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  • 1.
    Iakunkov, Artem
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sun, Jinhua
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rebrikova, Anastasia
    Korobov, Mikhail
    Klechikov, Alexey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Physics and Astronomy, Uppsala University, Uppsala, 751 20, Sweden.
    Vorobiev, Alexei
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Talyzin, Aleksandr V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Swelling of graphene oxide membranes in alcohols: effects of molecule size and air ageing.2019Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, s. 11331-11337Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Swelling of Hummers graphene oxide (HGO) membranes in a set of progressively longer liquid alcohols (methanol to 1-nonanol) was studied using synchrotron radiation XRD after air ageing over prolonged periods of time. Both precursor graphite oxides and freshly prepared HGO membranes were found to swell in the whole set of nine liquid alcohols with an increase of interlayer spacing from ∼7 Å (solvent free) up to ∼26 Å (in 1-nonanol). A pronounced effect of ageing on swelling in alcohols was found for HGO membranes stored in air. The HGO membranes aged for 0.5–1.5 years show progressively slower swelling kinetics, a non-monotonic decrease of saturated swelling in some alcohols and complete disappearance of swelling for alcohol molecules larger than hexanol. Moreover, the HGO membranes stored under ambient conditions for 5 years showed a nearly complete absence of swelling in all alcohols but preserved swelling in water. In contrast, precursor graphite oxide powder showed unmodified swelling in alcohols even after 4 years of ageing. Since the swelling defines the size of permeation channels, the ageing effect is one of the important parameters which could explain the strong variation in reported filtration/separation properties of GO membranes. The time and conditions of air storage require standardization for better reproducibility of results related to performance of GO membranes in various applications. The ageing of GO membranes can be considered not only as a hindrance/degradation for certain applications, but also as a method to tune the swelling properties of HGO membranes for better selectivity in sorption of solvents and for achieving better selective permeability.

  • 2. Kan, Zhipeng
    et al.
    Colella, Letizia
    Canesi, Eleonora V.
    Vorobiev, Alexei
    Skrypnychuk, Vasyl
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Terraneo, Giancarlo
    Barbero, David R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Bertarelli, Chiara
    MacKenzie, Roderick C. I.
    Keivanidis, Panagiotis E.
    Charge transport control via polymer polymorph modulation in ternary organic photovoltaic composites2016Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, nr 4, s. 1195-1201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The control on the charge transport properties of ternary organic photovoltaic P3HT : PCBM : QBT devices is enabled by modulating the distribution of P3HT polymorphs in the device photoactive layers. Negligible amounts of QBT induce striking modifications in the P3HT lamellar stacking direction, forming both densely packed and non-densely packed P3HT chains. The former reduce the charge carrier recombination rate, enabling an increased fill factor and short-circuit device photocurrent.

  • 3. Lin, Jhih-Fong
    et al.
    Kukkola, Jarmo
    Sipola, Teemu
    Raut, Dilip
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akad Univ, Dept Chem Engn, Proc Chem Ctr, FI-20500 Turku, Finland.
    Mohl, Melinda
    Toth, Geza
    Su, Wei-Fang
    Laurila, Tomi
    Kordas, Krisztian
    Trifluoroacetylazobenzene for optical and electrochemical detection of amines2015Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, nr 8, s. 4687-4694Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we demonstrate the solution processing of optical and electrochemical dye sensors based on 4-(dioctylamino)-4'-(trifluoroacetyl) azobenzene and its application in sensing different amine compounds. Distinct optical response of the sensors exposed to ammonia, tetramethylammonium hydroxide, ethylamine, cadaverine and putrescine (typical compounds upon the decomposition of proteins) is observed. Incorporation of inkjet deposited thin films of the dye as sensors in food packages of ground meat and salmon is found as a feasible route to detect the appearance of biogenic amines produced by the degrading food products. Furthermore, we demonstrate an electrochemical amine sensor based on (trifluoroacetyl) azobenzene dye added in carbon nanotube-Nafion (R) composites. The electrochemical sensor exploits the reaction between the dye and amines to detect amines in electrolytes, while the carbon nanotubes provide large surface for adsorption and also provide a percolating electrical network for allowing efficient charge transfer at the electrode electrolyte interface.

  • 4. Ng, Chun Hin
    et al.
    Winther-Jensen, Orawan
    Ohlin, C. Andre
    Winther-Jensen, Bjorn
    Exploration and optimisation of poly(2,2 ‘-bithiophene) as a stable photo-electrocatalyst for hydrogen production2015Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, nr 21, s. 11358-11366Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An organic photo-electrochemical catalyst for the hydrogen evolution reaction (HER) based on the conducting polymer, poly(2,2 ‘-bithiophene) (PBTh), is further explored. Long-term stability testing shows the successful operation of the catalyst over a period of 12 days at neutral pH with corresponding turnover numbers exceeding 6 x 10(4). Experimental parameters such as substrate type, electrolyte, pH and thickness of the film are explored and their subsequent effects on catalytic behaviour and performance discussed. Significant findings include the four-fold increase in performance by the reduction of thickness to better facilitate charge transfer and the successful photo-catalysis of the HER at pH 11, with an onset that is 0.14 V below E-0. Faradaic efficiency was also determined with a maximum recorded efficiency of 80% despite known losses such as crossover reactions and H-2 escape from within the system.

  • 5.
    Nitze, Florian
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Chemical and Biological Engineering, Chalmers University of Technology, Sweden.
    Sandström, Robin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Barzegar, Hamid Reza
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mazurkiewicz, Marta
    Malolepszy, Artur
    Stobinski, Leszek
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Direct support mixture painting, using Pd(0) organo-metallic compounds - an easy and environmentally sound approach to combine decoration and electrode preparation for fuel cells2014Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 48, s. 20973-20979Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An inventive, fast and straight-forward approach for the direct preparation of fuel cell electrodes has been developed and tested. Our approach avoids long catalyst preparation and post-synthesis treatment. It reduces the use of chemicals and thereby concomitantly lowers the environmental impact and improves cost efficiency. It combines decoration of the support by palladium nanoparticles with electrode preparation through a simple one-step ink-painting and annealing process. Composites have been investigated by high resolution transmission electron microscopy, scanning electron microscopy, and Xray diffraction. Crystalline particles are well-attached and well-distributed on the support. Particles are of few nanometers in size and spherical for decorated Vulcan whereas they are larger and irregularly shaped for decorated helical carbon nanofibers (HCNFs). Electrodes with a metal loading of 0.8 mg cm(-2) have been tested in a direct formic acid fuel cell. Both the Vulcan and the HCNF electrodes show a similar and high power output of up to 120 mW mg(-1). They also show similar performances in deactivation experiments conducted at 200 mA cm(-2) even when using only high purity grade formic acid. After deactivation the electrodes show no structural damage, making them superior to most commercial catalysts. The electrodes can be completely regenerated to initial activity by simple treatment with water. The easy regeneration process indicates that CO-adsorption on the fuel cell anode catalyst is not the main poisoning mechanism responsible for electrode degeneration.

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