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- ItemSimultaneous Effect of Ultraviolet Radiation and Surface Modification on the Work Function and Hole Injection Properties of ZnO Thin Films(Weinheim : Wiley-VCH, 2020) Raoufi, Meysam; Hörmann, Ulrich; Ligorio, Giovanni; Hildebrandt, Jana; Pätzel, Michael; Schultz, Thorsten; Perdigon, Lorena; Koch, Norbert; List-Kratochvil, Emil; Hecht, Stefan; Neher, DieterThe combined effect of ultraviolet (UV) light soaking and self-assembled monolayer deposition on the work function (WF) of thin ZnO layers and on the efficiency of hole injection into the prototypical conjugated polymer poly(3-hexylthiophen-2,5-diyl) (P3HT) is systematically investigated. It is shown that the WF and injection efficiency depend strongly on the history of UV light exposure. Proper treatment of the ZnO layer enables ohmic hole injection into P3HT, demonstrating ZnO as a potential anode material for organic optoelectronic devices. The results also suggest that valid conclusions on the energy-level alignment at the ZnO/organic interfaces may only be drawn if the illumination history is precisely known and controlled. This is inherently problematic when comparing electronic data from ultraviolet photoelectron spectroscopy (UPS) measurements carried out under different or ill-defined illumination conditions. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemAll-Conjugated Polymer Core-Shell and Core-Shell-Shell Particles with Tunable Emission Profiles and White Light Emission(Weinheim : Wiley-VCH, 2021) Haehnle, Bastian; Schuster, Philipp A.; Chen, Lisa; Kuehne, Alexander J. C.Future applications of conjugated polymer particles (CPP) in medicine, organic photonics, and optoelectronics greatly depend on high performance and precisely adjustable optical properties of the particles. To meet these criteria, current particle systems often combine conjugated polymers with inorganic particles in core-shell geometries, extending the possible optical characteristics of CPP. However, current conjugated polymer particles are restricted to a single polymer phase composed of a distinct polymer or a polymer blend. Here, a synthetic toolbox is presented that enables the synthesis of monodisperse core-shell and core-shell-shell particles, which consist entirely of conjugated polymers but of different types in the core and the shells. Seeded and fed-batch dispersion polymerizations based on Suzuki-Miyaura-type cross-coupling are investigated. The different approaches allow accurate control over the created interface between the conjugated polymer phases and thus also over the energy transfer phenomena between them. This approach opens up completely new synthetic freedom for fine tuning of the optical properties of CPP, enabling, for example, the synthesis of individual white light-emitting particles.
- ItemTailoring the Cavity of Hollow Polyelectrolyte Microgels(Weinheim : Wiley-VCH, 2020) Wypysek, Sarah K.; Scotti, Andrea; Alziyadi, Mohammed O.; Potemkin, Igor I.; Denton, Alan R.; Richtering, WalterThe authors demonstrate how the size and structure of the cavity of hollow charged microgels may be controlled by varying pH and ionic strength. Hollow charged microgels based on N-isopropylacrylamide with ionizable co-monomers (itaconic acid) combine advanced structure with enhanced responsiveness to external stimuli. Structural advantages accrue from the increased surface area provided by the extra internal surface. Extreme sensitivity to pH and ionic strength due to ionizable moieties in the polymer network differentiates these soft colloidal particles from their uncharged counterparts, which sustain a hollow structure only at cross-link densities sufficiently high that stimuli sensitivity is reduced. Using small-angle neutron and light scattering, increased swelling of the network in the charged state accompanied by an expanded internal cavity is observed. Upon addition of salt, the external fuzziness of the microgel surface diminishes while the internal fuzziness grows. These structural changes are interpreted via Poisson–Boltzmann theory in the cell model. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
- ItemUsing Active Surface Plasmons in a Multibit Optical Storage Device to Emulate Long-Term Synaptic Plasticity(Weinheim : Wiley-VCH, 2020) Rhim, Seon-Young; Ligorio, Giovanni; Hermerschmidt, Felix; Hildebrandt, Jana; Pätzel, Michael; Hecht, Stefan; List-Kratochvil, Emil J.W.Artificial intelligence takes inspiration from the functionalities and structure of the brain to solve complex tasks and allow learning. Yet, hardware realization that simulates the synaptic activities realized with electrical devices still lags behind computer software implementation, which has improved significantly during the past decade. Herein, the capability to emulate synaptic functionalities by exploiting surface plasmon polaritons (SPPs) is shown. By depositing photochromic switching molecules (diarylethene) on a thin film of gold, it is possible to reliably control the electronic configuration of the molecules upon illumination cycles with UV and visible light. These reversible changes modulate the dielectric function of the photochromic film and thus enable the effective control of the SPP dispersion relation at the molecule/gold interface. The plasmonic device displays fundamental functions of a synapse such as potentiation, depression, and long-term plasticity. The integration of such plasmonic devices in an artificial neural network is deployed in plasmonic neuroinspired circuits for optical computing and data transmission. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemZwitterionic Nanogels and Microgels: An Overview on Their Synthesis and Applications(Weinheim : Wiley-VCH, 2021) Saha, Pabitra; Ganguly, Ritabrata; Li, Xin; Das, Rohan; Singha, Nikhil K.; Pich, AndrijZwitterionic polymers by virtue of their unique chemical and physical attributes have attracted researchers in recent years. The simultaneous presence of positive and negative charges in the same repeat unit renders them of various interesting properties such as superhydrophilicity, which has significantly broadened their scope for being used in different applications. Among polyzwitterions of different architectures, micro- and/or nano-gels have started receiving attention only until recently. These 3D cross-linked colloidal structures show peculiar characteristics in context to their solution properties, which are attributable either to the comonomers present or the presence of different electrolytes and biological specimens. In this review, a concise yet detailed account is provided of the different synthetic techniques and application domains of zwitterion-based micro- and/or nanogels that have been explored in recent years. Here, the focus is kept solely on the “polybetaines,” which have garnered maximum research interest and remain the extensively studied polyzwitterions in literature. While their vast application potential in the biomedical sector is being detailed here, some other areas of scope such as using them as microreactors for the synthesis of metal nanoparticles or making smart membranes for water-treatment are discussed in this minireview as well.
- ItemUnraveling the Mechanism and Kinetics of Binding of an LCI-eGFP-Polymer for Antifouling Coatings(Weinheim : Wiley-VCH, 2021) Söder, Dominik; Garay-Sarmiento, Manuela; Rahimi, Khosrow; Obstals, Fabian; Dedisch, Sarah; Haraszti, Tamás; Davari, Mehdi D.; Jakob, Felix; Heß, Christoph; Schwaneberg, Ulrich; Rodriguez-Emmenegger, CesarThe ability of proteins to adsorb irreversibly onto surfaces opens new possibilities to functionalize biological interfaces. Herein, the mechanism and kinetics of adsorption of protein-polymer macromolecules with the ability to equip surfaces with antifouling properties are investigated. These macromolecules consist of the liquid chromatography peak I peptide from which antifouling polymer brushes are grafted using single electron transfer-living radical polymerization. Surface plasmon resonance spectroscopy reveals an adsorption mechanism that follows a Langmuir-type of binding with a strong binding affinity to gold. X-ray reflectivity supports this by proving that the binding occurs exclusively by the peptide. However, the lateral organization at the surface is directed by the cylindrical eGFP. The antifouling functionality of the unimolecular coatings is confirmed by contact with blood plasma. All coatings reduce the fouling from blood plasma by 8894% with only minor effect of the degree of polymerization for the studied range (DP between 101 and 932). The excellent antifouling properties, combined with the ease of polymerization and the straightforward coating procedure make this a very promising antifouling concept for a multiplicity of applications.
- ItemControlling Optical and Catalytic Activity of Genetically Engineered Proteins by Ultrasound(Weinheim : Wiley-VCH, 2021) Zhou, Yu; Huo, Shuaidong; Loznik, Mark; Göstl, Robert; Boersma, Arnold J.; Herrmann, AndreasUltrasound (US) produces cavitation-induced mechanical forces stretching and breaking polymer chains in solution. This type of polymer mechanochemistry is widely used for synthetic polymers, but not biomacromolecules, even though US is biocompatible and commonly used for medical therapy as well as in vivo imaging. The ability to control protein activity by US would thus be a major stepping-stone for these disciplines. Here, we provide the first examples of selective protein activation and deactivation by means of US. Using GFP as a model system, we engineer US sensitivity into proteins by design. The incorporation of long and highly charged domains enables the efficient transfer of force to the protein structure. We then use this principle to activate the catalytic activity of trypsin by inducing the release of its inhibitor. We expect that this concept to switch “on” and “off” protein activity by US will serve as a blueprint to remotely control other bioactive molecules. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemActivation of the Catalytic Activity of Thrombin for Fibrin Formation by Ultrasound(Weinheim : Wiley-VCH, 2021) Zhao, Pengkun; Huo, Shuaidong; Fan, Jilin; Chen, Junlin; Kiessling, Fabian; Boersma, Arnold J.; Göstl, Robert; Herrmann, AndreasThe regulation of enzyme activity is a method to control biological function. We report two systems enabling the ultrasound-induced activation of thrombin, which is vital for secondary hemostasis. First, we designed polyaptamers, which can specifically bind to thrombin, inhibiting its catalytic activity. With ultrasound generating inertial cavitation and therapeutic medical focused ultrasound, the interactions between polyaptamer and enzyme are cleaved, restoring the activity to catalyze the conversion of fibrinogen into fibrin. Second, we used split aptamers conjugated to the surface of gold nanoparticles (AuNPs). In the presence of thrombin, these assemble into an aptamer tertiary structure, induce AuNP aggregation, and deactivate the enzyme. By ultrasonication, the AuNP aggregates reversibly disassemble releasing and activating the enzyme. We envision that this approach will be a blueprint to control the function of other proteins by mechanical stimuli in the sonogenetics field. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemMulticolor Mechanofluorophores for the Quantitative Detection of Covalent Bond Scission in Polymers(Weinheim : Wiley-VCH, 2021) Baumann, Christoph; Stratigaki, Maria; Centeno, Silvia P.; Göstl, RobertThe fracture of polymer materials is a multiscale process starting with the scission of a single molecular bond advancing to a site of failure within the bulk. Quantifying the bonds broken during this process remains a big challenge yet would help to understand the distribution and dissipation of macroscopic mechanical energy. We here show the design and synthesis of fluorogenic molecular optical force probes (mechanofluorophores) covering the entire visible spectrum in both absorption and emission. Their dual fluorescent character allows to track non-broken and broken bonds in dissolved and bulk polymers by fluorescence spectroscopy and microscopy. Importantly, we develop an approach to determine the absolute number and relative fraction of intact and cleaved bonds with high local resolution. We anticipate that our mechanofluorophores in combination with our quantification methodology will allow to quantitatively describe fracture processes in materials ranging from soft hydrogels to high-performance polymers. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemReversibly Photo-Modulating Mechanical Stiffness and Toughness of Bioengineered Protein Fibers(Weinheim : Wiley-VCH, 2020) Sun, Jing; Ma, Chao; Maity, Sourav; Wang, Fan; Zhou, Yu; Portale, Giuseppe; Göstl, Robert; Roos, Wouter H.; Zhang, Hongjie; Liu, Kai; Herrmann, AndreasLight-responsive materials have been extensively studied due to the attractive possibility of manipulating their properties with high spatiotemporal control in a non-invasive fashion. This stimulated the development of a series of photo-deformable smart devices. However, it remained a challenge to reversibly modulate the stiffness and toughness of bulk materials. Here, we present bioengineered protein fibers and their optomechanical manipulation by employing electrostatic interactions between supercharged polypeptides (SUPs) and an azobenzene (Azo)-based surfactant. Photo-isomerization of the Azo moiety from the E- to Z-form reversibly triggered the modulation of tensile strength, stiffness, and toughness of the bulk protein fiber. Specifically, the photo-induced rearrangement into the Z-form of Azo possibly strengthened cation–π interactions within the fiber material, resulting in an around twofold increase in the fiber's mechanical performance. The outstanding mechanical and responsive properties open a path towards the development of SUP-Azo fibers as smart stimuli-responsive mechano-biomaterials. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH