base-catalyzed hydrolysis and condensation of tetraethyl orthosilicate is used for the synthesis of the monodisperse colloidal dispersion of silica particles. The silica particles are subsequently modified in situ with the surface grafting of the silane coupling agent, 3-(trimethoxysilyl)propyl methacrylate. Encapsulation is achieved using tetraethyl orthosilicate as a reaction medium, in which a thermally initiated radical polymerization of methyl methacrylate is promoted in the presence of the modified particles by a seeding method which leads to a thin coating of poly(methyl methacrylate), and hence silica core-shell particles. The complete encapsulation of individual silica spheres by poly(methyl methacrylate) is visually evidenced by TEM microscopy which reveals the presence of a polymer shell coating up to 10 nm. Evidence for the presence of a poly(methyl methacrylate) shell is further corroborated by DSC/TGA, DRIFT-IR and NMR measurements.

The formation of silica particles by the ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) in the polyoxyethylene (5) nonylphenyl ether (NP-5)/cyclohexane/water microemulsion system was investigated by time-resolved small-angle X-ray scattering (SAXS). The SAXS data could be modeled as a combination of two species where one describes the silica-particle containing microemulsion droplets and the other the reverse droplets. The analysis allowed the determination of the evolution of the system of particles of silica and reverse droplets. A model of nucleation and growth of the silica particles is confirmed and the volume fraction versus time data for the silica particles is in agreement with first order kinetics with respect to TEOS concentration. Moreover to describe the long time evolution of the system, a correlation among the silica particles has been taken into account by introducing a structure factor with a local silica volume fraction eta = 0.1. This high local density is 2 orders of magnitude larger than the global silica fraction and can be explained in terms of depleting interaction.

In this paper, high concentration (up to 40% of rare earth with respect to the metal oxides) Eu 3+ -doped ZrO 2 , Y 2 O 3 and ZrO 2 –Y 2 O 3 systems were prepared both as bulk material and as nanoparticles embedded in SiO 2 . The latter nanocomposites were obtained as a result of a thermal treatment at 1000 °C of powder samples prepared by the sol–gel method. The combination of transmission electron microscopy (TEM), X-ray scattering (WAXS) and photoluminescence (PL) spectroscopy enabled us to obtain detailed information about morphology and composition of the rare earth-doped nanoparticles. In particular, for nanostructured samples, high luminescence has been observed in spite of a very high rare earth concentration in the active host.

Class I organic–inorganic hybrid materials consisting of zirconia and zirconia/silica matrices doped with europium(III)–1,10-phenanthroline complex were prepared by a catalyst-free sol–gel route. Two different experimental procedures were developed to incorporate the coordination compound into the matrix in order to study the possible influence of the preparation method on the optical properties of the rare earth ion. Besides, the effects of the annealing temperature and the composition of the matrix were investigated. Infrared spectra, Eu(III) luminescence lifetimes, relative emission intensities, excitation and emission spectra are reported. The products yielded under UV excitation strong red emission similar to the one of the neat coordination compound. The relative emission intensities and lifetimes show a maxima when determined as a function of annealing temperature, preparation procedure and matrix composition.

Ruthenium dioxide films were prepared by radio-frequency magnetron sputtering onto Si and Ti substrates. Films of different thicknesses (100-500 nm) were synthesized at substrate temperatures of 40, 350, and 450 °C. Their composition has been studied by Rutherford backscattering spectrometry, elastic recoil detection, and ion beam nuclear reaction analysis. Scanning electron microscopy and wide-angle X-ray scattering have been used for studying the surface texture of the samples and for their microstructural characterization, respectively. The electrochemical characterization by cyclic voltammetry has shown that, despite the high physical density of the films, compared with that obtained by the thermochemical methods, they exhibit large charge-storage capacities. For the materials synthesized at 350-450 °C, an explanation of these results has been sought in specific features of the RuO 2 rutile-type cell and columnar texture of the oxide film. The much higher capacity of the films synthesized at 40 °C would be rather due to a poor sintering of the oxide phase. Study of the chlorine evolution reaction in the samples prepared at 350 and 450 °C points to a Volmer-Tafel mechanism, with a chemical desorption rate-determining step, and significant radical intermediate coverage. Films deposited at 40 °C exhibited an unsatisfactory wear resistance under the anodic polarization required for the chlorine evolution reaction investigation.

This is a systematic investigation, using in situ synchrotron small-angle X-ray scattering, of the mechanisms of aggregation of sulfate zirconia sols under different preparation conditions. We have studied the effects of the variations of acid, water, and sulfate contents on the process of aggregate growth. These effects were investigated using open and sealed sample cells. It was observed that two clearly different mechanisms govern the aggregation at the beginning and at advanced stages of the process. In the early stages, small needle-shaped clusters are formed. They have a time independent cross-section and progressively grow by increasing their length. At advanced stages, the initially isolated needle-shaped clusters start to build up a 3D structure, their aggregation being governed by the classical mechanism of diffusion-limited cluster aggregation (DLCA). The experimental results also suggested an effect of sulfate concentration on the structure of the aggregates. Even though the structures of the ...

A set of sulfated zirconia xerogels were prepared using a one and two step hydrolysis method, in different vessels (open or closed) and varying the molar ratio R = [HNO3]/[Zr(On-Pr)4]. In order to verify the influence of these variables on the gel time and the final samples, physisorpion, quantitative analysis of the sulfate, DTA and DTG, X-ray diffraction at small (SAXS) and wide (WAXS) angles, and FTIR measurements, were employed. The main differences were found regarding samples with different values of R. For samples with R constant, the preparation method and the kind of container employed only slightly influenced the samples.

The encapsulation of [Eu(dbm)3phen] into functionalized mesoporous silica nanoparticles (MSN) has been carried out to study the effect of chemical environments on the photoluminescence properties of the rare-earth complex. Surface functionalization was achieved by the reaction of the silanol groups on the surface of mesoporous silica with different organosilylating agents such as (3-aminopropyl)-triethoxysilane (APTES), (3-mercaptopropyl)-trimethoxysilane (MPTMS), and ethoxytrimethylsilane (ETMS). A change in the luminescence properties of the Eu(dbm)3phen complex has been observed on its encapsulation into surface modified mesoporous silica nanoparticles. The modification of photophysical properties is attributed to the interaction of Eu(dbm)3phen with the different chemical environments in the functionalized mesoporous silica nanoparticles (MSN). The luminescence properties of the rare-earth complex in surface-modified MSN increase in the order MSN < MSN-ETMS < MSN-MPTMS < MSN-APTES. The Eu(dbm)3phen complex encapsulated in the functionalized mesoporous silica nanoparticles shows an enhanced luminescence and an increased lifetime compared to the pure rare-earth complex in the solid state and that in unmodified MSN. This implies that some interactions of the lanthanide complexes take place during their incorporation process into the organically modified mesoporous silica nanoparticles. The organically modified mesoporous silica nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR) and N2 adsorption desorption measurements. The luminescence properties of the encapsulated Eu(dbm)3phen were studied in detail. Moreover, the effect of functionalized MSNs on the structural behaviour of the Eu(dbm)3phen was investigated by solid state nuclear magnetic resonance (SSNMR) techniques using an analogous diamagnetic model complex, Y(dbm)3phen, encapsulated into functionalized MSNs. These studies indicate that the encapsulated rare-earth complex shows some interactions with the functional groups anchored on the surface of MSNs.

Pd/SiO2 supported catalysts were investigated using anomalous small-angle X-ray scattering (ASAXS), wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM) and extended X-ray absorption fine structure spectroscopy (EXAFS). Samples containing about 3 wt.% and 6 wt.% of metal were obtained by impregnation, calcined at 773 K and reduced at 623 K. Two populations of nanoparticles were found in both samples. In the 3 wt.% sample, one population consisted of very small nanoparticles (average 3 nm), and the other of larger ones (average 13 nm). A higher metal load seems to cause a broadening of the size distribution of the first population and a consequent increase in its average dimension (6 nm), rather than to influence the larger nanoparticles. Despite the relatively high metal content and temperatures, the population of small particles was predominant in both samples: 80% in the 3 wt.% sample and 57% in the 6 wt.% one. A large number of the smallest particles (

Aim of the paper is to apply a modified version of the Rietveld method to two Au–Pd/C catalysts prepared by successive impregnation and reduced in situ by a special holder in order to show that a suitable WAXS analysis, performed in routine lab and using an X-ray conventional generator, can be very detailed and rich of information especially when a bimetallic catalyst has to be considered.

Several optical glass samples were studied by small-angle X-ray Scattering (SAXS) in order to verify the presence of inhomogeneity in the range (1–100 nm). The results were compared with Rayleigh scattering measurements in order to verify a possible correlation between microstructure and scattering losses. For most glasses investigated, the presence of phase separation was excluded and the Rayleigh scattering intensities were attributed to refractive index fluctuations. For glasses ZKN7 and SK11 evidence of phase separation, with size of about 8 nm and less than 2 nm respectively, was obtained using SAXS. The particle size was insensitive to annealing treatments in the case of SK11 and showed a continuous growth with annealing time at 610°C in the case of ZKN7. For these two glasses the overall Rayleigh scattering intensity includes a contribution due to the presence of phase separated particles.

Correction for ‘Unexpected optical activity of cerium in Y2O3:Ce3+, Yb3+, Er3+ up and down-conversion system’ by Riccardo Marin et al., Dalton Trans., 2013, 42, 16837–16845.

Using x-ray Rietveld analysis the fcc (fluorite-type) structure of a Na-containing nanocrystalline zirconia powder (9.5 nm estimated of crystallite size) obtained by precipitation and subsequent calcination has been confirmed. The result shows that using conventional x-ray diffraction techniques the cubic crystallographic form of ZrO{sub 2} from the tetragonal one in nanosized powders. These conclusions are supported by the findings of independent Raman scattering experiments. {copyright} {ital 1997 Materials Research Society.}

The rank of a natural coal is empirically correlated to the shape of its small-angle X-ray intensity collected with the infinite-slit geometry.

Among the various metals able to catalyze hydrogenation reactions, palladium is probably the most interesting one, due to its special feature of interacting with hydrogen in two different ways, surface adsorption and bulk absorption, both of them having relevance to the catalytic phenomenon. Various Pd-based bimetallic systems have been investigated with very interesting results, for instance Pd-Ni, Pd-Fe, and Pd-Mo. As very few data are available on the Pd-Ru system, the latter was chosen as the subject of this investigation, in particular to look for the presence of metal-metal interaction. An active carbon was used as support in order to minimize metal-support interactions. Temperature-programmed reduction (TPR) and wide-angle X-ray scattering (WAXS) were chosen as experimental techniques. 19 refs., 5 figs.

Pd-Fe/SiO2 bimetallic catalysts with a constant amount of Pd and a different Fe/Pd ratio were prepared by sequential wet impregnation and the hydrogenation of 2,4-dinitrotoluene was carried out at 25°C in a batch reactor. The presence of Fe enhances the Pd catalytic activity. The formation of a dispersed Pd-Fe alloy was evidenced through X-ray powder diffraction and is consistent with the data observed by FTIR analysis, TPR, and chemisorption features. The increase of the Fe total content of the catalysts results in the increase of the dispersion of the metallic phase and in the presence of partially oxidized Fe species. FTIR analysis shows that nitrocompounds chemisorb mainly on the support rather than on the metal surface. It is suggested that the Pd-Fe alloy formation is responsible for the increase of the catalytic activity because of a cooperative effect of Fe in the hydrogen transfer step.

Two series of pumice-supported palladium catalysts (W and U) have been tested in the liquid-phase selective hydrogenation of 1,3-cyclooctadiene (1,3-COD) to cyclooctene (COE). The two series of catalysts, obtained via organometallic precursors, differ in the preparation procedure. In the W series the reduced metal derives only from Pd intermediates anchored to pumice; in the U series the metal originates also from unreacted Pd(allyl){sub 2} species in solution. The U catalysts present agglomerated metal particles. The hydrogenations, free of any diffusion problems, were performed at constant pressure of hydrogen (1 atm). Analysis of the data suggests that the rate-determining step is a surface reaction involving activated 1,3-COD. Selectivity is very high since cyclooctane (COA) is detected only when all 1,3-COD is consumed. The turnover frequencies (TOF{sub 1}) of the first semihydrogenation do not change with palladium dispersion, determined from the Porod diameter D{sub p} up to D{sub x} < 35%, but thereafter they slowly decrease. Experimental evidence, such as the absence of oxidation when exposed to air and the negative shift of binding energy of the Pd 3d level in XPS measurements, indicate a different behavior of the present catalysts in comparison with other supported palladium catalysts. These differences are attributedmore » to the presence of alkali metal ions (Na{sup +}, K{sup +}) on the pumice surface and are explained on the basis of the change in electron density and/or in the ensemble size of the supported palladium. Several interesting features and differences in activity and selectivity between the two series of catalysts can be accounted for by the presence of agglomerated palladium particles in the U series and are discussed in terms of the evolution of parameters with dispersion. 40 refs., 8 figs., 2 tabs.« less

Two series of pumice-supported palladium catalysts (W = washed, U = unwashed) were prepared by the reaction of [Pd(C{sub 3}H{sub 5}){sub 2}] with the support, followed by reduction using H{sub 2}. W catalysts were washed before reduction to eliminate unreacted [Pd(C{sub 3}H{sub 5}){sub 2}]. U catalysts did not undergo this treatment. Microstructural characterization of the catalysts was performed by small-angle X-ray scattering (SAXS), wide-angle X-ray line broadening, and transmission electron microscopy (TEM). Line-broadening analysis revealed the presence of lattice imperfections, such as growth stacking faults and microstrains in the fcc structure of palladium. The average particle size values determined by SAXS were confirmed by TEM analysis and were employed to calculate the percentage of palladium exposed (catalyst dispersion). W catalysts showed well-dispersed spheroidal particles, whereas the U series displayed agglomerates. 38 refs., 9 figs., 2 tabs.

Porod plots of the small-angle X-ray intensities scattered by porous silicas that have undergone different coating processes show deviations from the predicted constant asymptotic behaviour. The deviations are ascribed to the effect of the coating film. We propose a constant-electron-density model for these films. The theoretical scattering function calculated from the model permits an estimate of the film thickness, electron density and average number of coating molecules per unit area of the support.

By using the X-ray diffraction profile-fitting technique, the microstructures of Sm, Mn-modified PbTiO3 piezoelectric ceramic discs, including ferroelectric domain sizes, microstrains, and their variations with the poling strength have been quantitatively investigated. The results manifest that the modified PbTiO3 ceramics contain a high density of domain walls due to the presence of finely-divided coherent domain structures (tens of nanometres in dimension). The poling treament can evidently influence the domain-size distribution, with a more homogeneous microstructure being developed; however, it simultaneously causes high anisotropic microstrains within the structure which, together with the high density of domain walls, is expected to be responsible for the unusual high electromechanical coupling properties possessed by this material.

A zirconium oxide aerogel with a 70% by weight degree of crystallinity was prepared from zirconium n-propoxide with an excess of water being used in the hydrolysis process. The small-angle X-ray scattering (SAXS) technique revealed that this system had a mass-fractal character. The elementary building blocks had a size of about 50 ,~, and displayed a nonfractal (smooth) boundary surface. The massfractal dimension, Din, was found by SAXS to be equal to 1.95 (5). The novelty of this fractal system lies in the fact that the elementary blocks are made up of zirconium oxide particles with a high degree of crystallinity (preponderantly tetragonal in form). The crystalline nature of this system has allowed an interesting comparison to be made between the particle size determined by the crossover in the log I(h) versus log h SAXS plot and the crystallite size determined ,by the line-broadening X-ray diffraction analysis.

The small-angle neutron scattering (SANS) technique was used to verify the presence of inhomogeneities of the order of 10–100 nm which were suggested to influence the forming behaviour of container glass. Ternary soda lime glass and multicomponent container glass samples taken during periods of good and bad workability were investigated. The collected intensities show a marked SANS signal only in the case of heat treated ternary glasses, thus suggesting the presence of inhomogeneities between 1 nm and a few hundreds of nanometres in size. No inhomogeneities larger than 1 nm were found in the commercial glasses, regardless of their workability level. The presence of smaller inhomogeneities cannot be excluded.

Thermally prepared mixed-oxide IrO2 + ZrO2 films have been studied by Rutherford backscattering spectrometry (RBS), wide-angle X-ray scattering (WAXS) and cyclic voltammetry. Concentration depth profiling by RBS has shown that electrode films containing less than 50 mol.% of iridium dioxide have layered structures where noble metal oxide and zirconium oxide enrichments alternate. The outermost layer is enriched with iridium oxide. By WAXS analysis it was possible to prove the existence of an IrO2 and a ZrO2 phase. From cell parameters, very limited solubility could be ascertained, restricted at the two limits of the composition coordinate. In the range 0–20 mol.% of iridium dioxide, a tetragonal ZrO2 phase is formed. For samples richer in IrO2, the ZrO2 phase becomes amorphous. The microstructural features of the tetragonal IrO2-rich phase do not change significantly with the film composition. The effective surface area of the samples, as determined by cyclic voltammetry, exhibits a maximum in the composition range 50–80 mol.% IrO2. This result has been interpreted on the basis of WAXS and RBS data.

Pd-Fe/SiO2 bimetallic catalysts with a constant amount of Pd and a different Fe/Pd ratio were prepared by sequential wet impregnation and the hydrogenation of 2,4-dinitrotoluene was carried out at 25°C in a batch reactor. The presence of Fe enhances the Pd catalytic activity. The formation of a dispersed Pd-Fe alloy was evidenced through X-ray powder diffraction and is consistent with the data observed by FTIR analysis, TPR, and chemisorption features. The increase of the Fe total content of the catalysts results in the increase of the dispersion of the metallic phase and in the presence of partially oxidized Fe species. FTIR analysis shows that nitrocompounds chemisorb mainly on the support rather than on the metal surface. It is suggested that the Pd-Fe alloy formation is responsible for the increase of the catalytic activity because of a cooperative effect of Fe in the hydrogen transfer step.

A model of size distribution and structural disorder for palladium grown on pumice is developed. The model parameters are determined by fitting the simulated powder pattern to the experimental data. Three samples, characterized by 2.4, 1.14 and 0.86 wt.% Pd respectively were examined. The results point to nearly spheroidal crystallites, with sizes ranging from 40 to 20 A, affected by stacking faults in the sequence of the close-packed (111) layers to an extent independent of size and by intralayer second-kind distortions. A comparison with the results obtained following classical procedures is supplied. In the Appendix a new approach for the determination of growth stacking faults from peak shifts is presented.

The absolute small‐angle x‐ray intensities, scattered by two activated carbons, are analyzed assuming that coals scatter as polydisperse distributions of uncorrelated layered cubic particles. The specific interphase surface areas and the densities of the samples are obtained by the particle populations resulting from the intensity best‐fits. The values agree, within a factor two, with those obtained by different experimental techniques.

A best-fitting version of the X-ray diffraction method of Gehrke & Zachmann [Makromol. Chem. (1981). 182, 627–635] for crystallinity determination, which is a modification of the method developed by Ruland [Acta Cryst. (1961). 14, 1180–1185], is presented. The data, corrected and normalized to electron units (e.u.), are plotted as I(s)s 2 vs s and fitted by pseudo-Voigt functions for the crystalline peaks added to a background scattering IB (s)s 2, with IB (s) = (1 − Xc )I am(s) + Xc 〈f(s)2〉[1 − exp(−ks 2)], where I am is the experimental intensity of a completely amorphous sample (also corrected and normalized to e.u.), 〈f(s)2〉 is the mean square atomic scattering factor in the material, Xc is the degree of crystallinity and k is a factor which includes either thermal or lattice disorder, where s = 2(sin θ)/λ. The use of the scattering of the amorphous sample in this non-integral form of the Ruland equations overcomes the problem, encountered with other procedures, of locating the continuous (background) scattering with accuracy. The degree of crystallinity and the disorder factor are supplied directly by the optimization process. Furthermore, the line broadening analysis which allows the determination of crystallite size is automatically obtained as a by product. Samples of polyethylene terephthalate (PET) with different degrees of crystallinity are investigated. The results are compared with those obtained by other methods which do not use fitting techniques.

The small‐angle x‐ray intensities, scattered by four of the most typical natural coals, are analyzed assuming that coals behave as polydisperse distributions of cubic particles having a layered structure with an interlayer spacing partly dependent on particle sizes. The particle distributions are determined by a rather fast numerical algorithm, and in the considered momentum‐transfer range, they appear independent of the interlayer spacing. The model reproduces quite well only the intensities which are neither particularly structured nor fractal at very small momentum transfers. Micropore, mesopore, and macropore relative sizes are estimated starting from the obtained particle distributions.