Concentrated sunlight for accelerated stability testing of organic photovoltaic materials: towards decoupling light intensity and temperature

Author(s): I. Visoly-Fisher, A. Mescheloff, M. Gabay, C. Bounioux, L. Zeiri, M.Sansotera, A.E. Goryachev, A. Braun, Y. Galagan, E.A. Katz

Source: Solar Energy Materials & Solar Cells
Volume: 134 Pages: 99-107
Published: Mar (2015)
DOI: 10.1016/j.solmat.2014.11.033

ABSTRACT:

We have demonstrated accelerated degradation studies of organic photovoltaic materials using concentrated sunlight, where the atmosphere, temperature and illumination intensity were independently controlled. Testing various schemes for controlling the sample temperature under concentrated sunlight showed that heating of P3HT:PCBM was caused by photons at the absorbed wavelength range and dissipation of excess photon energy, and not necessarily by IR photon absorption. Sunlight chopping was found to be an effective method for independent temperature control under illumination by concentrated sunlight.
The first accelerated degradation tests using sunlight concentration applied to P3HT:PCBM blends were reported. P3HT:PCBM blends exposed to concentrated sunlight in the presence of traces of oxygen/ humidity showed degradation induced by photo-oxidation of the P3HT backbone within the P3HT:PCBM blend, which is significantly thermally accelerated, in agreement with previous observations. However, this could be demonstrated in a time scale of minutes and hours, that is, significantly accelerated. Exposure of well encapsulated P3HT:PCBM films to concentrated sunlight demonstrated stability up to 3,600 sun?hours, corresponding to about 1.6 years of operating time. This result was obtained at 300 suns exposure after merely 12 h, demonstrating the advantage of using concentrated sunlight for accelerated stability tests. These tests can therefore combine extremely high acceleration factors with profound understanding of the effect of various, independently controlled factors on the degradation mechanisms.

Surface fluorination on TiO2 catalyst induced by photodegradation of perfluorooctanoic acid

Author(s): Sara Gatto, Maurizio Sansotera, Federico Persico, Massimo Gola, Carlo Pirola, Walter Panzeri, Walter Navarrini, Claudia L. Bianchi

Source: Catalysis Today
Volume: 241 Pages: 8-14
Published: Mar (2015)
DOI: 10.1016/j.cattod.2014.04.031

ABSTRACT:

The photoabatement of perfluorooctanoic acid in aqueous solution has been performed with a commercial nano-sized TiO2-based photocatalyst content of 0.66 g/L under an UV irradiation of 95 W/m2. PFOA degradation intermediates were investigated by HPLC-MS and 19F-NMR analysis. Evidences of adegradation mechanism based on two competitive pathways are discussed: photo-redox and beta-scission pathways. Shorter perfluorinated carboxylic acids, CnF2n+1COOH (n = 1-6), as expected degradation intermediates, were identified and their concentration trends over time were determined. The apparent pseudo-first order kinetic constant expressed as rate of PFOA disappearance was also measured: kapp 0.1296 h-1. The influence of fluoride ions on TiO2 surface was analyzed by XPS technique, revealing asurface modification that affects the performances of the catalyst.

Photocatalytic activity of TiO2-embedded fluorinated transparentcoating for oxidation of hydrosoluble pollutants in turbid suspensions

Author(s): Federico Persico, Maurizio Sansotera, Claudia L. Bianchi, Carlo Cavallotti, Walter Navarrini

Source: Applied Catalysis B: Environmental
Volume: 170 Pages: 83-89
Published: Jan (2015)
DOI: 10.1016/j.apcatb.2015.01.033

ABSTRACT:

The photodegradative activity of titanium dioxide immobilized into a multilayered transparent fluoropolymeric matrix was studied. The photoactive coating was developed by applying a TiO₂-containing fluorinated ionomeric dispersion and a perfluorinated amorphous polymer in an appropriate sequence directly on the UV source. The multilayered coating photocatalytic activity toward hydrosoluble organic pollutants was evaluated in clear as well as in highly turbid conditions obtained by dispersing barium sulfate microparticles in the polluted solution. Rhodamine B-base was chosen as reference organic pollutant. The photoabatement rates with TiO₂-embedded fluorinated coating in clear solution and turbid conditions were 0.0923 min^-1 and 0.0546 min^-1, respectively. In both clear and turbid conditions, TiO₂-embedded transparent coating revealed higher photocatalytic activity than merely dispersed TiO₂. This behavior was particularly evident at low pollutant concentrations. In addition, catalyst immobilization prevented TiO₂ separation and catalyst losses, allowing the development of a simple and efficientcontinuous apparatus.

Free-radical selective functionalization of 1,4-naphthoquinones by perfluorodiacyl peroxides

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.

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.

Decomposition of perfluorooctanoic acid photocatalyzed by titanium dioxide: Chemical modification of the catalyst surface induced by fluoride ions

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.

Effect of amorphous fluorinated coatings on photocatalytic properties of anodized titanium surfaces.

Author(s): PERSICO F., SANSOTERA M., DIAMANTI M. V., MAGAGNIN L., VENTURINI F., NAVARRINI W.

Source: THIN SOLID FILMS

Volume: 545 Pages: 210-216

DOI:10.1016/j.tsf.2013.08.004

ABSTRACT:

The photocatalytic activity promoted by anodized titanium surfaces coated with different amorphous perfluoropolymers was evaluated. A copolymer between tetrafluoroethylene and perfluoro-4-trifluoromethoxy-1,3-dioxole and two perfluoropolyethers containing ammonium phosphate and triethoxysilane functionalities, respectively, were tested as coating materials. These coatings revealed good adhesion to the anodized titanium substrate and conferred to it both hydrophobicity and oleophobicity. The photocatalytic activity of the coating on anodized titanium was evaluated by monitoring the degradation of stearic acid via Infrared spectroscopy. The degradation rate of stearic acid was reduced but not set to zero by the presence of the fluorinated coatings, leading to the development of advanced functional coatings. The morphological variations of the coatings as a result of photocatalysis were also determined by atomic force microscopy.

http://www.sciencedirect.com/science/article/pii/S0040609013012960#

Functionalization of multi-walled carbon nanotubes with perfluoropolyether peroxide to produce superhydrophobic properties

Author(s): TALAEEMASHHADI S.; SANSOTERA M.; GAMBAROTTI C.; FAMULARI A.; BIANCHI C. L.; GUARDA P. A.; NAVARRINI W.

Source: CARBON

Volume: 59 Pages: 150-159

DOI: 10.1016/j.carbon.2013.03.003 Published: AUG 2013

ABSTRACT:

Multi-walled carbon nanotubes (MWCNTs) have been functionalized through perfluoropolyether (PEPE) radicals obtained by thermal decomposition of linear PFPE peroxide. The reactivity of MWCNTs with PFPE peroxide has been compared with the direct fluorination of MWCNTs using elemental fluorine in mild conditions. The experimental results indicated that the functionalization with PFPE peroxide and the direct fluorination with elemental fluorine were suitable techniques to modify and control the physical-chemical properties of MWCNTs. After the introduction of PFPE chains on the MWCNT surface, the wettability of MWCNTs changed from hydrophilic to superhydrophobic, because the low surface energy properties of PFPE were transferred to the MWCNT surface. However, the linkage of PFPE chains weakly influenced the electrical properties of conductive MWCNTs. The amount of PFPE chains linked to the carbon nanotubes, the PFPE fluids obtained by homocoupling side-reactions and the decomposed portion of PFPE have been evaluated by mass balance. The modified MWCNTs have been characterized by X-ray photoelectron spectroscopy, thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, contact angle and surface area measurements. The effects of the chemical treatment on the conductive properties of MWCNTs have been studied by resistivity measurements at different applied pressures.

http://www.sciencedirect.com/science/article/pii/S0008622313002078

Electrodeposition of Fe-Ga thin films from eutectic-based ionic liquid.

Author(s): ZHAO F., FRANZ S., VICENZO A., BESTETTI M., VENTURINI F., CAVALLOTTI P. L.

Source: Electrochimica Acta.

doi:10.1016/j.electacta.2013.07.172 (2013).

ABSTRACT:

In the present work, a novel process for Fe-Ga thin films electrodeposition is addressed and the magnetic properties of the films are studied. The electrodeposition was carried out under ambient conditions using an ionic liquid electrolyte consisting of a mixture of choline chloride and ethylene glycol in the molar ratio 1:2, containing 0.3 M FeCl2 and 0.1 M GaCl3, either in the absence or in the presence of oxalic acid at 4 or 17 mM concentration. The effect of oxalic acid on the discharge reaction of the single ionic species Fe2+ and Ga3+ and on their codeposition was investigated by linear sweep voltammetry, suggesting a specific action of oxalic acid on the cathodic reduction of Ga3+ ionic species. Depending on deposition potential and oxalic acid concentration, alloy films with Ga content variable in the range up to about 20 at.% could be obtained. The Fe-Ga thin films showed a disordered body-cantered cubic phase (A2) with (110) preferred orientation and columnar microstructure, with a drastic change from pyramidal to granular surface morphology revealed raising the deposition potential. No superlattice reflections, indicating the formation of the D03 structure, were observed. A vibrating sample magnetometer was employed to measure hysteresis loops by applying longitudinal and transversal magnetic field on the Fe-Ga film plane. The saturation magnetization of as-deposited film reached 1.75 T for Fe83Ga17 thin films, confirming that good quality films were obtained. For the same alloy composition, the coercivity values were 67 Oe and 200 Oe, with applied field parallel and perpendicular to the film plane, respectively. http://www.sciencedirect.com/science/journal/aip/00134686

Recent developments in the chemistry of organic perfluoro hypofluorites.

Author(s): VENTURINI F., SANSOTERA M., NAVARRINI W.

Source: Journal of Fluorine Chemistry

Volume: 155 Pages: 2-20

DOI: 10.1016/j.jfluchem.2013.07.005 (2013)

ABSTRACT:

Recent findings in the synthesis of perfluoro-hypofluorites, their reactivity and their use in the preparation of important perfluoro monomers are herein summarized and analyzed. The experimental conditions to induce free radical or electrophilic reactivity as well as their use as initiation system in the oxidation and oxypolimerization of fluorinated olefins are also presented. Particular emphasis is dedicated to safety issues since organic hypofluorites have the tendency to self-decompose forming gaseous compounds.The hypofluorites considered in this review are: CF3OF, CF2(OF)2, CF3CF2OCF2OF, CF3OCF2CF2OCF2OF, CF3O(CF2O)nCF2OF, CF3OCF2CF2OF, (CF3)2CFOF (CF3)3COF, FS(O)2CF2CF2OF, CF3OCF2CF2CF2OF, cyclo-(CF2OCF2OCF)-CF2OF, (CF3)2N-CF2OF.

http://www.sciencedirect.com/science/article/pii/S0022113913002601

Serendipity and Murphy’s law are two sides of the same coin

Author(s): Navarrini, Walter.

Source: CHIMICA OGGI-CHEMISTRY TODAY Volume: 31 Issue: 4 Pages: 2-3 Published: JUL-AUG 2013

http://www.teknoscienze.com/Articles/Chimica-Oggi-Chemistry-Today-Serendipity-and-Murphy-rsquo-s-law-are-two-sides-of-the-same-coin.aspx#.Uo3g2ieiKP4

The environmental issue on CFCs in the optimization of the Italian system for WEEE recycling

Author(s): Sansotera, Maurizio; Gola, Massimo; Navarrini, Walter.

Source: CHIMICA OGGI-CHEMISTRY TODAY

Volume: 31 Issue: 3 Pages: 68-72

Published: MAY-JUN 2013

ABSTRACT:

The fast innovation cycle of electrical and electronic equipments (EEEs) pose the problem of a largewaste production. The correct disposal of WEEE is strictly needed because of their content in hazardous materials, like heavy metals and environmentally dangerous chemicals, which substances can be very dangerous both for the human health and the environment in which they are released. Chlorofluorocarbons (CFCs) are largely present in a particular class of WEEE, cooling and freezing equipment. CFCs are well recognized as ozone-depleting gases and can have an impact on the global warming higher than CO2. Being Northern Italy the primary source of CFC in Europe, the Italian WEEE Management System development has been investigated, with a focus on cooling and freezing equipment and related CFCs disposal.

http://www.teknoscienze.com/Articles/Chimica-Oggi-Chemistry-Today-The-environmental-issue-on-CFCs-in-the-optimization-of-the-Italian.aspx#.Uo3euSeiKP4

Italian WEEE management system and treatment of end-of-life cooling and freezing equipments for CFCs removal.

Author(s): SANSOTERA M., NAVARRINI W., TALAEEMASHHADI S., VENTURINI F.

Source: Waste management (New York, N.Y.).

DOI: 10.1016/j.wasman.2013.03.012 (2013).

ABSTRACT:

This study presents and analyzes the data of the Italian system for take-back and recovery of waste electrical and electronic equipments (WEEEs) in the start-up period 2008-2010. The analysis was focused particularly on the data about the treatment of end-of-life cooling and freezing equipments. In fact, the wastes of cooling and freezing equipments have a high environmental impact. Indeed, in their compressor oil and insulation polyurethane (PU) foams chlorofluorocarbon (CFC) ozone-depleting gases are still present. In the period 2001-2004 Northern Italy resulted the main source in Europe of CFCs. The European Directive on WEEE management was enacted in 2002, but in Italy it was implemented by the legislative Decree in 2005 and it became operational in 2008. Actually, in 2008 the national WEEE Coordination Centre was founded in order to organize the WEEE pick-up process and to control collection, recovery and recycling targets. As a result, in 2010 the average WEEE collection per capita exceeded the threshold of more than 4 kg per inhabitant, as well as cooling and freezing appliances represented more than one fourth of the Italian WEEE collection stream. During the treatment of end-of-life cooling and freezing equipments, CFCs were recovered and disposed principally by burner methods. The analyses of defined specimens collected in the treatment facilities were standardized to reliably determine the amount of recovered CFCs. Samples of alkaline solid salt, alkaline saline solution, polyurethane matrix and compressor oil collected during the audit assessment procedure were analyzed and the results were discussed. In particular, the analysis of PU samples after the shredding and the warm pressing procedures measured a residual CFCs content around 500-1300 mg/kg of CFCs within the foam matrix. http://www.sciencedirect.com/science/article/pii/S0956053X13001542

Advances in glass Microfabrication. Femtosecond laser irradiation followed by chemical etching.

Author(s): VENTURINI F., SANSOTERA M., OSELLAME R., CERULLO G., NAVARRINI W.

Source: Chimica Oggi – Chemistry Today.

Volume: 30 Pages: 10-13. December (2012).

ABSTRACT:

Femtosecond laser irradiation followed by chemical etching (F.L.I.C.E.) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure attested in literature, which has been widely studied in the past years, consists of irradiating a glass slab and subsequently apply a chemical etching step. The results obtained by different research groups vary widely. In this paper we present a review of the most recent advancements of this technique discussing several critical factors that affect the aspect ratio, the length and the etching speed of the microchannel.

http://www.teknoscienze.com/Articles/Chimica-Oggi-Chemistry-Today-Advances-in-glass-Microfabrication-Femtosecond-laser-irradiation.aspx#.UouCWycUlZM