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- ItemPolypropylene/Layered Double Hydroxide Nanocomposites: Influence of LDH Intralayer Metal Constituents on the Properties of Polypropylene(Washington, DC : ACS Publications, 2017) Nagendra, Baku; Rosely, C. V. Sijla; Leuteritz, Andreas; Reuter, Uta; Gowd, E. BhojeSonication-assisted delamination of layered double hydroxides (LDHs) resulted in smaller-sized LDH nanoparticles (∼50-200 nm). Such delaminated Co-Al LDH, Zn-Al LDH, and Co-Zn-Al LDH solutions were used for the preparation of highly dispersed isotactic polypropylene (iPP) nanocomposites. Transmission electron microscopy and wide-angle X-ray diffraction results revealed that the LDH nanoparticles were well dispersed within the iPP matrix. The intention of this study is to understand the influence of the intralayer metal composition of LDH on the various properties of iPP/LDH nanocomposites. The sonicated LDH nanoparticles showed a significant increase in the crystallization rate of iPP; however, not much difference in the crystallization rate of iPP was observed in the presence of different types of LDH. The dynamic mechanical analysis results indicated that the storage modulus of iPP was increased significantly with the addition of LDH. The incorporation of different types of LDH showed no influence on the storage modulus of iPP. But considerable differences were observed in the flame retardancy and thermal stability of iPP with the type of LDH used for the preparation of nanocomposites. The thermal stability (50% weight loss temperature (T0.5)) of the iPP nanocomposite containing three-metal LDH (Co-Zn-Al LDH) is superior to that of the nanocomposites made of two-metal LDH (Co-Al LDH and Zn-Al LDH). Preliminary studies on the flame-retardant properties of iPP/LDH nanocomposites using microscale combustion calorimetry showed that the peak heat release rate was reduced by 39% in the iPP/Co-Zn-Al LDH nanocomposite containing 6 wt % LDH, which is higher than that of the two-metal LDH containing nanocomposites, iPP/Co-Al LDH (24%) and iPP/Zn-Al LDH (31%). These results demonstrated that the nanocomposites prepared using three-metal LDH showed better thermal and flame-retardant properties compared to the nanocomposites prepared using two-metal LDH. This difference might be due to the better char formation capability of three-metal LDH compared to that of two-metal LDH.
- 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.
- ItemDevulcanization of Waste Rubber and Generation of Active Sites for Silica Reinforcement(Washington, DC : ACS Publications, 2019) Ghorai, Soumyajit; Mondal, Dipankar; Hait, Sakrit; Ghosh, Anik Kumar; Wiessner, Sven; Das, Amit; De, DebapriyaEach year, hundreds of millions of tires are produced and ultimately disposed into nature. To address this serious environmental issue, devulcanization could be one of the sustainable solutions that still remains as one of the biggest challenges across the globe. In this work, sulfur-vulcanized natural rubber (NR) is mechanochemically devulcanized utilizing a silane-based tetrasulfide as a devulcanizing agent, and subsequently, silica (SiO2)-based rubber composites are prepared. This method not only breaks the sulfur–sulfur cross-links but also produces reactive poly(isoprene) chains to interact with silica. The silica natural rubber composites are prepared by replacing 30% fresh NR by devulcanized NR with varying contents of silica. The composites exhibit excellent mechanical properties, tear strength, abrasion resistance, and dynamic mechanical properties as compared with the fresh natural rubber silica composites. The tensile strength of devulcanized rubber-based silica composites is ∼20 MPa, and the maximum elongation strain is ∼921%. The devulcanized composites are studied in detail by chemical, mechanical, and morphological analyses. Thus, the value added by the devulcanized rubber could attract the attention of recycling community for its sustainable applications.
- ItemBioinspired Polydopamine Coating as an Adhesion Enhancer Between Paraffin Microcapsules and an Epoxy Matrix(Washington, DC : ACS Publications, 2020) Fredi, Giulia; Simon, Frank; Sychev, Dmitrii; Melnyk, Inga; Janke, Andreas; Scheffler, Christina; Zimmerer, CordeliaMicroencapsulated phase change materials (PCMs) are attracting increasing attention as functional fillers in polymer matrices, to produce smart thermoregulating composites for applications in thermal energy storage (TES) and thermal management. In a polymer composite, the filler–matrix interfacial adhesion plays a fundamental role in the thermomechanical properties. Hence, this work aims to modify the surface of commercial PCM microcapsules through the formation of a layer of polydopamine (PDA), a bioinspired polymer that is emerging as a powerful tool to functionalize chemically inert surfaces due to its versatility and great adhesive potential in many different materials. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) evidenced that after PDA coating, the surface roughness increased from 9 to 86 nm, which is beneficial, as it allows a further increase in the interfacial interaction by mechanical interlocking. Spectroscopic techniques allowed investigating the surface chemistry and identifying reactive functional groups of the PDA layer and highlighted that, unlike the uncoated microcapsules, the PDA layer is able to react with oxirane groups, thereby forming a covalent bond with the epoxy matrix. Hot-stage optical microscopy and differential scanning calorimetry (DSC) highlighted that the PDA modification does not hinder the melting/crystallization process of the paraffinic core. Finally, SEM micrographs of the cryofracture surface of epoxy composites containing neat or PDA-modified microcapsules clearly evidenced improved adhesion between the capsule shell and the epoxy matrix. These results showed that PDA is a suitable coating material with considerable potential for increasing the interfacial adhesion between an epoxy matrix and polymer microcapsules with low surface reactivity. This is remarkably important not only for this specific application but also for other classes of composite materials. Future studies will investigate how the deposition parameters affect the morphology, roughness, and thickness of the PDA layer and how the layer properties influence the capsule–matrix adhesion.
- ItemDNAzymes as Catalysts for l-Tyrosine and Amyloid β Oxidation(Washington, DC : ACS Publications, 2020) Köhler, Tony; Patsis, Panagiotis A.; Hahn, Dominik; Ruland, André; Naas, Carolin; Müller, Martin; Thiele, JulianSingle-stranded deoxyribonucleic acids have an enormous potential for catalysis by applying tailored sequences of nucleotides for individual reaction conditions and substrates. If such a sequence is guanine-rich, it may arrange into a three-dimensional structure called G-quadruplex and give rise to a catalytically active DNA molecule, a DNAzyme, upon addition of hemin. Here, we present a DNAzyme-mediated reaction, which is the oxidation of l-tyrosine toward dityrosine by hydrogen peroxide. With an optimal stoichiometry between DNA and hemin of 1:10, we report an activity of 101.2 ± 3.5 μUnits (μU) of the artificial DNAzyme Dz-00 compared to 33.0 ± 1.8 μU of free hemin. Exemplarily, DNAzymes may take part in neurodegeneration caused by amyloid beta (Aβ) aggregation due to l-tyrosine oxidation. We show that the natural, human genome-derived DNAzyme In1-sp is able to oxidize Aβ peptides with a 4.6% higher yield and a 33.3% higher velocity of the reaction compared to free hemin. As the artificial DNAzyme Dz-00 is even able to catalyze Aβ peptide oxidation with a 64.2% higher yield and 337.1% higher velocity, an in-depth screening of human genome-derived DNAzymes may identify further candidates with similarly high catalytic activity in Aβ peptide oxidation.
- ItemA High-Voltage, Dendrite-Free, and Durable Zn–Graphite Battery(Weinheim : Wiley-VCH, 2019) Wang, Gang; Kohn, Benjamin; Scheler, Ulrich; Wang, Faxing; Oswald, Steffen; Löffler, Markus; Tan, Deming; Zhang, Panpan; Zhang, Jian; Feng, XinliangThe intrinsic advantages of metallic Zn, like high theoretical capacity (820 mAh g−1), high abundance, low toxicity, and high safety have driven the recent booming development of rechargeable Zn batteries. However, the lack of high-voltage electrolyte and cathode materials restricts the cell voltage mostly to below 2 V. Moreover, dendrite formation and the poor rechargeability of the Zn anode hinder the long-term operation of Zn batteries. Here a high-voltage and durable Zn–graphite battery, which is enabled by a LiPF6-containing hybrid electrolyte, is reported. The presence of LiPF6 efficiently suppresses the anodic oxidation of Zn electrolyte and leads to a super-wide electrochemical stability window of 4 V (vs Zn/Zn2+). Both dendrite-free Zn plating/stripping and reversible dual-anion intercalation into the graphite cathode are realized in the hybrid electrolyte. The resultant Zn–graphite battery performs stably at a high voltage of 2.8 V with a record midpoint discharge voltage of 2.2 V. After 2000 cycles at a high charge–discharge rate, high capacity retention of 97.5% is achieved with ≈100% Coulombic efficiency. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
- ItemComplex Metal Nanostructures with Programmable Shapes from Simple DNA Building Blocks(Weinheim : Wiley-VCH, 2021) Ye, Jingjing; Aftenieva, Olha; Bayrak, Türkan; Jain, Archa; König, Tobias A.F.; Erbe, Artur; Seidel, RalfAdvances in DNA nanotechnology allow the design and fabrication of highly complex DNA structures, uisng specific programmable interactions between smaller nucleic acid building blocks. To convey this concept to the fabrication of metallic nanoparticles, an assembly platform is developed based on a few basic DNA structures that can serve as molds. Programming specific interactions between these elements allows the assembly of mold superstructures with a range of different geometries. Subsequent seeded growth of gold within the mold cavities enables the synthesis of complex metal structures including tightly DNA-caged particles, rolling-pin- and dumbbell-shaped particles, as well as T-shaped and loop particles with high continuity. The method further supports the formation of higher-order assemblies of the obtained metal geometries. Based on electrical and optical characterizations, it is expected that the developed platform is a valuable tool for a self-assembly-based fabrication of nanoelectronic and nanooptic devices. © 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH
- ItemAmphiphilic Copolymers for Versatile, Facile, and In Situ Tunable Surface Biofunctionalization(Weinheim : Wiley-VCH, 2021) Ruland, André; Schenker, Saskia; Schirmer, Lucas; Friedrichs, Jens; Meinhardt, Andrea; Schwartz, Véronique B.; Kaiser, Nadine; Konradi, Rupert; MacDonald, William; Helmecke, Tina; Sikosana, Melissa K.L.N.; Valtin, Juliane; Hahn, Dominik; Renner, Lars D.; Werner, Carsten; Freudenberg, UwePrecision surface engineering is key to advanced biomaterials. A new platform of PEGylated styrene-maleic acid copolymers for adsorptive surface biofunctionalization is reported. Balanced amphiphilicity renders the copolymers water-soluble but strongly affine for surfaces. Fine-tuning of their molecular architecture provides control over adsorptive anchorage onto specific materials-which is why they are referred to as "anchor polymers" (APs)-and over structural characteristics of the adsorbed layers. Conjugatable with an array of bioactives-including cytokine-complexing glycosaminoglycans, cell-adhesion-mediating peptides and antimicrobials-APs can be applied to customize materials for demanding biotechnologies in uniquely versatile, simple, and robust ways. Moreover, homo- and heterodisplacement of adsorbed APs provide unprecedented means of in situ alteration and renewal of the functionalized surfaces. The related options are exemplified with proof-of-concept experiments of controlled bacterial adhesion, human umbilical vein endothelial cell, and induced pluripotent cell growth on AP-functionalized surfaces.
- ItemControlling Surface Wettability for Automated In Situ Array Synthesis and Direct Bioscreening(Weinheim : Wiley-VCH, 2021) Lin, Weilin; Gandhi, Shanil; Oviedo Lara, Alan Rodrigo; Thomas, Alvin K.; Helbig, Ralf; Zhang, YixinThe in situ synthesis of biomolecules on glass surfaces for direct bioscreening can be a powerful tool in the fields of pharmaceutical sciences, biomaterials, and chemical biology. However, it is still challenging to 1) achieve this conventional multistep combinatorial synthesis on glass surfaces with small feature sizes and high yields and 2) develop a surface which is compatible with solid-phase syntheses, as well as the subsequent bioscreening. This work reports an amphiphilic coating of a glass surface on which small droplets of polar aprotic organic solvents can be deposited with an enhanced contact angle and inhibited motion to permit fully automated multiple rounds of the combinatorial synthesis of small-molecule compounds and peptides. This amphiphilic coating can be switched into a hydrophilic network for protein- and cell-based screening. Employing this in situ synthesis method, chemical space can be probed via array technology with unprecedented speed for various applications, such as lead discovery/optimization in medicinal chemistry and biomaterial development.
- ItemThiophene-Bridged Donor–Acceptor sp2-Carbon-Linked 2D Conjugated Polymers as Photocathodes for Water Reduction(Weinheim : Wiley-VCH, 2021) Xu, Shunqi; Sun, Hanjun; Addicoat, Matthew; Biswal, Bishnu P.; He, Fan; Park, SangWook; Paasch, Silvia; Zhang, Tao; Sheng, Wenbo; Brunner, Eike; Hou, Yang; Richter, Marcus; Feng, XinliangPhotoelectrochemical (PEC) water reduction, converting solar energy into environmentally friendly hydrogen fuel, requires delicate design and synthesis of semiconductors with appropriate bandgaps, suitable energy levels of the frontier orbitals, and high intrinsic charge mobility. In this work, the synthesis of a novel bithiophene-bridged donor–acceptor-based 2D sp2-carbon-linked conjugated polymer (2D CCP) is demonstrated. The Knoevenagel polymerization between the electron-accepting building block 2,3,8,9,14,15-hexa(4-formylphenyl) diquinoxalino[2,3-a:2′,3′-c]phenazine (HATN-6CHO) and the first electron-donating linker 2,2′-([2,2′-bithiophene]-5,5′-diyl)diacetonitrile (ThDAN) provides the 2D CCP-HATNThDAN (2D CCP-Th). Compared with the corresponding biphenyl-bridged 2D CCP-HATN-BDAN (2D CCP-BD), the bithiophene-based 2D CCP-Th exhibits a wide light-harvesting range (up to 674 nm), a optical energy gap (2.04 eV), and highest energy occupied molecular orbital–lowest unoccupied molecular orbital distributions for facilitated charge transfer, which make 2D CCP-Th a promising candidate for PEC water reduction. As a result, 2D CCP-Th presents a superb H2-evolution photocurrent density up to ≈7.9 µA cm−2 at 0 V versus reversible hydrogen electrode, which is superior to the reported 2D covalent organic frameworks and most carbon nitride materials (0.09–6.0 µA cm−2). Density functional theory calculations identify the thiophene units and cyano substituents at the vinylene linkage as active sites for the evolution of H2. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH
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