The Peculiar H-Bonding Network of 4-Methylcatechol: A Coupled Diffraction and In Silico Study.

The crystal structure of 4-methylcatechol (4MEC) has, to date, never been solved, despite its very simple chemical formula C7O2H8 and the many possible applications envisaged for this molecule. In this work, this gap is filled and the structure of 4MEC is obtained by combining X-ray powder diffraction and first principle calculations to carefully locate hydrogen atoms. Two molecules are present in the asymmetric unit. Hirshfeld analysis confirmed the reliability of the solved structure, since the two molecules show rather different environments and H-bond interactions of different directionality and strength. The packing is characterised by a peculiar hydrogen bond network with hydroxyl nests formed by two adjacent octagonal frameworks. It is noteworthy that the observed short contacts suggest strong inter-molecular interactions, further confirmed by strong inter-crystalline aggregation observed by microscopic images, indicating the growth, in many crystallization attempts, of single aggregates taller than half a centimetre and, often, with spherical shapes. These peculiarities are induced by the presence of methyl group in 4MEC, since the parent compound catechol, despite its chemical similarity, shows a standard layered packing alternating hydrophobic and polar layers. Finally, the complexity and peculiarity of the packing and crystal growth features explain why a single crystal could not be obtained for a standard structural analysis.

New heterometallic Co/Zn, Ag/Co, and Ag/Zn imidazolates: structural characterization and catalytic activity in the oxidation of organic compounds.

Nanocrystalline powders of monometallic and bimetallic imidazolates of Co, Zn and Ag were produced by a reaction carried out in water. The powders were characterized by powder X-ray diffraction and the crystal structures of the new compounds Ag2ZnIm4 and Ag2CoIm4 (Im = imidazolate) were solved. Heterometallic Co/Zn imidazolates showed the known Zn-zni crystal structure while Ag/Zn and Ag/Co systems were isostructural to the copper analogs. The powders were further characterized by EDX, UV-Vis and FTIR ATR spectroscopy in the solid state. The catalytic experiments indicated that out of the studied heterometallic compounds only Ag2Co(Im)4 exhibits some catalytic activity in the oxidation reaction of 1-phenylethanol with tert-butylhydroperoxide at elevated temperatures.

Crystallization from solution versus mechanochemistry to obtain double-drug multicomponent crystals of ethacridine with salicylic/acetylsalicylic acids.

Salicylic and acetylsalicylic acids and ethacridine have complementary bioactive properties. They can be combined to obtain double-drug multicomponent crystals. Their reactivity in different environments was explored to obtain the possible compounds, stable at different hydration degrees. Solution, liquid-assisted grinding, and dry preparation approaches were applied to the couples of reactants in different stoichiometric ratios. Four compounds were obtained, and three out of them were stable and reproducible enough to determine their structures using SCXRD or PXRD methods. When coupled to ethacridine, salicylic acid gave two stable structures (1 and 3, both showing 1:1 ratio but different hydration degree) and a metastable one (5), while acetylsalicylic acid only one structure from solution (2 in 1:1 ratio), while LAG caused hydrolysis and formation of the same compound obtained by LAG of ethacridine with salicylic acid. While solution precipitation gave dihydrated (1) or monohydrated (2) structures with low yields, LAG of salicylic acid and ethacridine allowed obtaining an anhydrous salt complex (3) with a yield close to 1. The structures obtained by solution crystallizations maximize π(acridine)-π(acridine) contacts with a less compact packing, while the LAG structure is more compact with a packing driven by hydrogen bonds. For all compounds, NMR, ATR-FTIR, and Hirshfeld surface analysis and energy framework calculations were performed.

Multivariate versus traditional quantitative phase analysis of X-ray powder diffraction and fluorescence data of mixtures showing preferred orientation and microabsorption.

In materials and earth science, but also in chemistry, pharmaceutics and engineering, the quantification of elements and crystal phases in solid samples is often essential for a full characterization of materials. The most frequently used techniques for this purpose are X-ray fluorescence (XRF) for elemental analysis and X-ray powder diffraction (XRPD) for phase analysis. In both methods, relations between signal and quantity do exist but they are expressed in terms of complex equations including many parameters related to both sample and instruments, and the dependence on the active element or phase amounts to be determined is convoluted among those parameters. Often real-life samples hold relations not suitable for a direct quantification and, therefore, estimations based only on the values of the relative intensities are affected by large errors. Preferred orientation (PO) and microabsorption (MA) in XRPD cannot usually be avoided, and traditional corrections in Rietveld refinement, such as the Brindley MA correction, are not able, in general, to restore the correct phase quantification. In this work, a multivariate approach, where principal component analysis is exploited alone or combined with regression methods, is used on XRPD profiles collected on ad hoc designed mixtures to face and overcome the typical problems of traditional approaches. Moreover, the partial or no known crystal structure (PONKCS) method was tested on XRPD data, as an example of a hybrid approach between Rietveld and multivariate approaches, to correct for the MA effect. Particular attention is given to the comparison and selection of both method and pre-process, the two key steps for good performance when applying multivariate methods to obtain reliable quantitative estimations from XRPD data, especially when MA and PO are present. A similar approach was tested on XRF data to deal with matrix effects and compared with the more classical fundamental-parameter approach. Finally, useful indications to overcome the difficulties of the general user in managing the parameters for a successful application of multivariate approaches for XRPD and XRF data analysis are given.

Low-Cost Biobased Coatings for AM60 Magnesium Alloys for Food Contact and Harsh Environment Applications.

Low-cost, environmentally friendly and easily applicable coating for Mg alloys, able to resist in real world conditions, are studied. Coatings already used for other metals (aluminum, steel) and never tested on Mg alloy for its different surface and reactivity were deposited on AM60 magnesium alloys to facilitate their technological applications, also in presence of chemically aggressive conditions. A biobased PA11 powder coating was compared to synthetic silicon-based and polyester coatings, producing lab scale samples, probed by drop deposition tests and dipping in increasingly aggressive, salty, basic and acid solutions, at RT and at higher temperatures. Coatings were analyzed by SEM/EDX to assess their morphology and compositions, by optical and IR-ATR microscopy analyses, before and after the drop tests. Migration analyses from the samples were performed by immersion tests using food simulants followed by ICP-OES analysis of the recovered simulant to explore applications also in the food contact field. A 30 µm thick white lacquer and a 120 µm PA11 coating resulted the best solutions. The thinner siliconic and lacquer coatings, appearing brittle and thin in the SEM analysis, failed some drop and/or dipping test, with damages especially at the edges. The larger thickness is thus the unique solution for edgy or pointy samples. Finally, coffee cups in AM60 alloy were produced, as real word prototypes, with the best performing coatings and tested for both migration by dipping, simulating also real world aging (2 h in acetic acid at 70° and 24 h in hot coffee at 60 °C): PA11 resulted stable in all the tests and no migration of toxic metals was observed, resulting a promising candidate for many real world application in chemically aggressive environments and also food and beverage related applications.

XRF and XRPD data sets in ternary mixtures with high level micro-absorption and/or preferred orientations problems for phase quantification analysis.

Micro-absorption (MA) and/or preferred orientations (PO) are two among the major problems affecting quantitative phase analysis (QPA) by X-ray Powder Diffraction Data (XRPD) in industrial samples such as minerals and ores, additives, cements, friction materials, coal combustion by-products. Typically XRPD data are coupled to elemental analysis by X-ray Fluorescence (XRF) to facilitate phase recognition and quantification when elements heavier than sodium are present. Graphite and urea are typical examples of large production industrial commodities showing such analytical problems. The present article provides a recipe to produce sets of data of increasing difficulty to test the performances of different approaches and/or software's for QPA by XRPD in graphite, zinc acetate and urea containing samples. Graphite, due to its platelet morphology, can exhibit orientation and was chosen because it is possible to control its PO degree by sieving. Simplex-centroid design augmented was used for the design of the experiments to select the mixtures with the more possible homogeneous exploration of the ternary experimental domains, from pure phase to equal-weighted mixtures. The different data sets collected on the four experimental domains by XRF and XRPD are provided and stored as a repository on Mendeley Data. Using the same approach, additional data sets sets with different composition and/or experimental setup can be added by us or any other contributor with the same DoE approach to create a wide open access data set of standardized X-ray powder diffraction and X-ray fluorescence data.

Solvothermal synthesis and structural characterization of three polyoxotitanium-organic acid clusters.

Three new titanium oxo-clusters Ti4O2(OiPr)10(OOCPhMe)2 (I), Ti6O4(OEt)8(OOCPhMe)8 (II) and Ti6O6(OEt)6(OOCCHPh2)6 (III) were obtained by easy one-step solvothermal reactions of titanium(iv) isopropoxide, alcohols and carboxylic acids. The three compounds were characterized by single-crystal and powder X-ray diffraction, TGA/DSC, optical and electron microscopy, and FTIR and NMR spectroscopy. X-ray powder diffraction and spectroscopy confirmed the purity of the compounds. Structural analysis indicates that in all compounds the titanium(iv) ions are six-coordinated (distorted octahedra). (I) is a tetranuclear complex containing a Ti4(µ4-O)(µ2-O) core, which is linked by two (µ2-OOCPhMe), four (µ2-OiPr) and six OiPr ligands. (II) and (III) are hexanuclear complexes with different cores, respectively Ti6(µ3-O)2(µ2-O)2 and Ti6(µ3-O)6. The coordination sphere of the Ti atoms is filled by eight (µ2-OOCPhMe), two (µ2-OEt) and six OEt in (II) and six (µ2-OOCHPh2) and six OEt in (III). Different steric hindrance of substituents attached to the carboxyl group or different concentrations lead to three main different cluster geometries with two ligands. The tetranuclear and the hexanuclear clusters were obtained with the OOCPhMe ligand, while the hexagonal prism cluster was obtained with the OOCCHPh2 ligand. Hirshfeld surface calculations indicated that the packing is driven by C-O⋯H-C weak hydrogen bonds. The clusters can be used as molecular models of organic molecules bonded to titania surface, used in organic photovoltaic (dye sensitized solar cells) or other optoelectronic applications.

Light Weight, Easy Formable and Non-ToxicPolymer-Based Composites for Hard X-rayShielding: A Theoretical and Experimental Study.

Composite lightweight materials for X-ray shielding applications were studied anddeveloped with the goal of replacing traditional screens made of lead and steel, with innovativematerials with similar shielding properties, but lighter, more easily formed and workable, with lowerimpact on the environment and reduced toxicity for human health. New epoxy-based compositesadditivated with barium sulfate and bismuth oxide were designed through simulations performedwith software based on Geant4. Then, they were prepared and characterized using differenttechniques starting from digital radiography in order to test the radiopacity of the composites,in comparison with traditional materials. The lower environmental impact and toxicity of theseinnovative screens were quantified by Life Cycle Assessment (LCA) calculation based on the ecoinventdatabase, within the openLCA framework. Optimized mixtures are (i) 20% epoxy/60% bismuthoxide/20% barite, which guarantees the best performance in X-ray shielding, largely overcomingsteel, but higher in costs and a weight reduction of circa 60%; (ii) 20% epoxy/40% bismuth oxide/40%barite which has slightly lower performances in shielding, but it is lighter and cheaper than thefirst one and (iii) the 20% epoxy/20% bismuth oxide/60% barite which is the cheapest material, stillmaintaining the X-ray shielding of steel. Depending on the cost/efficiency request of the specificapplication (industrial ra.

The Use of POSS-Based Nanoadditives for Cable-Grade PVC: Effects on its Thermal Stability.

Plasticized-Poly(vinyl chloride) (P-PVC) for cables and insulation requires performances related to outdoor, indoor and submarine contexts and reduction of noxious release of HCl-containing fumes in case of thermal degradation or fire. Introducing suitable nanomaterials in polymer-based nanocomposites can be an answer to this clue. In this work, an industry-compliant cable-grade P-PVC formulation was added with nanostructured materials belonging to the family of Polyhedral Oligomeric Silsesquioxane (POSS). The effects of the nanomaterials, alone and in synergy with HCl scavenging agents as zeolites and hydrotalcites, on the thermal stability and HCl evolution of P-PVC were deeply investigated by thermogravimetric analysis and reference ASTM methods. Moreover, hardness and mechanical properties were studied in order to highlight the effects of these additives in the perspective of final industrial uses. The data demonstrated relevant improvements in the thermal stability of the samples added with nanomaterials, already with concentrations of POSS down to 0.31 phr and interesting additive effects of POSS with zeolites and hydrotalcites for HCl release reduction without losing mechanical performances.

New Hints on the Maya Blue Formation Process by PCA-Assisted In Situ XRPD/PDF and Optical Spectroscopy.

The exact recipe to prepare the ancient Maya Blue (MB), an incredibly resistant and brilliant pigment prepared from indigo (dye) and Palygorskite (clay), is lost to the ages. To unravel the key features of the MB formation process, several inorganic-dye couples were heated to 200 °C and cooled to RT, to investigate their reactivity and the diffusion and degree of sequestration of the dye into the inorganic host. In situ XRPD/PDF and fiber optic reflectance spectroscopy (FORS) data, along with TGA, provided a comprehensive overview on MB formation mechanism. XRPD/PDF gave information on long/short range behaviors of water desorption/adsorption and indigo sequestration, while TGA and in situ FORS gave information on mass and optical changes within temperature. Ex situ dye removal was used to understand the sample stability after the thermal treatment. A statistical approach based on principal component analysis was exploited to efficiently and jointly analyze the ≈3000 collected patterns. MB formation starts below 110 °C with disordered distribution of indigo within the channels, reaching maximum reaction speed and higher ordering at 150 °C. Above 175 °C, color changes and a stronger sequestration of indigo into framework channels are observed, whereas the affinity for water is dramatically reduced. The origin of different colors, hues, and stability in historical MB samples can then be explained in terms of different thermal histories of the starting mechanical indigo/palygorskite mixtures.

CO2 adsorption in Y zeolite: a structural and dynamic view by a novel principal-component-analysis-assisted in situ single-crystal X-ray diffraction experiment.

The increasing efficiency of detectors and brightness of X-rays in both laboratory and large-scale facilities allow the collection of full single-crystal X-ray data sets within minutes. The analysis of these `crystallographic big data' requires new tools and approaches. To answer these needs, the use of principal component analysis (PCA) is proposed to improve the efficiency and speed of the analysis. Potentialities and limitations of PCA were investigated using single-crystal X-ray diffraction (XRD) data collected in situ on Y zeolite, in which CO2, acting as an active species, is thermally adsorbed while cooling from 300 to 200 K. For the first time, thanks to the high sensitivity of single-crystal XRD, it was possible to determine the sites where CO2 is adsorbed, the increase in their occupancy while the temperature is decreased, and the correlated motion of active species, i.e. CO2, H2O and Na+. PCA allowed identification and elimination of problematic data sets, and better understanding of the trends of the occupancies of CO2, Na+ and water. The quality of the data allowed for the first time calculation of the enthalpy (ΔH) and entropy (ΔS) of the CO2 adsorption by applying the van 't Hoff equation to in situ single-crystal data. The calculation of thermodynamic values was carried out by both traditional and PCA-based approaches, producing comparable results. The obtained ΔH value is significant and involves systems (CO2 and Y zeolite) with no toxicity, superb stability and chemical inertness. Such features, coupled with the absence of carbonate formation and framework inertness upon adsorption, were demonstrated for the bulk crystal by the single-crystal experiment, and suggest that the phenomenon can be easily reversed for a large number of cycles, with CO2 released on demand. The main advantages of PCA-assisted analysis reside in its speed and in the possibility of it being applied directly to raw data, possibly as an `online' data-quality test during data collection, without any a priori knowledge of the crystal structure.

Principal component analysis for automatic extraction of solid-state kinetics from combined in situ experiments.

Solid-state reactivity is often studied by in situ experiments with a multi-technique approach, where complementarity of different probes is exploited. In situ data are usually analysed using a complex protocol: first the reaction model most suited to describe the specific solid-state reaction is chosen, second the reaction coordinate is obtained from the data, the order of reaction is then calculated by applying a specific kinetic equation, and finally kinetic parameters are obtained with an Arrhenius plot. The approach is both time consuming and subject to errors due to the arbitrariness of extraction of the reaction coordinate, typically from individual peak intensity variations during the reaction. In addition, application of the different kinetic equations to obtain the best fitting one is tedious and no general method to select the best model with an unbiased approach is available. Here we propose a new procedure based on principal component analysis to get kinetic information from in situ data, which simplifies and speeds up the process of kinetic parameter calculation from a three- to a two- or even a one-step form, reaching a high degree of automation and the ability to manage the huge amount of data produced by in situ multi-technique experiments. The new approach treats data as a whole, without biases introduced by manual methods of obtaining the reaction coordinate by peak intensity evaluation from individual patterns typical of the traditional approach. The procedure is described in its theoretical framework and applied to the formation of a molecular complex, monitored by in situ X-ray powder diffraction and Raman measurements.

On the structure of superbasic (MgO)n sites solvated in a faujasite zeolite.

We report the synthesis and characterisation of a HY/MgO zeolite/oxide nanocomposite material with high crystallinity and highly dispersed, highly basic MgO sites. Preparation was optimized in order to preserve sample crystallinity, to avoid the formation of mesoporosity and to minimize the formation of separate Mg-containing phases. These features were checked by means of electron microscopy, X-ray powder diffraction, porosimetry and IR spectroscopy. A highly dispersed material was obtained, comprising nanoclusters of magnesium oxide and hydroxide hosted by the microporous zeolite framework. The location and structure of the Mg-containing clusters have been studied by means of a combination of Rietveld refinement of XRPD data and high quality quantum mechanical simulations. The refinement has shown the presence of magnesium and oxygen atoms in the double six-membered ring cages, consistent with the presence of mononuclear Mg moieties. However, the composition and IR spectroscopy demonstrate that other Mg species must exist, likely located in the zeolite pores. In order to propose candidate structures for these species, several hypothetic periodic models of the material were built by placing (MgO)n clusters in different locations of the zeolite structure, taking into account the material composition and other constraints imposed by the experimental observations. Periodic structures with P1 symmetry were optimized at the B3LYP-D*/DZVP level with the CRYSTAL code and classified according to their stability. Two families of possible sites were identified: highly solvated (MgO)n units in narrow cavities and less coordinated clusters in the supercages. The stability of these clusters appears to be regulated by the ability of Mg2+ and O2- ions to interact with the pore walls and by the formation of Mg-OH species as result of the reaction of Mg-O couples with remaining acidic protons. The reactivity of four representative models with CO2 has been simulated at the B3LYP-D*/TZVP level. CO2 forms very stable linear end-on adducts with low coordinated Mg ions in most cases. Isolated sites give rise to bridge bidentate complexes in agreement with previous spectroscopic observations. The formation of hydrogen-carbonates is observed only on specific sites, through a process having a low adsorption energy because of the high deformation of the adsorption site.

Improved multivariate analysis for fast and selective monitoring of structural dynamics by in situ X-ray powder diffraction.

The development of two solid-state reactions, Xe absorption into MFI and molecular complex formation, where samples are affected by changes of crystal lattice due to temperature or pressure variation was structurally monitored through in situ or in operando X-ray powder diffraction experiments. Consequent variations of the peak positions prevent collective analysis of measured patterns, aiming at investigating structural changes occurring within the crystal cell. Moreover, an intrinsic and variable error in peak position is unavoidable when using the Bragg-Brentano geometry and, in some cases (sticky, bulky, aggregate samples) the sample mounting can increase the error within a dataset. Here we present a general multivariate analysis method to process in a fast and automatic way in situ XRPD data collected on charge transfer complexes and porous materials, with the capacity of disentangling peak shifts from intensity and shape variations in diffraction signals, thus allowing an efficient separation of the contribution of crystal lattice changes from structural changes. The peak shift correction allowed an improved PCA analysis that turned out to be more sensible than the traditional single pattern Rietveld analysis. The developed algorithms allowed, with respect to the traditional approach, the location of two new Xe positions into MFI with a better interpretation of the experimental data, while a much faster and more efficient recovery of the reaction coordinate was achieved in the molecular complex formation reaction.

High-Throughput Preparation of New Photoactive Nanocomposites.

New low-cost photoactive hybrid materials based on organic luminescent molecules inserted into hydrotalcite (layered double hydroxides; LDH) were produced, which exploit the high-throughput liquid-assisted grinding (LAG) method. These materials are conceived for applications in dye-sensitized solar cells (DSSCs) as a co-absorbers and in silicon photovoltaic (PV) panels to improve their efficiency as they are able to emit where PV modules show the maximum efficiency. A molecule that shows a large Stokes' shift was designed, synthesized, and intercalated into LDH. Two dyes already used in DSSCs were also intercalated to produce two new nanocomposites. LDH intercalation allows the stability of organic dyes to be improved and their direct use in polymer melt blending. The prepared nanocomposites absorb sunlight from UV to visible and emit from blue to near-IR and thus can be exploited for light-energy management. Finally one nanocomposite was dispersed by melt blending into a poly(methyl methacrylate)-block-poly(n-butyl acrylate) copolymer to obtain a photoactive film.

Structural Characterisation of Complex Layered Double Hydroxides and TGA-GC-MS Study on Thermal Response and Carbonate Contamination in Nitrate- and Organic-Exchanged Hydrotalcites.

Layered double hydroxides (LDHs) are versatile materials used for intercalating bioactive molecules in the fields of pharmaceuticals, nutraceuticals and cosmetics, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability and improving their pharmacokinetic properties and formulation stability. Moreover, LDHs are used in various technological applications to improve stability and processability. The crystal chemistry of hydrotalcite-like compounds was investigated by X-ray powder diffraction (XRPD), automated electron diffraction tomography (ADT) and thermogravimetric analysis (TGA)-GC-MS to shed light on the mechanisms involved in ion exchange and absorption of contaminants, mainly carbonate anions. For the first time, ADT allowed a structural model of LDH_NO3 to be obtained from experiment, shedding light on the conformation of nitrate inside LDH and on the loss of crystallinity due to the layer morphology. The ADT analysis of a hybrid LDH sample (LDH_EUS) clearly revealed an increase in defectivity in this material. XRPD demonstrated that the presence of carbonate can influence the intercalation of organic molecules into LDH, since CO3 -contaminated samples tend to adopt d spacings that are approximate multiples of the d spacing of LDH_CO3 . TGA-GC-MS allowed intercalated and surface- adsorbed organic molecules to be distinguished and quantified, the presence and amount of carbonate to be confirmed, especially at low concentrations (<2 wt %), and the different types and strengths of adsorption to be classified with respect to the temperature of elimination.

Chemical selectivity in structure determination by the time dependent analysis of in situ XRPD data: a clear view of Xe thermal behavior inside a MFI zeolite.

X-ray diffraction methods in general provide a representation of the average structure, thus allowing only limited chemical selectivity. As recently shown [D. Chernyshov, et al., Acta Crystallogr., Sect. A: Found. Crystallogr., 2011, 67, 327], some structural information on a subset of atoms can be obtained using the modulation enhanced diffraction (MED), thus providing a new tool that is able to enhance selectivity in diffraction. MED uses a periodic stimulus supplied in situ on a crystal while diffraction data are collected continuously during one or more stimulation periods. Such large data sets can then be treated by different methods. Herein, we present and compare phase sensitive detection (PSD) and principal component analysis (PCA) for in situ X-ray powder diffraction (XRPD) data treatment. The application of PCA to MED data is described for the first time in the present paper. Simulated and experimental MED powder data were produced using an MFI zeolite as a static spectator in which Xe, acting as the active species, is adsorbed and desorbed in a periodic manner. By demodulating the simulated and experimental data, MED allowed the powder diffraction pattern of the responding scattering density to be obtained and enabled the selective extraction of crystallographic information on Xe by solving the crystal structure of the active species independently of the static zeolite framework. The "real world" experiments indicated that the PSD-MED approach has some limitations related to the degree of fulfilment of some theoretical assumptions. When applied to in situ XRPD data, PCA, despite being based on blind statistical analysis, gave results similar to those obtained by PSD (based on Fourier analysis) for simulated data. Moreover, PCA is complementary to PSD thanks to its capability of gathering information on the Xe substructure even in the presence of a non-periodic stimulus, i.e. using the most simple stimulus shape as a single temperature ramp. In particular, PC1 results are able to perfectly reproduce the corresponding 1Ω signal from a traditional PSD analysis. Moreover PCA can be applied directly to raw non periodic XRPD data, opening the possibility of using it during an "in situ" experiment. PCA can thus be envisaged as a very useful, fast and efficient tool to improve data collection and maximize data quality. To date, however, PSD remains superior for substructure solution from the analysis of 2Ω demodulated data.

POSS as building-blocks for the preparation of polysilsesquioxanes through an innovative synthetic approach.

A novel solvent-free solid-state synthesis was used to prepare a non-crystalline polysilsesquioxane sample, with a peculiar viscous form. The material was synthesized through direct self-condensation of a partially condensed polyhedral oligomeric silsesquioxane (POSS) and its physico-chemical properties, in terms of composition/structure, thermal stability and hydrophobicity, were investigated.

Rationalization of dye uptake on titania slides for dye-sensitized solar cells by a combined chemometric and structural approach.

A model photosensitizer (D5) for application in dye-sensitized solar cells has been studied by a combination of XRD, theoretical calculations, and spectroscopic/chemometric methods. The conformational stability and flexibility of D5 and molecular interactions between adjacent molecules were characterized to obtain the driving forces that govern D5 uptake and grafting and to infer the most likely arrangement of the molecules on the surface of TiO2. A spectroscopic/chemometric approach was then used to yield information about the correlations between three variables that govern the uptake itself: D5 concentration, dispersant (chenodeoxycholic acid; CDCA) concentration, and contact time. The obtained regression model shows that large uptakes can be obtained at high D5 concentrations in the presence of CDCA with a long contact time, or in absence of CDCA if the contact time is short, which suggests how dye uptake and photovoltaic device preparation can be optimized.

Structural characterization and thermal and chemical stability of bioactive molecule-hydrotalcite (LDH) nanocomposites.

Layered double hydroxides (LDH) are versatile materials used for intercalating bioactive molecules, both in pharmaceutical and cosmetic fields, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability, and/or obtaining modified release properties. The properties of the intercalation compounds of Mg/Al_LDH and Zn/Al_LDH with different drugs and sunscreens, namely diclofenac, ketoprofen, gliclazide, retinoic acid, furosemide, para-aminobenzoic acid and 2-phenylbenzimidazolsulfonic (Eusolex) acid, have been studied by crystallographic, spectroscopic and thermogravimetric techniques and by solid state NMR, to shed light on their structure, their molecular interactions and their stability from the thermal and chemical viewpoint. The structural features were described with particular attention to the interaction between the organic and inorganic components and to the stability of the intercalation products. For the first time two synchrotron radiation powder diffraction patterns of organic-containing LDH were solved and refined by Rietveld methods to obtain an experimental crystal structure.