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Pagina personale di Alfonso PEDONE

Dipartimento di Scienze Chimiche e Geologiche
Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche

Muniz-Miranda, Francesco; Menziani, Maria Cristina; Pedone, Alfonso ( 2016 ) - Assessment of the basis set effect on the structural and electronic properties of organic-protected gold nanoclusters - THEORETICAL CHEMISTRY ACCOUNTS - n. volume 135(94) - pp. da 1 a 9 ISSN: 1432-881X [Articolo in rivista (262) - Articolo su rivista]
Abstract

We have investigated the structural and optical properties of five monolayer-protected gold nanoclusters with a combination of exchange–correlation functionals, namely B-PBE for the geometry relaxation and CAM-B3LYP for the time-dependent calculations. We have tested the accuracy of five different basis sets in reproducing the experimental structures of these nanoclusters, and we have found that even a rather small basis set (single zeta) can outperform a significantly larger one (double zeta) if some selected atoms are treated with polarization functions. Namely, the sulfur and phosphorous atoms of the capping thiols and phosphines usually are hypervalent when bonded to the gold inner core; therefore, polarization functions allow them significantly more structural flexibility. With the two best performing basis sets, we carried out optical calculations and found that the resulting UV–Vis profiles are largely similar, in particular the energy and orbital contributions of the optical gaps are very close. The results support the use of the small basis set proposed here to investigate larger nanoclusters with general hybrid and range-corrected hybrid functionals.

Presti, Davide; Pedone, Alfonso; Ciofini, Ilaria; Labat, Frédéric; Menziani, Maria Cristina; Adamo, Carlo ( 2016 ) - Optical properties of the dibenzothiazolylphenol molecular crystals through ONIOM calculations: the effect of the electrostatic embedding scheme - THEORETICAL CHEMISTRY ACCOUNTS - n. volume 135(86) - pp. da 1 a 11 ISSN: 1432-881X [Articolo in rivista (262) - Articolo su rivista]
Abstract

Periodic density functional theory (DFT) and hybrid ONIOM time-dependent DFT/MM cluster calculations have been carried out to investigate the ground- and excited-state properties of the crystalline structures of the enolic and ketonic tautomeric forms of a propoxy-substituted dibenzothiazolylphenol molecule (OPr), a prototype for systems undergoing the excited-state intramolecular proton transfer process. The crystalline structures of the tautomeric forms are well reproduced and, as expected, at the ground state, the enol polymorph is predicted to be more stable than the keto one. At the excited state, the effect of the environment on time-dependent DFT calculations has been accounted for by including a charge embedding scheme, and the influence of different kinds of point charges (Mulliken, CM5, RESP and QEq) in determining the optical properties of the central molecule has been investigated. The results reveal that, in fair agreement with experimental data, the absorption (emission) energies of the enol (keto) OPr molecule is red-shifted of about 3 (3) nm going from the gas phase to chloroform and blue-shifted of 10 (23) nm going from the gas to the crystal phase when the electronic embedding with Mulliken charges is employed. The electrostatic embedding influences the excited-state properties more severely than the ground-state properties, and apart the QEq charges, all other models provide Stokes shifts in reasonable agreement with experimental data.

Baccarani, A; Pedone, A.; Loschi, P.; Zaccaria, G.; Boscaini, G.; Spinzo, G.; Pompei, B.; De Santis, G. ( 2014 ) - Composite scalp replacement and negative pressure therapy for successful graft take and hair regrowth - CHIRURGIA - n. volume 27 - pp. da 209 a 212 ISSN: 0394-9508 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Microvascular scalp replantation is the procedure of choice after devastating scalp avulsion injuries. When replantation is not possible, alternative procedures should be considered to provide 1) wound closure and, possibly, 2) acceptable cosmetic results. A number of elective procedures including local and microsurgical flaps have historically been described. None of those procedures allow for obtaining superior cosmetic results in one single stage, as tissues being replaced are not "like with like". The use of spare parts from the avulsed scalp as a non vascularized composite hair bearing graft is reported herein, in association to negative pressure therapy. Despite very low success rate of composite scalp grafts reported into the literature, our patient had a 100% graft take and a favourable cosmetic result in terms of hair re-growth. At 6 months follow-up the graft is stable, pliable, and covered by a considerable amount of hair. The patient is very satisfied with the result. We think negative pressure device as the key factor in enhancing non-vascularized composite tissue survival including follicles. This is to our knowledge the first case of successful non-vascularized scalp replacement associated to negative pressure therapy. We think this approach should be considered when microsurgical replantation is not possible, still being available the use of spare parts, before attempting further elective procedures.

A. Pedone; E. Gambuzzi; M. C. Menziani ( 2012 ) - Unambiguous Description of the Oxygen Environment in Multicomponent Aluminosilicate Glasses from 17O Solid State NMR Computational Spectroscopy - JOURNAL OF PHYSICAL CHEMISTRY. C - n. volume 116 - pp. da 14599 a 14609 ISSN: 1932-7447 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Classical molecular dynamics simulations, density functional theory calculations, and spin-effective Hamiltonians have been used to simulate the 17O MAS and 3QMAS NMR spectra of Ca−Na silicate and aluminosilicate glasses and melts employed as simplified models for basaltic, andesitic, and rhyolitic magmas. The direct comparison of the theoretical NMR spectra of molecular dynamics derived structural models with the experimental counterparts available in the literature has allowed the investigation of the nature of nonframework cation mixing and the extent of intermixing among framework units in Na−Ca aluminosilicate glasses. In particular, in agreement with previous experimental evidence, the results show a nonrandomdistribution of the network-modifying Ca and Na in soda-lime glasses with the prevalence of dissimilar Na−Ca pairs around nonbridging oxygens. The oxygen sites are not completely resolved in the MAS spectra of the aluminosilicate glasses. On the contrary, in the 17O 3QMAS spectra the multiple oxygen sites, in particular the Si−O−Si,Al−O−Al, Al−O−Si, and the nonbridging oxygen peaks, are distinguishable. The small amount of Al−O−Al sites found in theinvestigated glasses reveals that the Al avoidance rule is not respected in amorphous solids. The Si−O−Al sites are surrounded byNa ions, which play a preferential role as a charge-balancing cation, while Ca can act as a network-modifying cation. Finally, correlations between the structural characteristic and the values of the NMR parameters have been attempted with the aim of helping the interpretation of NMR spectra of glasses with similar compositions.

A. Pedone; J. Bloino; V. Barone ( 2012 ) - Role of Host-Guest Interactions in Tuning the Optical Properties of Coumarin Derivatives Incorporated in MCM-41: A TD-DFTInvestigation - JOURNAL OF PHYSICAL CHEMISTRY. C - n. volume 116 - pp. da 17807 a 17818 ISSN: 1932-7447 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The encapsulation of organic dye molecules insilica-based nanostructures leads to composite materials withnovel optical properties and a wide range of applications in thefield of nanotechnology. The design of new dye-doped silicabaseddevices requires a deep understanding of how host−guest interactions affect the optical properties and stability ofthe dye/silica assembly. In this work, density functional theory(DFT) and time-dependent DFT (TD-DFT) calculations havebeen employed to investigate the effect of the host−guestinteractions on the structural, optical, and electronic propertiesof two 7-aminocoumarin dyes (labeled C339 and C340) incorporated into MCM-41. Our calculations show that the interactionof the carbonyl groups of the coumarin molecules with the silanol groups on the silica surface is responsible for the dyestabilization and is strengthened upon photoexcitation. As a result, the computed absorption and emission spectra of theincorporated dyes are red-shifted compared to those in toluene, in perfect agreement with experimental measurements. Thecomputed electronic spectra reproduce well both the solvatochromic and Stokes shifts of the dye molecule in toluene and MCM-41, and also, the band-shape can be reconstructed by simply including the vibrational fine structure associated to the electronictransition.

PEDONE A; PAVONE M; M. MENZIANI; BARONE V ( 2008 ) - Accurate First-Principle Prediction of 29Si and 17O NMR Parameters in SiO2 Polymorphs: The Cases of Zeolites Sigma-2 and Ferrierite (Washington, D.C. : American Chemical Society, 2005- ) - JOURNAL OF CHEMICAL THEORY AND COMPUTATION - n. volume 4(12) - pp. da 2130 a 2140 ISSN: 1549-9618 [Articolo in rivista (262) - Articolo su rivista]
Abstract

Abstract: The magnetic shielding tensors of silica polymorphs have been investigated by meansof quantum chemical calculations. Several levels of theory, from Hartree-Fock to the lastgeneration of Density Functional Theory based approaches, have been tested on predicting29Si and 17O isotropic and principal components of the chemical shift tensors together with 17Oquadrupolar coupling constants. The NMR parameters have been computed on all known silicasystems, namely, R-quartz, R-cristobalite, coesite, Sigma-2, and ferrierite zeolites. Besides, clusterbased approaches have been compared to a hybrid Quantum-Mechanics/Molecular-Mechanics(QM/MM) method, within the ONIOM scheme. The convergence of computed 17O NMRparameters with respect to cluster size is found to be system-dependent. Excellent agreementbetween computed and experimental data has been found for 29Si NMR parameters of thedifferent Si sites of silica polymorphs and of Sigma-2 and ferrierite zeolites.

PEDONE A; G. MALAVASI; SEGRE U; MENZIANI M. C; MUSSO F; CORNO M; CIVALLERI B; UGLIENGO P ( 2008 ) - FFSiOH: a New Force Field for Silica Polymorphs and Their Hydroxylated Surfaces Based on Periodic B3LYP Calculations - CHEMISTRY OF MATERIALS - n. volume 20 (7) - pp. da 2522 a 2531 ISSN: 0897-4756 [Articolo in rivista (262) - Articolo su rivista]
Abstract

A partial charge shell-ion model potential for silica polymorphs and their hydroxylated surfaces(FFSiOH) was parametrized in a self-consistent way using periodic B3LYP results for bulk R-cristobaliteand the (100) and (001) hydroxylated surfaces. The reliability of the new potentials was checked bycomparing structures, vibrational frequencies and relative phase stabilities of dense bulk silica polymorphs,namely R-quartz, R-cristobalite, R-tridymite, and Stishovite with both experimental and B3LYP data.The FFSiOH was also checked for computing structural and vibrational features of representative all-silica microporous materials, namely edingtonite, chabazite, and faujasite. As a last step, FFSiOH wasadopted to predict OH stretching vibrational frequencies and relative thermodynamic stability of themost common fully hydroxylated surfaces of the dense silica polymorphs, the (100) and (001) facesof all-silica edingtonite, the features of the local Si-defect in chabazite and sodalite known as (SiOH)4hydrogarnet and the geometries of H-bonded silanol groups of an amorphous silica surface. In all casesexcellent agreement resulted between FFSiOH and B3LYP periodic data and experimental data, whenavailable. The new FFSiOH force field opens up the molecular simulation of materials in which thesurface hydroxyl groups play a key role, as is the case for amorphous silica surfaces, all-silica zeoliteexternal surfaces, and the internal walls of mesoporous materials.

CASTELLINI E.; ANDREOLI R.; MALAVASI G.; PEDONE A. ( 2008 ) - Deflocculant effect on the surface properties of kaolinite investigated through malachite green adsorption - COLLOIDS AND SURFACES. A, PHYSICOCHEMICAL AND ENGINEERING ASPECTS - n. volume 329 - pp. da 31 a 37 ISSN: 0927-7757 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The adsorption of malachite green (MG) on sodium-exchanged kaolinite and on the same clay treated with two widely used deflocculants, sodium hexametaphosphate (NaHMP) and sodium disilicate (NaDIS), was investigated. The results indicate that the deflocculants affect the adsorption process. In particular, DIS treatment increases physisorption, whereas HMP treatment almost completely prevents it. The Frumkin isotherm accurately describes MG adsorption for all of the adsorbents investigated and the Frumkin inter- action parameter is found to be repulsive, in keeping with the cationic nature of the adsorbed species. TheKeywords: temperature dependences of the adsorption constant and the related thermodynamic parameters H◦ adsAdsorption and S◦ ads were also determined and discussed.

PEDONE A.; MALAVASI G.; MENZIANI M. C.; SEGRE U.; CORMACK A.N. ( 2008 ) - Role of Magnesium in Soda-Lime Glasses: Insight into Structural, Transport, and Mechanical Properties through Computer Simulations - JOURNAL OF PHYSICAL CHEMISTRY. C - n. volume 112 (29) - pp. da 11034 a 11041 ISSN: 1932-7447 [Articolo in rivista (262) - Articolo su rivista]
Abstract

The role of Mg in soda-lime glasses was elucidated by classical molecular dynamics (MD) simulations. Theeffect of the replacement of CaO for MgO on the structure, transport, and elastic properties of a series ofglasses with compositions 15Na2O · (10 - x)CaO · xMgO · 75SiO2 (x ) 0, 5, and 10 mol) was studied. Differentstructural roles were found for the Ca and Mg ions. The former, coordinated by six oxygen atoms, acts as anetwork modifier, while the latter, four-fold coordinated, participates in the silica network. Consequently, Naion diffusion is favored by the replacement of MgO for CaO in these glasses, as shown by variation in thecomputed diffusion coefficients and activation energy of the process in the series of glasses studied. Moreover,the consequences of these structural modifications on the elastic properties (Young’s modulus, shear modulus,bulk modulus, Poisson’s ratio, and compressibility) of the glasses were evaluated by means of energyminimization techniques carried out on the structures obtained by MD simulations.

G.Lusvardi; G.Malavasi; L.Menabue; M.C. Menziani; A.Pedone; D.Zaffe ( 2006 ) - Physico-chemical characterization and in vivo evaluation of zinc-glasses biocompatibility ( 1st European Chemistry Congress - - 27-31 august 2006) ( - Abstract book ) (EUCHEMS Budapest HUN ) - n. volume 1 - pp. da 164 a 164 ISBN: 9789639319615 ISSN: - [Abstract in Atti di convegno (274) - Abstract in Atti di Convegno]
Abstract

Study of soda-lime-phosphosilicate glasses based on Bioglass® and modified by zinc. "In vitro"(SBF) bioactivity was investigated through apatite forming ability and through a preliminary "in vivo" study. Zinc improves chemical durability but does not inhibit the apatite formation; a mixed-metal (Ca-Zn) phosphate-based crystalline layer is identified on the surface of HP5Z5. The improvement of the observed chemical durability can also be rationalized by Molecular Dynamics simulations

G. LUSVARDI; G.MALAVASI; A.PEDONE; L.MENABUE; M.C. MENZIANI; V.BOLIS; M. BORSETTI; F.BOCCAFOSCHI; M.CANNAS ( 2006 ) - Cell configuration for focal adhesions in cells seeded onto Zinc-doped silicate-bioglasses ( - Ceramic, Cells and Tissues; Materials for Scaffolding of Biologically engineered systems-Interface and Interactions on a Nanoscale ) (CNR Faenza FAENZA ) - pp. da 166 a 170 ISBN: 9788880800712 ISSN: - [Contributo in volume (Capitolo o Saggio) (268) - Capitolo/Saggio]
Abstract

G. Lusvardi; G. Malavasi; L. Menabue; M. C. Menziani;A.Pedone; U. Segre ( 2005 ) - A Computational Tool for the Prediction of Crystalline Phases Obtained from Controlled Crystallization of Glasses - JOURNAL OF PHYSICAL CHEMISTRY. B, CONDENSED MATTER, MATERIALS, SURFACES, INTERFACES & BIOPHYSICAL - n. volume 109 - pp. da 21586 a 21592 ISSN: 1520-6106 [Articolo in rivista (262) - Articolo su rivista]
Abstract

An automatic tool (named CLUSTER) for the prediction of the most probable crystal phases that can separatefrom glasses has been developed. The program analyzes the output of molecular dynamics simulations ofglasses or glass ceramics, systematically sampling the ratios of the ions in different portions of the simulationbox and comparing them to the stoichiometric ratio of compositionally equivalent crystalline phases retrievedfrom a crystal structure database. The efficacy of the similarity index elaborated has been judged by comparingthe results obtained with the crystal phases identified by XRD analysis after thermal treatment in a series ofmulticomponent potential bioactive glasses and glass ceramics for which the advantages of rational-designederosion-controlled release is straightforward.

Lusvardi G.; Zaffe D.; Bertoldi C.; Malavasi G.; Menabue L.; Menziani M.C.; Pedone A. ( 2004 ) - Vetri bioattivi contenenti zinco: comportamento in viotro ed in vivo ( Congresso nazionale biomateriali 2006 - - 13-16 Settembre 2006) ( - Congresso nazionale Biomateriali ) (Società chimica Italiana, Gruppo interdivisionale biomateriali Napoli ITA ) - n. volume Volume unico [Abstract in Atti di convegno (274) - Abstract in Atti di Convegno]
Abstract

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