pinecone/core-2020-05-10-deduplication huggingface dataset:
Functional Graphenic Materials Via a Johnson−Claisen Rearrangement

Current research in materials has devoted much attention to graphene, with a considerable amount of the chemical manipulation going through the oxidized state of the material, known as graphene oxide (GO). In this report, the hydroxyl functionalities in GO, the vast majority that must be allylic alcohols, are subjected to Johnson−Claisen rearrangement conditions. In these conditions, a [3, 3] sigmatropic rearrangement after reaction with triethyl orthoacetate gives rise to an ester functional group, attached to the graphitic framework via a robust C−C bond. This variation of the Claisen rearrangement offers an unprecedented versatility of further functionalizations, while maintaining the desirable properties of unfunctionalized graphene. The resultant functional groups were found to withstand reductive treatments for the deoxygenation of graphene sheets and a resumption of electronic conductivity is observed. The ester groups are easily saponified to carboxylic acids in situ with basic conditions, to give water-soluble graphene. The ester functionality can be further reacted as is, or the carboxylic acid can easily be converted to the more reactive acid chloride. Subsequent amide formation yields up to 1 amide in 15 graphene carbons and increases intergallery spacing up to 12.8 Å, suggesting utility of this material in capacitors and in gas storage. Other functionalization schemes, which include the installation of terminal alkynes and dipolar cycloadditions, allow for the synthesis of a highly positively charged, water-soluble graphene. The highly negatively and positively charged graphenes (zeta potentials of −75 mV and +56 mV, respectively), are successfully used to build layer-by-layer (LBL) constructs.Massachusetts Institute of Technology. Institute for Soldier NanotechnologiesNational Science Foundation (U.S.). Graduate Research Fellowship Progra
Mussel inspired dynamic cross-linking of self-healing peptide nanofiber network

Cataloged from PDF version of article.A general drawback of supramolecular peptide networks is their weak
mechanical properties. In order to overcome a similar challenge, mussels
have adapted to a pH-dependent iron complexation strategy for adhesion and
curing. This strategy also provides successful stiffening and self-healing properties.
The present study is inspired by the mussel curing strategy to establish
iron cross-link points in self-assembled peptide networks. The impact of
peptide-iron complexation on the morphology and secondary structure of the
supramolecular nanofi bers is characterized by scanning electron microscopy,
circular dichroism and Fourier transform infrared spectroscopy. Mechanical
properties of the cross-linked network are probed by small angle oscillatory
rheology and nanoindentation by atomic force microscopy. It is shown that
iron complexation has no infl uence on self-assembly and β -sheet-driven
elongation of the nanofi bers. On the other hand, the organic-inorganic hybrid
network of iron cross-linked nanofi bers demonstrates strong mechanical
properties comparable to that of covalently cross-linked network. Strikingly,
iron cross-linking does not inhibit intrinsic reversibility of supramolecular
peptide polymers into disassembled building blocks and the self-healing
ability upon high shear load. The strategy described here could be extended
to improve mechanical properties of a wide range of supramolecular polymer
networks
A Stiff Injectable Biodegradable Elastomer

Injectable materials often have shortcomings in mechanical and drug-eluting properties that are attributable to their high water contents. A water-free, liquid four-armed PEG modified with dopamine end groups is described which changes from liquid to elastic solid by reaction with a small volume of Fe3+ solution. The elastic modulus and degradation times increase with increasing Fe3+ concentrations. Both the free base and the water-soluble form of lidocaine can be dissolved in the PEG4-dopamine and released in a sustained manner from the cross-linked matrix. PEG4-dopamine is retained in the subcutaneous space in vivo for up to 3 weeks with minimal inflammation. This material's tailorable mechanical properties, biocompatibility, ability to incorporate hydrophilic and hydrophobic drugs and release them slowly are desirable traits for drug delivery and other biomedical applications.National Institute on Deafness and Other Communication Disorders (U.S.) (NIDCD R21 DC 009986)National Institutes of Health (U.S.) (NIH Ruth L. Kirschstein National Research Service  Award (no. F32GM096546))National Institutes of Health (U.S.) (NIH R01 EB00244
A giant electrocaloric effect in nanoscale antiferroelectric and ferroelectric phases coexisting in a relaxor Pb0.8Ba0.2ZrO3 thin film at room temperature

Recently large electrocaloric effects (ΔT = 12 K and ΔS = 8 JK-1kg-1 at 776 kV/cm) in antiferroelectric sol-gel PbZr0.95Ti0.05O3 thin film and (ΔT = 12.6 K and ΔS = 60 JK-1kg-1 at 2090 kV/cm) in ferroelectric polymer P(VDF-TrFE)55/45 thin film have been observed near their ferroelectric Curie temperatures 495 K and 353 K, respectively. Here the authors demonstrate a giant EC effect (ΔT = 45.3 K and ΔS = 46.9 JK-1kg-1 at 598 kV/cm) in the nano-scaled antiferroelectric and ferroelectric phases coexisted relaxor Pb0.8Ba0.2ZrO3 (PBZ) thin film at the room temperature 290 K rather than at its Curie temperature 408 K. Field-induced antiferroelectric to ferroelectric phase transition played a crucial role in the dramatic EC property of PBZ thin film.. The giant EC effect of PBZ thin film makes it an attractive material for applications in cooling systems near room temperature
Aqueous Two‐Phase System Patterning of Microbubbles: Localized Induction of Apoptosis in Sonoporated Cells

Ultrasound‐driven microbubbles produce mechanical forces that can disrupt cell membranes (sonoporation). However, it is difficult to control microbubble location with respect to cells. This lack of control leads to low sonoporation efficiencies and variable outcomes. In this study, aqueous two‐phase system (ATPS) droplets are used to localize microbubbles in select micro‐regions at the surface of living cells. This is achieved by stably partitioning microbubbles in dextran (DEX) droplets, deposited on living adherent cells in medium containing polyethylene glycol (PEG). The interfacial energy at the PEG‐DEX interface overcomes microbubble buoyancy and prevents microbubbles from floating away from the cells. Spreading of the small DEX droplets retains microbubbles at the cell surface in defined lateral positions without the need for antibody or cell‐binding ligand conjugation. The patterned microbubbles are activated on a cell monolayer exposed to a broadly applied ultrasound field (center frequency 1.25 MHz, active element diameter 0.6 cm, pulse duration 8 μs or 30 s). This system enables efficient testing of different ultrasound conditions for their effects on sonoporation‐mediated membrane disruption and cell viability. Regions of cells without patterned microbubbles show no injury or membrane disruption. In microbubble patterned regions, 8 μs ultrasound pulses (0.2‐0.6 MPa) produce cell death that is primarily apoptotic. Ultrasound‐induced apoptosis increases with higher extracellular calcium concentrations, with cells displaying all of the hallmarks of apoptosis including annexinV labeling, loss of mitochondrial membrane potential, caspase activation and changes in nuclear morphology.     A new method is described for patterning microbubbles on cell monolayers  to target ultrasound treatment to cells. This novel platform provides a controlled system for high throughput testing of the effects of ultrasound‐mediated cell membrane disruption on cell physiology. Using this patterning method, it is possible to induce apoptosis in select populations of cells
Silk as a Multifunctional Biomaterial Substrate for Reduced Glial Scarring around Brain‐Penetrating Electrodes

The reliability of chronic, brain‐penetrating electrodes must be improved for these ‐neural recording technologies to be viable in widespread clinical applications. One approach to improving electrode reliability is to reduce the foreign body response at the probe‐tissue interface. In this work, silk fibroin is investigated as a candidate material for fabricating mechanically dynamic neural probes with enhanced biocompatibility compared to traditional electrode materials. Silk coatings are applied to flexible cortical electrodes to produce devices that transition from stiff to flexible upon hydration. Theoretical modeling and in vitro testing show that the silk coatings impart mechanical properties sufficient for the electrodes to penetrate brain tissue. Further, it is demonstrated that silk coatings may reduce some markers of gliosis in an in vitro model and that silk can encapsulate and release the gliosis‐modifying enzyme chondroitinase ABC. This work establishes a basis for future in vivo studies of silk‐based brain‐penetrating electrodes, as well as the use of silk materials for other applications in the central nervous system where gliosis must be controlled.     Silk fibroin is investigated as a novel material for fabricating brain‐penetrating electrodes  with dynamic mechanical properties and the capacity to deliver sensitive therapeutics. Silk coatings are shown to natively reduce some markers of gliosis in vitro, and a further reduction is demonstrated by encapsulation and release of the enzyme chondroitinase ABC
Development of Degradable, pH‐Sensitive Star Vectors for Enhancing the Cytoplasmic Delivery of Nucleic Acids

The report describes the synthesis of degradable, pH‐sensitive, membrane‐destabilizing, star‐shaped polymers where copolymers of hydrophobic hexyl methacrylate (HMA) and 2‐(dimethylamino)ethyl methacrylate (DMAEMA) monomers are grafted from the secondary face of a beta‐cyclodextrin (β‐CD) core via acid‐labile hydrazone linkages using atom transfer radical polymerization. The effect of the graft's molecular weight, HMA/DMAEMA molar ratio, and the fraction of DMAEMA converted to cationic N,N,N‐trimethylaminoethyl methacrylate (TMAEMA) monomers on polymer's transfection capacity is systematically investigated. Results show that all star‐shaped polymers condense anti‐GAPDH silencing RNA (siRNA) into nanosized particles at +/‐ ratio ≤ 4:1. Star polymers with shorter (25kDa) P(HMA‐ co ‐DMAEMA‐ co ‐TMAEMA) grafts are more efficient and less cytotoxic than carriers with longer (40kDa) grafts. The results show that increasing the ratio of hydrophobic HMA monomers in graft's composition higher than 50 mole% dramatically reduces polymer's aqueous solubility and abolishes their transfection capacity. Further, retention of DMAEMA monomers in graft's composition provide a buffering capacity that enhanced the endosomal escape and transfection capacity of the polymers. These systematic studies show that β‐CD‐P(HMA‐ co ‐DMAEMA‐ co ‐TMAEMA) 4.8  polymer with a 25 kDa average graft's molecular weight and a 50/25/25 ratio of HMA/DMAEMA/TMAEMA monomers is the most efficient carrier in delivering the siRNA cargo into the cytoplasm of epithelial cancer cells.     A series of degradable, pH‐sensitive, membrane‐destabilizing, star‐shaped polymers  is synthesized. Star polymers are engineered to “sense” the drop in endosomal pH, which triggers the hydrolysis of acid‐labile hydrazone linkages and release of membrane‐active grafts that rupture the endosomal membrane and release the loaded siRNA cargo into the cytoplasm to produce the desired knockdown of targeted gene expression at both the mRNA and protein levels
Sensory Arrays of Covalently Functionalized Single-Walled Carbon Nanotubes for Explosive Detection

Chemiresistive sensor arrays for cyclohexanone and nitromethane are fabricated using single-walled carbon nanotubes (SWCNTs) that are covalently functionalized with urea, thiourea, and squaramide containing selector units. Based on initial sensing results and [superscript 1]H NMR binding studies, the most promising selectors are chosen and further optimized. These optimized selectors are attached to SWCNTs and simultaneously tested in a sensor array. The sensors show a very high level of reproducibility between measurements with the same sensor and across different sensors of the same type. Furthermore, the sensors show promising long-term stability, which renders them suitable for practical applications.Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (W911NF-07-D-004
Turning ABO$_3$ antiferroelectrics into ferroelectrics: Design rules for
  practical rotation-driven ferroelectricity in double perovskites and
  A$_3$B$_2$O$_7$ Ruddlesden-Popper compounds

Ferroic transition metal oxides, which exhibit spontaneous elastic,
electrical, magnetic or toroidal order, exhibit functional properties that find
use in ultrastable solid-state memories to sensors and medical imaging
technologies. To realize multifunctional behavior, where one order parameter
can be coupled to the conjugate field of another order parameter, however,
requires a common microscopic origin for the long-range order. Here, we
formulate a complete theory for a novel form of ferroelectricity, whereby a
spontaneous and switchable polarization emerges from the destruction of an
antiferroelectric state due to octahedral rotations and ordered cation
sublattices. We then construct a materials design framework based on
crystal-chemistry descriptors rooted in group theory, which enables the facile
design of artificial oxides with large electric polarizations, P, simultaneous
with small energetic switching barriers between +P and -P. We validate the
theory with first principles density functional calculations on more than 16
perovskite-structured oxides, illustrating it could be operative in any
materials classes exhibiting two- or three-dimensional corner-connected
octahedral frameworks. We show the principles governing materials selection of
the "layered" systems originate in the lattice dynamics of the A cation
displacements stabilized by the pervasive BO$_6$ rotations of single phase
ABO$_3$ materials, whereby the latter distortions govern the optical band gaps,
magnetic order and critical transition temperatures. Our approach provides the
elusive route to the ultimate multifunctionality property control by an
external electric field.Comment: 13 pages, 11 figure
Highly transmissive carbon nanotube forests grown at low substrate temperature

Despite the "darker than black" association attributed to carbon nanotube forests, here is shown that it is also possible to grow these structures, over heat-sensitive substrates, featuring highly transmissive characteristics from the UV to infrared wavelengths, for forest heights as high as 20 μm. The optical transmission is interpreted in terms of light propagation along channels that are self-generated by localized bundling of tubes, acting as waveguides. A good correlation is shown between the distribution of diameter sizes of these sub-wavelength voids and the transmission spectrum of the forests. For the shorter visible and near-UV wavelengths, this model shows that light propagates by channeling along individual vertical voids in the forests, which elucidates the origin for the widely-reported near-zero reflectance values observed in forests. For the longer infrared wavelengths, the mode spreads over many nanotubes and voids, and propagates along a "homogeneous effective medium". The strong absorption of the forest at the shorter wavelengths is correlated in terms of the stronger attenuation inside a waveguide cavity, according to the λ attenuation dependency of standard waveguide theory. The realization of this material can lead to novel avenues in new optoelectronic device design, where the carbon nanotube forests can be used as highly conducting "scaffolds" for optically active materials, whilst also allowing light to penetrate to significant depths into the structure, in excess of 20 μm, enabling optical functionality. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Influence of cavity thickness and emitter orientation on the efficiency roll-off of phosphorescent organic light-emitting diodes

This article describes the first systematic investigation of how the efficiency roll-off in organic light-emitting diodes (OLEDs) is influenced by the position and orientation of the emitter molecules within the OLED cavity. The efficiency roll-off is investigated for two OLED stacks containing either the phosphorescent emitter Ir(MDQ)2(acac) or Ir(ppy)3 by varying the distance between emitter and metal cathode; a strong influence of emitter position and orientation on roll-off is observed. The measurements are modeled by triplet-triplet-annihilation (TTA) theory yielding the critical current density and the TTA rate constant. It is found that Ir(MDQ)2(acac) shows the lowest roll-off when the emitter is located in the first optical maximum of the electromagnetic field, whereas the roll-off of the Ir(ppy)3 stack is lowest when the emitter is positioned closer to the metal cathode. Measurement and modeling of time-resolved electroluminescence show that the different roll-off behavior is due to the different orientation and the corresponding change of the decay rate of the emissive dipoles of Ir(MDQ)2(acac) and Ir(ppy)3. Finally, design principles are developed for optimal high-brightness performance by modeling the roll-off as a function of emitter-cathode distance, emissive dipole orientation, and radiative efficiency.PostprintPeer reviewe
Spray-Layer-by-Layer Carbon Nanotube/Electrospun Fiber Electrodes for Flexible Chemiresistive Sensor Applications

Development of a versatile method for incorporating conductive materials into textiles could enable advances in wearable electronics and smart textiles. One area of critical importance is the detection of chemicals in the environment for security and industrial process monitoring. Here, the fabrication of a flexible, sensor material based on functionalized multi-walled carbon nanotube (MWNT) films on a porous electrospun fiber mat for real-time detection of a nerve agent simulant is reported. The material is constructed by layer-by-layer (LbL) assembly of MWNTs with opposite charges, creating multilayer films of MWNTs without binder. The vacuum-assisted spray-LbL process enables conformal coatings of nanostructured MWNT films on individual electrospun fibers throughout the bulk of the mat with controlled loading and electrical conductivity. A thiourea-based receptor is covalently attached to the primary amine groups on the MWNT films to enhance the sensing response to dimethyl methylphosphonate (DMMP), a simulant for sarin nerve agent. Chemiresistive sensors based on the engineered textiles display reversible responses and detection limits for DMMP as low as 10 ppb in the aqueous phase and 5 ppm in the vapor phase. This fabrication technique provides a versatile and easily scalable strategy for incorporating conformal MWNT films into three-dimensional substrates for numerous applications.United States. Army Research Office. Institute for Soldier Nanotechnologies (Contract No. DAAD-19–02–0002
Interface Immobilization Chemistry of c RGD-based Peptides Regulates Integrin Mediated Cell Adhesion

The interaction of specifi c surface receptors of the integrin family with different extracellular matrix-based ligands is of utmost importance for the cellular adhesion process. A ligand consists of an integrin-binding group, here cyclic RGDfX, a spacer molecule that lifts the integrin-binding group from the surface and a surface anchoring group. c (-RGDfX-) peptides are bound to gold nanoparticle structured surfaces via polyproline, polyethylene glycol or aminohexanoic acid containing spacers of different lengths. Although keeping the integrin-binding c (-RGDfX-) peptides constant for all compounds, changes of the ligand´s spacer chemistry and length reveal signifi cant differences in cell adhesion activation and focal adhesion formation. Polyproline-based peptides demonstrate improved cell adhesion kinetics and focal adhesion formation compared with common aminohexanoic acid or polyethylene glycol spacers. Binding activity can additionally be improved  by applying ligands with two head groups, inducing a multimeric effect. This study gives insights into spacer-based differences in integrin-driven cell adhesion processes and remarkably highlights the polyproline-based spacers as suitable ligand-presenting templates for surface functionalization.Fil: Pallarola, Diego Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Max Planck Institute for intelligent Systems; Alemania. University of Heidelberg; AlemaniaFil: Bochen, Alexander. Universitat Technical Zu Munich; Alemania. Max Planck Institute for intelligent Systems; AlemaniaFil: Boehm, Heike. Max Planck Institute for intelligent Systems; Alemania. University of Heidelberg; AlemaniaFil: Rechenmacher, Florian. Universitat Technical Zu Munich; AlemaniaFil: Sobahi, Tarik R.. King Abdulaziz University; Arabia SauditaFil: Spatz, Joachim P.. Max Planck Institute for intelligent Systems; Alemania. University of Heidelberg; AlemaniaFil: Kessler, Horst. Universitat Technical Zu Munich; Alemani
Modelling and prediction of bacterial attachment to polymers

YesInfection by pathogenic bacteria on implanted and indwelling medical devices during surgery causes large morbidity and mortality worldwide. Attempts to ameliorate this important medical issue have included development of antimicrobial surfaces on materials, “no touch” surgical procedures, and development of materials with inherent low pathogen attachment. The search for new materials is increasingly being carried out by high throughput methods. Efficient methods for extracting knowledge from these large data sets are essential. Data from a large polymer microarray exposed to three clinical pathogens is used to derive robust and predictive machine-learning models of pathogen attachment. The models can predict pathogen attachment for the polymer library quantitatively. The models also successfully predict pathogen attachment for a second-generation library, and identify polymer surface chemistries that enhance or diminish pathogen attachment.CSIRO Advanced Materials Transformational Capability Platform. Newton Turner Award for Exceptional Senior Scientists. Wellcome Trust. Grant Number: 085245. NIH. Grant Number: R01 DE01651
Interesting evidence for template-induced ferroelectric behavior in ultra-thin titanium dioxide films grown on (110) neodymium gallium oxide substrates

The first evidence for room-temperature ferroelectric behavior in anatase-phase titanium dioxide (a-TiO2) is reported. Behavior strongly indicative of ferroelectric characteristics is induced in ultra-thin (20 nm to 80 nm) biaxially-strained epitaxial films of a-TiO2 deposited by liquid injection chemical vapor deposition onto (110) neodymium gallium oxide (NGO) substrates. The films exhibit significant orthorhombic strain, as analyzed by X-ray diffraction and high-resolution transmission electron microscopy. The films on NGO show a switchable dielectric spontaneous polarization when probed by piezoresponse force microscopy (PFM), the ability to retain polarization information written into the film using the PFM tip for extended periods (several hours) and at elevated temperatures (up to 100 °C) without significant loss, and the disappearance of the polarization at a temperature between 180 and 200 °C, indicative of a Curie temperature within this range. This combination of effects constitutes strong experimental evidence for ferroelectric behavior, which has not hitherto been reported in a-TiO2 and opens up the possibility for a range of new applications. A model is presented for the effects of large in-plane strains on the crystal structure of anatase which provides a possible explanation for the experimental observations