2020, Rodriguez, Raul D., Khalelov, Alimzhan, Postnikov, Pavel S., Lipovka, Anna, Dorozhko, Elena, Amin, Ihsan, Murastov, Gennadiy V., Chen, Jin-Ju, Sheng, Wenbo, Trusova, Marina E., Chehimi, Mohamed M., Sheremet, Evgeniya

Carbon nanomaterials, especially graphene, are promising due to their abundance and the possibility to exploit them in lightweight, flexible, and wearable electronics enabling paradigms such as the Internet of Things. However, conventional methods to synthesize and integrate graphene into functional materials and flexible devices are either hazardous, time demanding, or excessively energy-consuming. To overcome these issues, here we propose a new concept based on the laser processing of single-layer diazonium-functionalized graphene. This is a safe, inexpensive, and environmentally-friendly method making it a competitive alternative for graphene-device fabrication. Flexible chemiresistors exhibit sensitivity for breath (water vapor and CO2) and ethanol detection up to 1500% higher than laser-reduced graphene oxide devices. We attribute this enhanced sensitivity to an optimal balance between structural defects and electrical conductivity. Flexible electronic circuits demonstrate a superb resilience against scratching and high current stability up to 98% with durability against 180° bending cycles for continuous operation of several weeks. This work can impact biomedical technology and electronics where tunable electrical conductivity, sensitivity, and mechanical stability are of uttermost importance. © 2020 The Royal Society of Chemistry.

2016, Karpov, Yevhen, Maiti, Jatindranath, Tkachov, Roman, Beryozkina, Tetyana, Bakulev, Vasiliy, Liu, Wei, Komber, Hartmut, Lappan, Uwe, Al-Hussein, Mahmoud, Stamm, Manfred, Voit, Brigitte, Kiriy, Anton

The present work aims at the extension of the scope of a recently discovered polycondensation of AB-type anion-radical monomers. To this end, we investigate the polymerization of isoindigo-based monomer and its copolymerization with the naphthalenediimide-based monomer. Although polycondensations of parent naphthalenediimide- and perylenediimide-based monomers involve chain-growth mechanism, we found that the corresponding isoindigo-based monomer polymerizes in a step-growth manner under the same reaction conditions. In contrast to Stille, Suzuki and direct arylation polycondensations which require prolonged stirring at high temperatures, the polymerization approach we employed in this study proceeds fast at room temperature. It was found that near statistical copolymerization of isoindigo-based anion-radical monomers with corresponding naphtalenediimide-based monomers proceeds smoothly resulting in a library of copolymers with varying composition and properties depending on the ratio of the monomers.

2020, Daubian, Davy, Gaitzsch, Jens, Meier, Wolfgang

We report on the synthesis and self-assembly of poly(ethylene oxide)-block-poly(2-(3-ethylheptyl)-2-oxazoline) (PEO-b-PEHOx), a new amphiphilic diblock copolymer obtained via microwave-assisted polymerization of EHOx using a new nosylated PEO macroinitiator. The kinetics of the polymerization in different solvents was crucial to optimize the synthesis and revealed a controlled, yet fast polymerization of the AB diblock copolymer. Differential scanning calorimetry proved that PEO-b-PEHOx shows glass transition temperatures below room temperature, making it suitable for a wide range of self-assembly methods, especially under mild and solvent-free conditions. Self-assembly of PEO-b-PEHOx was then performed using film rehydration and solvent switch. In both cases, we were able to show the formation of various complex structures (multi-compartment micelles (MCMs), pseudo-vesicles and yolk/shell nanoparticles) by light scattering, TEM and Cryo-TEM. Our results show that PEO-b-PEHOx is a potent new AB diblock copolymer due to its fast synthesis and unique self-assembly behavior.

2018, Newland, B., Taplan, C., Pette, D., Friedrichs, J., Steinhart, M., Wang, W., Voit, B., Seib, F. P., Werner, C.

Nanotubes are emerging as promising materials for healthcare applications but the selection of clinically relevant starting materials for their synthesis remains largely unexplored. Here we present, for the first time, the synthesis of poly(ethylene glycol) (PEG) based nanotubes via the photopolymerization of poly(ethylene glycol) diacrylate and other diacrylate derivatives within the pores of anodized aluminum oxide templates. Template-assisted synthesis allowed the manufacture of a diverse set of polymeric nanotubes with tunable physical characteristics including diameter (∼200-400 nm) and stiffness (405-902 kPa). PEG nanotubes were subjected to cytotoxicty assessment in cell lines and primary stem cells and showed excellent cytocompatability (IC50 > 120 μg ml-1). Nanotubes were readily drug loaded but released the majority of the drug over 5 days. Direct administration of drug loaded nanotubes to human orthotopic breast tumors substantially reduced tumor growth and metastasis and outperformed i.v. administration at the equivalent dose. Overall, this nanotube templating platform is emerging as a facile route for the manufacture of poly(ethylene glycol) nanotubes.

2016, Singh, C.R., Honold, T., Gujar, T.P., Retsch, M., Fery, A., Karg, M., Thelakkat, M.

Plasmonic particles can contribute via multiple processes to the light absorption process in solar cells. These particles are commonly introduced into organic solar cells via deposition techniques such as spin-coating or dip-coating. However, such techniques are inherently challenging to achieve homogenous surface coatings as they lack control of inter-particle spacing and particle density on larger areas. Here we introduce interface assisted colloidal self-assembly as a concept for the fabrication of well-defined macroscopic 2-dimensional monolayers of hydrogel encapsulated plasmonic gold nanoparticles. The monolayers showed a pronounced extinction in the visible wavelength range due to localized surface plasmon resonance with excellent optical homogeneity. Moreover this strategy allowed for the investigation of the potential of plasmonic monolayers at different interfaces of P3HT:PCBM based inverted organic solar cells. In general, for monolayers located anywhere underneath the active layer, the solar cell performance decreased due to parasitic absorption. However with thick active layers, where low hole mobility limited the charge transport to the top electrode, the plasmonic monolayer near that electrode spatially redistributed the light and charge generation close to the electrode led to an improved performance. This work systematically highlights the trade-offs that need to be critically considered for designing an efficient plasmonically enhanced organic solar cell.

2015, Liu, Fangyao, Jiang, Shaohua, Ionov, Leonid, Agarwal, Seema

Photo cross-linkable thermoresponsive polymers of UCST-type based on acrylamide (AAm) and acrylonitrile (AN) useful for preparing thermophilic hydrogel films and fibers are presented. The polymers prepared via free radical and reversible addition fragmentation chain-transfer (RAFT) polymerization methods using N-(4-benzoylphenyl)acrylamide (BPAm) as photo cross-linkable comonomers provided highly stable UCST-type phase transition in water reproducible without hysteresis for many cycles. The cloud point could be manipulated by varying the acrylonitrile amount in the feed. Chemically cross-linked hydrogel films and nanofibers (average diameter 500 nm) were successfully prepared from the ter-copolymers by solution casting and electrospinning followed by UV irradiation. These hydrogels showed a continuous positive volume transition behavior in water with increasing temperature that was utilized for the design of microactuators.

2019, Kuttner, Christian, Höller, Roland P. M., Quintanilla, Marta, Schnepf, Max J., Dulle, Martin, Fery, Andreas, Liz-Marzán, Luis M.

The optical properties of nanoparticle assemblies can be tailored via hybridization of plasmon modes. Isotropic core/satellite superstructures made of spherical nanoparticles are known to exhibit coupled modes with a strongly scattering (radiative) character, and provide hot spots yielding high activity in surface-enhanced Raman scattering (SERS). However, to complement this functionality with plasmonic heating, additional absorbing (non-radiative) modes are required. We introduce herein anisotropic superstructures formed by decorating a central nanorod with spherical satellite nanoparticles, which feature two coupled modes that allow application for both SERS and heating. On the basis of diffuse reflectance spectroscopy, small-angle X-ray scattering (SAXS), and electromagnetic simulations, the origin of the coupled modes is disclosed and thus serves as a basis toward alternative designs of functional superstructures. This work represents a proof-of-principle for the combination of high SERS efficiency with efficient plasmonic heating by near-infrared irradiation.

2019, Schubert, Jonas, Radeke, Carmen, Fery, Andreas, Chanana, Munish

In this study, we investigated charge inversion of protein-coated Au nanoparticles caused by the addition of metal ions. The addition of hydrolyzable metal ions (Lewis acids) can induce drastic pH changes and depending on this pH, the metal ions (e.g. M3+) are readily converted into the hydrolyzed species (MOH2+, M(OH)2+) or even into hydroxides (M(OH)3). Adsorbed metal hydroxides were identified to cause the charge inversion of the NPs by using a combination of cryo-TEM, EFTEM and ζ-potential measurements.

2015, Metzler, Lukas, Reichenbach, Thomas, Brügner, Oliver, Komber, Hartmut, Lombeck, Florian, Müllers, Stefan, Hanselmann, Ralf, Hillebrecht, Harald, Walter, Michael, Sommer, Michael

Suzuki–Miyaura polycondensation (SPC) is widely used to prepare a variety of copolymers for a broad range of applications. Although SPC protocols are often used in many instances, the limits of this method and issues of molecular weight reproducibility are not often looked at in detail. By using a spiropyran-based (SP) mechanochromic copolymer, we present an optimized protocol for the microwave-assisted synthesis of a mechanochromic, alternating copolymer P(SP-alt-C10) via SPC that allows the reproduction of molecular weight distributions. Several parameters such as microwave power, temperature, stoichiometry, and ligand are screened, leading to molecular weights up to Mw ∼ 174 kg mol−1. The process of optimization is guided by NMR end group analysis which shows that dehalogenation, oxidative deborylation and SP cleavage are the limiting factors that impede further increase of molar mass, while other classical side reactions such as protiodeborylation are not observed. Embossing films of P(SP-alt-C10) yields the colored merocyanine (MC) copolymer P(MC-alt-C10) that undergoes a thermally facilitated back reaction to P(SP-alt-C10). DFT suggests that the barrier of the SP → MC transition has two contributions, with the first one being related to the color change and the second one to internal bond reorganizations. The barrier height is 1.5 eV, which suggests that the ease of the thermally facilitated back reaction is either due to residual energy stored in the deformed polymer matrix, or arises from an MC isomer that is not in the thermodynamically most stable state.

2020, Kühne, Tim, Au-Yeung, Kwan Ho, Eisenhut, Frank, Aiboudi, Oumaima, Ryndyk, Dmitry A., Cuniberti, Gianaurelio, Lissel, Franziska, Moresco, Francesca

Among the different mechanisms that can be used to drive a molecule on a surface by the tip of a scanning tunneling microscope at low temperature, we used voltage pulses to move azulene-based single molecules and nanostructures on Au(111). Upon evaporation, the molecules partially cleave and form metallo-organic dimers while single molecules are very scarce, as confirmed by simulations. By applying voltage pulses to the different structures under similar conditions, we observe that only one type of dimer can be controllably driven on the surface, which has the lowest dipole moment of all investigated structures. Experiments under different bias and tip height conditions reveal that the electric field is the main driving force of the directed motion. We discuss the different observed structures and their movement properties with respect to their dipole moment and charge distribution on the surface.