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published August 26, 2014
posted in Papers - 2014
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Free-radical selective functionalization of 1,4-naphthoquinones by perfluorodiacyl peroxides

Cover image Tetrahedron

Author(s): Maurizio Sansotera, Cristian Gambarotti, Antonino Famulari, Alberto Baggioli, Raffaella Soave, Francesco Venturini, Stefano V. Meille, Ivan Wlassics, Walter Navarrini

Source: Tetrahedron

Volume: 70 Pages: 5298-5309

Published: Aug (2014)

DOI: 10.1016/j.tet.2014.05.024

 

ABSTRACT:

Perfluoroalkyl radicals, generated by thermal decomposition of perfluorodiacyl peroxides, react selectively with quinone rings of 1,4-naphthoquinones. In the presence of a non-conjugated alkene such as 1-hexene, perfluoroalkyl radicals add to the double bonds of the olefin forming a radical adduct, which selectively adds to the naphthoquinone ring. Several perfluorodiacyl peroxides have been synthesized and used for the direct and alkene-mediated functionalization of naphthoquinones. Geometrical parameters and electron density topology of all perfluorodiacyl peroxides have been calculated by the density functional formalism and quantum theory of atoms in molecules to attempt a rationalization of the experimental reactivity.

published July 15, 2014
posted in Carbon Functionalization, Fuel-Cell, Papers - 2014
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Perfluoropolyether-functionalized gas diffusion layers for proton exchange membrane fuel cells

Author(s): Massimo Gola, Maurizio Sansotera, Walter Navarribi, Claudia L. Bianchi, Paola Gallo Stampino, Saverio Latorrata, Giovanni Dotelli

Source: Journal of Power Sources

Volume: 258 Pages: 351-355

Published: Jul (2014)

DOI: 10.1016/j.jpowsour.2014.02.025

 

ABSTRACT:

Linear perfluoropolyether (PFPE) peroxide was used to confer superhydrophobic surface properties to gas diffusion layer (GDL) by means of direct functionalization of a GDL based on carbon cloth (CC) material. The thermal decomposition of a linear PFPE peroxide produces linear PFPE radicals that covalently bond the unsaturated moieties on the surface. Perfluorinated radicals are directly and covalently bound to the carbonaceous structure of the CC without any spacer that could decrease both thermal and chemical stability of the GDL. The obtained CC hydrophobicity exceeded the superhydrophobicity threshold and was enduringly stable. The relationship between the linkage of fluorinated chains and the variations of surface chemical?physical properties were studied combining X-ray photoelectron spectroscopy (XPS), resistivity measurements, scanning electron microscopy (SEM) and contact angle measurements. Despite the excellent insulating properties of the PFPE polymer, the functionalized carbonaceous materials substantially retained their conductive properties. The PFPE-modified GDLs were tested in a single fuel cell at the lab scale. The cell tests were run at two temperatures (60C and 80C) with a relative humidity (RH) of hydrogen and air feeding gases equal to 80/100% and 60/100%, respectively.

published April 27, 2014
posted in Papers - 2014, Photochemistry
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Decomposition of perfluorooctanoic acid photocatalyzed by titanium dioxide: Chemical modification of the catalyst surface induced by fluoride ions

Cover image Applied Catalysis B: Environmental

Author(s): Maurizio Sansotera, Federico Persico, Carlo Pirola, Walter Navarrini, Alessandro Di Michele, Claudia L. Bianchi

Source: Applied Catalysis B: Environmental

Volume: 148-149 Pages: 29-35

Published: Apr (2014)

DOI: 10.1016/j.apcatb.2013.10.038

 

ABSTRACT:

The degradation of perfluorooctanoic acid (PFOA) in water was investigated both as photolysis and photocatalysis by slurry titanium dioxide. Different surfactant concentrations, the catalyst nature and concentration as well as the irradiation power of the UV lamp were evaluated. The reactions were conducted using merely the natural dissolved oxygen (DO), in order to simulate conditions of non-enriched water, as industrially feasible. The photomineralization of PFOA was monitored by total organic carbon (TOC) analysis and ionic chromatography (IC). Finally, the photocatalytic powder was analyzed at different reaction times by X-ray photoelectron spectroscopy (XPS) and by X-ray powder diffraction (XRD) technique in order to study and interpret the catalyst deactivation phenomena occurred during the treatment.

published February 17, 2014
posted in FLICE, Papers - 2014
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Maskless, fast and highly selective etching of fused silica with gaseous fluorine and gaseous hydrogen fluoride

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Cover image Author(s): Francesco Venturini, Rebeca Martinez Vazquez, Roberto Osellame, Giulio Cerullo, Maurizio Sansotera and Walter Navarrini

Source: Journal of Micromechanics and Microengineering

Volume: 24 Issue:2 – 025004 (7 pp)

Published: Feb (2014)

DOI: 10.1088/0960-1317/24/2/025004

 

ABSTRACT:

In this paper, we have directly buried microchannels in a fused silica substrate using femtosecond laser irradiation followed by chemical etching. By exploiting a synergic effect between gaseous hydrofluoric acid and fluorine (F2), we have obtained microchannels having an outstanding aspect ratio of 86 with a relative etching speed of 17m min?1. Using fluorine we successfully regenerated the etchant ‘in situ‘, thus providing a way to control the bore shape, in particular, the strong conically shaped microchannel can be adjusted by modifying the etching mixture composition. We have avoided water formation during the microchannel construction, thus overcoming one of the major limits that prevents any further increase in the length and the aspect ratio.