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  • 1.
    Munoz, William Armando
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Singh, Sandeep Kumar
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Franco Gonzalez, Felipe
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Bioinformatics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Insulator to semimetallic transition in conducting polymers2016In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 20, article id 205202Article in journal (Refereed)
    Abstract [en]

    We report a multiscale modeling of electronic structure of a conducting polymer poly(3,4-ethylenedioxythiopehene) (PEDOT) based on a realistic model of its morphology. We show that when the charge carrier concentration increases, the character of the density of states (DOS) gradually evolves from the insulating to the semimetallic, exhibiting a collapse of the gap between the bipolaron and valence bands with the drastic increase of the DOS between the bands. The origin of the observed behavior is attributed to the effect of randomly located counterions giving rise to the states in the gap. These results are discussed in light of recent experiments. The method developed in this work is general and can be applied to study the electronic structure of other conducting polymers.

  • 2.
    Peymanirad, F.
    et al.
    Shahid Rajaee Teacher Training Univ, Iran.
    Singh, Sandeep Kumar
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Ghorbanfekr-Kalashami, H.
    Univ Antwerp, Belgium.
    Novoselov, K. S.
    Univ Manchester, England.
    Peeters, F. M.
    Univ Antwerp, Belgium.
    Neek-Amal, M.
    Shahid Rajaee Teacher Training Univ, Iran; Univ Antwerp, Belgium.
    Thermal activated rotation of graphene flake on graphene2017In: 2D MATERIALS, ISSN 2053-1583, Vol. 4, no 2, article id 025015Article in journal (Refereed)
    Abstract [en]

    The self rotation of a graphene flake over graphite is controlled by the size, initial misalignment and temperature. Using both ab initio calculations and molecular dynamics simulations, we investigate annealing effects on the self rotation of a graphene flake on a graphene substrate. The energy barriers for rotation and drift of a graphene flake over graphene is found to be smaller than 25 meV/atom which is comparable to thermal energy. We found that small flakes (of about similar to 4 nm) are more sensitive to temperature and initial misorientation angles than larger one (beyond 10 nm). The initial stacking configuration of the flake is found to be important for its dynamics and time evolution of misalignment. Large flakes, which are initially in the AA-or AB-stacking state with small misorientation angle, rotate and end up in the AB-stacking configuration. However small flakes can they stay in an incommensurate state specially when the initial misorientation angle is larger than 2 degrees. Our results are in agreement with recent experiments.

  • 3.
    Rudd, Sam
    et al.
    University of South Australia, Australia.
    Franco Gonzalez, Felipe
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Singh, Sandeep Kumar
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Ullah Khan, Zia
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Andreasen, Jens W.
    Technical University of Denmark, Denmark.
    Zozoulenko, Igor
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Evans, Drew
    University of South Australia, Australia.
    Charge transport and structure in semimetallic polymers2018In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 56, no 1, p. 97-104Article in journal (Refereed)
    Abstract [en]

    Owing to changes in their chemistry and structure, polymers can be fabricated to demonstrate vastly different electrical conductivities over many orders of magnitude. At the high end of conductivity is the class of conducting polymers, which are ideal candidates for many applications in low-cost electronics. Here, we report the influence of the nature of the doping anion at high doping levels within the semi-metallic conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) on its electronic transport properties. Hall effect measurements on a variety of PEDOT samples show that the choice of doping anion can lead to an order of magnitude enhancement in the charge carrier mobilityamp;gt;3 cm(2)/Vs at conductivities approaching 3000 S/cm under ambient conditions. Grazing Incidence Wide Angle X-ray Scattering, Density Functional Theory calculations, and Molecular Dynamics simulations indicate that the chosen doping anion modifies the way PEDOT chains stack together. This link between structure and specific anion doping at high doping levels has ramifications for the fabrication of conducting polymer-based devices. (c) 2017 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 97-104

  • 4.
    Singh, Sandeep Kumar
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Oxygen Reduction Reaction in Conducting Polymer PEDOT: Density Functional Theory Study2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 22, p. 12270-12277Article in journal (Refereed)
    Abstract [en]

    An oxygen reduction reaction (ORR) mechanism in conducting polymer PEDOT is studied using the density functional theory. It is demonstrated that pure PEDOT chains possess the catalytic activity, where no platinum catalyst or external dopants are needed to sustain the electrocatalysis. This remarkable property of PEDOT is related to the formation of polaronic states, which leads to the decrease of the HOMO LUMO gap and thus to the enhancement of the reactivity of the system. It is shown that ORR on PEDOT chains can proceed via two pathways, whether via a four-electron process when the oxygen reacts with protons and is reduced directly into water in four steps (Reaction path I) or via the two-electron process leading to formation of the hydrogen peroxide as an intermediate specimen (Reaction path II). Path I is demonstrated to be energetically preferable. This conclusion also holds for ORR on two pi-pi stacked chains and ORR for the case when PEDOT is reduced during the reaction. It is also found that ORR on PEDOT effectively proceeds in the presence of H3O+ but does not occur in the absence of acidic environment.

  • 5.
    Stavrinidou, Eleni
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Gabrielsson, Roger
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Nilsson, K. Peter R.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Chemistry.
    Singh, Sandeep Kumar
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Franco- Gonzalez, Juan Felipe
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Volkov, Anton V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Jonsson, Magnus P.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Grimoldi, Andrea
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Elgland, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor V.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Simon, Daniel
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    In vivo polymerization and manufacturing of wires and supercapacitors in plants2017In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 114, no 11, p. 2807-2812Article in journal (Refereed)
    Abstract [en]

    Electronic plants, e-Plants, are an organic bioelectronic platform that allows electronic interfacing with plants. Recently we have demonstrated plants with augmented electronic functionality. Using the vascular system and organs of a plant, we manufactured organic electronic devices and circuits in vivo, leveraging the internal structure and physiology of the plant as the template, and an integral part of the devices. However, this electronic functionality was only achieved in localized regions, whereas new electronic materials that could be distributed to every part of the plant would provide versatility in device and circuit fabrication and create possibilities for new device concepts. Here we report the synthesis of such a conjugated oligomer that can be distributed and form longer oligomers and polymer in every part of the xylem vascular tissue of a Rosa floribunda cutting, forming long-range conducting wires. The plant’s structure acts as a physical template, whereas the plant’s biochemical response mechanism acts as the catalyst for polymerization. In addition, the oligomer can cross through the veins and enter the apoplastic space in the leaves. Finally, using the plant’s natural architecture we manufacture supercapacitors along the stem. Our results are preludes to autonomous energy systems integrated within plants and distribute interconnected sensor-actuator systems for plant control and optimization

  • 6.
    Volkov, Anton
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Singh, Sandeep Kumar
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Stavrinidou, Eleni
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Gabrielsson, Roger
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Franco Gonzalez, Felipe
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Cruce, Alex
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Simon, Daniel
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Spectroelectrochemistry and Nature of Charge Carriers in Self-Doped Conducting Polymer2017In: Advanced Electronic Materials, ISSN 2199-160X, Vol. 3, no 8, article id 1700096Article in journal (Refereed)
    Abstract [en]

    A recently developed water-soluble self-doped sodium salt of bis[3,4-ethylenedioxythiophene] 3thiophene butyric acid (ETE-S) is electropolymerized and characterized by means of spectroelectrochemistry, electron paramagnetic resonance spectroscopy, and cyclic voltammetry, combined with the density functional theory (DFT) and time-dependent DFT calculations. The focus of the studies is to underline the nature of the charge carriers when the electrochemically polymerized ETE-S films undergo a reversible transition from reduced to electrically conductive oxidized states. Spectroelectrochemistry shows clear distinctions between absorption features from reduced and charged species. In the reduced state, the absorption spectrum of ETE-S electropolymerized film shows a peak that is attributed to HOMO. LUMO transition. As the oxidation level increases, this peak diminishes and the absorption of the film is dominated by spinless bipolaronic states with some admixture of polaronic states possessing a magnetic momentum. For fully oxidized samples, the bipolaronic states fully dominate, and the features in the absorption spectra are related to the drastic changes of the band structure, exhibiting a strong decrease of the band gap when a polymeric film undergoes oxidation.

  • 7.
    Zozoulenko, Igor
    et al.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Singh, Amritpal
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Chalmers Univ Technol, Sweden.
    Singh, Sandeep Kumar
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Gueskine, Viktor
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Polarons, Bipolarons, And Absorption Spectroscopy of PEDOT2019In: ACS APPLIED POLYMER MATERIALS, ISSN 2637-6105, Vol. 1, no 1, p. 83-94Article in journal (Refereed)
    Abstract [en]

    Electronic structure and optical absorption spectra of poly(3,4-ethyl-enedioxythiophene) (PEDOT) for different oxidation levels were studied using density functional theory (DFT) and time-dependent DFT. It is shown, that the DFT-based predictions for the polaronic and bipolaronic states and the nature of corresponding optical transitions are qualitatively different from the widely used traditional picture based on semi-empirical pre-DFT approaches that still dominate the current literature. On the basis of the results of our calculations, the experimental Vis/NIR absorbance spectroscopy and the electron paramagnetic resonance spectroscopy are re-examined, and a new interpretation of the measured spectra and the spin signal, which is qualitatively different from the traditional interpretation, is provided. The findings and conclusions concerning the nature of polaronic and bipolaronic states, band structure and absorption spectra presented for PEDOT, are generic for a wide class of conducting polymers (such as polythiophenes and their derivatives) that have a similar structure of monomer units.

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