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- ItemFe3O4 Nanoparticles Grown on Cellulose/GO Hydrogels as Advanced Catalytic Materials for the Heterogeneous Fenton-like Reaction(Washington, DC : ACS Publications, 2019) Chen, Yian; Pötschke, Petra; Pionteck, Jürgen; Voit, Brigitte; Qi, HaisongCellulose/graphene oxide (GO)/iron oxide (Fe3O4) composites were prepared by coprecipitating iron salts onto cellulose/GO hydrogels in a basic solution. X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared, and X-ray diffraction characterization showed that Fe3O4 was successfully coated on GO sheets and cellulose. Cellulose/GO/Fe3O4 composites showed excellent catalytic activity by maintaining almost 98% of the removal of acid orange 7 (AO7) and showed stability over 20 consecutive cycles. This performance is attributable to the synergistic effect of Fe3O4 and GO during the heterogeneous Fenton-like reaction. Especially, the cellulose/GO/Fe3O4 composites preserve their activity by keeping the ratio of Fe3+/Fe2+ at 2 even after 20 catalysis cycles, which is supported by XPS analysis.
- ItemSqualenyl Hydrogen Sulfate Nanoparticles for Simultaneous Delivery of Tobramycin and an Alkylquinolone Quorum Sensing Inhibitor Enable the Eradication of P. aeruginosa Biofilm Infections(Weinheim : Wiley-VCH Verlag, 2020) Ho, D.-K.; Murgia, X.; De Rossi, C.; Christmann, R.; Hüfner de Mello Martins, A.G.; Koch, M.; Andreas, A.; Herrmann, J.; Müller, R.; Empting, M.; Hartmann, R.W.; Desmaele, D.; Loretz, B.; Couvreur, P.; Lehr, C.-M.Elimination of pulmonary Pseudomonas aeruginosa (PA) infections is challenging to accomplish with antibiotic therapies, mainly due to resistance mechanisms. Quorum sensing inhibitors (QSIs) interfering with biofilm formation can thus complement antibiotics. For simultaneous and improved delivery of both active agents to the infection sites, self-assembling nanoparticles of a newly synthesized squalenyl hydrogen sulfate (SqNPs) were prepared. These nanocarriers allowed for remarkably high loading capacities of hydrophilic antibiotic tobramycin (Tob) and a novel lipophilic QSI at 30 % and circa 10 %, respectively. The drug-loaded SqNPs showed improved biofilm penetration and enhanced efficacy in relevant biological barriers (mucin/human tracheal mucus, biofilm), leading to complete eradication of PA biofilms at circa 16-fold lower Tob concentration than Tob alone. This study offers a viable therapy optimization and invigorates the research and development of QSIs for clinical use.
- Item2D/3D Metallic Nano-objects Self-Organized in an Organic Molecular Thin Film(Washington, DC : ACS Publications, 2020) Molodtsova, Olga V.; Aristova, Irina M.; Potorochin, Dmitrii V.; Babenkov, Sergey V.; Khodos, Igor I.; Molodtsov, Serguei L.; Makarova, Anna A.; Smirnov, Dmitry A.; Aristov, Victor Yu.We present the fabrication and investigation of the properties of nanocomposite structures consisting of two-dimensional (2D) and three-dimensional (3D) metallic nano-objects self-organized on the surface and inside of organic molecular thin-film copper tetrafluorophthalocyanine (CuPcF4). Metallic atoms, deposited under ultrahigh vacuum (UHV) conditions onto the organic ultrathin film, diffuse along the surface and self-assemble into a system of 2D metallic overlayers. At the same time, the majority of the metal atoms diffuse into the organic matrix and self-organize into 3D nanoparticles (NPs) in a well-defined manner. The evolution of the morphology and electronic properties of such structures as a function of nominal metal content is studied under UHV conditions using transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and photoelectron spectroscopy (PES) techniques. Using HR-TEM, we have observed the periodicity of atomic planes of individual silver NPs. The steady formation of agglomerates from individual single nanocrystallites with intercrystallite boundaries is observed as well. PES reveals generally weak chemical interactions between silver and the organic matrix and n-doping of CuPcF4 at the initial stages of silver deposition, which is associated with charge transfer from the 2D wetting layer on the basis of core-level spectra shift analysis. Copyright © 2020 American Chemical Society.
- ItemHigh-Performance, Lightweight, and Flexible Thermoplastic Polyurethane Nanocomposites with Zn2+-Substituted CoFe2O4 Nanoparticles and Reduced Graphene Oxide as Shielding Materials against Electromagnetic Pollution(Washington, DC : ACS Publications, 2021-10-11) Anju; Yadav, Raghvendra Singh; Pötschke, Petra; Pionteck, Jürgen; Krause, Beate; Kuřitka, Ivo; Vilcakova, Jarmila; Skoda, David; Urbánek, Pavel; Machovsky, Michal; Masař, Milan; Urbánek, Michal; Jurca, Marek; Kalina, Lukas; Havlica, JaromirThe development of flexible, lightweight, and thin high-performance electromagnetic interference shielding materials is urgently needed for the protection of humans, the environment, and electronic devices against electromagnetic radiation. To achieve this, the spinel ferrite nanoparticles CoFe2O4 (CZ1), Co0.67Zn0.33Fe2O4 (CZ2), and Co0.33Zn0.67Fe2O4 (CZ3) were prepared by the sonochemical synthesis method. Further, these prepared spinel ferrite nanoparticles and reduced graphene oxide (rGO) were embedded in a thermoplastic polyurethane (TPU) matrix. The maximum electromagnetic interference (EMI) total shielding effectiveness (SET) values in the frequency range 8.2-12.4 GHz of these nanocomposites with a thickness of only 0.8 mm were 48.3, 61.8, and 67.8 dB for CZ1-rGO-TPU, CZ2-rGO-TPU, and CZ3-rGO-TPU, respectively. The high-performance electromagnetic interference shielding characteristics of the CZ3-rGO-TPU nanocomposite stem from dipole and interfacial polarization, conduction loss, multiple scattering, eddy current effect, natural resonance, high attenuation constant, and impedance matching. The optimized CZ3-rGO-TPU nanocomposite can be a potential candidate as a lightweight, flexible, thin, and high-performance electromagnetic interference shielding material.
- ItemSelective hydrogenation of fluorinated arenes using rhodium nanoparticles on molecularly modified silica(London : RSC Publ., 2020) Kacem, Souha; Emondts, Meike; Bordet, Alexis; Leitner, WalterThe production of fluorinated cyclohexane derivatives is accomplished through the selective hydrogenation of readily available fluorinated arenes using Rh nanoparticles on molecularly modified silica supports (Rh@Si-R) as highly effective and recyclable catalysts. The catalyst preparation comprises grafting non-polar molecular entities on the SiO2 surface generating a hydrophobic environment for controlled deposition of well-defined rhodium particles from a simple organometallic precursor. A broad range of fluorinated cyclohexane derivatives was shown to be accessible with excellent efficacy (0.05-0.5 mol% Rh, 10-55 bar H2, 80-100 °C, 1-2 h), including industrially relevant building blocks. Addition of CaO as scavenger for trace amounts of HF greatly improves the recyclability of the catalytic system and prevents the risks associated to the presence of HF, without compromising the activity and selectivity of the reaction. © The Royal Society of Chemistry.
- ItemOn the Resistances of a Slurry Electrode Vanadium Redox Flow Battery(Weinheim : Wiley-VCH, 2020) Percin, Korcan; van der Zee, Bart; Wessling, MatthiasWe studied the half-cell performance of a slurry-based vanadium redox flow battery via the polarization and electrochemical impedance spectroscopy methods. First, the conductive static mixers are examined and lower ohmic and diffusion resistances are shown. Further analyses of the slurry electrodes for the catholyte (VO2+−VO2 +) and anolyte (V3+−V2+) are presented for the graphite powder slurry containing up to 15.0 wt.% particle content. Overall, the anolyte persists as the more resistive half-cell, while ohmic and diffusion-related limitations are the dominating resistances for both electrolytes. The battery is further improved by the addition of Ketjen black nanoparticles, which results in lower cell resistances. The best results are achieved when 0.5 wt.% Ketjen black nanoparticles are dispersed with graphite powder since the addition of nanoparticles reduces ohmic, charge transfer and mass diffusion resistances by improving particle-particle dynamics. The results prove the importance of understanding resistances in a slurry electrode system. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemRoom temperature single-step synthesis of metal decorated boron-rich nanowires via laser ablation(Heidelberg : Springer Verlag, 2019) Gonzalez-Martinez, I.G.; Bachmatiuk, A.; Gemming, T.; Cuniberti, G.; Trzebicka, B.; Rummeli, M.H.Hybrid nanostructures, such as those with nanoparticles anchored on the surface of nanowires, or decorated nanowires, have a large number of potential and tested applications such as: gas sensing, catalysis, plasmonic waveguides, supercapacitors and more. The downside of these nanostructures is their production. Generally, multi-step synthesis procedures are used, with the nanowires and the nanoparticles typically produced separately and then integrated. The few existent single-step methods are lengthy or necessitate highly dedicated setups. In this paper we report a single-step and rapid (ca. 1 min) laser ablation synthesis method which produces a wide variety of boron-rich decorated nanowires. Furthermore, the method is carried at room temperature. The synthesis process consists on a filamentary jet ejection process driven by pressure gradients generated by the ablation plume on the rims of the irradiation crater. Simultaneously nanoparticles are nucleated and deposited on the filaments thus producing hybrid decorated nanowires.
- ItemDynamic Light Scattering on Nanoparticles in Microgravity in a Drop Tower(Heidelberg : Springer, 2022) Pyttlik, Andrea; Kuttich, Björn; Kraus, TobiasGravity affects colloidal dispersions via sedimentation and convection. We used dynamic light scattering (DLS) to quantify the mobility of nanoparticles on ground and in microgravity. A DLS instrument was adapted to withstand the accelerations in a drop tower, and a liquid handling set-up was connected in order to stabilize the liquid temperature and enable rapid cooling or heating. Light scattering experiments were performed in the drop tower at ZARM (Bremen, Germany) during a microgravity interval of 9.1 s and compared to measurements on ground. Particle dynamics were analyzed at constant temperature and after a rapid temperature drop using a series of DLS measurements with 1 s integration time. We observed nanoparticles with average gold core diameters of 7.8 nm and non-polar oleylamine shells that were dispersed in tetradecane and had an average hydrodynamic diameter of 21 nm. The particles did not change their diameter in the observed temperature range. The particle dynamics inferred from DLS on ground and in microgravity were in good agreement, demonstrating the possibility to perform reliable DLS measurements in a drop tower.
- ItemAn efficient two-polymer binder for high-performance silicon nanoparticle-based lithium-ion batteries: A systematic case study with commercial polyacrylic acid and polyvinyl butyral polymers(Pennington, NJ : Electrochemical Society Inc., 2019) Urbanski, A.; Omar, A.; Guo, J.; Janke, A.; Reuter, U.; Malanin, M.; Schmidt, F.; Jehnichen, D.; Holzschuh, M.; Simon, F.; Eichhorn, K.-J.; Giebeler, L.; Uhlmann, P.Silicon is one of the most promising anode materials for high energy density lithium ion batteries (LIBs) due to its high theoretical capacity and natural abundance. Unfortunately, significant challenges arise due to the large volume change of silicon upon lithiation/delithiation which inhibit its broad commercialization. An advanced binder can, in principle, reversibly buffer the volume change, and maintain strong adhesion toward various components as well as the current collector. In this work, we present the first report on the applicability of polyvinyl butyral (PVB) polymer as a binder component for silicon nanoparticles-based LIBs. Characteristic binder properties of commercial PVB and polyacrylic acid (PAA) polymers are compared. The work focuses on polymer mixtures of PVB polymers with PAA, for an improved binder composition which incorporates their individual advantages. Different ratios of polymers are systematically studied to understand the effect of particular polymer chains, functional groups and mass fractions, on the electrochemical performance. We demonstrate a high-performance polymer mixture which exhibits good binder-particle interaction and strong adhesion to Cu-foil. PAA/PVB-based electrode with a Si loading of ∼1 mg/cm2 tested between 0.01 and 1.2 V vs. Li/Li+ demonstrate specific capacities as high as 2170 mAh/g after the first hundred cycles. © The Author(s) 2019.
- ItemUltra-small cobalt nanoparticles from molecularly-defined Co-salen complexes for catalytic synthesis of amines(Cambridge : RSC, 2020) Senthamarai, Thirusangumurugan; Chandrashekhar, Vishwas G.; Gawande, Manoj B.; Kalevaru, Narayana V.; Zbořil, Radek; Kamer, Paul C.J.; Jagadeesh, Rajenahally V.; Beller, MatthiasWe report the synthesis of in situ generated cobalt nanoparticles from molecularly defined complexes as efficient and selective catalysts for reductive amination reactions. In the presence of ammonia and hydrogen, cobalt-salen complexes such as cobalt(ii)-N,N′-bis(salicylidene)-1,2-phenylenediamine produce ultra-small (2-4 nm) cobalt-nanoparticles embedded in a carbon-nitrogen framework. The resulting materials constitute stable, reusable and magnetically separable catalysts, which enable the synthesis of linear and branched benzylic, heterocyclic and aliphatic primary amines from carbonyl compounds and ammonia. The isolated nanoparticles also represent excellent catalysts for the synthesis of primary, secondary as well as tertiary amines including biologically relevant N-methyl amines. This journal is © The Royal Society of Chemistry.