Luciano Montanari

Proton exchange and isomerisation reactions of photochromic and reverse photochromic spiro-pyrans and their merocyanine forms

Photochromic 1′,3′,3′-trimethyl-6,8-dinitro-spiro- [2H-1-benzopyran-2,2-indoline], (6,8-dinitro BIPS) has been studied in different solvents using 1H-NMR techniques, UV/visible spectroscopy, X-ray diffraction and electrospray ionisation mass spectroscopy (ESI-MS). Molar decadic absorption coefficients for 6,8-dinitro BIPS were found to range between 35000–45000 d mol-1 cm-1. 1H–1H NOESY and 1H-NMR experiments have established that in solution the merocyanine form of 6,8-dinitro BIPS is in rapid exchange between the trans-trans-cis (TTC) and trans-trans-trans (TTT) isomers. The 3B proton on the central bridging double bond of spiro-pyran merocyanines is labile in organic solvents. The closed form of 6,8-dinitro BIPS enantiomerises about the spiro C(2) carbon at a rate of 18 s-1 at 300 K. The activation energy for this process was estimated to be 46 kJ mol-1 using dynamic NMR.

Model oxide supported MoS2 HDS catalysts: structure and surface properties

Supported hydrodesulfidation (HDS) MoS2/SiO2, MoS2/γ-Al2O3 and MoS2/MgO catalysts having a model character have been synthesized by using CS2 as the sulfiding agent and deeply investigated by means of several techniques. XRPD, HRTEM, Raman and UV-Vis methods have been applied to obtain information on the morphology and the structure of the catalysts as well as on the vibrational and spectroscopic properties. It is shown that, when compared with HRTEM results, XRPD, Raman and UV-Vis data give realistic information on the stacking degree, on the particle size distribution and on the heterogeneity of supported MoS2 particles on the various supports. (S K-, Mo L3- and K- edges) EXAFS and XANES spectroscopies have been also used to set up the best sulfidation procedure. UV-vis analysis under controlled atmosphere has been performed to understand the presence of sulfur vacancies and the valence state of Mo ions associated with them. To explore the structure of coordinatively unsaturated Mo sites after reducing or sulfiding treatments (with CS2 or, occasionally, with H2S), in situFTIR of adsorbed CO has been performed. It is demonstrated that CO is a sensitive probe for coordinatively unsaturated sites and that the formation of sulfur vacancies on the MoS2 surface upon reduction in pure H2 at 673 K is accompanied by an increase of the coordinative unsaturation and a decrease of the valence state of a fraction of surface Mo cations, mainly located on corner and edge sites. Furthermore, it is demonstrated that this process can be reversed upon interaction with the sulfiding agent and that this reversible behavior is really mimicking some of the elementary acts occurring in the HDS process. The complexity of the IR results suggests that the adopted reduction procedure in pure H2 at 673 K induces the formation of several types of sulfur vacancies, presumably located in different crystallographic positions. It is also concluded that the sulfiding steps are strongly involving the surface of the support and that reductive treatments at high T in H2 are causing sulfur depletion not only from supported MoS2 particles, but also from the supporting phase. The involvement of the support is particularly relevant for Al2O3 and MgO.

Synthesis and characterization of a potassium borosilicate with ANA framework type structure

Abstract An ANA-type microporous crystalline borosilicate has been synthesized hydrothermally from gels containing potassium ions. Refinement by Rietveld analysis of X-ray diffraction pattern confirmed B-ANA to be isostructural with leucite (KAlSi 2 O 6 ). B-ANA displays an unusually high thermal stability, as demonstrated by the lack of any signals due to trigonal boron species in the 11 B MAS NMR spectra of the calcined material.

Can crude oils be distinguished by different component distribution obtained by laser desorption ionization mass spectrometry and evaluated by chemometrics

Fourteen different crude oil samples were analyzed as collected by mass spectrometry. For two of them the results obtained by means of different techniques, i.e. electrospray ionization, atmospheric pressure chemical ionization, laser desorption/ionization, were compared. The latter technique leads to the best results: even if unable to give specific information on heteroatom-containing components, it allows a general view to be obtained of the panorama of the oil composition in terms of molecular weight distribution. The statistical evaluation of the mass spectrometry data by multivariate techniques, such as cluster analysis (Average Linkage) and correspondence analysis, allows evidence for the differences and similarities among the crude oils under study.

Crystalline Microporous Organosilicates with Reversed Functionalities of Organic and Inorganic Components for Room-Temperature Gas Sensing

A deepened investigation on an innovative organic-inorganic hybrid material, referred to as ECS-14 (where ECS = Eni carbon silicates), revealed the possibility to use them as gas sensors. Indeed, among ECS phases, the crystalline state and the hexagonal microplateletlike morphology characteristic of ECS-14 seemed favorable properties to obtain continuous and uniform films. ECS-14 phase was used as functional material in screen-printable compositions and was thus deposited by drop coating for morphological, structural, thermal, and electrical characterizations. Possible operation at room temperature was investigated as technological progress, offering intrinsic safety in sensors working in harsh or industrial environments and avoiding high power consumption of most common sensors based on metal oxide semiconductors. Electrical characterization of the sensors based on ECS-14 versus concentrations of gaseous analytes gave significant results at room temperature in the presence of humidity, thereby demonstrating fundamental properties for a good quality sensor (speed, reversibility, and selectivity) that make them competitive with respect to systems currently in use. Remarkably, we observed functionality reversal of the organic and inorganic components; that is, in contrast to other hybrids, for ECS-14 the functional site has been ascribed to the inorganic phase while the organic component provided structural stability to the material. The sensing mechanism for humidity was also investigated.

Eni Carbon Silicates: Innovative Hybrid Materials for Room-Temperature Gas Sensing

The purpose of this work was to satisfy both materials and technological sciences, on the one hand implementing innovative hybrid materials referred to as ECS (Eni Carbon Silicate) in gas sensors manufacturing, and on the other hand verifying their possible operation at room temperature as a technological progress. The ECS-14 and ECS-13 phases were employed as functional materials for films deposited by drop coating onto alumina substrates. Room-temperature gas tests were performed to study their potential sensing properties. In humidity conditions, the ECS-14 based sensor showed outstanding performance and a complete calibration vs. moisture concentration was obtained.

Characterisation of the Surfactant Shell Stabilising Calcium Carbonate Dispersions in Overbased Detergent Additives: Molecular Modelling and Spin-Probe-ESR Studies

The surfactant shell stabilising the calcium cabonate core in overbased detergent additives of lubricant base oils was characterised by computational and experimental methods, comprising classical force-field based molecular simulations and spin-probe Electron Spin Resonance spectroscopy. An atomistic model is proposed for the detergents micelle structure. The dynamical behaviour observed during diffusion simulations of three nitroxide spin-probe molecules into micelle models could be correlated to their mobility as determined from ESR spectra analysis. The molecular mobility was found to be dependent on the chemical nature of the surfactants in the micelle external shell.