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177 results on '"Soave, Raffaella"'

7. How the Interplay between SnO2and Zn(II) Porphyrins Impacts on the Electronic Features of Gaseous Acetone Chemiresistors

Author

Tessore, Francesca, Pargoletti, Eleonora, Di Carlo, Gabriele, Albanese, Cecilia, Soave, Raffaella, Trioni, Mario Italo, Marelli, Federica, and Cappelletti, Giuseppe

Abstract

Herein, the integration of SnO2nanoparticles with two Zn(II) porphyrins─Zn(II) 5,10,15,20-tetraphenylporphyrin (ZnTPP) and its perfluorinated counterpart, Zn(II) 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (ZnTPPF20)─was investigated for the sensing of gaseous acetone at 120 °C, adopting three Zn-porphyrin/SnO2weight ratios (1:4, 1:32, and 1:64). For the first time, we were able to provide evidence of the correlation between the materials’ conductivity and these nanocomposites’ sensing performances, obtaining optimal results with a 1:32 ratio for ZnTPPF20/SnO2and showcasing a remarkable detection limit of 200 ppb together with a boosted sensing signal with respect to bare SnO2. To delve deeper, the combination of experimental data with density functional theory calculations unveiled an electron-donating behavior of both porphyrins when interacting with tin dioxide semiconductor, especially for the nonfluorinated one. The study suggested that the interplay between electrons injected, from the porphyrins’ highest occupied molecular orbital to SnO2conduction band, and the latter’s available electronic states has a dramatic impact to boost the chemiresistive sensing. Indeed, we highlighted that the key lies in preventing the full saturation of SnO2electronic states concomitantly increasing the materials’ conductivity: in this respect, the best compromise turned out to be the perfluorinated porphyrin. A further corroboration of our findings was obtained by illuminating the sensors during measurements with light-emitting diode (LED) light. Actually, we demonstrated that it does not have any impact on improving the sensing behavior, most probably due to the electronic oversaturation and scattering caused by LED excitation in porphyrins. Lastly, the most effective hybrids (1:32 ratio) were physicochemically characterized, confirming the physisorption of the macrocycles onto the SnO2surface. In conclusion, herein, we underscore the feasibility of customizing the porphyrin chemistry and porphyrin-to-SnO2ratio to enhance the gaseous sensing of bare metal oxides, providing valuable insights for the engineering of highly performing light-free chemiresistors.

Published
2024
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8. New Insight into the Electronic and Magnetic Properties of Sub-Stoichiometric WO 3 : A Theoretical Perspective.

Author

Trioni, Mario Italo, Cargnoni, Fausto, Americo, Stefano, and Soave, Raffaella

Subjects
TRANSITION metal oxides, MAGNETIC properties, STANNIC oxide, DENSITY functional theory, POINT defects, OXIDATION states
Abstract

We present a theoretical investigation on the wide-band-gap semiconductor WO   3 in its room-temperature monoclinic structure. We carried out density functional theory and GGA-1/2 calculations on the bulk phase and the most stable (001) surface of the material, either in their stoichiometric form or in the presence of oxygen vacancies at various concentrations. Concerning the bulk phase, our results show how the inclusion of these defects correctly reproduces the intrinsic n-type doping of the material. The system is also found to be magnetic at reasonably high defect concentrations. As for the surface, the presence of vacancies gives rise to a magnetic behavior, whose features depend on the relative arrangement of native point defects. Oxygen vacancies are also responsible for additional tungsten oxidation states in both bulk and surface. Based on these results, we provide a rationale for the interpretation of most experimental data of this material and, possibly, other widespread transition metal oxides with similar properties and applications such as ReO   3 , TiO   2 , and SnO   2 . [ABSTRACT FROM AUTHOR]

Published
2024
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17. On the interplay between CH...O an OH...O interactions in determining crystal packing and molecular conformation: An experimental and theoretical charge density study of the fungal secondary metabolite austdiol [C(sub12)H(sub 12)O(sub 5)]

Author

Presti, Leonardo Lo, Soave, Raffaella, and Destro, Riccardo

Subjects
Molecular dynamics -- Research, Hydrogen bonding -- Research, Metabolites -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

An extensive quantitative study of all intra- and intermolecular H...O reactions based on geometrical criteria and on topological analysis of rho(r) is conducted. An experimental, quantititative evidence is given that CH...O HBs are very similar to the conventional OH...O HBs, albeit generally weaker.

Published
2006

21. Observation of an exotic lattice structure in the transparent KTa1−xNbxO3 perovskite supercrystal

Author

Lo Presti, Leonardo, primary, Parravicini, Jacopo, additional, Soave, Raffaella, additional, Parravicini, Gianbattista, additional, Mauri, Michele, additional, Loconte, Laura, additional, Di Mei, Fabrizio, additional, Falsi, Ludovica, additional, Tartara, Luca, additional, Binetti, Simona, additional, Agranat, Aharon J., additional, and DelRe, Eugenio, additional

Published
2020
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24. N2- radical anion reversibly formed at the surface of 'electron-rich' alkaline-earth oxides

Author

Giamello, Elio, Paganini, Maria Cristina, Chiesa, Mario, Murphy, Damien M., Pacchioni, Gianfranco, Soave, Raffaella, and Rockenbauer, Antal

Subjects
Chemistry, Physical and theoretical -- Research, Quantum chemistry -- Research, Chemicals, plastics and rubber industries
Abstract

A new study provides evidence for the first observation of the adsorption of the N2- radical anion on an oxide surface, itself formed directly by nitrogen adsorption.

Published
2000

26. Experimental Charge Density Analysis and Electrostatic Properties of Crystalline 1,3-Bis(Dimethylamino)Squaraine and Its Dihydrate from Low Temperature (T=18 and 20 K) XRD Data

Author

Destro, Riccardo, Roversi, Pietro, Soave, Raffaella, Hovestad, Arjan, and Lo Presti, Leonardo

Subjects
non&#8211, charge density, Quantum Theory of Atoms in Molecules, squaraine, covalent interactions, low temperature, single crystal, electrostatics, X-ray diffraction
Abstract

Multipolar refinements of structural models fitting extensive sets of X-ray diffraction (XRD) data from single crystals of 1,3-bis(dimethylamino)squaraine [SQ, C8H12N2O2] and its dihydrate [SQDH, C8H12N2O2 center dot 2H(2)O], collected at very low T (18 +/- 1 K for SQ, 20 +/- 1 K for SQDH), led to an accurate description of their crystal electron density distributions. Atomic volumes and charges have been estimated from the experimental charge densities using the Quantum Theory of Atoms in Molecules (QTAIM) formalism. Our analysis confirms the common representation (in the literature and textbooks) of the squaraine central, four-membered squarylium ring as carrying two positive charges, a representation that has been recently questioned by some theoretical calculations: the integrated total charge on the C4 fragment is estimated as ca. +2.4e in SQ and +2.2e in SQDH. The topology of the experimental electron density for the SQ squaraine molecule is modified in the dihydrated crystal by interactions between the methyl groups and the H2O molecules in the crystal. Maps of the molecular electrostatic potential in the main molecular planes in both crystals clearly reveal the quadrupolar charge distribution of the squaraine molecules. Molecular quadrupole tensors, as calculated with the PAMoC package using both Stewart and QTAIM distributed multipole analysis (DMA), are the same within experimental error.

Published
2020
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35. Physicochemical properties of Zwitterionic L- and DL-alanine crystals from their experimental and theoretical charge densities

Author

Destro, Riccardo, Soave, Raffaella, and Barzaghi, Mario

Subjects
Zwitterions -- Structure, Zwitterions -- Chemical properties, Zwitterions -- Electric properties, Electrostatic interactions -- Analysis, Alanine -- Structure, Alanine -- Chemical properties, Alanine -- Electric properties, Hydrogen bonding -- Research, X-rays -- Diffraction, X-rays -- Observations, Chemicals, plastics and rubber industries
Abstract

The structural, topological, and electrostatic features of amino acid alanine in the crystal state are discussed. The two crystals, DL-alanine and L-alanine have similar cell dimensions and hydrogen-bond patterns but exhibit different densities.

Published
2008

38. Reductive activation of the nitrogen molecule at the surface of 'Electron-Rich' MgO and CaO. The N(sub 2)(super -) surface adsorbed radical ion

Author

Chiesa, Mario, Giamello, Elio, Murphy, Damien M, Pacchloni, Gianfranco, Paganini, Cristina M., Soave, Raffaella, and Sojka, Zbigniew

Subjects
Electron paramagnetic resonance -- Analysis, Lime -- Atomic properties, Magnesium oxide -- Atomic properties, Chemicals, plastics and rubber industries
Abstract

The 11-electron N(sub 2)(super -) radical anion so formed is detected by electron paramagnetic resonance for N(sub 2) and (super 15)N(sub 2). The electron transfer is reversible and N(sub 2) molecules desorb generating the original F(sub S)(super +) center when the pressure is lowered or temperature is increased.

Published
2001

42. A new monoclinic polymorph of 3-diethylamino-4-(4-methoxyphenyl)-1,1-dioxo-4H-1 lambda 6,2-thiazete-4-carbonitrile

Author

Orlando, Ahmed M., Lo Presti, Leonardo, and Soave, Raffaella

Subjects
R=0.037, x-ray, T=293 K, Single-crystal
Abstract

A new monoclinic form of the title compound, C14H17N3O3S, has been found upon slow crystallization from water. Another monoclinic form of the compound was obtained previously from a mixture of dichloromethane and diethyl ether[Clerici, F.; Gelmi, M. L.; Soave, R.; Lo Presti, L. Tetrahedron 2002, 58, 5173-5178.]. Both phases crystallize in space group P21/n with one molecule in the asymmetric unit. The formally single exocyclic C-N bond that connects the -NEt2 unit with the thiazete ring is considerably shorter than the adjacent, formally double, endocyclic C=N bond. This is likely to be due to the extended conjugated system between the electron-donor diethylammine fragment and the electron-withdrawing sulfonyl group. In the newly discovered polymorph, the methoxy group is rotated by almost 180° around the phenyl-OCH3 bond, resulting in a different molecular conformation.

Published
2010

43. Anharmonic motions versus dynamic disorder at the Mg ion from the charge densities in pyrope (Mg3Al2Si3O12) crystals at 30 K: six of one, half a dozen of the other.

Author

Destro, Riccardo, Ruffo, Riccardo, Roversi, Pietro, Soave, Raffaella, Loconte, Laura, and Lo Presti, Leonardo

Subjects
X-ray diffraction, CRYSTALS
Abstract

The possible occurrence of static/dynamic disorder at the Mg site in pyrope (Mg3Al2Si3O12), with or without anharmonic contribution to the thermal vibrations even at low temperatures, has been largely debated but conclusions were contrasting. Here a report is given on the experimental charge density distribution, ρEXP, of synthetic pyrope at T = 30 K, built through a Stewart multipolar expansion up to l = 5 and based on a very precise and accurate set of in-home measured single-crystal X-ray diffraction amplitudes with a maximum resolution of 0.44 Å. Local and integral topological properties of ρEXP are in substantial agreement with those of ρTHEO, the corresponding DFT-grade quantum charge density of an ideal pyrope crystal, and those derived from synchrotron investigations of chemical bonding in olivines. Relevant thermal atomic displacements, probably anharmonic in nature, clearly affect the whole structure down to 30 K. No significant (> 2.5σ) residual Fourier peaks are detectable from the ρEXP distribution around Mg, after least-squares refinement of a multipole model with anharmonic thermal motion at the Mg site. Experimental findings were confirmed by a full analysis of normal vibration modes of the DFT-optimized structure of the perfect pyrope crystal. Mg undergoes wide displacements from its equilibrium position even at very low temperatures, as it is allocated in a ∼ 4.5 Å large dodecahedral cavity and involved in several soft phonon modes. Implications on the interplay among static/dynamic disorder of Mg and lattice vibrational degrees of freedom are discussed. [ABSTRACT FROM AUTHOR]

Published
2017
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44. Model peptides containing the 3-sulfanyl-norbornene amino acid, a conformationally constrained cysteine analogue effective inducer of 310-helix secondary structures

Author

Ruffoni, Alessandro, primary, Contini, Alessandro, additional, Soave, Raffaella, additional, Lo Presti, Leonardo, additional, Esposto, Irene, additional, Maffucci, Irene, additional, Nava, Donatella, additional, Pellegrino, Sara, additional, Gelmi, Maria Luisa, additional, and Clerici, Francesca, additional

Published
2015
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