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T Caruso,
C Lenardi,
R G Agostino,
M Amati,
G Bongiorno,
T Mazza,
A Policicchio,
V Formoso, E Maccallini,
E Colavita,
G Chiarello,
P Finetti,
F Sutara,
T Skála,
P Piseri,
K C Prince,
P Milani
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Fuel. 01/2012;
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ABSTRACT: We report on the reorganization and bundling of titanium oxide nanostructured layers, induced by wetting with different solvents and subsequent drying. TiO(2) layers are deposited by pulsed laser deposition and are characterized by vertically oriented, columnar-like structures resulting from assembling of nanosized particles; capillary forces acting during evaporation induce bundling of these structures and lead to a micrometer-size patterning with statistically uniform islands separated by channels. The resulting surface is characterized by a hierarchical, multiscale morphology over the nanometer-micrometer length range. The structural features of the pattern, i.e., characteristic length, island size, and channel width, are shown to depend on properties of the liquid (i.e., surface tension) and thickness and density of the TiO(2) layers. The studied phenomenon permits the controlled production of multiscale hierarchically patterned surfaces of nanostructured TiO(2) with large porosity and large surface area, characterized by superhydrophilic wetting behavior without need for UV irradiation.
Langmuir 03/2011; 27(5):1935-41. · 4.19 Impact Factor
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ABSTRACT: Titanium dioxide Surface structure and defects Pulsed laser deposition PLD Electron spectroscopy UPS XPS X-ray absorption spectroscopy XAS NEXAFS Synchrotron radiation Titanium oxide nanostructured thin films synthesized by pulsed laser deposition (PLD) were here characterized with a multi-technique approach to investigate the relation between surface electronic, structural and morphological properties. Depending on the growth parameters, these films present characteristic morphologies ranging from compact to columnar and to an extremely open structure. As-deposited films have a disordered structure both in the bulk and on the surface, as shown by Raman spectroscopy and by the fine structure of X-ray absorption spectra near the Ti and O edge (NEXAFS). The surface reactivity towards the atmosphere, with consequent formation of surface hydroxyl terminal groups, turns out to be dependent not only on the effective surface but also on the surface structure. By ultraviolet photoemission spectroscopy, we observed that, depending on the sample structure and morphology, defect states at 1 eV binding energy in the valence band can be induced by exposing the samples to the intense synchrotron photon beam. After annealing in air at 673 K, the structural order increases towards a mainly anatase phase in which the presence of rutile increases in films with a more open morphology. Such structural modifications influence the surface stability since the defect formation in the valence band is strongly reduced in all the annealed films, and it is completely hindered in the most compact films.
11/2010;
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T Caruso,
C Lenardi,
R G Agostino,
M Amati,
G Bongiorno,
T Mazza,
A Policicchio,
V Formoso, E Maccallini,
E Colavita,
G Chiarello,
P Finetti,
F Sutara,
T Skála,
P Piseri,
K C Prince,
P Milani
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ABSTRACT: The electronic structure of cluster assembled nanostructured TiO(2) thin films has been investigated by resonant photoemission experiments with photon energies across the Ti L(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.
The Journal of Chemical Physics 04/2008; 128(9):094704. · 3.33 Impact Factor
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Journal of Physics Conference Series 01/2008; 100(PART 5).
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G Chiarello, E Maccallini,
R G Agostino,
T Caruso,
V Formoso,
L Papagno,
E Colavita,
A Goldoni,
R Larciprete,
S Lizzit,
L Petaccia
Physical Review B - Condensed Matter and Materials Physics. 01/2004; 69(15):153409-1-153409-4.
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G CHIARELLO, E MACCALLINI,
R G AGOSTINO,
V FORMOSO,
A CUPOLILLO,
L PAPAGNO,
E COLAVITA,
L PETACCIA,
R LARCIPRETE,
S LIZZIT,
A GOLDONI
Carbon 01/2003; 41:985-992. · 5.38 Impact Factor
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G. Chiarello, E. Maccallini,
R.G. Agostino,
V. Formoso,
A. Cupolillo,
D. Pacilé,
E. Colavita,
L. Papagno,
L. Petaccia,
R. Larciprete,
S. Lizzit,
A. Goldoni
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ABSTRACT: We investigated the electronic and vibrational properties of single wall carbon nanotubes by reflection electron energy loss and X-ray absorption spectroscopies. We report on single particle excitations measured at the C-1s edge and on collective excitations of the valence band region. The comparison between the two techniques allows us to locate empty electronic states of the carbonaceous sample. Loss spectra taken in the infrared region reveal two loss features at 90 and 170 meV assigned to the excitation of optical phonon modes.
Carbon. 41(5):985-992.
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ABSTRACT: The effect of the textural properties and morphology of zeolite Y, used as support of iron (Fe) or cobalt (Co) oxides, on the quantity and quality of the multi-wall carbon nanotubes (MWNTs) synthesized by catalytic chemical vapour deposition (CCVD) of acetylene was studied. The parent zeolite Y was modified by various dealumination procedures, namely hydrothermal treatment (steaming), treatment with ammonium hexafluorosilicate (AHFS) and combined steaming-AHFS. The ion-exchange and wet impregnation methods were used for supporting the metals on the zeolite Y samples, with the latter method providing the most effective catalysts for carbon nanotube (CNT) formation. Severe dealumination of zeolite-Y by steaming, which induced the formation of secondary meso/macropores and of relatively large particles/aggregates, resulted in significant decrease in the formation of CNTs compared to the catalysts based on the parent zeolite-Y. Post-treatment of the steamed samples with AHFS had no beneficial effect on the catalysts’ activity. Moderate dealumination of the parent zeolite Y by AHFS also inhibited the formation of CNTs, but to a lesser extent compared to the catalysts based on steamed zeolite Y. The TGA studies revealed the presence of carbon phases with different thermal stability in the zeolite–CNT composites, ranging from amorphous carbon to well-graphitized MWNTs. TEM images and micro-Raman spectra taken right after growth confirmed the formation of high quality MWNTs with a low degree of disorder irrespective of the catalysts used, the degree of dealumination of the zeolite Y and the textural and morphological characteristics of the zeolitic support.
