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- ItemWafer-sized multifunctional polyimine-based two-dimensional conjugated polymers with high mechanical stiffness([London] : Nature Publishing Group UK, 2016) Sahabudeen, Hafeesudeen; Qi, Haoyuan; Glatz, Bernhard Alexander; Tranca, Diana; Dong, Renhao; Hou, Yang; Zhang, Tao; Kuttner, Christian; Lehnert, Tibor; Seifert, Gotthard; Kaiser, Ute; Fery, Andreas; Zheng, Zhikun; Feng, XinliangOne of the key challenges in two-dimensional (2D) materials is to go beyond graphene, a prototype 2D polymer (2DP), and to synthesize its organic analogues with structural control at the atomic- or molecular-level. Here we show the successful preparation of porphyrin-containing monolayer and multilayer 2DPs through Schiff-base polycondensation reaction at an air-water and liquid-liquid interface, respectively. Both the monolayer and multilayer 2DPs have crystalline structures as indicated by selected area electron diffraction. The monolayer 2DP has a thickness of∼0.7 nm with a lateral size of 4-inch wafer, and it has a Young's modulus of 267±30 GPa. Notably, the monolayer 2DP functions as an active semiconducting layer in a thin film transistor, while the multilayer 2DP from cobalt-porphyrin monomer efficiently catalyses hydrogen generation from water. This work presents an advance in the synthesis of novel 2D materials for electronics and energy-related applications.
- ItemNanorattles with tailored electric field enhancement(Cambridge : RSC Publ., 2017) Schnepf, Max J.; Mayer, Martin; Kuttner, Christian; Tebbe, Moritz; Wolf, Daniel; Dulle, Martin; Altantzis, Thomas; Formanek, Petr; Förster, Stephan; Bals, Sara; König, Tobias A. F.; Fery, AndreasNanorattles are metallic core-shell particles with core and shell separated by a dielectric spacer. These nanorattles have been identified as a promising class of nanoparticles, due to their extraordinary high electric-field enhancement inside the cavity. Limiting factors are reproducibility and loss of axial symmetry owing to the movable metal core; movement of the core results in fluctuation of the nanocavity dimensions and commensurate variations in enhancement factor. We present a novel synthetic approach for the robust fixation of the central gold rod within a well-defined box, which results in an axisymmetric nanorattle. We determine the structure of the resulting axisymmetric nanorattles by advanced transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Optical absorption and scattering cross-sections obtained from UV-vis-NIR spectroscopy quantitatively agree with finite-difference time-domain (FDTD) simulations based on the structural model derived from SAXS. The predictions of high and homogenous field enhancement are evidenced by scanning TEM electron energy loss spectroscopy (STEM-EELS) measurement on single-particle level. Thus, comprehensive understanding of structural and optical properties is achieved for this class of nanoparticles, paving the way for photonic applications where a defined and robust unit cell is crucial.
- ItemUltrasoft and High-Mobility Block Copolymers for Skin-Compatible Electronics(Weinheim : Wiley-VCH, 2020) Ditte, Kristina; Perez, Jonathan; Chae, Soosang; Hambsch, Mike; Al-Hussein, Mahmoud; Komber, Hartmut; Formanek, Peter; Mannsfeld, Stefan C.B.; Fery, Andreas; Kiriy, Anton; Lissel, FranziskaPolymer semiconductors (PSCs) are an essential component of organic field-effect transistors (OFETs), but their potential for stretchable electronics is limited by their brittleness and failure susceptibility upon strain. Herein, a covalent connection of two state-of-the-art polymers—semiconducting poly-diketo-pyrrolopyrrole-thienothiophene (PDPP-TT) and elastomeric poly(dimethylsiloxane) (PDMS)—in a single triblock copolymer (TBC) chain is reported, which enables high charge carrier mobility and low modulus in one system. Three TBCs containing up to 65 wt% PDMS were obtained, and the TBC with 65 wt% PDMS content exhibits mobilities up to 0.1 cm2 V−1 s−1, in the range of the fully conjugated reference polymer PDPP-TT (0.7 cm2 V−1 s−1). The TBC is ultrasoft with a low elastic modulus (5 MPa) in the range of mammalian tissue. The TBC exhibits an excellent stretchability and extraordinary durability, fully maintaining the initial electric conductivity in a doped state after 1500 cycles to 50% strain. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH
- ItemThermoresponsive Microgel Coatings as Versatile Functional Compounds for Novel Cell Manipulation Tools(Basel : MDPI, 2018) Uhlig, Katja; Wegener, Thomas; Hertle, Yvonne; Bookhold, Johannes; Jaeger, Magnus; Hellweg, Thomas; Fery, Andreas; Duschl, ClausFor the effective use of live cells in biomedicine as in vitro test systems or in biotechnology, non-invasive cell processing and characterisation are key elements. Thermoresponsive polymer coatings have been demonstrated to be highly beneficial for controlling the interaction of adherent cells through their cultivation support. However, the widespread application of these coatings is hampered by limitations in their adaptability to different cell types and because the full range of applications has not yet been fully explored. In the work presented here, we address these issues by focusing on three different aspects. With regard to the first aspect, by using well-defined laminar flow in a microchannel, a highly controllable and reproducible shear force can be applied to adherent cells. Employing this tool, we demonstrate that cells can be non-invasively detached from a support using a defined shear flow. The second aspect relates to the recent development of simple methods for patterning thermoresponsive coatings. Here, we show how such patterned coatings can be used for improving the handling and reliability of a wound-healing assay. Two pattern geometries are tested using mouse fibroblasts and CHO cells. In terms of the third aspect, the adhesiveness of cells depends on the cell type. Standard thermoresponsive coatings are not functional for all types of cells. By coadsorbing charged nanoparticles and thermoresponsive microgels, it is demonstrated that the adhesion and detachment behaviour of cells on such coatings can be modulated.
- ItemMechanotunable Surface Lattice Resonances in the Visible Optical Range by Soft Lithography Templates and Directed Self-Assembly(Washington, DC : Soc., 2019) Gupta, Vaibhav; Probst, Patrick T.; Goßler, Fabian R.; Steiner, Anja Maria; Schubert, Jonas; Brasse, Yannic; König, Tobias A.F.; Fery, AndreasWe demonstrate a novel colloidal self-assembly approach toward obtaining mechanically tunable, cost-efficient, and low-loss plasmonic nanostructures that show pronounced optical anisotropy upon mechanical deformation. Soft lithography and template-assisted colloidal self-assembly are used to fabricate a stretchable periodic square lattice of gold nanoparticles on macroscopic areas. We stress the impact of particle size distribution on the resulting optical properties. To this end, lattices of narrowly distributed particles (∼2% standard deviation in diameter) are compared with those composed of polydisperse ones (∼14% standard deviation). The enhanced particle quality sharpens the collective surface lattice resonances by 40% to achieve a full width at half-maximum as low as 16 nm. This high optical quality approaches the theoretical limit for this system, as revealed by electromagnetic simulations. One hundred stretching cycles demonstrate a reversible transformation from a square to a rectangular lattice, accompanied by polarization-dependent optical properties. On the basis of these findings we envisage the potential applications as strain sensors and mechanically tunable filters. © 2019 American Chemical Society.
- ItemExploiting Combinatorics to Investigate Plasmonic Properties in Heterogeneous Ag-Au Nanosphere Chain Assemblies(Weinheim : Wiley-VCH, 2021) Schletz, Daniel; Schultz, Johannes; Potapov, Pavel L.; Steiner, Anja Maria; Krehl, Jonas; König, Tobias A.F.; Mayer, Martin; Lubk, Axel; Fery, AndreasChains of coupled metallic nanoparticles are of special interest for plasmonic applications because they can sustain highly dispersive plasmon bands, allowing strong ballistic plasmon wave transport. Whereas early studies focused on homogeneous particle chains exhibiting only one dominant band, heterogeneous assemblies consisting of different nanoparticle species came into the spotlight recently. Their increased configuration space principally allows engineering multiple bands, bandgaps, or topological states. Simultaneously, the challenge of the precise arrangement of nanoparticles, including their distances and geometric patterns, as well as the precise characterization of the plasmonics in these systems, persists. Here, the surface plasmon resonances in heterogeneous Ag-Au nanoparticle chains are reported. Wrinkled templates are used for directed self-assembly of monodisperse gold and silver nanospheres as chains, which allows assembling statistical combinations of more than 109 particles. To reveal the spatial and spectral distribution of the plasmonic response, state-of-the-art scanning transmission electron microscopy coupled with electron energy loss spectroscopy accompanied by boundary element simulations is used. A variety of modes in the heterogeneous chains are found, ranging from localized surface plasmon modes occurring in single gold or silver spheres, respectively, to modes that result from the hybridization of the single particles. This approach opens a novel avenue toward combinatorial studies of plasmonic properties in heterosystems. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
- ItemAmphiphilic block copolymer micelles in selective solvents: The effect of solvent selectivity on micelle formation(Basel : MDPI, 2019) Kumar, Labeesh; Horechyy, Andriy; Bittrich, Eva; Nandan, Bhanu; Uhlmann, Petra; Fery, AndreasWe investigated the micellar behavior of a series of asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers in different P4VP-selective alcoholic solvents. The micellar behavior was further correlated with the spectroscopic ellipsometry results obtained on swelling of PS and P4VP polymer films in the corresponding solvent vapors. The time-resolved (in situ) dynamic light scattering (DLS) measurements, in combination with (ex situ) electron microscopy imaging, revealed information about the aggregation state of PS-b-P4VP BCP in different alcohols and the effect of heat treatment. The ellipsometry measurements allowed us to estimate the difference in solvent selectivity toward PS/P4VP pair. Both DLS and ellipsometric studies suggested that less polar alcohols (i.e., 1-propanol, 1-butanol, and 1-pentanol) are likely to be close to each other in terms of their selectivity toward PS/P4VP pair, whereas more polar ethanol and methanol show the highest and the lowest affinity toward P4VP, respectively.
- ItemSeeded Growth Synthesis of Gold Nanotriangles: Size Control, SAXS Analysis, and SERS Performance(Washington, DC : Soc., 2018) Kuttner, Christian; Mayer, Martin; Dulle, Martin; Moscoso, Ana; López-Romero, Juan Manuel; Förster, Stephan; Fery, Andreas; Pérez-Juste, Jorge; Contreras-Cáceres, RafaelWe studied the controlled growth of triangular prismatic Au nanoparticles with different beveled sides for surface-enhanced Raman spectroscopy (SERS) applications. First, in a seedless synthesis using 3-butenoic acid (3BA) and benzyldimethylammonium chloride (BDAC), gold nanotriangles (AuNTs) were synthesized in a mixture with gold nanooctahedra (AuNOCs) and separated by depletion-induced flocculation. Here, the influence of temperature, pH, and reducing agent on the reaction kinetics was initially investigated by UV–vis and correlated to the size and yield of AuNT seeds. In a second step, the AuNT size was increased by seed-mediated overgrowth with Au. We show for the first time that preformed 3BA-synthesized AuNT seeds can be overgrown up to a final edge length of 175 nm and a thickness of 80 nm while maintaining their triangular shape and tip sharpness. The NT morphology, including edge length, thickness, and tip rounding, was precisely characterized in dispersion by small-angle X-ray scattering and in dry state by transmission electron microscopy and field-emission scanning electron microscopy. For sensor purposes, we studied the size-dependent SERS performance of AuNTs yielding analytical enhancement factors between 0.9 × 104 and 5.6 × 104 and nanomolar limit of detection (10–8–10–9 M) for 4-mercaptobenzoic acid and BDAC. These results confirm that the 3BA approach allows the fabrication of AuNTs in a whole range of sizes maintaining the NT morphology. This enables tailoring of localized surface plasmon resonances between 590 and 740 nm, even in the near-infrared window of a biological tissue, for use as colloidal SERS sensing agents or for optoelectronic applications.
- ItemJanus particles: from concepts to environmentally friendly materials and sustainable applications(Berlin ; Heidelberg : Springer, 2020) Marschelke, Claudia; Fery, Andreas; Synytska, AllaJanus particles represent a unique group of patchy particles combining two or more different physical or chemical functionalities at their opposite sides. Especially, individual Janus particles (JPs) with both chemical and geometrical anisotropy as well as their assembled layers provide considerable advantages over the conventional monofunctional particles or surfactant molecules offering (a) a high surface-to-volume ratio; (b) high interfacial activity; (c) target controlling and manipulation of their interfacial activity by external signals such as temperature, light, pH, or ionic strength and achieving switching between stable emulsions and macro-phase separation; (d) recovery and recycling; (e) controlling the mass transport across the interface between the two phases; and finally (f) tunable several functionalities in one particle allowing their use either as carrier materials for immobilized catalytically active substances or, alternatively, their site-selective attachment to substrates keeping another functionality active for further reactions. All these advantages of JPs make them exclusive materials for application in (bio-)catalysis and (bio-)sensing. Considering “green chemistry” aspects covering biogenic materials based on either natural or fully synthetic biocompatible and biodegradable polymers for the design of JPs may solve the problem of toxicity of some existing materials and open new paths for the development of more environmentally friendly and sustainable materials in the very near future. Considering the number of contributions published each year on the topic of Janus particles in general, the number of contributions regarding their environmentally friendly and sustainable applications is by far smaller. This certainly pinpoints an important challenge and is addressed in this review article. The first part of the review focuses on the synthesis of sustainable biogenic or biocompatible Janus particles, as well as strategies for their recovery, recycling, and reusability. The second part addresses recent advances in applications of biogenic/biocompatible and non-biocompatible JPs in environmental and biotechnological fields such as sensing of hazardous pollutants, water decontamination, and hydrogen production. Finally, we provide implications for the rational design of environmentally friendly and sustainable materials based on Janus particles. [Figure not available: see fulltext.]. © 2020, The Author(s).
- ItemSurface Functionalization by Stimuli-Sensitive Microgels for Effective Enzyme Uptake and Rational Design of Biosensor Setups(Basel : MDPI, 2018) Sigolaeva, Larisa V.; Pergushov, Dmitry V.; Oelmann, Marina; Schwarz, Simona; Brugnoni, Monia; Kurochkin, Ilya N.; Plamper, Felix A.; Fery, Andreas; Richtering, WalterWe highlight microgel/enzyme thin films that were deposited onto solid interfaces via two sequential steps, the adsorption of temperature- and pH-sensitive microgels, followed by their complexation with the enzyme choline oxidase, ChO. Two kinds of functional (ionic) microgels were compared in this work in regard to their adsorptive behavior and interaction with ChO, that is, poly(N-isopropylacrylamide-co-N-(3-aminopropyl)methacrylamide), P(NIPAM-co-APMA), bearing primary amino groups, and poly(N-isopropylacrylamide-co-N-[3-(dimethylamino) propyl]methacrylamide), P(NIPAM-co-DMAPMA), bearing tertiary amino groups. The stimuli-sensitive properties of the microgels in the solution were characterized by potentiometric titration, dynamic light scattering (DLS), and laser microelectrophoresis. The peculiarities of the adsorptive behavior of both the microgels and the specific character of their interaction with ChO were revealed by a combination of surface characterization techniques. The surface charge was characterized by electrokinetic analysis (EKA) for the initial graphite surface and the same one after the subsequent deposition of the microgels and the enzyme under different adsorption regimes. The masses of wet microgel and microgel/enzyme films were determined by quartz crystal microbalance with dissipation monitoring (QCM-D) upon the subsequent deposition of the components under the same adsorption conditions, on a surface of gold-coated quartz crystals. Finally, the enzymatic responses of the microgel/enzyme films deposited on graphite electrodes to choline were tested amperometrically. The presence of functional primary amino groups in the P(NIPAM-co-APMA) microgel enables a covalent enzyme-to-microgel coupling via glutar aldehyde cross-linking, thereby resulting in a considerable improvement of the biosensor operational stability.