Selective Iterative Etching of Fused Silica with Gaseous Hydrofluoric Acid.

Author(s): Venturini, Francesco; Navarrini, Walter; Resnati, Giuseppe; Metrangolo, Pierangelo; Vazquez, Rebeca Martinez; Osellame, Roberto; Cerullo, Giulio.

Source: JOURNAL OF PHYSICAL CHEMISTRY C

Volume: 114 Issue: 43 Pages: 18712-18716

DOI: 10.1021/jp107055s

Published: NOV 4 2010

ABSTRACT:

Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrofluoric acid (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels. With liquid HF, the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of approximate to 1.5 mm. A strategy to overcome this limitation would be to perform iterative etching, periodically removing the exhausted products and replenishing the partially etched channel with fresh acid; this procedure is, however, quite cumbersome in the liquid phase. In this paper we present what is to our knowledge the first implementation of the FLICE technique with low-pressure gaseous HF etchant. The use of a gas-phase etchant naturally lends itself to the application of iterative etching techniques, since it is very easy to remove the etchant, by pumping vacuum in the reaction chamber after each etching step. We demonstrate that iterative etching in the gas phase overcomes the limitations of wet etching and allows to achieve nearly constant etching rate for a microchannel length up to approximate to 3 mm.

http://pubs.acs.org/doi/abs/10.1021/jp107055s

Hydrophobic carbonaceous materials obtained by covalent bonding of perfluorocarbon and perfluoropolyether chains.

Author(s): Sansotera, Maurizio; Navarrini, Walter; Magagnin, Luca; Bianchi, Claudia L.; Sanguineti, Aldo; Metrangolo, Pierangelo; Resnati, Giuseppe.

Source: JOURNAL OF MATERIALS CHEMISTRY.

Volume: 20 Issue: 39 Pages: 8607-8616.

DOI: 10.1039/c0jm02077j. Published: 2010

ABSTRACT:

Perfluorocarbon residues, i.e. perfluoroethyl (PFE), CF(3)CF(2)-, perfluoro-n-propyl (PFnP), CF(3)CF(2)CF(2)-, perfluoro-isopropyl (PFiP), (CF(3))(2)CF-, and perfluoropolyether (PFPE) chains, e. g. (CF(2)CF(2)O)(m)(CF(2)O)(n), were covalently bonded on the surface of carbon black (CB) and diamond-like carbon (DLC) using PFPE and perfluorodiacyl (PFDA) peroxides. The thermal decomposition of the peroxidic moieties of these perfluorinated peroxides generated reactive perfluorinated radicals. The perfluorinated free radicals could directly bond to the sp(2) sites avoiding any spacer, which usually decreases both thermal and chemical stabilities of the resulting materials. The effects of chemical treatment on the carbonaceous materials were studied using X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Contact Angle (CA) measurements. The surface areas of CB powders were determined by the BET technique; the morphology of the DLC coatings was evaluated by Atomic Force Microscopy (AFM) and the friction forces were measured by means of Lateral Force Microscopy (LFM).

http://pubs.rsc.org/en/Content/ArticleLanding/2010/JM/c0jm02077j#!divAbstract

Preparation and characterization of superhydrophobic conductive fluorinated carbon blacks.

Author(s): SANSOTERA M., NAVARRINI W., RESNATI G., METRANGOLO P., FAMULARI A., BIANCHI C. L., GUARDA P. A.

Source: Carbon.

Volume: 48 Issue: 15 Pages: 4382-4390.

DOI: 10.1016/j.carbon.2010.07.052. Published: Dec. (2010).

ABSTRACT:

Superhydrophobic conductive carbon blacks were prepared by covalent bonding of perfluorocarbon and perfluoropolyether chains on the conductive carbon black surface. Perfluorodiacyl and perfluoropolyether peroxides were used as reagents for the chemical treatment. Their thermal decomposition produced respectively, perfluoroalkyl and perfluoropolyether radicals that directly bonded the polycyclic aromatic structure of carbon black surface. Measurements of contact angles with water on molded pellets made with carbon black powder demonstrated that water droplets were enduringly stable on the treated carbon blacks. Contact angle values were significantly high, exceeding the superhydrophobicity threshold. On the contrary, the droplets were adsorbed in few seconds by the native carbon black. Conductivity measurements showed that the covalent linkage of fluorinated chains weakly modified the electrical properties of the conductive carbon black, even if the surface properties changed so deeply. The relationship between the linkage of fluorinated chains and the variations of physical?chemical properties were studied combining electron spectroscopy, resistivity measurements, X-ray diffraction, scanning electron microscopy, surface area analysis and thermal gravimetric analysis. The superhydrophobic conductive carbon blacks were compared with a superhydrophobic carbon black obtained by direct fluorination of conductive carbon black with elemental fluorine, F2.

http://www.sciencedirect.com/science/article/pii/S0008622310005567

Low surface energy coatings covalently bonded on diamond-like carbon films

Author(s):Navarrini, Walter; Bianchi, Claudia L.; Magagnin, Luca; Nobili, Luca; Carignano, Gabriella; Metrangolo, Pierangelo; Resnati, Giuseppe; Sansotera, Maurizio.

Source: DIAMOND AND RELATED MATERIALS

Volume: 19 Issue: 4 Pages: 336-341

DOI: 10.1016/j.diamond.2010.01.004 Published: APR 2010

ABSTRACT:

In the present work, a chemical treatment with perfluorinated peroxides is proposed to obtain protective layers covalently linked to a diamond-like carbon (DLC) surface. The lubricant properties of perfiuorinated compounds and the stability of the chemical modification of DLC surface simultaneously cooperate in this technical approach. Each fluorinated layer is deposed on an bare DLC surface by a dip coating application technique and the covalent linkage of the fluorinated layers is obtained by the thermal decomposition of the peroxidic moieties of the perfluorinated peroxides. Reactive perfluorinated radicals are generated close to the sp(2) sites of the DLC surface, allowing the formation of covalent bonds. The fluorinated peroxides used in this work belong to the class of the PIPE peroxides and to the class of the perfluorodiacyl (PFDA) peroxides. The effect of the fluorinated coatings on the DLC surface is studied using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), with contact angle (CA) measurements and, in particular, the friction forces are evaluated by means of lateral force microscopy (LFM).

http://www.sciencedirect.com/science/article/pii/S0925963510000130

Linear and branched perfluoropolyether coatings on diamond-like carbon films: covalent linkage and physical deposition.

Author(s): NAVARRINI W., SANSOTERA M., VENTURINI F., BIANCHI C. L., GUARDA P. A., RESNATI G.

Source: Chimica Oggi – Chemistry Today.

Volume: 28 Pages: 24-27. Published: Apr (2010).

ABSTRACT:

The progresses in the magnetic media technology brought to the application of liquid lubricant films on diamond-like carbon (DLC) coatings. Hard surfaces are typically lubricated with fluorinated or perfluorinated organic compounds, such as perfluoropolyethers (PFPE). Many attempts have been done to obtain a stable layer of PFPE lubricant on the DLC surface by dip-coating or by vapour deposition so as to minimize any friction and wear . Diamond-like carbons are formed by an amorphous mixture of sp3 and sp2 hybridized carbon atoms with hydrogen atoms incorporated in the structure (a-C:H DLC). We have established a specific methodology for the straight-forward introduction of perfluorinated groups with carbon-carbon bond formation on a variety of unsaturated materials . Indeed, by using this methodology, perfluorinated radicals can directly bond to the sp2 sites of the DLC structure avoiding any spacer, that usually decreases both thermal and chemical stabilities of the resulting fluorinated layers .

Linear and branched perfluoropolyether coatings on diamond-like carbon films: covalent linkage and physical deposition

Author(s):Navarrini, Walter; Sansotera, Maurizio; Venturini, Francesco; Bianchi, Claudia L.; Guarda, Antonio;Resnati, Giuseppe.

Source: CHIMICA OGGI-CHEMISTRY TODAY

Volume: 28 Issue: 2 Pages: 24- Published: MAR-APR 2010

ABSTRACT:

The progresses in the magnetic media technology brought to the application of liquid lubricant films on diamond-like carbon (DLC) coatings Hard surfaces are typically lubricated with fluorinated or perfluorinated organic compounds, such as perfluoropolyethers (PFPE). Many attempts have been done to obtain a stable layer of PFPE lubricant on the DLC surface by dip-coating or by vapour deposition so as to minimize any friction and wear. Diamond-like carbons are formed by an amorphous mixture of sp(3) and sp(2) hybridized carbon atoms with hydrogen atoms incorporated in the structure (a-C H DLC). We have established a specific methodology for the straight-forward introduction of perfluorinated groups with carbon-carbon bond formation on a variety of unsaturated materials. Indeed, by using this methodology, perfluorinated radicals can directly bond to the sp(2) sites of the DLC structure avoiding any spacer, that usually decreases both thermal and chemical stabilities of the resulting fluorinated layers.

The little, juvenile and aggressive “fluorine atom” is growing up

Author(s): Navarrini, Walter.

Source: CHIMICA OGGI-CHEMISTRY TODAY Volume: 28 Issue: 2 Pages: 2-2 Published: MAR-APR 2010

Nanostructured TiO2 modified by perfluoropolyethers: Gas phase photocatalytic activity

Author(s): Bianchi, Claudia L.; Ardizzone, Silvia; Cappelletti, Giuseppe; Cerrato, Giuseppina; Navarrini, Walter; Sansotera, Maurizio.

Source: JOURNAL OF MATERIALS RESEARCH

Volume: 25 Issue: 1 Special Issue: SI Pages: 96-103

DOI: 10.1557/JMR.2010.0008 Published: JAN 2010

ABSTRACT:

A high-molecular-weight perfluoropolyether (PFPE-YR) and a perfluoropolyether containing ammonium phosphate (PFPE-F10) have been evaluated as fluorinated coating for high-surface-area titanium oxides. Coated nano-TiO2 shows hydrophobic properties and excellent buoyancy on water. In addition to photoactivity toward the degradation of toluene in gas phase, specific trial analyses have been completed to estimate the modified titanium oxide features. Brunauer-Emmett-Teller (BET) analysis for the surface area determination, ultraviolet-visible spectroscopy (UV-Vis) for the material electronic band gap, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) for the morphology, structure, and surface composition, respectively, and water contact angle and infrared (IR) analysis have been performed to estimate the wettability and stability of coated titanium.

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7938175