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Independent Geometrical Control of Spin and Charge Resistances in Curved Spintronics
Spintronic devices operating with pure spin currents represent a new paradigm in nanoelectronics, with a higher energy efficiency and lower dissipation as compared to charge currents. This technology, however, will be viable only if the amount of spin current diffusing in a nanochannel can be tuned on demand while guaranteeing electrical compatibility with other device elements, to which it should be integrated in high-density three-dimensional architectures. Here, we address these two crucial milestones and demonstrate that pure spin currents can effectively propagate in metallic nanochannels with a three-dimensional curved geometry. Remarkably, the geometric design of the nanochannels can be used to reach an independent tuning of spin transport and charge transport characteristics. These results laid the foundation for the design of efficient pure spin current-based electronics, which can be integrated in complex three-dimensional architectures. © 2019 American Chemical Society.
Molecularly Engineered Black Phosphorus Heterostructures with Improved Ambient Stability and Enhanced Charge Carrier Mobility
Overcoming the intrinsic instability and preserving unique electronic properties are key challenges for the practical applications of black phosphorus (BP) under ambient conditions. Here, it is demonstrated that molecular heterostructures of BP and hexaazatriphenylene derivatives (BP/HATs) enable improved environmental stability and charge transport properties. The strong interfacial coupling and charge transfer between the HATs and the BP lattice decrease the surface electron density and protect BP sheets from oxidation, resulting in an excellent ambient lifetime of up to 21 d. Importantly, HATs increase the charge scattering time of BP, contributing to an improved carrier mobility of 97 cm2 V-1 s-1 , almost three times of the pristine BP films, based on noninvasive THz spectroscopic studies. The film mobility is an order of magnitude larger than previously reported values in exfoliated 2D materials. The strategy opens up new avenues for versatile applications of BP sheets and provides an effective method for tuning the physicochemical properties of other air-sensitive 2D semiconductors.
A New Highly Anisotropic Rh-Based Heusler Compound for Magnetic Recording
The development of high-density magnetic recording media is limited by superparamagnetism in very small ferromagnetic crystals. Hard magnetic materials with strong perpendicular anisotropy offer stability and high recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted magnetic recording was developed, rapidly heating the media to the Curie temperature Tc before writing, followed by rapid cooling. Requirements are a suitable Tc, coupled with anisotropic thermal conductivity and hard magnetic properties. Here, Rh2CoSb is introduced as a new hard magnet with potential for thin-film magnetic recording. A magnetocrystalline anisotropy of 3.6 MJ m−3 is combined with a saturation magnetization of μ0Ms = 0.52 T at 2 K (2.2 MJ m−3 and 0.44 T at room temperature). The magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μB on Co, which is hybridized with neighboring Rh atoms with a large spin–orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its Tc of 450 K, together with a thermal conductivity of 20 W m−1 K−1, make Rh2CoSb a candidate for the development of heat-assisted writing with a recording density in excess of 10 Tb in.−2. © 2020 The Authors. Published by Wiley-VCH GmbH
Halloysite Nanotubes Noncovalently Functionalised with SDS Anionic Surfactant and PS-b-P4VP Block Copolymer for Their Effective Dispersion in Polystyrene as UV-Blocking Nanocomposite Films
Asimple and versatilemethod is reported for the noncovalent functionalisation of natural and "green" halloysite nanotubes (HNTs) allowing their effective dispersion in a polystyrene (PS) thermoplastic matrix via solvent mixing. Initially, HNTs (pristine HNTs) were modified with physically adsorbed surfactant molecules of sodium dodecyl sulphate (SDS) and PS-b-P4VP [P4VP: poly(4-vinylpyridine)] block copolymer (BCP). Hereafter, SDS and BCP modified HNTs will be indicated as SDS-m-HNT and BCP-m-HNT.Nanocomposite films with 1, 2, and 5 wt.%HNTloadingswere prepared, abbreviated as PS-SDS-m-HNT1, PS-SDS-m-HNT2, and PS-SDS-m-HNT5 and PS-BCP-m-HNT1, PS-BCP-m-HNT2, and PS-BCP-m-HNT5 (where 1, 2, and 5 correspond to the wt.% of HNTs). All nanocomposites depicted improved thermal degradation compared to the neat PS as revealed by thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) confirmed the good dispersion state of HNTs and the importance of modification by SDS and BCP. X-ray diffraction (XRD) studies showed the characteristic interlayer spacing between the two silicate layers of pristine and modified HNTs. The PS/HNT nanocomposite films exhibited excellent ultraviolent-visible (UV-vis) absorbance properties and their potential application as UV-filters could be envisaged.
Membrane Functionalization in Pilot Scale: Roll‐to‐Roll Electron Beam System with Inline Contact Angle Determination
To increase the permeation performance and antifouling properties of polymer membranes, a one-step reaction using electron irradiation was developed. This process combines the surface activation of the membrane polymer and the simultaneous permanent immobilization of hydrophilic molecules. This technology can be applied to various polymers, flat sheet/hollow fiber membranes and all pore ranges. The roll-to-roll system developed for this enables all process steps including inline analysis for quality control of the membrane surface in a continuously operated system. © 2021 The Authors. Chemie Ingenieur Technik published by Wiley-VCH GmbH
Supercharged Proteins and Polypeptides
Electrostatic interactions play a vital role in nature. Biomacromolecules such as proteins are orchestrated by electrostatics, among other intermolecular forces, to assemble and organize biochemistry. Natural proteins with a high net charge exist in a folded state or are unstructured and can be an inspiration for scientists to artificially supercharge other protein entities. Recent findings show that supercharging proteins allows for control of their properties such as temperature resistance and catalytic activity. One elegant method to transfer the favorable properties of supercharged proteins to other proteins is the fabrication of fusions. Genetically engineered, supercharged unstructured polypeptides (SUPs) are just one promising fusion tool. SUPs can also be complexed with artificial entities to yield thermotropic and lyotropic liquid crystals and liquids. These architectures represent novel bulk materials that are sensitive to external stimuli. Interestingly, SUPs undergo fluid–fluid phase separation to form coacervates. These coacervates can even be directly generated in living cells or can be combined with dissipative fiber assemblies that induce life-like features. Supercharged proteins and SUPs are developed into exciting classes of materials. Their synthesis, structures, and properties are summarized. Moreover, potential applications are highlighted and challenges are discussed. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Specific Signal Enhancement on an RNA-Protein Interface by Dynamic Nuclear Polarization
Sensitivity and specificity are both crucial for the efficient solid-state NMR structure determination of large biomolecules. We present an approach that features both advantages by site-specific enhancement of NMR spectroscopic signals from the protein-RNA binding site within a ribonucleoprotein (RNP) by dynamic nuclear polarization (DNP). This approach uses modern biochemical techniques for sparse isotope labeling and exploits the molecular dynamics of 13C-labeled methyl groups exclusively present in the protein. These dynamics drive heteronuclear cross relaxation and thus allow specific hyperpolarization transfer across the biomolecular complex's interface. For the example of the L7Ae protein in complex with a 26mer guide RNA minimal construct from the box C/D complex in archaea, we demonstrate that a single methyl-nucleotide contact is responsible for most of the polarization transfer to the RNA, and that this specific transfer can be used to boost both NMR spectral sensitivity and specificity by DNP.
Enlightening Materials with Photoswitches
Incorporating molecular photoswitches into various materials provides unique opportunities for controlling their properties and functions with high spatiotemporal resolution using remote optical stimuli. The great and largely still untapped potential of these photoresponsive systems has not yet been fully exploited due to the fundamental challenges in harnessing geometrical and electronic changes on the molecular level to modulate macroscopic and bulk material properties. Herein, progress made during the past decade in the field of photoswitchable materials is highlighted. After pointing to some general design principles, materials with an increasing order of the integrated photoswitchable units are discussed, spanning the range from amorphous settings over surfaces/interfaces and supramolecular ensembles, to liquid crystalline and crystalline phases. Finally, some potential future directions are pointed out in the conclusion. In view of the exciting recent achievements in the field, the future emergence and further development of light-driven and optically programmable (inter)active materials and systems are eagerly anticipated. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Digital Electrochemistry for On-Chip Heterogeneous Material Integration
Many modern electronic applications rely on functional units arranged in an active-matrix integrated on a single chip. The active-matrix allows numerous identical device pixels to be addressed within a single system. However, next-generation electronics requires heterogeneous integration of dissimilar devices, where sensors, actuators, and display pixels sense and interact with the local environment. Heterogeneous material integration allows the reduction of size, increase of functionality, and enhancement of performance; however, it is challenging since front-end fabrication technologies in microelectronics put extremely high demands on materials, fabrication protocols, and processing environments. To overcome the obstacle in heterogeneous material integration, digital electrochemistry is explored here, which site-selectively carries out electrochemical processes to deposit and address electroactive materials within the pixel array. More specifically, an amorphous indium-gallium-zinc oxide (a-IGZO) thin-film-transistor (TFT) active-matrix is used to address pixels within the matrix and locally control electrochemical reactions for material growth and actuation. The digital electrochemistry procedure is studied in-depth by using polypyrrole (PPy) as a model material. Active-matrix-driven multicolored electrochromic patterns and actuator arrays are fabricated to demonstrate the capabilities of this approach for material integration. The approach can be extended to a broad range of materials and structures, opening up a new path for advanced heterogeneous microsystem integration.
Devulcanization of Waste Rubber and Generation of Active Sites for Silica Reinforcement
Each 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.