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End date: 2019 Ɨ Start date: 2018 Ɨ DDC: 540 Ɨ Type: Text Ɨ Subject: self-assembly Ɨ

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Now showing 1 - 2 of 2
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    Self-Regenerating Soft Biophotovoltaic Devices
    (Washington, DC : ACS Publications, 2018) Qiu, Xinkai; CastaƱeda Ocampo, Olga; de Vries, Hendrik W.; van Putten, Maikel; Loznik, Mark; Herrmann, Andreas; Chiechi, Ryan C.
    This paper describes the fabrication of soft, stretchable biophotovoltaic devices that generate photocurrent from photosystem I (PSI) complexes that are self-assembled onto Au electrodes with a preferred orientation. Charge is collected by the direct injection of electrons into the Au electrode and the transport of holes through a redox couple to liquid eutectic gallium-indium (EGaIn) electrodes that are confined to microfluidic pseudochannels by arrays of posts. The pseudochannels are defined in a single fabrication step that leverages the non-Newtonian rheology of EGaIn. This strategy is extended to the fabrication of reticulated electrodes that are inherently stretchable. A simple shadow evaporation technique is used to increase the surface area of the Au electrodes by a factor of approximately 106 compared to planar electrodes. The power conversion efficiency of the biophotovoltaic devices decreases over time, presumably as the PSI complexes denature and/or detach from the Au electrodes. However, by circulating a solution of active PSI complexes the devices self-regenerate by mass action/self-assembly. These devices leverage simple fabrication techniques to produce complex function and prove that photovoltaic devices comprising PSI can retain the ability to regenerate, one of the most important functions of photosynthetic organisms. Ā© 2018 American Chemical Society.
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    Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling
    (Basel : MDPI, 2019) Savchenko, Vladyslav; Koch, Markus; Pavlov, Aleksander S.; Saphiannikova, Marina; Guskova, Olga
    In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analyzed theoretically by applying a combination of computer simulation techniques. Without a light stimulus, the azobenzene arms adopt the trans-state and build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies-fibers, spheres, gels, and others. Here, we determine the most favorable mutual orientations of the trans-stars in the stack in terms of (i) the p - p distance between the cores lengthwise the aggregate, (ii) the lateral displacements due to slippage and (iii) the rotation promoting the helical twist and chirality of the aggregate. To this end, we calculate the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of the stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moments and the binding energies as functions of the columnar length. For this, molecular dynamics trajectories are analyzed. Finally, we conclude about the cooperative nature of the self-assembly of star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core in aqueous solution.