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Monica MONTECCHI

Personale tecnico amministrativo
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2024 - Initial stages of growth and electronic properties of epitaxial SrF2 thin films on Ag(1 1 1) [Articolo su rivista]
Borghi, M.; Mescola, A.; Paolicelli, G.; Montecchi, M.; D'Addato, S.; Vacondio, S.; Bursi, L.; Ruini, A.; Doyle, B. P.; Grasser, T.; Pasquali, L.
abstract

2023 - Growth Dynamics of Ultrathin Films of Benzo[1,2-b:4,5-b']dithiophene Derivatives on Au(111): A Photoelectron Spectroscopy Investigation [Articolo su rivista]
Stummo, Angelo; Montecchi, Monica; Parenti, Francesca; Vanossi, Davide; Fontanesi, Claudio; Capelli, Raffaella; Pasquali, Luca
abstract

: Ultrathin films of a stereoisomeric mixture of benzo[1,2-b:4,5-b']dithiophene derivatives were grown by thermal evaporation in vacuum on Au(111), and they were studied in situ by photoelectron spectroscopy. X-ray photons from a non-monochromatic Mg Kα conventional X-ray source and UV photons from a He I discharge lamp equipped with a linear polarizer were used. He I photoemission results were compared with density functional theory (DFT) calculations: density of states (DOS) and 3D molecular orbital density distribution. Au 4f, C 1s, O 1s, and S 2p core-level components suggest a surface rearrangement as a function of film nominal thickness, with the variation of the molecular orientation, from flat-laying at the initial deposition to tilted toward the surface normal at coverages exceeding 2 nm. Eventually, the DFT results were exploited in assigning of the valence band experimental structures. Moreover, polarization-dependent photoemission confirmed the tilted arrangement of the molecules, starting at 2 nm. A variation of the work function of 1.4 eV with respect to the clean substrate was measured, together with a valence band offset of 1.3 eV between the organic layer and gold.

2023 - In-situ growth of nonstoichiometric CrO0.87 and Co3O4 hybrid system for the enhanced electrocatalytic water splitting in alkaline media [Articolo su rivista]
Solangi, M. Y.; Aftab, U.; Tahira, A.; Hanan, A.; Montecchi, M.; Pasquali, L.; Tonezzer, M.; Mazzaro, R.; Morandi, V.; Laghari, A. J.; Nafady, A.; Abro, M. I.; Emo, M.; Vigolo, B.; Dawi, E.; Mustafa, E.; Ibupoto, Z. H.
abstract

2022 - Role of cobalt precursors in the synthesis of Co3O4 hierarchical nanostructures toward the development of cobalt-based functional electrocatalysts for bifunctional water splitting in alkaline and acidic media [Articolo su rivista]
Tahira, A.; Ibupoto, Z. H.; Montecchi, M.; Pasquali, L.; Tonezzer, M.; Nafady, A.; Khalil, H. F.; Mazzaro, R.; Morandi, V.; Vagin, M.; Vomiero, A.
abstract

The precursors have significant influence on the catalytic activity of nonprecious electrocatalysts for effective water splitting. Herein, we report active electrocatalysts based on cobalt oxide (Co3O4) hierarchical nanostructures derived from four different precursors of cobalt (acetate, nitrate, chloride, and sulfate salts) using the low-temperature aqueous chemical growth method. It has been found that the effect of precursor on the morphology of nanostructured material depends on the synthetic method. The Co3O4 nanostructures exhibited cubic phase derived from these four precursors. The Co3O4 nanostructures obtained from chloride precursor have demonstrated improved oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to other precursors due relatively higher content of Co3O4 nanostructures at the surface of material. An overpotential of 400 mV versus reversible hydrogen electrode (RHE) at 10 mA cm−2 was observed for HER. The Co3O4 nanostructures derived from the chloride precursor have shown favorable reaction kinetics via 34 mV dec−1 value of the Tafel slope for HER reaction. The Co3O4 nanostructures derived from chloride precursor have also shown an excellent HER durability for 15 hr in alkaline media. Furthermore, the OER functional characterization was carried out onto Co3O4 nanostructures derived from chloride precursor exhibited 220 mV overpotential at 10 mA cm−2 and Tafel slope of 56 mV dec−1. Importantly, the reason behind the favorable catalytic activity of Co3O4 nanostructures derived from chloride precursor was linked to one order of magnitude smaller charge transfer resistance and higher amount of Co3O4 content at the surface of nanostructures than the Co3O4 nanostructures derived from other precursors. The performance of Co3O4 nanostructures derived from chloride precursor via the wet chemical method suggests that cobalt chloride precursor could be of great interest for the development of efficient, stable, nonprecious, and environmentally friendly electrocatalysts for the chemical energy conversion and storage devices.

2022 - Surface Optimization of Commercial Porous Ti Substrates by EPD of Titanium Nitride [Articolo su rivista]
Mortalò, Cecilia; Cannio, Maria; Zin, Valentina; Miorin, Enrico; Montagner, Francesco; Pasquali, Luca; Montecchi, Monica; Boccaccini, Dino Norberto; Fabrizio, Monica; Deambrosis, Silvia Maria
abstract

In this work, the infiltration of TiN powders by electrophoretic deposition (EPD) in aqueous media was considered as alternative method to reduce the size craters and the roughness of commercial porous Ti substrates. Ti substrates can be used as suitable supports for the deposition of dense hydrogen separation TiNx-based membranes by physical vapor deposition (PVD) techniques. The influence of various EPD deposition parameters on surface morphology and roughness of TiN-infiltrated substrates were investigated in order to optimize their surface properties. The results suggest that a multi-step EPD procedure is an effective technique for reducing substrate surface defects of commercial porous Ti substrates which could then be successfully used as proper supports for the deposition of dense and defect-free TiNx layers, also aligning the thermal mismatch between the active layer and the porous substrate.

2021 - Production Strategies of TiNx Coatings via Reactive High Power Impulse Magnetron Sputtering for Selective H2 Separation [Articolo su rivista]
Mortalò, Cecilia; Deambrosis, Silvia Maria; Montagner, Francesco; Zin, Valentina; Fabrizio, Monica; Pasquali, Luca; Capelli, Raffaella; Montecchi, Monica; Miorin, Enrico
abstract

This scientific work aims to optimize the preparation of titanium nitride coatings for selective H-2 separation using the Reactive High Power Impulse Magnetron Sputtering technology (RHiPIMS). Currently, nitride-based thin films are considered promising membranes for hydrogen. The first series of TiNx/Si test samples were developed while changing the reactive gas percentage (N-2%) during the process. Obtained coatings were extensively characterized in terms of morphology, composition, and microstructure. A 500 nm thick, dense TiNx coating was then deposited on a porous alumina substrate and widely investigated. Moreover, the as-prepared TiNx films were heat-treated in an atmosphere containing hydrogen in order to prove their chemical and structural stability; which revealed to be promising. This study highlighted how the RHiPIMS method permits fine control of the grown layer's stoichiometry and microstructure. Moreover, it pointed out the need for a protective layer to prevent surface oxidation of the nitride membrane by air and the necessity to deepen the study of TiNx/alumina interface in order to improve film/substrate adhesion.

2019 - Redox-Active Ferrocene grafted on H-Terminated Si(111): Electrochemical Characterization of the Charge Transport Mechanism and Dynamics [Articolo su rivista]
Fontanesi, C.; Como, E. D.; Vanossi, D.; Montecchi, M.; Cannio, M.; Mondal, P. C.; Giurlani, W.; Innocenti, M.; Pasquali, L.
abstract

Electroactive self-assembled monolayers (SAMs) bearing a ferrocene (Fc) redox couple were chemically assembled on H-terminated semiconducting degenerate-doped n-type Si(111) substrate. This allows to create a Si(111)|organic-spacer|Fc hybrid interface, where the ferrocene moiety is covalently immobilized on the silicon, via two alkyl molecular spacers of different length. Organic monolayer formation was probed by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) and X-ray photoelectron spectroscopy (XPS) measurements, which were also used to estimate thickness and surface assembled monolayer (SAM) surface coverage. Atomic force microscopy (AFM) measurements allowed to ascertain surface morphology and roughness. The single electron transfer process, between the ferrocene redox probe and the Si electrode surface, was probed by cyclic voltammetry (CV) measurements. CVs recorded at different scan rates, in the 10 to 500 mV s−1 range, allowed to determine peak-to-peak separation, half-wave potential, and charge-transfer rate constant (KET). The experimental findings suggest that the electron transfer is a one electron quasi-reversible process. The present demonstration of surface engineering of functional redox-active organometallic molecule can be efficient in the field of molecular electronics, surface-base redox chemistry, opto-electronic applications.

2019 - The Impact of Lipid Corona on Rifampicin Intramacrophagic Transport Using Inhaled Solid Lipid Nanoparticles Surface-Decorated with a Mannosylated Surfactant [Articolo su rivista]
Maretti, Eleonora; Rustichelli, Cecilia; Gualtieri, Eva Magdalena; Costantino, Luca; Siligardi, Cristina; Miselli, Paola; Buttini, Francesca; Montecchi, Monica; Leo, Eliana Grazia; Truzzi, Eleonora; Iannuccelli, Valentina
abstract

The mimicking of physiological conditions is crucial for the success of accurate in vitro studies. For inhaled nanoparticles, which are designed for being deposited on alveolar epithelium and taken up by macrophages, it is relevant to investigate the interactions with pulmonary surfactant lining alveoli. As a matter of fact, the formation of a lipid corona layer around the nanoparticles could modulate the cell internalization and the fate of the transported drugs. Based on this concept, the present research focused on the interactions between pulmonary surfactant and Solid Lipid Nanoparticle assemblies (SLNas), loaded with rifampicin, an anti-tuberculosis drug. SLNas were functionalized with a synthesized mannosylated surfactant, both alone and in a blend with sodium taurocholate, to achieve an active targeting to mannose receptors present on alveolar macrophages (AM). Physico-chemical properties of the mannosylated SLNas satisfied the requirements relative to suitable respirability, drug payload, and AM active targeting. Our studies have shown that a lipid corona is formed around SLNas in the presence of Curosurf, a commercial substitute of the natural pulmonary surfactant. The lipid corona promoted an additional resistance to the drug diffusion for SLNas functionalized with the mannosylated surfactant and this improved drug retention within SLNas before AM phagocytosis takes place. Moreover, lipid corona formation did not modify the role of nanoparticle mannosylation towards the specific receptors on MH-S cell membrane.

2019 - Understanding adhesion of gold conductive films on sodium-alginate by photoelectron spectroscopy [Articolo su rivista]
Capelli, Raffaella; Maccagnani, Piera; Dinelli, Franco; Murgia, Mauro; Bertoldo, Monica; Montecchi, Monica; Doyle, Bryan P.; Carleschi, Emanuela; Pasquali, Luca
abstract

Ultrathin layers of gold, from 2 to 25 nm of nominal coverage, have been deposited on sodium-alginate biopolymer foils applying two alternative approaches: low power sputtering and thermal evaporation. The morphology of the deposited layers was obtained by means of atomic force microscopy. In the early stages of growth, thermal evaporation gives rise to a top surface resembling the underlying substrate, whereas low power sputtering produces a topography characterized by smoother areas. This indicates that the film growth occurs in different ways. X-ray photoelectron spectroscopy with two photon energies, corresponding to Al Kα and Ag Lα photons, was used to get information on the chemistry at the interface and on the degree of intermixing between Au and sodium-alginate. While no chemical modifications with respect to the bare materials could be detected, the evolution of the intensities of the relevant core levels of Au and sodium alginate (Au 4f and Na 1s in particular) indicated a strong intermixing in the case of films deposited by low power sputtering. This is further supported by optical measurements. The observed behaviour can be correlated with the enhanced adhesion of sputtered films compared to thermally evaporated ones.

2018 - Influence of domestic and environmental weathering in the self-cleaning performance and durability of TiO2 photocatalytic coatings [Articolo su rivista]
CEDILLO GONZALEZ, ERIKA IVETH; Barbieri, Virginia; Paolo, Falcaro; Torres-Martínez, Leticia M.; Isaías, Juárez-Ramírez; Laura, Villanova; Montecchi, Monica; Pasquali, Luca; Siligardi, Cristina
abstract

Weathering of photocatalytic TiO2 coatings represents an important issue for the successful application of TiO2- based self-cleaning materials. Photocatalytic efficiency of the as-prepared materials is crucial for commercialization; however, changes in the coating performance due to weathering become a critical factor for practical applications. Moreover, chemical durability should be considered as weathering can promote the release of photocatalyst nanoparticles, which can pollute the environment and be hazardous for human health. In this study, two photocatalytic TiO2 coatings with different microstructures (namely compact and mesoporous) were exposed to chemical treatments to simulate domestic and environmental weathering. Results show that dense TiO2 coatings with a slow photocatalytic activity are suitable for domestic applications as minimum leaching of photoactive material was observed. Conversely, once exposed to chemical solutions commonly present in domestic environments, the initially highly active mesoporous TiO2 coatings showed a dramatic drop of the selfcleaning performance and a significant release of nanoparticles in the surrounding environment. It is expected that the results reported here will be of particular relevance for the construction sector, as the manuscript discloses important knowledge for the development of TiO2-based self-cleaning materials once exposed to indoor or outdoor environments.

2018 - Role of gallium diffusion in the formation of a magnetically dead layer at the Y3Fe5O12/Gd3Ga5O12 epitaxial interface [Articolo su rivista]
Suturin, S. M.; Korovin, A. M.; Bursian, V. E.; Lutsev, L. V.; Bourobina, V.; Yakovlev, N. L.; Montecchi, M.; Pasquali, L.; Ukleev, V.; Vorobiev, A.; Devishvili, A.; Sokolov, N. S.
abstract

We have clarified the origin of a magnetically dead interface layer formed in yttrium iron garnet (YIG) films grown at above 700 degrees C onto a gadolinium gallium garnet (GGG) substrate by means of laser molecular beam epitaxy. The diffusion-assisted formation of a Ga-rich region at the YIG/GGG interface is demonstrated by means of composition depth profiling performed by x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and x-ray and neutron reflectometry. Our finding is in sharp contrast to the earlier expressed assumption that Gd acts as a migrant element in the YIG/GGG system. We further correlate the presence of a Ga-rich transition layer with considerable quenching of ferromagnetic resonance and spin wave propagation in thin YIG films. Finally, we clarify the origin of the enigmatic low-density overlayer that is often observed in neutron and x-ray reflectometry studies of the YIG/GGG epitaxial system.

2016 - Structural origin of electrical conductivity of copper lithium metaphosphate glasses [Articolo su rivista]
Mugoni, Consuelo; Jain, H; Montorsi, Monia; Montecchi, Monica; Kovalskiy, A.; Siligardi, Cristina
abstract

Wehave sought the structural origin of the recently reported electrical conductivity of lithium copper phosphate glass system (50-x) Li2O-xCu2O-50 P2O5, as lithium oxide is gradually replaced by Cu2O. The structure of these glasses was determined by X-ray photoelectron spectroscopy, Fourier Transform Infrared Spectroscopy and Raman spectroscopy. The results show the presence of both mobile Cu+ and relatively immobile Cu2+ ions. The relative fraction of Cu2+ [Cu2+ / Cutot] and non-bridging oxygen increases with x; the latter indicating a tendency towards depolymerization of the network. On the other hand, there is enhanced crosslinking within the network as P\\O⋯Li bonds are replaced by relatively covalent P\\O⋯Cu bonds. This leads to a more crosslinked structure and a progressive reduction of the optimumsites for the jumping of both Li+ and Cu+, in agreement with the observed increase of the energy barrier for ion transport as Li2O is replaced by Cu2O.

2015 - Electrowetting of nitro-functionalized oligoarylene thiols self-assembled on polycrystalline gold [Articolo su rivista]
Casalini, Stefano; Berto, Marcello; Bortolotti, Carlo Augusto; Foschi, Giulia; Operamolla, Alessandra; DI LAURO, Michele; Omar, Omar Hassan; Liscio, Andrea; Pasquali, Luca; Montecchi, Monica; Farinola, Gianluca M; Borsari, Marco
abstract

Four linear terarylene molecules (i) 4-nitro-terphenyl-4″-methanethiol (NTM), (ii) 4-nitro-terphenyl-3″,5″-dimethanethiol (NTD), (iii) ([1,1';4',1″] terphenyl-3,5-diyl)methanethiol (TM), and (iv) ([1,1';4',1″] terphenyl-3,5-diyl)dimethanethiol (TD) have been synthesized and their self-assembled monolayers (SAMs) have been obtained on polycrystalline gold. NTM and NTD SAMs have been characterized by X-ray photoelectron spectroscopy, Kelvin probe measurements, electrochemistry, and contact angle measurements. The terminal nitro group (-NO2) is irreversibly reduced to hydroxylamine (-NHOH), which can be reversibly turned into nitroso group (-NO). The direct comparison between NTM/NTD and TM/TD SAMs unambiguously shows the crucial influence of the nitro group on electrowetting properties of polycrystalline Au. The higher grade of surface tension related to NHOH has been successfully exploited for basic operations of digital μ-fluidics, such as droplets motion and merging.

2014 - CRYSTAL CHEMISTRY AND SURFACE CONFIGURATIONS OF TWO IRON-BEARING TRIOCTAHEDRAL MICA-1M POLYTYPES [Articolo su rivista]
Elmi, Chiara; Brigatti, Maria Franca; Guggenheim, S.; Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano
abstract

The aim of this paper is to explore the crystal chemical features of both the bulk and the uppermost surface layers of two trioctahedral Fe-rich mica-1M (space group C2/m) polytypes: a tetra-ferriphlogopite from an alkali-carbonatic complex near Tapira (Belo Horizonte, Minas Gerals, Brazil) and a Fe2+-bearing phlogopite also containing Fe3+ in tetrahedral sites from the Kovdor carbonatite-bearing alkaline-ultrabasic complex (Kola Peninsula, Russia). The chemical formulae are [XII](K0.99) [VI](Fe2+0.08 Fe3+0.15 Mg2.76 Ti0.01) [IV](Fe3+0.82 Si3.18) O10.37 (F0.24 OH1.39) and [XII](K0.94 Na0.06) [VI](Fe2+0.17 Fe3+0.05 Mg2.75 Mn0.01 Ti0.05) [IV](Fe3+0.16 Al0.84 Si3.00) O10.21 (F0.35 OH1.44) for tetra-ferriphlogopite and Fe-bearing phlogopite, respectively. The two minerals show a pronounced difference in tetrahedral composition, where Fe for Si substitution is at 20.5% in tetra-ferriphlogopite and at 4% in Fe-bearing phlogopite. Fe3+ substitution produces an increase of the tetrahedral sheet thickness and of mean tetrahedral edge lengths in tetra-ferriphlogopite with respect to Fe-bearing phlogopite. The tetrahedral rotation angle (α) changes remarkably from tetra-ferriphlogopite (α = 10.5°) to the Fe-bearing phlogopite (α = 8.5°), thus indicating a significantly greater tetrahedral ring distortion in the tetra-ferriphlogopite with respect to the Fe-bearing phlogopite. The interconnection between α and tetrahedral flattening angle () may indirectly suggest the variation of  due to Fe for Si tetrahedral substitution. Crystal chemical modifications at the mineral surface were investigated via X-ray Photoelectron Spectroscopy by comparing data related to the surface to data originating from the bulk. The local population at the anionic position can be obtained by considering that the binding energy of photoelectron peaks is dependent on the chemical state of atoms and their local environment. If oxygen is substituted by fluorine, the binding energy of Mg was observed to shift to higher values. By considering the Mg1s binding energies of tetra-ferriphlogopite and Fe-bearing phlogopite, Mg is preferentially coordinated to F and not to OH groups. This is consistent with higher BE values observed for Fe-rich phlogopite characterized by higher F content with respect to tetra-ferriphlogopite.

2014 - Crystal chemistry and surface configurations of two polylithionite-1M crystals [Articolo su rivista]
Elmi, Chiara; Brigatti, Maria Franca; Guggenheim, S.; Pasquali, Luca; Montecchi, Monica; Nannarone, S.
abstract

This paper explores the crystal chemical features of the bulk and the outermost (001) surface layers of two trioctahedral Li-rich mica-1M (space group C2) polytypes, i.e. a polylithionite (MLG-114) from Li-mica granitic pegmatite at St. Austell (SW England) and a Fe2+-rich polylithionite (Ch-140) from a rhyolite at Profitis Ilias, Chios Island, Greece. Structural formulae are [xii](K0.952Na0.019Rb0.019) [vi](Al1.034Li1.459Fe2+0.389Fe3+0.046Mn0.038Mg0.002Zn0.002Ti0.001) [iv](Al3+0.477 Si3.523)O10.081(F1.735OH0.184) and [xii](K0.992Na0.014) [vi](Al0.980Li1.028Fe2+0.787Fe3+0.022 Mn0.059Mg0.052Zn0.010Ti0.024) [iv](Al3+0.857Si3.143) O10.095 (F1.617 OH0.288) for MLG-114 and Ch-140, respectively. Each mineral is characterized by a high F content in the anion site and has tetrahedral and octahedral compositions related to the exchange vector [vi]Li-1[iv]Si-1 [vi]Fe2+ [iv]Al. Unit cell dimensions are a = 5.251(1), b = 9.066(2), c = 10.087(2) Å; β = 100.694(5)° for polylithionite MLG-114 and a = 5.282(1), b = 9.121(3), c = 10.080(3) Å; β = 100.764(5)° for Ch-140. Crystal structure refinements (agreement factors are R = 3.58% and R = 3.75% for MLG-114 and Ch-140, respectively) demonstrate that the [vi]Li-1[vi]Fe2+ [iv]Si-1[iv]Al exchange vector produces a decrease in the lateral dimensions of the tetrahedral and octahedral sheets. The decrease in basal oxygen distances results from the effect of the strain caused by the orientation of opposing tetrahedral sheets within a 2:1 layer. The decrease reduces the strain so that the basal oxygen plane can remain nearly planar. Changes in these dimensions via distortions of the tetrahedral basal-oxygen ring (α = 3.3° and α = 4.1° for MLG-114 and Ch-140, respectively) are limited. Octahedral M1 and M3 sites are similar in size and much larger than M2 and the mean electron count is M3 < M1 < M2 in MLG-114 and M1  M2 < M3 in Ch-140. Al preferentially occupies the M2 site, whereas Fe and Li are nearly disordered between M1 and M3 sites with a slight preference of Fe for the M1 site in MLG-114 and for M3 site in Ch-140. Element concentrations on the (001) surface, obtained through X-ray photoelectron spectroscopy (XPS) high-resolution spectra for Si2p, Al2p, Fe2p, K2p, Li1s, and F1s core levels, indicates that a greater amount of lithium and a smaller amount of potassium characterize the surface with respect to the bulk. The decrease in K content, commonly observed in micas, is related to its location on the cleavage surface, because the cation must be distributed equally between the two (001) surfaces generated upon cleavage. The increase in Li content on or near the (001) cleavage surface suggests a preference for cleavage near lithium-enriched regions. The surface structure of the polylithionite crystals suggests that Al, Li, and Fe cations maintain coordination features at the surface similar to the bulk. Silicon, however, which is generally in four-fold coordination, shows also a small number of [1]-fold coordinated components at a binding energy of 99.85 eV.

2014 - High-Energy X-ray Photoemission and Structural Study of Ultrapure LaF3Superionic Conductor Thin Films on Si [Articolo su rivista]
Koshmak, Konstantin; A., Banshchikov; T., Vergentev; Montecchi, Monica; D., Céolin; J. P., Rueff; N. S., Sokolov; Pasquali, Luca
abstract

LaF3 films in the 5−40 nm thickness range were grown on Si(111) by molecular beam epitaxy. The substrates were kept at 450 °C during deposition. The films were investigated by high- energy X-ray photoemission flanked by conventional X-ray photoemission, reflection high-energy electron diffraction, and atomic force microscopy. The film growth was layer-by-layer. The surface of the films presented flat terraces, ∼100 nm wide, separated by monatomic steps, reproducing the morphology of the substrate. La 3d, F 1s, O 1s, and Si 2p core levels and valence band were measured by high-energy photoemission to investigate the reactivity of the system and the surface and bulk composition of the films, following varying sample treatments (X-ray irradiation, sputtering, heating). The fresh prepared films resulted of high purity, with no traces of reaction or intermixing at the buried interface between the substrate and the trifluoride. The X-ray beam was seen to induce F depletion at the surface and promote oxide formation. F depletion enhancement was obtained through Ar ion sputtering. An irreversible variation of the film composition was finally observed for samples heated above 300 °C, with the development of La oxides and oxofluorides. These effects were related to the high mobility of F ions in the LaF3 lattice and to the high tendency of defects formation involving F sites.

2014 - Interface Functionalities in Multilayer Stack Organic Light Emitting Transistors (OLETs) [Articolo su rivista]
Capelli, R.; Dinelli, F.; Gazzano, M.; D’Alpaos, R.; Stefani, A.; Generali, G.; Riva, M.; Montecchi, Monica; Giglia, A.; Pasquali, Luca
abstract

Herein is described a multidisciplinary approach to understand the per- formance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture poten- tially competitive with the state of the art and more flexible for spectral emis- sion control. The processes of charge injection and field-effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface mor- phology and the initial growth stages of organic films where charge transport actually occurs. X-ray diffraction and near edge X-ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non-ordered domains. Moreover, chemical reactivity at the interfaces are measured by X-ray photoelectron spectroscopy. It is found that a strong reac- tion occurs at the metal-organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties.

2013 - And Yet it Moves! Microfluidics Without Channels and Troughs [Articolo su rivista]
Francesca, Lugli; Giulia, Fioravanti; Denise, Pattini; Pasquali, Luca; Montecchi, Monica; Denis, Gentili; Mauro, Murgia; Zahra, Hemmatian; Massimiliano, Cavallini; Francesco, Zerbetto
abstract

A simple, versatile, rapid, and inexpensive procedure based on the immersion method is developed to fabricate chemical gradients on chemically activated Si/SiO2 surfaces by a trichloro (1H,1H,2H,2H-perfluorooctyl) silane self-assembly monolayer (SAM). Contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy data based on the intensity of the signals of C1s and F1s, which progressively increase, indicate that the surface is characterized by the presence of increasing amounts of the SAM along the gradient direction. Experimental conditions are optimized by maximizing the variation of the contact angle of water drops at the starting and the ending points of the gradient. The application of the chemical gradient to droplet motion is demonstrated. The results are rationalized by dissipative particle dynamics simulations that well match the observed contact angles and the velocities of the drops. The simulations also show that the intrinsic nature of the gradient affects the velocity of the motion.

2013 - Highly luminescent yttria–silica core–shell nanoparticles by the sacrificial polymer shell method [Articolo su rivista]
M., Ghahari; P., Fabbri; F., Pilati; Pasquali, Luca; Montecchi, Monica; R., Aghababazadeh
abstract

This paper describes the correlation existing between the photoluminescence of core–shell SiO2@Y2O3:Eu3+ nanoparticles synthesised by a method based on a sacrificial polymer-shell intermediate, and the thickness of that polymer shell. The method is based on the synthesis of a covalently bonded sacrificial polymer shell by polymerization of methacryl oxyethyl isocyanate (MOI) onto silica cores; the polymer shell was demonstrated to act as a promoter and stabilizer of the adsorption of yttrium and europium ions on the surface of silica, and its thickness plays an important role on the final luminescent intensity of the hybrid particles, which is related to the adhesion and continuity of the lanthanide shell of SiO2@Y2O3:Eu3+ nanoparticles. Yttria shells were obtained with thickness varying in the range 3–20 nm by tuning the polymer shell thickness in the range 0–50 nm. Results demonstrate that photoluminescence of SiO2@Y2O3:Eu3+ nanoparticles prepared via the sacrificial polymer shell method is much higher with respect to nanoparticles obtained by a traditional procedure.

2013 - Sodian muscovite-2M1: crystal chemistry and surface features [Articolo su rivista]
Elmi, Chiara; Brigatti, Maria Franca; Guggenheim, S.; Pasquali, Luca; Montecchi, Monica; Malferrari, Daniele; Nannarone, Stefano
abstract

his study explores crystal chemical features of a sodian muscovite from Antarctica, both in the bulk of the mineral and at the uppermost surface layers. These features may support a deeper comprehension of processes affecting mineral surface and mineral physical properties. The muscovite under analysis is characterized by limited celadonite and paragonite substitutions and shows the following chemical formula: [XII](K1.73 Na0.27) [VI](Fe2+ 0.14 Al3+ 3.77 Mg 0.07 Ti0.01) [IV](Al1.91 Si6.09) O20 (F0.11 OH3.89). The sample is monoclinic, 2M1 polytype, with symmetry C2/c and unit cell parameters a = 5.1969(1), b = 9.0138(3), c = 20.0835(7) A, and β = 95.763(2)°. The two tetrahedral sites, T1 and T2, present similar distances (>T1.O< = 1.643A and >T2.O< = 1.647 A) and distortion parameter values, evidencing a disordered distribution of Si and Al at tetrahedral sites. The tetrahedral ring is significantly distorted (α = 11.2°) and the tetrahedral basal oxygen atom plane is remarkably wavy (δz = 0.224 A).Crystal chemical modifications at mineral surface were investigated by X-ray photoelectron spectroscopy. The interlayer cation K is eight-fold coordinated both in the bulk and at the surface, and its amount decreases at the surface. Sodium substitutes K and its coordination at the mineral surface is six. This evidence, together with a significant Na increase at the surface, is consistent with Na clustering close to the cleavage plane.

2012 - Electrochemical method for pickling and passivation of austenitic steel welds [Articolo su rivista]
Giovanardi, Roberto; Poli, Giorgio; Pasquali, Luca; Montecchi, Monica; L., Filippetti; G., Orlando
abstract

The aim of this work is to develop an innovative process for pickling and passivating tungsten inert gas welds on austenitic stainless steel in order to obtain complete removal of non-protective oxides and to passivate the metal surface. In particular, the treatment intends to increase both corrosion resistance and surface appearance of the steel without making use of traditional pickling solutions (which usually contain high concentrations of strong acids). The treatment, based on an electrochemical approach, uses specific electrolytes, and to evaluate their effect in terms of corrosion resistance and surface finish, different solutions were prepared and tested using low concentrations of weak organic acids, e.g. citric, oxalic, sulphamic, gluconic and lactic acids. This aspect is very important to reduce the hazardousness of the solution compared to the traditional pickling acids.

2011 - Atomic and electronic structure of ultrathin fluoride barrier layers at the oxide/Si interface [Articolo su rivista]
Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano; F., Boscherini
abstract

A SrF2 ultrathin barrier layer on Si(001) is used to form a sharp interface and block reactivity and intermixing between the semiconductor and a Yb2O3 overlayer. Yb2O3/Si(001) and Yb2O3/SrF2/Si(001) interfaces grown in ultra high vacuum by molecular beam epitaxy are studied by photoemission and x-ray absorption fine structure. Without the fluoride interlayer, Yb2O3/Si(001) presents an interface reacted region formed by SiOx and/or silicate compounds, which is about 9 A ̊ thick and increases up to 14–15 A ̊ after annealing at 500–700 ◦C. A uniform single layer of SrF2 molecules blocks intermixing and reduces the oxidized Si region to 2.4 A ̊ after deposition and to 3.5 A ̊ after annealing at 500 ◦C. In both cases we estimate a conduction band offset and a valence band offset of ∼1.7 eV and 2.4 eV between the oxide and Si, respectively. X-ray absorption fine structure measurements at the Yb LIII edge suggest that the Yb oxide films exhibit a significant degree of static disorder with and without the fluoride barrier. Sr K edge measurements indicate that the ultrathin fluoride films are reacted, with the formation of bonds between Si and Sr; the Sr–Sr and Sr–F interatomic distances in the ultrathin fluoride barrier film are relaxed to the bulk value.

2011 - Crystal chemistry and surface features of a 2M1 paragonitic muscovite [Abstract in Rivista]
Elmi, Chiara; Brigatti, Maria Franca; Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano; Malferrari, Daniele
abstract

The paragonitic muscovite considered [XII](K1.722 Na0.251 Ba0.010) [VI](Fe2+0.140 Al3+3.769 Cr3+0.003 Mg0.074 Ti0.012 Mn0.002) [IV](Al1.897 Si6.103) O20 (F0.109 OH3.891) came from Antarctica, it is monoclinic, 2M1 polytype, with symmetry C2/c and unit cell parameters a = 5.1969(1), b = 9.0138(3), c = 20.0835(7) (Å) and β = 95.763(2) (°).By using a multi-analytical approach this study describes the crystal chemical features of muscovite determined both in the bulk and on the uppermost surface layers. The bulk structure was refined by single crystal X-ray diffraction and the final refinement yielded the following agreement factor R = 0.0299. The two tetrahedral sites, T1 and T2, present similar distances (<T1-O> = 1.643 Å and <T2-O> = 1.647 Å) and distortion parameter values, thus evidencing a disordered distribution of [IV]Si and [IV]Al in tetrahedral sites. Tetrahedral ring is significantly distorted (α = 11.2°) and the tetrahedral basal oxygen atoms plane is remarkably wavy (Δz = 0.224Å). tetrahedral ring distortion affects not only the topology of the cleavage plane, but also the coordination of the interlayer cation, which reduces from twelve to eight. Crystal chemical modifications at mineral surface were investigated via X-ray Photoelectron Spectroscopy (XPS), by comparing data related to surface to the ones characterizing the bulk. A peculiarity of muscovite from Antarctica is a limited Na for K interlayer substitution, which was found in the bulk as well as on the mineral surface. It is well known that in micas the coordination of the interlayer cation can vary from twelve to six, depending on the distortion of the hexagonal tetrahedral ring, as measured by  angle, as observed and predicted by Weiss et al. [1].The interlayer cation K (binding energy = 293.36 eV) is confirmed to be eight-fold coordinated [2]. Na (binding energy = 1071.02 eV) substitutes K both in the bulk and at the surface. Na coordination, at mineral surface, reduces from eight to six [3]. The six-fold coordination presented by Na is consistent with  ≈ 16°, which is typical for paragonite, whose interlayer is completely occupied by Na. Chemical composition at the surface was compared to bulk chemical composition obtained by electron microprobe analysis. This comparison highlights a decrease in K content, which can be explained by its location on the cleavage surface, since the cation is expected to be distributed equally along the two surfaces generated after cleavage, and an increase in Na which can be related to Na domains close to the cleavage surface.These aspects may relate muscovite cleavage processes to the presence of “defects”, or better in-homogeneities in layer crystal chemistry. This fact may thus suggest that Na content in paragonitic muscovite could not be only attributed to a solid solution mechanism, where this cation substitutes for K, but rather to the presence of Na-dominant clusters.

2011 - High-temperature vesuvianite: crystal chemistry and surfaceconsiderations [Articolo su rivista]
Elmi, Chiara; Brigatti, Maria Franca; Pasquali, Luca; Montecchi, Monica; Laurora, Angela; Malferrari, Daniele; Nannarone, Stefano
abstract

A multi-methodical approach has been appliedfor characterizing the bulk and surface crystal chemical featuresof a high-temperature vesuvianite crystal from skarns ofMount Somma-Vesuvius Volcano (Naples, Italy). Vesuvianitebelongs to the space group P4/nnc with unit cellparameters a = 15.633(1)A ° , c = 11.834(1)A ° and chemicalformula (Ca18.858 Na0.028 Ba0.004 K0.006 Sr0.005 h0.098)19.000(Al8.813 Ti0.037 Mg2.954 Mn0.008 Fe0.1142? Fe1.3753? Cr0.008B0.202)13.511 Si18.000(O0.261 F0.940 OH7.799)9.000. Structurerefinement, which converges at R = 0.0328, demonstrates astrong positional disorder down the fourfold axes, indicatingthat the Y1 site is split into two positions (Y1A and Y1B)alternatively occupied. However, because of X4 proximity toY1B and Y1A, X4 cannot be occupied if Y1B or Y1A are.OverallY1 occupancy (Y1A ? Y1B) reaches approximately0.5, as common in vesuvianite and occupancy of Y1B site isextremely limited. Moreover, T1 position, limitedly occupied,accommodates the excess of cations generally related toY position. A small quantity (0.202 apfu) of boron is sited atthe T2 site that, like T1, is poorly occupied. The determination of the amount of each element on the (100)vesuvianite surface, obtained through X-ray photoelectronspectroscopy high-resolution spectra in the region of the Si2p,Al2p, Mg1s, and Ca2p core levels, evidences that a greateramount of aluminum and a smaller amount of calciumcharacterize the surface with respect to the bulk. Althoughboth of these features require further investigation, we mayconsider the Al increase can be related to preferential orientationof Al-rich sites on the (100) plane. Furthermore, thesurface structure of vesuvianite suggests that Al, Ca, and Mgcations maintain coordination features at the surface similarto the bulk. Silica, however, while presenting fourfold coordination,shows also a [1]-fold small coordinated componentat binding energy 99.85 eV, due to broken Si–O bonds at thesurface. The presence of eight- and nine-coordinated Cacations is suggested by a large XPS feature resulting from themerging of Ca2p3/2 and Ca2p1/2 peaks at 348.45 and352.05 eV, respectively.

2011 - Local structure at interfaces between hydride-forming metals: A case study of Mg-Pd nanoparticles by x-ray spectroscopy [Articolo su rivista]
L., Pasquini; F., Boscherini; E., Callini; C., Maurizio; Pasquali, Luca; Montecchi, Monica; E., Bonetti
abstract

The structure at the interface between elements or phases that exhibit different hydrogen (H) binding energies exerts a profound influence on the thermodynamics of H in nanophase materials. In this paper, we study the local structure at the Mg/Pd interface in Mg nanoparticles with partial Pd coating, and we map its evolution in response to annealing and H sorption. This task is accomplished by x-ray photoelectron spectroscopy and x-ray absorption spectroscopy, also including in situ experiments, with the support of crystallographic information from x-ray diffraction. It is shown that the initial Pd surface layer reacts with Mg at relatively low temperatures, leading to irreversible formation of a Mg-rich intermetallic phase Mg6Pd. Due to the high Mg-H binding energy, this phase reversibly transforms, upon H absorption, into a nanophase mixture of magnesium hydride and a Pd-rich intermetallic with H in solid solution, MgPdHδ . These reversible structural changes are discussed with reference to recent calculations that highlight their relevance to the thermodynamics of the metal-hydride transition. The picture drawn here might be relevant to other multiphase materials presently investigated in the field of hydrogen-related science and technology.

2011 - New Insights on the Interaction between Thiophene Derivatives and Au Surfaces. The Case of 3,4-Ethylenedioxythiophene and the Relevant Polymer [Articolo su rivista]
Terzi, Fabio; Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano; A., Viinikanoja; T., Aaritalo; M., Salomaki; J., Lukkari; B. P., Doyle; Seeber, Renato
abstract

The nature of the interface between electrogen-erated poly(3,4-ethylenedioxythiophene) and the Au substrateis studied in detail. In particular, the adsorption of the relevantmonomer, namely, 3,4-ethylenedioxythiophene, is investigatedand compared with that of other thiophene derivatives. Di!er-ent deposition procedures have been adopted: very thin "lms ofthe thiophene derivatives have been obtained through chemi-sorption processes from vapor and liquid phases, on Au poly-crystalline substrates, Au nanoparticles possessing di!erent size,and a Au(111) single crystal. Di!erent techniques, operatingboth in situ and ex situ, have been employed for the characterization of these deposits, that is, X-ray photoemission and surface- enhanced Raman spectroscopy. The results show that the poly(3,4-ethylenedioxythiophene)/metal interface is far from being simply constituted by unreacted molecules in contact with the substrate; rather, the formation of oligothiophene species and sulfur atoms at the interface has been ascertained.

2010 - Ceria-containing frit for luster in modern ceramic glaze [Articolo su rivista]
Siligardi, Cristina; Montecchi, Monica; Montorsi, Monia; Pasquali, Luca
abstract

The main goal of this work was to study the formation of theluster effect in a glaze manufactured from a ceria-containingfrit. The glazes obtained under industrial firing were studied usingX-ray photoelectron spectroscopy, X-ray diffraction at roomtemperature and high temperature, and scanning electron microscopywith energy-dispersion spectroscopy. The mechanismof the luster effect on the surface was explained. The resultsindicated that the glaze presents iridescent colors on the surface,mainly associated with the formation of a very thin layer ofCeO2 crystals.Moreover, the CeO2 crystals show a preferentialorientation and different dimensions. The CeO2 crystallizationon the glaze was also studied using a hot-stage X-ray technique.

2010 - Crystal chemistry, surface morphology and X-ray photoelectron spectroscopy of Fe-rich osumilite from Mt. Arci, Sardinia (Italy) [Articolo su rivista]
Elmi, Chiara; Brigatti, Maria Franca; Pasquali, Luca; Montecchi, Monica; Laurora, Angela; Malferrari, Daniele; Nannarone, Stefano
abstract

Microprobe anal., single crystal X-ray diffraction, XPS, at. force microscopy, and X-ray absorption spectroscopy were applied on Fe-rich osumilite from the volcanic massif of Mt. Arci, Sardinia, Italy. Osumilite belongs to the space group P6/mcc with unit cell parameters a = 10.1550(6), c = 14.306(1) Å and chem. formula (K0.729)C (Na0.029)B (Si10.498 Al1.502)T1 (Al2.706 Fe0.2942+)T2 (Mg0.735 Mn0.091 Fe1.1842+)AO30. Structure refinement converged at R = 0.0201. Unit cell parameter a is related to octahedral edge length as well as to Fe2+ content, unlike the c parameter which does not seem to be affected by chem. compn. The detn. of the amt. of each element on the mineral surface, obtained through XPS high-resoln. spectra in the region of the Si2p, Al2p, Mg1s and Fe2p core levels, suggests that Fe presents Fe2+ oxidn. state and octahedral coordination. Two peaks at 103.1 and 100.6 eV can be related to Si4+ and Si1+ components, resp., both in tetrahedral coordination. The binding energy of Al2p, at 74.5 eV, indicates that Al is mostly present in the distorted T2 site, whereas the Mg peak at 1,305.2 eV suggests that this cation is located at the octahedral site. X-ray absorption at the Fe L2,3-edges confirms that iron is present in the mineral structure, prevalently in the divalent state and at the A octahedral site.

2010 - The relationships of bulk structure, surface structure, chemistry, and physical properties of mineral phases with six- and eight-membered silicate rings [Abstract in Atti di Convegno]
Elmi, Chiara; Brigatti, Maria Franca; Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano; Laurora, Angela; Malferrari, Daniele
abstract

The goal of this research is to better understand the relationship between chemical composition and atomic structure (both bulk and surface structure) of minerals having six-membered silicate rings, such as osumilite and eight-membered silicate rings, such as vesuvianite. Osumilite under investigation occurs in thin fissures within a rhyolite from the volcanic massif of Mt. Arci, Sardinia (Italy). Vesuvianite sample is from skarns of Somma-Vesuvius volcano (Italy) instead.The osumilite and vesuvianite bulk structures were refined via single crystal X-ray diffraction. Osumilite sample is hexagonal, with symmetry P6/mcc and unit cell parameters a = 10.1550(6) c = 14.306(1) (Å). The structural formula is (K0.729)C (Na0.029)B’ (Si10.498 Al1.502)T1 (Al2.706 Fe2+0.219 Mg0.075)T2 (Mg0.660 Mn0.091 Fe2+1.258)AO30. When compared to literature data [1], osumilite sample from Mt. Arci is characterized by a significantly high Fe2+ content (1.478 apfu).X-ray photoelectron spectroscopy (XPS) enabled the crystal chemical characterization of osumilite surface, where iron was still observed in its divalent state, thus confirming a similarity in osumilite surface and bulk chemical composition. A further evidence of Fe oxidation state at osumilite surface is provided from X-ray absorption spectroscopy (XAS) at Fe-L2,3 edge.Vesuvianite is a complex tetragonal silicate. Vesuvianite ideal formula is Ca19(Al,Mg)13(B, Si)18O68(OH, O, F)10 and crystallizes, generally, in the space group P4/nnc. Vesuvianite presents in nature two different structural type: a high temperature type (at about 1000 °C) and a low temperature type (at about 900 °C). To recognize which type of vesuvianite, our sample belongs to, we studied its thermal decomposition via X-ray powder diffraction method by using a Philips X’Pert PRO diffractometer equipped with X’Celerator area detector. Finally we could assure that our sample is a high temperature vesuvianite with high symmetry P4/nnc.Unlike osumilite, vesuvianite surface is very complex to study because of its roughness on given faces of the crystal. However we could obtain preliminary information on the chemical composition of the surface via XPS and subsequently compare these data to bulk chemical composition. Moreover, unlike osumilite sample, vesuvianite presents Fe in octahedral site both in divalent and trivalent state, as confirmed by XAS experiments performed at the L2,3 edge of iron.

2009 - Adsorption of 3,4-ethylenedioxythiophene (EDOT) on noble metal surfaces: a photoemission and x-ray absorption study [Articolo su rivista]
Pasquali, Luca; Terzi, Fabio; Montecchi, Monica; B., Doyle; J., Lukkari; Zanfrognini, Barbara; Seeber, Renato; Nannarone, Stefano
abstract

The adsorption of 3,4-ethylenedioxythiophene (EDOT) on Au and Pt surfaces is studied by core level and valence band photoemission using synchrotron radiation and by near edgeX-ray absorption spectroscopy.To closer simulate real applications, the films are grown from aqueous solution at room temperature and are compared to an ‘ideal’ film prepared by dosing the molecules from the vapour phase on a clean Au(1 1 1) single crystal. The S 2p, C 1s and O 1s levels show multiple components which are associatedto molecular fragmentation. NEXAFS confirms that fragmentation takes place at the surface. Thiophene species as well as alkyl chains and Sn species are identified as the most probable fragmentation products.

2009 - Formation and distribution of compounds at the Ru - Si(001) ultrathin film interface [Articolo su rivista]
Pasquali, Luca; N., Mahne; Montecchi, Monica; V., Mattarello; Nannarone, Stefano
abstract

Interface formation between Ru and Si(001) has been studied by x-ray and ultraviolet photoemissions. The film properties were investigated, for metal deposition at room temperature, as a function of the Ru film thickness and as a function of the annealing temperature of a thick grown film. From the evolution of the Ru and Si core levels, we find that alloying takes place at the interface during growth and estimate the thickness of the intermixed region to be of the order of 15–20 ML. Annealing at increasingly high temperatures causes the formation of different silicide phases, which are discussed in relation to theoretical and experimental data on related transition metal silicides.

2009 - Lead free Cu-Containing Frit for Modern Metallic Glaze [Articolo su rivista]
Siligardi, Cristina; Montecchi, Monica; Montorsi, Monia; Pasquali, Luca
abstract

A lead-free frit containing high amount of copper and its glazeconceived for fine porcelain stoneware tiles were investigated.The glazes obtained under industrial firing were studied using Xrayphotoelectron spectroscopy, X-ray diffraction, optical andscanning electron microscopy with energy dispersion spectroscopy.The mechanism of the red color formation on the surfacewas explained. The results indicated that the glaze presents ametallic gloss and iridescent colors on the surface, mainly associatedto the formation of CuO crystallites and Cu metallicparticles. Moreover, the Cu glaze showed a good chemical durability;this is particularly interesting because commercial Cufrits usually present poor chemical properties.

2009 - Lustre Ce-glazes: scientific aspects of materials having high aesthetic properties [Relazione in Atti di Convegno]
Siligardi, Cristina; Montecchi, Monica; Pasquali, Luca; Claudio, Ansaloni
abstract

Three frits conceived for high porosity single firing tiles containing different amounts of cerium oxide and their glazes were investigated. The glazes obtained under industrial firing were studied using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS). The mechanism of the lustre effect on the surface was explained. The results indicate that the glaze presents iridescent colours on the surface, mainly associated to the formation of a very thin layer of CeO2 crystals. Moreover, the CeO2 crystals present a preferential orientation and different dimensions.

2009 - Osumilite from Mount Arci (Sardinia, Italy): bulk and surface crystal chemistry [Abstract in Rivista]
Elmi, Chiara; Brigatti, Maria Franca; Pasquali, Luca; Montecchi, Monica; Laurora, Angela; Malferrari, Daniele; Nannarone, Stefano
abstract

This study is focused on osumilite crystal chemistry and on its surface chemical characteristics and properties. Osumilite belongs to the milarite mineral group. This mineral, with the ideal formula XIICIXB’2VIA2(T2)3IV(T1)12O30 crystallizes in the space group P6/mcc. T1 is mainly occupied by Si and to a smaller amount by Al, T2 is usually occupied by Al with Fe and little Mg, whereas A octahedron mostly contains Mg and Fe. The ring arrangement defines structural channels occupied by the twelve-coordinated C site which is characterized by the presence of alkaline cations (Na, K).The osumilite from Mt Arci (Sardinia) occurs in thin fissures and small cavities within a rhyolite from the volcanic massif of Mt. Arci, Sardinia. The mineral forms regular dark blue hexagonal prismatic-tabular crystals associated to trydimite and sporadic phlogopite crystals. The osumilite structure was refined by single crystal X-ray diffraction and the final refinement yielded the following agreement factors R = 0.0199. The sample studied is hexagonal, with symmetry P6/mcc and unit cell parameters a = 10.1550(6) c = 14.306(1) (Å). The structural formula is (K0.729)C (Na0.029)B’ (Si10.498 Al1.502)T1 (Al2.706 Fe2+0.219 Mg0.075)T2 (Mg0.660 Mn0.091 Fe2+1.258)AO30. In respect of data from literature [2], osumilite sample from Mt. Arci is characterized by a significantly high Fe content (1.478 apfu).In order to study the morphology of osumilite from Mt. Arci, an atomic force microscopy (AFM) filtered images of osumilite was performed. The (001) surface roughness of osumilite is about 0.40 nm, thus it confirms the presence of the channels defined by the double rings of tetrahedra. The distance between two dark areas, defining channel position, is 1 nm, which well agree with the unit cell parameter a value.X-ray photoelectron spectroscopy (XPS) analysis was carried out to measure chemical composition and quantity of each element on the osumilite surface. Higher resolution spectra in the region of Si2p, Al2p, Mg1s and Fe2p core levels were measured. From data collected, we could say that the osumilite surface is chemically well characterized and the elemental composition of surface totally corresponds to the bulk chemical composition. Moreover, comparing our results to data from literature we obtained also crystal chemical information on Fe, Mg, Si and Al high resolution spectra, compared to the crystal chemical characteristics of the bulk.In order to confirm the valence of Fe and the position of this element in the A site, X-ray absorption spectroscopy (XAS) was also made in the L2,3 edge of iron comparing data from literature.

2008 - Molecular states of polyacenes grown on noble metal surfaces [Relazione in Atti di Convegno]
M., Pedio; B., Doyle; N., Mahne; A., Giglia; Nannarone, Stefano; Montecchi, Monica; Pasquali, Luca
abstract

Here we present a combined photoemission (UPS), metastable deexcitation (MDS) and optical absorption (NEXAFS) at C K-edge study of molecular states of polyacenes grown on Ag(111) and Au(111), from submonolayer to multilayer thicknesses. We focus on the evolution of the HOMO and LUMO molecular states induced by the adsorption from submonolayer to monolayer thickness and we find a different redistribution of these states in the various systems formed at RT: while a strong redistribution of the molecular states takes place in Pn/Ag(111) and Tc/Ag(111) interface, a weaker interaction is indicated for Tc/Au(111).

2008 - Parallel-local anodic oxidation of silicon surfaces by soft stamps [Articolo su rivista]
Albonetti, C; Martinez, J; Losilla, Ns; Greco, P; Cavallini, M; Borgatti, F; Montecchi, Monica; Pasquali, Luca; Garcia, R; Biscarini, Fabio
abstract

We investigate the fabrication of nanometric patterns on silicon surfaces by using the parallel-local anodic oxidation technique with soft stamps. This method yields silicon oxide nanostructures 15 nm high, namely at least five times higher than the nanostructures made with local anodic oxidation using atomic force microscopy, and thanks to the size of the stamp enables one to pattern the surface across a centimetre length scale. To implement this technique, we built a machine to bring the metallized polydimethylsiloxane stamp in contact with the silicon surface, subsequently inserted in a sealed chamber with controlled relative humidity. The oxide nanostructures are fabricated when a bias voltage of 36 V is applied between the stamp and the silicon for 2 min, with a relative humidity of 90%. The flexibility of the stamp enables a homogeneous conformal contact with the silicon surface, resulting in an excellent reproducibility of the process. Moreover, by means of two subsequent oxidations with the same stamp and just rotating the sample, we are able to fabricate complex nanostructures. Finally, a detailed study of the oxidation mechanism, also using a finite element analysis, has been performed to understand the underlying mechanism.

2006 - Perfluoropolyether-based organic-inorganic hybrid coatings [Articolo su rivista]
Fabbri, Paola; Messori, Massimo; Montecchi, Monica; Nannarone, Stefano; Pasquali, Luca; Pilati, Francesco; C., Tonelli; M., Toselli
abstract

Perfluoropolyether-based organic-inorganic hybrids were prepared by sol-gel process and applied as functional coatings onto glass substrates. Contact angle analysis and X-ray photoemission spectroscopy were carried out in order to characterize the surface of the prepared coatings. A strong hydrophobic and lipophobic character was observed for all tested compositions. The wettability behaviour was found to be dependent on both the coating technique and the reaction time of the sol-gel reaction. A strong surface segregation of perfluoropolyether segments was noted for all the prepared samples as evidenced by XPS analysis. On the basis of the obtained results, these materials could be used as functional coatings to prepare water and oil repellent glasses or other substrates.

2006 - Surface properties of fluorinated hybrid coatings [Articolo su rivista]
Fabbri, Paola; Messori, Massimo; Montecchi, Monica; Pilati, Francesco; Taurino, Rosa; C., Tonelli; M., Toselli
abstract

A commercial perfluoropolyether containing alkoxysilane functionalities was employed to prepare organic-inorganic hybrid coatings by using the sol-gel process in the presence of tetraethoxysilane. Contact angle analysis revealed a strong hydrophobic and oleophobic character of the coatings almost independently from the molecular weight of the starting fluorinated oligomer. Surface tension values were in the range of 14-16 mN/m, suggesting a preferential segregation of fluorinated segments onto the surface of the coating. Atomic force microscopy showed the presence very smooth surfaces permitting to neglect the contribution of the surface roughness to wettability. Friction coefficient values were markedly lower with respect to the value of uncoated glass substrate.

2005 - Perfluoropolyether-based Organic-Inorganic Hybrid Coatings: Preparation and Surface Characterization [Articolo su rivista]
Messori, Massimo; Toselli, M.; Pilati, Francesco; Fabbri, Paola; Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano; Tonelli, C.
abstract

not available

2005 - Perfluoropolyether-silica hybrids: preparation and surface characterization [Articolo su rivista]
Messori, Massimo; M., Toselli; Pilati, Francesco; Fabbri, Elena; Fabbri, Paola; Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano; C., Tonelli
abstract

α,ω-Triethoxysilane terminated perfluoropolyether-polycaprolactone block copolymers, TXCL(x)Si, were synthesised, characterised and subsequently reacted with tetraethoxysilane to prepare transparent organicinorganic hybrid materials by using the sol–gel process. Surface characterization was carried out through contact angle measurements. All the materials investigated (independently on both the reaction time of the sol–gel reaction before coating application and the bulk organic-inorganic ratio) showed a strong hydrophobic character when compared with non-fluorinated and fully inorganic control materials. The highest water contact angles were obtained when TXCL(x)Si oligomer used for the preparation of the hybrid contained short hydrogenated polycaprolactone segments. In all cases, the surface tension values indicated that the very surface at the air-coating interface showed almost completely perfluoropolyether segments.

2005 - Rivestimenti ibridi organici-inorganici a base di perfluoropolieteri: preparazione e caratterizzazione superficiale [Articolo su rivista]
M., Messori; M., Toselli; Pilati, Francesco; Fabbri, Paola; Pasquali, Luca; Montecchi, Monica; Nannarone, Stefano; C., Tonelli
abstract

not available