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Processes
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Photosensitive Molecular Switches: From Isolated Molecules to Processes
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Photosensitive Molecular Switches: From Isolated Molecules to Processes

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Materials Processes".

Deadline for manuscript submissions: 25 November 2024 | Viewed by 6248

Special Issue Editor

Dr. Olga Guskova

E-Mail Website
Guest Editor
Material Theory and Modeling Group, Institute Theory of Polymers, Leibniz-Institute of Polymer Research Dresden, 01069 Dresden, Germany
Interests: photosensitive molecular switches; computational modelling; conjugated polymers; DFT; MD; coarse-grained simulations; self-assembly at surfaces and interfaces; organic electronics; polymers

Special Issue Information

Dear Colleagues,

The development of molecular switches using small photochromes (azobenzenes, spiropyrans, stilbenes, etc.) is critical for many fields of modern nanotechnology, ranging from organic electronics and sensing to biomedical applications. This requires not only (i) understanding the switching effects triggered by light on the monomolecular scale and (ii) the coupling between a photochrome and a surrounding bulk medium, such as polymer matrices or surfaces and interfaces, but also the characterization of their mutual response to irradiation.

This Special Issue aims to collect original scientific articles and reviews from various topics related to the photosensitive molecular switches acting in solvents, polymers, aligned media, or on various surfaces and at interfaces and on reversibly actuating their properties upon exposure UV/vis light. Examples of acceptable research topics include (but are not limited to) experimental, theoretical, and joint studies on processes in:

  • Single-molecules devices;
  • Self-assembled photoresponsive monolayers;
  • Photosensitive polymers;
  • Photochromes and their complexes with metals for biomedical applications;
  • Light-programmable control of wetting;
  • Light-driven particle and droplet transport;
  • Photo-controlled stability of various phases.

The creation of moleculer switches is of great importance to the nanotechnological world, but we believe that their greatest moments are yet to come.

Dr. Olga Guskova
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • photosensitive materials
  • molecular switch
  • photoisomerization
  • computational modelling
  • functional materials
  • remote control of structures and properties
  • molecular junctions

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Published Papers (4 papers)

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Research

21 pages, 1954 KiB  
Article
Adsorption of Low Density Lipoproteins on an Azobenzene-Containing Polymer Brush: Modelling by Coarse-Grained Molecular Dynamics
by Jaroslav Ilnytskyi, Dmytro Yaremchuk and Orest Komarytsia
Processes 2023, 11(10), 2913; https://doi.org/10.3390/pr11102913 - 4 Oct 2023
Cited by 1 | Viewed by 1151
Abstract
One of the strategies to reduce the contents of low density lipoproteins (LDLs) in blood is a hemoperfusion, when they are selectively retracted from plasma by an adsorber located outside the patient’s body. Recently, a photo-controllable smart surface was developed experimentally, that is [...] Read more.
One of the strategies to reduce the contents of low density lipoproteins (LDLs) in blood is a hemoperfusion, when they are selectively retracted from plasma by an adsorber located outside the patient’s body. Recently, a photo-controllable smart surface was developed experimentally, that is characterized by high selectivity and reusability. It comprises a nanocarrier functionalised by a brush of azobenzene-containing polymer chains. We present a mesoscopic model that mimics principal features of this setup and focus our study on the role played by the length and flexibility of the chains and grafting density of a brush. The model for LDL comprises a spherical core covered by a shell of model phospholipids. The model is studied via coarse-grained molecular dynamics simulation, performed with the aid of the GMBOLDD package modified for the case of soft-core beads. We examined the dependencies of the binding energy on both the length of polymer chains and the grafting density of a brush and established optimal conditions for adsorption. These are explained by competition between the concentration of azobenzenes and phospholipids in the same spatial region, flexibility of polymer chains, and excluded volume effects. Full article
(This article belongs to the Special Issue Photosensitive Molecular Switches: From Isolated Molecules to Processes)
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17 pages, 5164 KiB  
Article
Photo-Programmable Processes in Bithiophene–Azobenzene Monolayers on Gold Probed via Simulations
by Vladyslav Savchenko, Moufdi Hadjab, Alexander S. Pavlov and Olga Guskova
Processes 2023, 11(9), 2657; https://doi.org/10.3390/pr11092657 - 5 Sep 2023
Viewed by 1178
Abstract
In this study, we investigate the structural changes, electronic properties, and charge redistribution within azo-bithiophene (Azo-BT)-chemisorbed monolayers under different light stimuli using the density functional theory and molecular dynamics simulations. We consider two types of switches, Azo-BT and BT-Azo, with different arrangements of [...] Read more.
In this study, we investigate the structural changes, electronic properties, and charge redistribution within azo-bithiophene (Azo-BT)-chemisorbed monolayers under different light stimuli using the density functional theory and molecular dynamics simulations. We consider two types of switches, Azo-BT and BT-Azo, with different arrangements of the Azo and BT blocks counting from the anchor thiol group. The chemisorbed monolayers of pure cis- and trans-isomers with a surface concentration of approximately 2.7 molecules per nm2 are modeled on a gold surface using the classical all-atom molecular dynamics. Our results reveal a significant shrinkage of the BT-Azo layer under UV illumination, whereas the thicknesses of the Azo-BT layer remain comparable for both isomers. This difference in behavior is attributed to the ordering of the trans-molecules in the layers, which is more pronounced for Azo-BT, leading to a narrow distribution of the inclination angle to the gold surface. Conversely, both layers consisting of cis-switches exhibit disorder, resulting in similar brush heights. To study charge transfer within the immobilized layers, we analyze each snapshot of the layer and calculate the mean charge transfer integrals using Nelsen’s algorithm for a number of interacting neighboring molecules. Combining these integrals with reorganization energies defined for the isolated molecules, we evaluate the charge transfer rates and mobilities for electron and hole hopping within the layers at room temperature based on Marcus’ theory. This research offers new perspectives for the innovative design of electrode surface modifications and provides insights into controlling charge transfer within immobilized layers using light triggers. Additionally, we identify molecular properties that are enhanced via specific molecular design, which contributes to the development of more efficient molecular switches for various electronic applications. Full article
(This article belongs to the Special Issue Photosensitive Molecular Switches: From Isolated Molecules to Processes)
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12 pages, 2292 KiB  
Article
Photosensitive Spherical Polymer Brushes: Light-Triggered Process of Particle Repulsion
by Marek Bekir, Sarah Loebner, Alexej Kopyshev, Nino Lomadze and Svetlana Santer
Processes 2023, 11(3), 773; https://doi.org/10.3390/pr11030773 - 6 Mar 2023
Cited by 3 | Viewed by 1506
Abstract
We report on a light-triggered process at which repulsive interactions between microparticles with a polyelectrolyte (PE) brush coating can be remotely controlled. The spherical polyelectrolyte brushes are loaded with photosensitive azobenzene containing surfactant which can undergo reversible photo-isomerization from trans to cis state. [...] Read more.
We report on a light-triggered process at which repulsive interactions between microparticles with a polyelectrolyte (PE) brush coating can be remotely controlled. The spherical polyelectrolyte brushes are loaded with photosensitive azobenzene containing surfactant which can undergo reversible photo-isomerization from trans to cis state. The surfactant hydrophilicity is altered by illumination with light of an appropriate wavelength, at which a dynamic exchange of the more surface-active trans isomer in comparison to the more water soluble cis isomer with the PE brush generates a concentration gradient of the cis isomers near a solid surface where the particle is sedimented. In this way, each spherical brush produces its local lateral diffusioosmotic flow pointing outside in a radial direction resulting in mutual long-range repulsive interactions. We demonstrate that a PE layer has a higher tendency to absorb surfactant in comparison to plain silica particles, yielding a larger flow strength. This correlation holds true up to a critical intensity, where the dynamic exchange is adsorption limited with respect to trans isomers and especially pronounced for the PE-coated particles. Full article
(This article belongs to the Special Issue Photosensitive Molecular Switches: From Isolated Molecules to Processes)
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Graphical abstract

11 pages, 1903 KiB  
Article
Photo-Ordering and Deformation in Azobenzene-Containing Polymer Networks under Irradiation with Elliptically Polarized Light
by Vladimir Toshchevikov and Marina Saphiannikova
Processes 2023, 11(1), 129; https://doi.org/10.3390/pr11010129 - 1 Jan 2023
Cited by 3 | Viewed by 1727
Abstract
Azobenzene-containing polymers (azo-polymers) have been a subject of extensive investigations during the last two and half decades, due to their remarkable ability to undergo pronounced alignment and deformation under irradiation with light. The molecular ordering and deformation in azo-polymers of various structures under [...] Read more.
Azobenzene-containing polymers (azo-polymers) have been a subject of extensive investigations during the last two and half decades, due to their remarkable ability to undergo pronounced alignment and deformation under irradiation with light. The molecular ordering and deformation in azo-polymers of various structures under irradiation with linearly polarized light was described in a series of theoretical works, based on the effect of the reorientation of azobenzene moieties due to the anisotropic character of the photoisomerization processes. In the present study, we generalize the previous orientation approach to describe the photo-alignment and deformation of azo-polymer networks under irradiation with elliptically polarized light. We demonstrate that, in general, the light-induced ordering and deformation have a biaxial symmetry defined by the polarization ellipse. Azobenzene chromophores have a tendency to align along the direction of light propagation, the orientation in the other two directions being dependent of the aspect ratio of the polarization ellipse. This causes deformation of azo-polymer networks along the direction of light propagation, the sign of which (expansion/contraction) is defined by a chemical structure of network strands. Theoretical results are in agreement with experiments and have a practical importance to predict the photo-mechanical response of azo-polymers depending on their structure and on the polarization of light. Full article
(This article belongs to the Special Issue Photosensitive Molecular Switches: From Isolated Molecules to Processes)
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