P. Piseri

University of Milan, Milano, Lombardy, Italy

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Publications (119)321.57 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The growth of nanostructured nickel : carbon (Ni : C) nanocomposite thin films by the supersonic cluster beam deposition of nickel and carbon clusters co-deposited from two separate beam sources has been demonstrated. Ni : C films retain the typical highly disordered structure with predominant sp(2) hybridization, low density, high surface roughness and granular nanoscale morphology of cluster assembled nanostructured carbon, but display enhanced electric conductivity. The electric double layer (EDL) capacitance of Ni : C films featuring the same thickness (200 nm) and different nickel volumetric concentrations (0-35%) has been investigated by electrochemical impedance spectroscopy employing an aqueous solution of potassium hydroxide (KOH 1 M) as electrolyte solution. Evidence of increased electric conductivity, facilitated EDL formation and negligible porous structure modification was found as consequence of Ni embedding. This results in the ability to synthesize electrodes with tailored specific power and energy density by the accurate control of the amount of deposited Ni and C clusters. Moreover, nickel nanoparticles were shown to catalyze the formation of tubular onion-like carbon structures upon mild thermal treatment in inert atmosphere. Electrochemical characterization of the heated nanocomposite electrodes revealed that the presence of long range ordered sp(2) structures further improves the power density and energy storage properties.
    Nanotechnology 10/2014; 25(43):435401. DOI:10.1088/0957-4484/25/43/435401 · 3.67 Impact Factor
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    ABSTRACT: Photoactive membranes coated with TiO2 and Pt/TiO2 nanostructured thin films were produced by one-step deposition of gas phase nanoparticles on glass fiber filters. Pt/TiO2 nanoparticles (0–1.5 wt.% Pt content) were produced by flame spray pyrolysis, starting from liquid solutions of the Ti and Pt precursors, and then expanded in a supersonic beam to be deposited on the filters. The nanostructured coatings were composed of crystalline nanoparticles (mainly anatase phase), without any need of post-deposition annealing. The so obtained photocatalytic membranes were tested in hydrogen production by photo-steam reforming of ethanol in an expressly set-up diffusive photoreactor. The reaction rate was found to increase with increasing the Pt content in the photoactive material, up to 1.5 wt.% Pt. The use of these membranes allowed a significant increase of the hydrogen production rate compared to that obtained with the same photoactive Pt/TiO2 films deposited on a quartz substrate.
    International Journal of Hydrogen Energy 08/2014; 39(25):13098–13104. DOI:10.1016/j.ijhydene.2014.06.088 · 2.93 Impact Factor
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    ABSTRACT: The ionization dynamics of He nanodroplets irradiated with intense femtosecond extreme ultraviolet pulses of up to 1013 W/cm2 power density have been investigated by photoelectron spectroscopy. Helium droplets were resonantly excited to atomiclike 2p states with a photon energy of 21.4 eV, below the ionization potential (Ip), and directly into the ionization continuum with 42.8 eV photons. While electron emission following direct ionization above Ip is well explained within a model based on a sequence of direct electron emission events, the resonant excitation provides evidence of a new, collective ionization mechanism involving many excited atomiclike 2p states. With increasing power density the direct photoline due to an interatomic Coulombic decay disappears. It indicates that ionization occurs due to energy exchange between at least three excited atoms proceeding on a femtosecond time scale. In agreement with recent theoretical work the novel ionization process is very efficient and it is expected to be important for many other systems.
    Physical Review Letters 02/2014; 112(7):073401. DOI:10.1103/PhysRevLett.112.073401 · 7.73 Impact Factor
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    ABSTRACT: Free electron lasers (FELs) offer the unprecedented capability to study reaction dynamics and image the structure of complex systems. When multiple photons are absorbed in complex systems, a plasma-like state is formed where many atoms are ionized on a femtosecond timescale. If multiphoton absorption is resonantly-enhanced, the system becomes electronically-excited prior to plasma formation, with subsequent decay paths which have been scarcely investigated to date. Here, we show using helium nanodroplets as an example that these systems can decay by a new type of process, named collective autoionization. In addition, we show that this process is surprisingly efficient, leading to ion abundances much greater than that of direct single-photon ionization. This novel collective ionization process is expected to be important in many other complex systems, e.g. macromolecules and nanoparticles, exposed to high intensity radiation fields.
    Scientific Reports 01/2014; 4:3621. DOI:10.1038/srep03621 · 5.08 Impact Factor
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    ABSTRACT: The low density matter end-station at the new seeded free electron laser FERMI@Elettra is a versatile instrument for the study of atoms, molecules and clusters by means of electron and ion spectroscopies. Beams of atoms, molecules and helium droplets as well as clusters of atoms, molecules and metals can be produced by three different pulsed valves. The atomic and molecular beams may be seeded, and the clusters and droplets may be pure, or doped with other atoms and molecules. The electrons and ions produced by the ionization and fragmentation of the samples by the intense light of FERMI can be analysed by the available spectrometers, to give mass spectra and energy as well as angular distributions of charged particles. The design of the detector allows simultaneous detection of electrons and ions using velocity map imaging and time-of-flight techniques respectively. The instruments have a high energy/mass resolution and large solid-angle collection efficiency. We describe the current status of the apparatus and illustrate the potential for future experiments.
    Journal of Physics B Atomic Molecular and Optical Physics 08/2013; 46(16):164007. DOI:10.1088/0953-4075/46/16/164007 · 1.92 Impact Factor
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    ABSTRACT: The fabrication of a planar supercapacitor based on cluster-assembled nanostructured carbon (ns-C) thin films deposited by supersonic cluster beam deposition and ionic liquid as electrolyte has been demonstrated. Cluster-assembled carbon has a density of about 0.5 g/cm3 and a highly disordered structure with predominant sp2 hybridization, high surface roughness and granular nanoscale morphology. The electric double layer capacity of ns-C films (thickness variable in the range of 140–500 nm) was investigated by electrochemical impedance spectroscopy and cyclic voltammetry employing four different hydrophobic room-temperature ionic liquids featuring the same anion and with different cations as electrolyte. Evidence of good impregnation of the ns-C nanoporous matrix by the different ionic liquids was found. The highest EDL capacity, 75 F/g, was obtained by using [Bmim][NTf2], the ionic liquid with the shortest alkyl chain. Using [Bmim][NTf2] a supercapacitor with single electrode area of 0.2 cm2 and specific capacity of ∼80 μF/cm2 was obtained.
    Carbon 08/2013; 59:212-220. DOI:10.1016/j.carbon.2013.03.011 · 6.16 Impact Factor
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    ABSTRACT: A new design for targets employed in laser induced shock-compression experiments is presented. Numerical simulations to optimize target parameters and to clarify shock dynamics are realized. The experiments proved the new scheme is reliable and appropriate for reflectivity measurements of thermodynamical states lying out of the standard graphite or diamond Hugoniot: the final state reached in compression can be varied tuning the carbon layer characteristics (initial density and thickness) and the laser intensity, with the possibility to determine the reflectivity of carbon and the position on the phase diagram. An increase of reflectivity in carbon has been observed at 260 GPa and 14 000 K while no increase in reflectivity is found at 200 GPa and 20 000 K.
    The European Physical Journal D 07/2013; 67(7). DOI:10.1140/epjd/e2013-30630-8 · 1.40 Impact Factor
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    ABSTRACT: Nanostructured porous films of carbon with density of about 0.5 g/cm3 and 200 nm thickness were deposited at room temperature by supersonic cluster beam deposition (SCBD) from carbon clusters formed in the gas phase. Carbon film surface topography, determined by atomic force microscopy, reveals a surface roughness of 16 nm and a granular morphology arising from the low kinetic energy ballistic deposition regime. The material is characterized by a highly disordered carbon structure with predominant sp2 hybridization as evidenced by Raman spectroscopy. The interface properties of nanostructured carbon electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy employing KOH 1 M solution as aqueous electrolyte. An increase of the double layer capacitance is observed when the electrodes are heat treated in air or when a nanostructured nickel layer deposited by SCBD on top of a sputter deposited film of the same metal is employed as a current collector instead of a plain metallic film. This enhancement is consistent with an improved charge injection in the active material and is ascribed to the modification of the electrical contact at the interface between the carbon and the metal current collector. Specific capacitance values up to 120 F/g have been measured for the electrodes with nanostructured metal/carbon interface.
    Journal of Nanoparticle Research 02/2013; 15(2-2). DOI:10.1007/s11051-013-1429-4 · 2.28 Impact Factor
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    ABSTRACT: Riassunto. Il Centro Interdisciplinare Materiali e Interfacce Nanostrutturati (CIMaINa) dell’Universit`a degli Studi di Milano e il Museo Nazionale della Scienza e della Tecnologia “Leonardo da Vinci” di Milano, grazie al progetto europeo NanoToTouch, finanziato dall’Unione Europea all’interno del Settimo Programma Quadro, hanno inaugurato un vero e proprio laboratorio di ricerca (Open Nano Lab) all’interno del Museo. Il laboratorio, dedicato alla caratterizzazione di materiali nanostrutturati, ha lo scopo di creare un ambiente innovativo dove favorire l’incontro e il dialogo tra il pubblico del Museo e gli scienziati impegnati nella quotidiana attivit`a di ricerca nel campo delle nanoscienze. Il fascino delle nanotecnologie e la forte attualit`a delle ricerche legate all’ambito energetico condotte nell’Open Nano Lab suscitano ampio interesse e originano un’importante occasione di confronto e scambio tra esperti e non addetti ai lavori su temi di ampio interesse collettivo. Abstract. The Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) of the University of Milano and the National Science and Technology Museum “Leonardo da Vinci” are partners within the NanoToTouch project, an EU FP7 initiative with the aim of creating innovative environments for the broad public to learn about nanoscience and nanotechnology, and to discuss with active players in research fields of nanoscience. To this purpose, a research lab (Open Nano Lab) for nanostructured materials characterization was created inside the public space of the Museum, with a specifically designed layout to promote interaction between researchers of CIMaINa and visitors of the museum. The participation of the visitors owes to the curiosity and fascination of nanotechnology, with significant boost related to the choice of a topic attracting very strong interest from general public: nanotechnology for energy applications.
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    ABSTRACT: The electronic structure of cluster assembled nanostructured TiO{sub 2} thin films has been investigated by resonant photoemission experiments with photon energies across the Ti L{sub 2,3} edge. The samples were produced by supersonic cluster beam deposition with a pulsed microplasma cluster source. The valence band shows resonance enhancements in the binding energy region between 4 and 8 eV, populated by O 2p and hybridized Ti 3d states, and in the region about 1 eV below the Fermi level associated with defects related Ti 3d states. The data show that in as-deposited films Ti atoms are mainly fully (sixfolds) coordinated to oxygen atoms in octahedral symmetry and only a small fraction is in a broken symmetry environment. Since resonant photoemission is closely linked to the local electronic and structural configurations around the Ti atom, it is possible to correlate the resonant photoemission intensity and lineshape with the presence of defects of the films and with the degree of hybridization between the titanium and oxygen atoms.
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    ABSTRACT: The design and evaluation of a velocity map imaging spectrometer specifically optimised for experiments at the FERMI free electron laser source are described. Optimisation of the set-up for the detection of high energy electrons (experimentally calibrated up to 45 eV), reduction of scattered light and characterisation of the pulsed gas source are outlined. The instrument has been tested using synchrotron light at the GasPhase beamline at Elettra, the Italian synchrotron source, and the results are presented
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 08/2012; 284:69. DOI:10.1016/j.nimb.2011.07.020 · 1.19 Impact Factor
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    ABSTRACT: The fabrication of functional thin films and devices by direct deposition of nanoparticles from the gas phase is a promising approach enabling, for instance, the integration of complex analytical and sensing capabilities on microfabricated platforms. Aerosol-based techniques ensure large-scale nanoparticle production and they are potentially suited for this goal. However, they are not adequate in terms of fine control over the lateral resolution of the coatings, mild processing conditions (avoiding high temperature and aggressive chemicals), low contamination and compatibility with microfabrication processes. Here we report the high-rate and efficient production of functional nanostructured films by nanoparticle assembling obtained by the combination of flame spray pyrolysis and supersonic expansion. Our approach merges the advantages of flame spray pyrolysis for bulk nanopowders such as process stability and wide material library availability with those of supersonic cluster beam deposition in terms of lateral resolution and of direct integration of nanomaterials on devices. We efficiently produced nanostructured films and devices (such as gas sensors) using metal oxide, pure noble metal and oxide-supported noble metal nanoparticles.
    Nanotechnology 05/2012; 23(18):185603. DOI:10.1088/0957-4484/23/18/185603 · 3.67 Impact Factor
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    ABSTRACT: The presence and stability of sp hybridized atoms in free carbon nanoparticles was investigated by NEXAFS spectroscopy. The experiments show that a predominant fraction of carbon atoms is found in linear sp-chains and that conversion into sp(2) structures proceeds already at low temperature and in the gas phase.
    Chemical Communications 03/2011; 47(10):2952-4. DOI:10.1039/c0cc03778h · 6.38 Impact Factor
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    ABSTRACT: In this paper a method for the quantitative determination of a morphology descriptor of free clusters with complex nanostructure is presented and applied to transition metal nanoparticles produced by a pulsed vaporization source. The method, which is based on the low-pressure aerodynamic mobility of neutral particles, can be applied as a characterization tool to a broad class of gas-phase nanoparticle sources for on-line investigation of particle growth and for quantifying coalescence versus agglomerate aggregation. We report on the application of this method for the characterization of free titanium clusters produced by a pulsed microplasma cluster source in the size range of approximately 300–6000 atoms. The clusters have an open fractal-like structure, with the fractal dimension depending on their thermal history during growth and evolving towards softer aggregates for longer residence times where lower-temperature conditions characterize the growth environment.
    New Journal of Physics 02/2011; 13(2):023009. DOI:10.1088/1367-2630/13/2/023009 · 3.67 Impact Factor
  • P. Piseri, E. Barborini, P. Milani
    MRS Online Proceeding Library 01/2011; 400. DOI:10.1557/PROC-400-59
  • MRS Online Proceeding Library 01/2011; 593. DOI:10.1557/PROC-593-75
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    ABSTRACT: We have investigated the ionization of the Ar atom by 51 nm extreme-ultraviolet light pulses at the free-electron laser facility, SPring-8 Compact SASE Source test accelerator, in Japan. The angle-resolved photoelectron spectra contain lines due to sequential three-photon double ionization with the second ionization step proceeding via the resonantly enhanced two-photon absorption. The relative intensities of the corresponding photoelectron peaks and their angular dependence are explained in the framework of a three-step model of the process.
    Journal of Physics B Atomic Molecular and Optical Physics 05/2010; 43(11):111001. DOI:10.1088/0953-4075/43/11/111001 · 1.92 Impact Factor
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    ABSTRACT: The photocatalytic activity of thin, nanostructured films of titanium dioxide, synthesized by supersonic cluster beam deposition (SCBD) from the gas phase, has been investigated employing the photodegradation of salicylic acid as test reaction. Because of the low deposition energy, the so-deposited highly porous TiO2 films are composed of nanoparticles maintaining their original properties in the film, which can be fully controlled by tuning the deposition and post-deposition treatment conditions. A systematic investigation on the evolution of light absorption properties and photoactivity of the films in relation to their morphology, determined by AFM analysis, and phase composition, determined by Raman spectroscopy, has been performed. The absorption and photocatalytic activity of the nanostructured films in the visible region could be enhanced either through post-deposition annealing treatment in ammonia containing atmosphere or employing mild oxidation conditions, followed by annealing in N2 at 600°C.
    Journal of Nanoparticle Research 08/2009; 11(6):1339-1348. DOI:10.1007/s11051-009-9691-1 · 2.28 Impact Factor
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    ABSTRACT: Ab initio calculations within density-functional theory combined with experimental Raman spectra on cluster-beam deposited pure-carbon films provide a consistent picture of sp-carbon chains stabilized by sp;{3} or sp;{2} terminations, the latter being sensitive to torsional strain. This unexplored effect promises many exciting applications since it allows one to modify the conductive states near the Fermi level and to switch on and off the on-chain pi-electron magnetism.
    Physical Review Letters 07/2009; 102(24):245502. DOI:10.1103/PhysRevLett.102.245502 · 7.73 Impact Factor
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    ABSTRACT: Ab-initio calculations within Density Functional Theory combined with experimental Raman spectra on cluster-beam deposited pure carbon films provide a consistent picture of sp-carbon chains stabilized by sp^3 or sp^2 terminations, the latter being sensitive to torsional strain. This unexplored effect promises many exciting applications since it allows one to modify the conductive states near the Fermi level and to switch on and off the on-chain pi-electron magnetism. Comment: in print in Phys Rev Lett

Publication Stats

2k Citations
321.57 Total Impact Points

Institutions

  • 1996–2014
    • University of Milan
      • Department of Physics
      Milano, Lombardy, Italy
  • 2010
    • Tohoku University
      • Institute of Multidisciplinary Research for Advanced Materials (IMRAM)
      Sendai-shi, Miyagi-ken, Japan
  • 1999–2006
    • Politecnico di Milano
      • Department of Energy
      Milano, Lombardy, Italy
  • 2004
    • Università degli Studi di Milano-Bicocca
      Milano, Lombardy, Italy