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Natural polymer materials have high biocompatibility and are not toxic because they can decompose into metabolites in the body; thus, they are widely used as medical polymer materials as well as porous support materials. As a biopolymer, alginate has a negative charge; in contrast, chitosan has a positive charge. Therefore, when the two substances are mixed, they form a relatively stable structure by ionic bonding. Beta-glucan is known to contribute to material stability and have high skin penetration, skin moisturizing and soothing effects, and burn and wound healing effects. In this study, antimicrobial activity was assessed by preparing alginate-chitosan hydrogel patches containing beta-glucan nanoemulsions. This could contribute to the development of wound dressings with antibacterial properties.

This paper describes a facile method for fabricating polyaniline (PANI) films with well-defined three-dimensional (3D) porous networks and improved electrochemical activity. The PANI hydrogel pastes with different compositions are directly cast into thin films by the doctor blade technique. After a dehydration step, the conductivity of the PANI drastically increases, while the porous structure with hierarchical macro- and meso-porosity is formed in the PANI film. The electrical conductivity tends to increase with the thickness of the porous PANI film until it fails to form a mechanically stable film not exhibiting cracking problems. We found that the amount of the initiator, the aniline monomer, and the crosslinker significantly affect not only the micro-morphology of PANI films, but also their electrical and electrochemical characteristics. Importantly, when the amounts of the crosslinker and the initiator increase, the polymer film forms with a dense internal morphology with smaller pores. Based on the engineered synthesis composition, we demonstrate a supercapacitor with porous PANI electrodes. Due to the hierarchical porous structure, large surface area and the improved conductivity, the resulting devices show excellent volumetric capacitances, which are comparable to or much higher than those previously reported.

We report agarose-polymer-based composite microfibers with enhanced conductivity and fast humidity sensing owing to incorporation of conductive nanofillers. The microfibers are fabricated by extruding a hydrogel filament containing silver nanowires (AgNWs) and graphene oxide (GO, chemically reduced after extrusion) as 1D and 2D nanofillers, respectively. For the same concentration, GO enhances the mechanical properties of the microfibers more effectively than AgNWs. The microfiber with nanofillers has a higher Young's modulus than commercial nylon-6 and polyamide. Due to synergy between AgNWs and reduced GO (rGO), the microfiber with both fillers shows higher conductivity than those with only one filler. The flexible microfiber retains its conductivity well under repeated bending/unbending cycles. Since rGO ionizes water molecules, the conductivity of the microfiber increases with increasing environmental humidity. Humidity sensing ability of the composite microfiber, based on the humidity-dependent conductivity, is demonstrated. The microfiber with both nanofillers respond rapidly and reversibly to humidity changes because the AgNWs facilitate charge carrier transport and water adsorption/desorption. The humidity sensor based on the composite microfiber also reliably detects repeated short human breaths.

Organic solvents used for electrolytes of dye-sensitized solar cells (DSSCs) are generally not only toxic and explosive but also prone to leakage due to volatility and low surface tension. The representative dyes of DSSCs are ruthenium-complex molecules, which are expensive and require a complicated synthesis process. In this paper, the eco-friendly DSSCs were presented based on water-based electrolytes and a commercially available organic dye. The effect of aging time after the device fabrication and the electrolyte composition on the photovoltaic performance of the eco-friendly DSSCs were investigated. Plasma treatment of TiO2 was adopted to improve the dye adsorption as well as the wettability of the water-based electrolytes on TiO2. It turned out that the plasma treatment was an effective way of improving the photovoltaic performance of the eco-friendly DSSCs by increasing the efficiency by 3.4 times. For more eco-friendly DSSCs, the organic-synthetic dye was replaced by chlorophyll extracted from spinach. With the plasma treatment, the efficiency of the eco-friendly DSSCs based on water-electrolytes and chlorophyll was comparable to those of the previously reported chlorophyll-based DSSCs with non-aqueous electrolytes.

This paper introduces composite microfibers that can distinguish liquid, normal, aliphatic alcohols with high selectivity. The composite microfibers are composed of a hydrophilic agarose polymer and carbon nanotube (CNT) fillers. The CNTs distributed in the CNT-agarose composite microfiber (CAF) enable the material to sensitively change its electrical conductivity upon exposure to alcohols, induced by a change in the volume of the polymer matrix. When a CAF is highly hydrated, its resistance distinctly changes depending on the molecular weight of the alcohol via competitive mass transfer of alcohol and water. As a result, highly hydrated CAFs can selectively distinguish normal, aliphatic alcohols ranging from methanol to 1-pentanol. A provisional mechanism for the alcohol-dependent change in resistance of hydrated CAFs is suggested based on the permeation of alcohols and the discharge of water and is supported by numerical calculations using a simple diffusion model. The effects of the CNT loading ratio and the as-prepared CAF diameter on the alcohol-dependent resistance change are investigated. Furthermore, the highly hydrated CAFs are used to determine the volume ratios of binary mixtures of methanol/ethanol and ethanol/water. Finally, we demonstrate that a CAF alcohol sensor can identify commercial liquors with different alcohol contents.

Fiber electrodes provide interesting opportunities for energy storage by providing both mechanical flexibility and the opportunity to impart multifunctionality to fabrics. We show here carbon nanotube (CNT)-embedded agarose gel composite fiber electrodes, with a diameter of ∼120 μm, consisting of 60 wt % CNTs that can serve as the basis for flexible and wearable fiber microsupercapacitors (mSCs). Via an extrusion process, CNT bundles are induced to align in an agarose filament matrix. Due to the shear alignment of the CNT bundles, the dehydrated filaments have an electrical conductivity as high as 8.3 S cm–1. The composite fiber electrodes are mechanically stable, enabling formation of twisted two-ply fiber mSCs integrated with a solid electrolyte. The fiber mSC shows a high capacitance (∼1.2 F cm–3), good rate retention (∼90%) at discharge current densities ranging from 5.1 to 38 mA cm–3, long cycle life under repeated charging/discharging (10% fade after 10 000 cycles) and good performance after at leas...

The unique profile of upregulated glycosylation in metastatic cancer cells may form the basis for the development of new biomarkers for the targeting and diagnosis of specific cancers. This study introduces a pancreatic cancer cell-derived exosome detection technology, which is based on the specific binding of lectins to distinctive glycan profiles on the surface of exosomes. Lectins with a high and specific affinity for sialic acid or fucose were attached to bifunctional Janus nanoparticles (JNPs), which facilitated interactions with pancreatic cancer cell-derived exosomes in a microfluidic device. Here, we show that pancreatic cancer cell-derived exosomes from two cell lines and plasma samples collected from patients diagnosed with pancreatic cancer were successfully captured on the lectin-conjugated JNPs with affinities that were comparable to those of CA19-9, a conventional antibody. In addition, exosome detection using our platform could differentiate between metastatic and nonmetastatic pancreatic cancer cells. This study opens the possibility to achieve a new early diagnosis marker based on the glycan properties of pancreatic cancer cell-derived exosomes.

With the growing demand for measurements of organophosphate (OP) pesticide use in agriculture along with the potential threat of OP-based chemical warfare agents, there is a need for new devices or surfaces that can quickly degrade OPs into less toxic substances in a variety of environments. Using surface-initiated atom transfer radical polymerization and post-polymerization synthesis, we prepared a series of quaternary ammonium fluoride-based polymer brushes designed to absorb and degrade OPs. Specifically, a polymer brush was formed using 2-dimethylamino-ethyl methacrylate (DMAEMA) as monomer, which, following post-polymerization quaternization of the tertiary amine with alkylating agents and fluoride ion exchange, afforded the OP-reactive polymer surfaces. Poly(DMAEMA) brushes were grown to thicknesses of ~100 nm on silicon wafers and glass slides and characterized by ellipsometry, atomic force microscopy, and Raman spectroscopy. Quaternization and subsequent ion exchange of the brushes were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy, respectively. The interaction of the brushes with OPs was evaluated using the OP-based pesticide coumaphos, through the presence of the highly fluorescent degradation product chlorferon; analyzed qualitatively via fluorescence microscopy; and confirmed via nuclear magnetic resonance and mass spectrometry. We found that the fluoride form of the brush reliably degraded coumaphos deposited via controlled solution-based applications and aerosol applications (electrohydrodynamic jetting) and from microcontact printing of the dried solid directly onto the brush. No degradation was seen for coumaphos deposited on poly(DMAEMA) or the iodide form of the quaternized brush. Copyright © 2016 John Wiley & Sons, Ltd.

We report a general diffusion based method to form micrometer-scale lateral chemical gradients in polymer brushes via selective alkylation. A quaternized brush gradient is derived from a concentration gradient of alkylating agent formed by diffusion in permeable media around a microchannel carrying the alkylating agent. Polymer brushes containing both charge and aromatic gradients are formed using the alkylating agents, methyl iodide and benzyl bromide, respectively. The gradients are quantitatively characterized by confocal Raman spectroscopy and qualitatively by fluorescence microscopy. The length and gradient strength can be controlled by varying the diffusion time, concentrations, and solvents of the alkylating agent solutions. This microfluidic brush gradient generation method enables formation of 2-D chemical potential gradients with a diversity of shapes.

Graphene based electrical conductors are under consideration for numerous applications in energy storage, energy conversion devices, electronics and sensors. Here, we report a facile and versatile method for fabrication of graphene based composite microwires ranging from ∼20 to 250 μm in diameter via size reduction during dehydration of extruded larger diameter graphene oxide-loaded agarose hydrogel fibers. The graphene oxide is effectively reduced to graphene by chemical and thermal treatment. After dehydration and reduction, the resulting graphene composite microwires exhibit high electrical conductivities of up to 1.8 S m−1.

A soft-matter-based diode composed of hydrogel and liquid metal (eutectic gallium indium, EGaIn) is presented. The ability to control the thickness, and thus resistivity, of an oxide skin on the metal enables rectification. First, a simple model system with liquid-metal/electrolyte-solution/Pt interfaces is characterized. The electrically insulating oxide skin on the EGaIn electrode is reduced or oxidized further depending on the direction of the bias, thereby allowing unidirectional ionic current. The forward current of the diode increases as the conductivity of the electrolyte increases, whereas backward current depends on the pH of the medium in contact with the insulating oxide layer on the EGaIn electrode. As a result, the diode shows a higher rectification ratio (defined as the ratio of forward to backward current measured at the same absolute bias) with more conductive electrolyte at neutral pH. Replacement of the liquid electrolyte solution with a hydrogel improves the structural stability of the soft diode. The rectification performance also improves due to the increased ionic conductivity by the gel. Finally, a diode composed entirely of soft materials by replacing the platinum electrode with a second liquid-metal electrode is presented. Contacting each liquid metal with a polyelectrolyte gel featuring different pH values provided asymmetry in the device, which is necessary for rectification. A hydrogel layer infused with a strong basic polyelectrolyte removes the insulating oxide layer, allowing one interface with the EGaIn electrode to be conductive regardless of the direction of bias. Thus, the oxide layer at the other interface rectifies the current.

Materials which induce molecular motion without external input offer unique opportunities for spatial manipulation of molecules. Here, we present the use of polyacrylamide hydrogel films containing built-in chemical gradients (enthalpic gradients) to direct molecular transport. Using a cationic tertiary amine gradient, anionic molecules were directionally transported up to several millimeters. A 40-fold concentration of anionic molecules dosed in aerosol form on a substrate to a small region at the center of a radially symmetric cationic gradient was observed. The separation of mixtures of charged dye molecules was demonstrated using a boronic acid-to-cationic gradient where one molecule was attracted to the boronic acid end of the gradient, and the other to the cationic end of the gradient. Theoretical and computational analysis provides a quantitative description of such anisotropic molecular transport, and reveals that the gradient-imposed drift velocity is in the range of hundreds of nanometers per second, comparable to the transport velocities of biomolecular motors. This general concept of enthalpy gradient-directed molecular transport should enable the autonomous processing of a diversity of chemical species.

Three 2 : 1 salts of the organic donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) with trifluoromethylsulfonyl-based anions N(SO2CF3)2−, CH(SO2CF3)2− and C(SO2CF3)3− were prepared by electrocrystallization. These salts were characterized by single-crystal X-ray diffraction, electron spin resonance (ESR) spectroscopy, electrical resistivity measurements and electronic band structure calculations. (ET)2N(SO2CF3)2 is a two-dimensional (2D) metal, but its ESR spin susceptibility above 150 K shows a weakly semiconducting behavior, presumably because during ESR measurements the sample cooling rate is slow hence allowing the disordered anions to readjust their positions. (ET)2CH (SO2CF3)2 is a 2D metal and undergoes a metal-to-insulator (MI) transition at 110 K due probably to a geometry change of the donor molecule layers. (ET)2C(SO2CF3)3 is a one-dimensional (1D) metal and undergoes an MI between 180 and 240 K, which is expected to be of charge density wave type.

In an attempt to synthesize new synthetic metals which couple magnetic properties to conductivity, we prepared the novel salt (BEDT-TTF)2[Fe(tdas)2] [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, hereafter referred to as ET; tdas = 1,2,5-thiadiazole-3,4-dithiolate] by the electrocrystallization technique. The crystal structure of this compound, as determined by single crystal X-ray diffraction, contains conducting, organic ET layers separated by dimerized, magnetic [Fe(tdas)2]22− anions. Due to the magnetic insulating ground electronic state of the ET layer, thermally activated conductivity is observed, with a room temperature value of about 1 S cm−1. This salt was also characterized by EPR spectroscopy, dc magnetization measurements and Raman spectroscopy. The electronic structure of the ET layers was investigated by extended Huckel tight-binding calculations, and the spin exchange interactions of the ET and [Fe(tdas)2]− layers were examined by spin-dimer analysis.

The structural and electronic consequences of the metal–metal sigma bonding in the hexagonal perovskite sulfides were examined by calculating the electronic band structures of Sr9/8TiS3 and Sr8/7TiS3, by synthesizing Sr8/7[Ti6/7Fe1/7]S3 and characterizing its crystal structure, and by measuring the magnetic susceptibilities of Sr9/8TiS3, Sr8/7TiS3, and Sr8/7[Ti6/7Fe1/7]S3. The (TiS3)∞ chains of Sr9/8TiS3 and Sr8/7TiS3 contain oligomer units (Oh)n (n=4, 5) made up of face-sharing TiS6 octahedra (Oh). Given the (TiS3)∞ chains aligned along the z direction, the only occupied d-block levels of each (TiS3)∞ chain are the most sigma bonding level of each (Oh)n oligomer, which is constructed from its nz2 orbitals. This “n-orbital two-electron” metal–metal sigma bonding controls the d-orbital density distribution and the Ti–Ti distances of the (Oh)n oligomers and is ultimately responsible for the semiconducting property of Sr9/8TiS3, Sr8/7TiS3, and Sr8/7[Ti6/7Fe1/7]S3. The Sr8/7[Ti6/7 Fe1/7]S3 structure is described by the trigonal symmetry, R3m (00γ)0s superspace group with the following parameters: as=11.4935(11) A, cs=2.9986(7) A, q=0.57161(15) c*, and Vs=343.05(15) A3.

A new organic conductor, β″-(BEDT-TTF)2SF5CHFCF2SO3 [BEDT-TTF, hereafter abbreviated ET, refers to bis(ethylenedithio)tetrathiafulvalene], was prepared by electrocrystallization. The crystal structure of this salt was determined by single crystal X-ray diffraction at 298 and 150 K, its physical properties were examined by electrical resistivity, Raman spectroscopy and EPR measurements, and its electronic structure was calculated and compared with that of the analogous salt β″-(ET)2SF5CH2CF2SO3. Whereas β″-(ET)2SF5CHFCF2SO3 has disordered anions and undergoes a metal-to-insulator transition at ∼190 K, β″-(ET)2SF5CH2CF2SO3 has ordered anions and is semiconducting down to ∼100 K, metallic below ∼100 K, and superconducting below 5 K. At room temperature both β″-(ET)2SF5CHFCF2SO3 and β″-(ET)2SF5CH2CF2SO3 have similar electronic band structures and physical properties. When the temperature is lowered, each donor molecule stack becomes dimerized in both salts. However, the interdimer interaction within each donor stack nearly vanishes in β″-(ET)2SF5CHFCF2SO3, but remains substantial in β″-(ET)2SF5CH2CF2SO3.

The spin exchange interactions of the vanadium oxides A V 4 O 9 ( A =Ca, Sr, Cs 2 , and NH 2 (CH 2 ) 4 NH 2 ) were examined by calculating the spin orbital interaction energies of their spin dimers based on the extended Huckel method. The temperature T max at which the magnetic susceptibility maximum occurs in A V 4 O 9 ( A =Ca, Sr, Cs 2 , and NH 2 (CH 2 ) 4 NH 2 ) shows a wide variation (from 30 to 600 K) and increases in the order [NH 2 (CH 2 ) 4 NH 2 ]V 4 O 9 4 O 9 2 V 4 O 9 . The susceptibility at T max increases in the opposite order, and the room temperature susceptibility of [NH 2 (CH 2 ) 4 NH 2 ]V 4 O 9 is about twice as high as the maximum susceptibility of CaV 4 O 9 . These observations were examined by estimating the magnetic excitation energies of the strongly interacting spin units of A V 4 O 9 .

Salts of the donor molecule, bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET), with pentafluorothiomethylsulfonate (SF{sub 5}CX{sub 2}SO{sub 3}{sup -}, X = H or F) anions have been prepared. Three phases, {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}SO{sub 3}, {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3}, and {beta}'-(ET){sub 2}SF{sub 5}CHFSO{sub 3} were obtained by electrocrystallization with the corresponding LiSF{sub 5}CX{sub 2}SO{sub 3} electrolytes. The structures of these salts were determined by single-crystal X-ray diffraction, and their physical properties were examined by electrical resistivity measurements as well as by ESR and Raman spectroscopy. The {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}SO{sub 3}, {beta}'-(ET){sub 2}SF{sub 5}CHFSO{sub 3} and {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3} salts are considerably different in their crystal structures, physical properties, and electronic structures despite the similarity in the structures of the SF{sub 5}CX{sub 2}SO{sub 3}{sup -} (X = H, F) anions. The {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}SO{sub 3} salt has two kinds of ET donor molecules with considerably different charge densities. The electronic structure of {beta}'-(ET){sub 2}SF{sub 5}CHFSO{sub 3} has both one-dimensional (1D) and two-dimensional (2D) Fermi surfaces which are similar to those found in the organic superconductor {beta}'-(ET){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}. The ESR data for the {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3} salt indicate that it opens a spin gapmore » below 45 K. The differences in the physical properties of the three salts were analyzed by calculating the HOMO-HOMO interaction energies between nearest-neighbor ET molecules in their donor molecule layers.« less

The magnetic properties of Cu{sub 2}(dca){sub 4}(2,5-me{sub 2}pyz) have been reexamined. The extended structure of Cu{sub 2}(dca){sub 4}(2,5-me{sub 2}pyz) can be viewed in terms of Cu{sub 2}(2,5-me{sub 2}pyz){sup 4+} dimer units interconnected via {mu}{sub 1,5}-dca ligands. The bulk magnetic susceptibility {chi}(T) and the isothermal M(H) of Cu{sub 2}(dca){sub 4}(2,5-me{sub 2}pyz) are shown to be well described by an isolated dimer model. This finding was confirmed by carrying out a spin dimer analysis based on tight-binding calculations, which shows that the 2,5-me{sub 2}pyz ligand provides a substantial spin exchange interaction between the Cu{sup 2+} ions while the dca ligands do not.