2023, Presentazione, ENG
Rutigliano M.
Inelastic scattering of molecules from the surfaces: the role of long-range interactions.
2021, Articolo in rivista, ENG
Hong Q.; Bartolomei M.; Esposito F.; Coletti C.; Sun Q.; Pirani F.
Molecular dynamics calculations of inelastic collisions of atomic oxygen with molecular nitrogen are known to show orders of magnitude discrepancies with experimental results in the range from room temperature to many thousands of degrees Kelvin. In this work, we have achieved an unprecedented quantitative agreement with experiments even at low temperature, by including a non-adiabatic treatment involving vibronic states on newly developed potential energy surfaces. This result paves the way for the calculation of accurate and detailed databases of vibrational energy exchange rates for this collisional system. This is bound to have an impact on air plasma simulations under a wide range of conditions and on the development of Very Low Earth Orbit (VLEO) satellites, operating in the low thermosphere, objects of great technological interest due to their potential at a competitive cost.
2020, Articolo in rivista, ENG
Marri, Ivan; Amato, Michele; Bertocchi, Matteo; Ferretti, Andrea; Varsano, Daniele; Ossicini, Stefano
We combine density functional theory and many body perturbation theory to investigate the electronic properties of Si(100) and Ge(100) surfaces terminated with halogen atoms (-I, -Br, -Cl, -F) and other chemical functionalizations (-H, -OH, -CH3) addressing the absolute values of their work function, electronic affinity and ionization potential. Our results point out that electronic properties of functionalized surfaces strongly depend on the chemisorbed species and much less on the surface crystal orientation. The presence of halogens at the surface always leads to an increment of the work function, ionization potential and electronic affinity with respect to fully hydrogenated surfaces. On the contrary, the presence of polar -OH and -CH3 groups at the surface leads to a reduction of the aforementioned quantities with respect to the H-terminated system. Starting from the work functions calculated for the Si and Ge passivated surfaces, we apply a simple model to estimate the properties of functionalized SiGe surfaces. The possibility of modulating the work function by changing the chemisorbed species and composition is predicted. The effects induced by different terminations on the band energy line-up profile of SiGe surfaces are then analyzed. Interestingly, our calculations predict a type-II band offset for the H-terminated systems and a type-I band offset for the other cases.
2019, Articolo in rivista, ENG
Alberti, Alessandra; Deretzis, Ioannis; Mannino, Giovanni; Smecca, Emanuele; Giannazzo, Filippo; Listorti, Andrea; Colella, Silvia; Masi, Sofia; La Magna, Antonino
On the basis of experiment and theory, a general paradigm is drawn that reconsiders N2 not simply being an inert species but rather an effective healing gas molecule if entering a methylammonium lead iodide (MAPbI3) layer. Nitrogen is soaked into polycrystalline MAPbI3 via a postdeposition mild thermal treatment under slightly overpressure conditions to promote its diffusion across the whole layer. A significant reduction of radiative recombi- nation and a concurrent increase of light absorption, with a maximum benefit at 80 °C, are observed. Concomitantly, the current of holes drawn from the surfaces with nanometer resolution through a biased tip is raised by a factor of 3 under N2. This is framed by a reduction of the barrier for carrier extrac- tion. The achieved improvements are linked to a nitrogen-assisted recovery of intrinsic lattice disorder at the grain shells along with a simultaneous stabilization of undercoordinated Pb2+ and MA+ cations through weak electro- static interactions. Defect mitigation under N2 is reinforced in comparison to the benchmark behavior under argon. It is additionally unveiled that surface stabilization through N2 is morphology-independent and thus can be applied after any preparation procedure. Such simple and low-cost strategy can com- plement other stabilizing solutions for perovskite solar cells or light-emitting diode engineering.
2017, Articolo in rivista, ENG
Girolami, Marco; Bellucci, Alessandro; Mastellone, Matteo; Orlando, Stefano; Valentini, Veronica; Montereali, Rosa M.; Vincenti, Maria A.; Polini, Riccardo; Trucchi, Daniele M.
Black diamond, obtained by femtosecond laser treatment of natively transparent diamond, is a promising material for solar applications. The enhancement of the interaction between the active material and the solar spectrum is obtained by a controlled texturing of the diamond surface at the nanoscale, the impact of which on the optical and electronic properties of the bulk material is strongly influenced by the laser parameters. In this work, the properties of black diamond samples obtained by using two different laser wavelengths (400 and 800nm) are compared, showing that texturing periodicity (80 and 170nm, respectively) is strictly related to the laser wavelength used. Conversely, a unique optimal accumulated absorbed laser fluence (2.10kJcm(-2)) demonstrated to return the best results in terms of responsivity in the solar spectrum, regardless of the wavelength used for laser treatment.
2016, Articolo in rivista, ENG
Giuliano D.; Sodano P.; Tagliacozzo A.; Trombettoni A.
We consider the Kondo effect in Y-junctions of anisotropic XY models in an applied magnetic field along the critical lines characterized by a gapless excitation spectrum. We find that, while the boundary interaction Hamiltonian describing the junction can be recasted in the form of a four-channel, spin-1/2 antiferromagnetic Kondo Hamiltonian, the number of channels effectively participating in the Kondo effect depends on the chain parameters, as well as on the boundary couplings at the junction. The system evolves from an effective four-channel topological Kondo effect for a junction of XX-chains with symmetric boundary couplings into a two-channel one at a junction of three quantum critical Ising chains. The effective number of Kondo channels depends on the properties of the boundary and of the bulk. The XX-line is a "critical" line, where a four-channel topological Kondo effect can be recovered by fine-tuning the boundary parameter, while along the line in parameter space connecting the XX-line and the critical Ising point the junction is effectively equivalent to a two-channel topological Kondo Hamiltonian. Using a renormalization group approach, we determine the flow of the boundary couplings, which allows us to define and estimate the critical couplings and Kondo temperatures of the different Kondo (pair) channels. Finally, we study the local transverse magnetization in the center of the Y-junction, eventually arguing that it provides an effective tool to monitor the onset of the two-channel Kondo effect.
2016, Rassegna della letteratura scientifica in rivista (Literature review), ENG
Costa D.; Savio L.; Pradier C-M.
Amino acids and peptides are often used as "model" segments of proteins for studying their behavior in various types of environments, and/or elaborating functional surfaces. Indeed, though the protein behavior is much more complex than that of their isolated segments, knowledge of the binding mode as well as of the chemical structure of peptides on metal or oxide surfaces is a significant step toward the control of materials in a biological environment. Such knowledge has considerably increased in the past few years, thanks to the combination of advanced characterization techniques and of modeling methods. Investigations of biomolecule-surface interactions in water/solvent environments are quite numerous, but only in a few cases is it possible to reach an understanding of the molecule (water) surface interaction with a level of detail comparable to that of the UHV studies. This contribution aims at reviewing the recent data describing the amino acid and peptide interaction with metal or oxide surfaces in the presence of water.
2015, Rassegna della letteratura scientifica in rivista (Literature review), ENG
Costa D.; Pradier C.-M.; Tielens F.; Savio L.
Understanding the bio-physical-chemical interactions at nanostructured biointerfaces and the assembly mechanisms of so-called hybrid nano-composites is nowadays a key issue for nanoscience in view of the many possible applications foreseen. The contribution of surface science in this field is noteworthy since, using a bottom-up approach, it allows the investigation of the fundamental processes at the basis of complex interfacial phenomena and thus it helps to unravel the elementary mechanisms governing them. Nowadays it is well demonstrated that a wide variety of different molecular assemblies can form upon adsorption of small biomolecules at surfaces. The geometry of such self-organized structures can often be tuned by a careful control of the experimental conditions during the deposition process. Indeed an impressive number of studies exists (both experimental and - to a lesser extent - theoretical), which demonstrates the ability of molecular self-assembly to create different structural motifs in a more or less predictable manner, by tuning the molecular building blocks as well as the metallic substrate. In this frame, amino acids and small peptides at surfaces are key, basic, systems to be studied. The amino acids structure is simple enough to serve as a model for the chemisorption of biofunctional molecules, but their adsorption at surfaces has applications in surface functionalization, in enantiospecific catalysis, biosensing, shape control of nanoparticles or in emerging fields such as "green" corrosion inhibition. In this paper we review the most recent advances in this field. We shall start from the adsorption of amino acids at metal surfaces and we will evolve then in the direction of more complex systems, in the light of the latest improvements of surface science techniques and of computational methods. On one side, we will focus on amino acids adsorption at oxide surfaces, on the other on peptide adsorption both at metal and oxide substrates. Particular attention will be drawn to the added value provided by the combination of several experimental surface science techniques and to the precious contribution of advanced complementary computational methods to resolve the details of systems of increased complexity. Finally, some hints on experiments performed in presence of water and then characterized in UHV and in the related theoretical work will be presented. This is a further step towards a better approximation of real biological systems. However, since the methods employed are often not typical of surface science, this topic is not developed in detail.
2014, Contributo in volume, ENG
Annarosa Gugliuzza
This chapter is dedicated to deal with membrane surface sensitivity as a powerful tool to direct events such as fouling mitigation, self-cleaning, liquid flows and self-repairing. Wettability and self-healing concepts are discussed through the chapter with emphasis on the attractive opportunity to combine different strategies for switching and adjusting morphology and chemistry of the surfaces depending on desired target. Membrane ability to cause in situ-cleaning, liquid diffusion, self- restoring and auto-recovery is argued in relation to self-adjustment, adaptability and actuation mechanisms.
2014, Articolo in rivista, ENG
Pratesi, Stefano; Sani, Elisa; De Lucia, Maurizio
The development of spectrally selective materials is gaining an increasing role in solar thermal technology. The ideal spectrally selective solar absorber requires high absorbance at the solar spectrum wavelengths and low emittance at the wavelengths of thermal spectrum. Selective coating represents a promising route to improve the receiver efficiency for parabolic trough collectors (PTCs). In this work, we describe an intermediate step in the fabrication of black-chrome based solar absorbers, namely, the fabrication and characterization of nickel coatings on stainless steel substrates. Microstructural characteristics of nickel surfaces are known to favorably affect further black chrome deposition. Moreover, the high reflectivity of nickel in the thermal infrared wavelength region can be advantageously exploited for reducing thermal emission losses. Thus, this report investigates structural features and optical properties of the nickel surfaces, correlating them to coating thickness and deposition process, in the perspective to assess optimal conditions for solar absorber applications.
2013, Rapporto tecnico, ENG
Nocera L; Palumbo LJ
We present exact, weak, two species Vlasov equlibria as solutions of a mixed Stjelties-Hilbert integral inverse problem. We apply these solutions to the steady state electron rich sheath associated with a non monotonic potential profile and an asymmetric potential minimum. The electron distribution on one side of this minimum is smooth, but differs from that on the other side, which is jump discontinuous on the separatrix, but otherwise stable against the bump on tail instability: their difference is related to the distribution of the finite mass, mobile ions, which is log singular at the virtual cathode.
2013, Articolo in rivista, ENG
R. Gotter, M. Sbroscia, M. Caminale, S.R. Vaidya, E. Perfetto, R. Moroni, F. Bisio, S. Iacobucci, G. Di Filippo, F. Offi, A. Ruocco, G. Stefani, L. Mattera, M. Cini
Spin selectivity in angle-resolved Auger photoelectron coincidence spectroscopy (AR-APECS) is used to probe electronic structure in antiferromagnetic thin films. In particular, exploiting the AR-APECS capability to discriminate Auger electron emission events characterized by a different spin of the ion in its final state, a sharp multiplet structure in the Ni MVV Auger line shape of NiO/Ag(001) thin films is measured below the critical Nèel temperature. The assignment of multiplet terms follows from a close comparison of the experimental AR-APECS line shapes with the predictions based on semiempirical calculations on a cluster model and an open-band extension of the Cini-Sawatzky approach. In analogy to CoO, also in NiO, above the Nèel temperature a more featureless Auger spectrum appears and AR-APECS does not disentangle anymore high-spin and low-spin contributions to the total Auger intensity. Such a behavior, which seems to be a general result for metal oxide antiferromagnetic systems, is discussed.
2012, Abstract in atti di convegno, ENG
Bertoni G.; Torre B.; Fragouli D.; Athanassiou A.; Cingolani R.
2012, Articolo in rivista, ENG
Shi Q.; Zhao J.; Stagnaro P.; Yang H.-W.; Luan S.-F.; Yin J.-H
To construct biocompatible surfaces of polypropylene (PP), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) was melt-grafted onto PP backbones; this was followed by the restructuring of the surface mircostructure of the grafted PP by water treatment. The grafted products were analyzed by Fourier transform infrared spectroscopy and 1H-NMR; the surface microstructure of the graft copolymer was characterized by X-ray photoelectron spectroscopy and atomic force microscopy, and the biocompatibility was evaluated by water contact angle, protein adsorption, and platelet adhesion measurements. This study showed that highly biocompatible surfaces of PP could be obtained by a combination of melt grafting and surface restructuring techniques, and the formation of hole-with-rim patterns and the enrichment of the PEGMEMA chains on the topmost surface were the key factors for the improved biocompatibility. This work advances functionalized PP generated by melt grafting as a promising candidate for applications in blood-contact devices.
2010, Articolo in rivista
Vittadini, A.; Casarin, M.; Selloni, A.
Density functional calculations are carried out to investigate the interaction of water with the low-index stoichiometric surfaces of the TiO2-B polymorph of titanium dioxide. Dissociative adsorption is predicted for the (100) surface, whereas mixed dissociative/molecular adsorption is favored on both the (010) and (110) surfaces. On the (001) surface, water is able to stabilize the type-II termination, which is metastable in a dry environment, by converting the oxo ions into hydroxyls. At high temperature, water desorption is likely to convert the hydroxylated type-II surface to a type-I termination, whereas the reverse type-I -> type-II transition is not allowed when re-adsorption occurs. This could explain the experimental observation that surface hydroxyls on TiO2-B surfaces are not fully regenerated upon successive heating and cooling cycles.
2010, Articolo in rivista, ENG
Vittadini, A.; Sedona, F.; Agnoli, S.; Artiglia, L.; Casarin, M.; Rizzi, G.A.; Sambi, M.; Granozzi, G.
The structure of two ordered stoichiometric TiO2 nanophases supported on Pt(111) and (1x2)-Pt(110) substrates, prepared by reactive evaporation of Ti in a high-oxygen background, is compared by discussing experimental data (i.e. low-energy electron diffraction, scanning tunneling microscopy) and density functional theory calculations. Two rectangular phases, called rect-TiO2 and rect-TiO2 were obtained on both the hexagonal Pt(111) and the rectangular (1x2)-Pt(110) substrates, generally suggesting that they are weakly interacting with the substrates. The rect-TiO2 phase is actually confined to a TiO2 double layer, while the rect-TiO2 can extend up to a thickness of several layers and is obtained when higher Ti doses are evaporated. While the rect-TiO2 is best described as a thickness-limited lepidocrocite-like nanosheet, growing as a single-domain-commensurate (14x4) phase on (1x2)-Pt(110) and as a six-domains-incommensurate phase on Pt(111), the thicker rect-TiO2 phase can be best described as a TiO2(B) supported nanolayer (NL). This represents the first example of the TiO2(B) phase in the form of a supported NL, whose properties are still largely unexplored. The important point is that, because of the weak interaction between the oxide NLs and the Pt surfaces, the substrate does not play a role in stabilizing the 2D nanostructures. Rather, it acts as a sort of lab bench where subnanosized titania crystallites self-assemble, so that the final NLs are representative of 2D confined titania at the bottom of the nanoscale.
2010, Articolo in rivista, ENG
HOGAN Conor1; MAGRI Rita2; R. Del Sole1
This Letter solves the long-standing puzzle [Phys. Rev. Lett. 79, 693 (1997)] of why GaSb(001) apparently violates the electron counting rule (ECR) in forming a reconstruction featuring long Sb-dimer chains, rather than the c(4×4) reconstruction found in all other arsenide and antimonide III–V compounds in the V-rich regime. We find that an alternative strategy, that in fact satisfies the ECR, is followed by the Sb-rich GaSb(001) surface, whereby long Sb-dimer chains are stabilized by randomly distributed subsurface Ga antisite defects. The excess of surface Sb drives the defect formation that in turn stabilizes the surface in a metastable phase. The transition to the c(4×4) reconstruction, where the ECR is instead satisfied through missing dimers, is therefore inhibited. Our conclusions are supported by ab initio simulations of experimental reflectance anisotropy spectra.
2009, Comunicazione in rivista (Letter - Letter to editor), ENG
Colonna, Stefano; Ronci, Fabio; Cricenti, Antonio; Le Lay, Guy
2008, Articolo in rivista, ENG
Pappalardo L; Pappalardo G; Amorini F; Branciforti M G; Romano F P; de Sanoit J; Rizzo F; Scafiri E; Taormina A; Gatto Rotondo G
This work presents the results of a non-destructive analysis carried out using the portable PIXE-alpha (particle-induced X-ray emission) system developed in collaboration by the INFN/LANDIS (Catania, Italy), the CNR/IBAM (Catania, Italy) and the CEA/LIST (Saclay, France), and the portable XRD (x-ray diffraction) diffractometer recently upgraded at the INFN/LANDIS. It is shown that using a combination of the two techniques, quantitative analysis is possible in some cases. The results of its application to Roman fresco fragments obtained from different archaeological sites in Catania (Italy) are presented. These results make it possible to identify the quantitative presence of various pigments: coloured earths, ochre, hematite, goethite, cinnabar, and Egyptian blue have been identified and quantified.
2006, Contributo in volume, ENG
Samori, Bruno; Zuccheri, Giampaolo; Scipioni, Anita; De Santis, Pasquale
Hierarchical self-assembly is nature's solution to build up complex structures starting from components that are orders of magnitude smaller. This integration of components over disparate length scales might include inorganic matter. Along this line, it has been speculated about the possibility of constructing intricate hybrid structures composed of inorganics and proteins.Our understanding about recognition mechanisms between DNA and inorganic materials is still far behind with respect to the case of proteins. Nucleic acid bases are differently adsorbed on the surface of crystalline graphite. The adsorption behavior on this surface of the bases is markedly different. One can tailor possible applications of this recognition effect to the self-assembled integration of inorganic material in the construction of complex DNA-based nanostructures.