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Research demonstrates the preparation of molecular recognition ion gating membranes by the peroxide plasma graft copolymerization process. Results show that the membranes exhibit molecular recognition properties and spontaneously control the solution flux and change the pore size in response to specific ion concentration.

A new diffusion-adsorption method for estimating the permability of zeolite membranes is presented.

The transport mechanism, electrical conductivity, water uptake and benzene vapor transports of silver-containing solid-type carrier membranes have been studied. AgBF4/Nafion blend membrane and silver form Nafion membrane are used as models for the salt/polymer blend membrane and ion-exchange type membrane. Results indicated that ionic carriers in the AgBF4/Nafion blend membrane are mobile at low humidity. The AgBF4/Nafion's water uptake is low similar to an ion-exchange Nafion membrane. The membrane selects benzene over cyclohexane at low humidity.

A high-surface-area biofuel cell electrode formed by immobilization of hydroquinone through a spacer to polymer grafted on carbon black is described. The potential at which an anodic current began to increase was more negative by about 0.2 V than that for a vinylferrocene-mediated electrode while the increase in the anodic current density was of the same order.

Osmotic pressure, that is important in both artificial membranes and in biomembranes, is controlled by a few gating membranes that mimic the function of biomembranes. A molecular recognition ion gating membrane was developed that can control the size of its pores in response to a specific ion signal.

The presence of hydrogen bonding in chloroform-acrylate polymer mixtures was demonstrated by observation of (super 1)H and (super 13)C NMR chemical shifts. Comparison of the NMR chemical shifts in polymer solutions with their low molecular weight analogues showed the effect of stearic hindrance on hydrogen bonding.

A fast response molecular recognition ion gating membrane has been developed using a thermosensitive linear polymer having a crown ether receptor. The thermosensitive polymer, N-isopropylacrylamide, displays a remarkable gating effect caused by gel swelling, while the crown ether receptor allows ionic molecular sensing. This polymer is ideal for making a molecular recognition gate membrane because the gel itself is capable of recognizing the chemical signal, and the polymer may exhibit very fast sensing and high gating characteristics.

Molecular diffusivity in polymericsystems is often the determiningfactor in performance and efficiency of devices and systems and thusis one of the most important dynamic properties. In polymeric systems,various penetrants, including gas, solvent, and solute molecules candiffuse, and therefore, a general model that can broadly provide theirmolecular diffusivity could strongly accelerate the designing of polymericdevices. On the other hand, from the microscopic viewpoint, the moleculardiffusive motion can be regarded as a random walk movement subjectto an enormous number of molecular collisions with neighboring molecules.Therefore, in the present study, both of the microscopic descriptionscommon for all penetrants in polymeric systems have been unified intoone model. The resultant model is the first general diffusion modelthat can describe diffusivity of all penetrants, including gas, solvent,and solute molecules in rubbery polymeric systems. The applicabilityof the microscopic model is demonstrated to be acceptable, exceptin pure polymer near its glass transition temperature. [ABSTRACT FROM AUTHOR]

Osmotic pressure control of blood relates to sympathetic nerve activity. It has been reported that osmotic pressure drives phage DNA to host cells. The balance of osmotic pressure and surface tension determines the volume, surface area, and form of liposomes. In this way, osmotic pressure plays many important roles and is controlled by molecular signals in biosystems. Researchers have developed a molecular recognition ion gating membrane that can control its pore size in response to a specific ion signal. The copolymer of N-isopropylacrylamide (NIPAM) and benzo[18]-crown-6-acrylamide (BCAm) was grafted onto the pore surface of this membrane. NIPAM is a thermosensitive polymer and acts as an actuator by its volume phase transition. BCAm has a crown ether receptor and works as an ion sensor.

Mixed-anion compounds have recently attracted attention as solid-state materials that exhibit properties unattainable with those of their single-anion counterparts. However, the use of mixed-anion compounds to control the morphology and engineer the crystal facets of electrocatalysts has been limited because their synthesis method is still immature. This study explored the electrocatalytic properties of a Pb-Fe oxyfluoride, Pb 3 Fe 2 O 5 F 2 , with a layered perovskite structure for oxygen evolution reaction (OER) and compared its properties in detail with those of a bulk-type cubic three-dimensional (3D) perovskite, PbFeO 2 F. A Pb 3 Fe 2 O 5 F 2 electrode prepared with carbon nanotubes and a graphite sheet as a conductive support and a substrate, respectively, demonstrated better OER performance than a PbFeO 2 F electrode. The role of specific crystal facets of Pb 3 Fe 2 O 5 F 2 in enhancing the OER activity was elucidated through electrochemical analysis. Density functional theory calculations indicated that the Pb 3 Fe 2 O 5 F 2 (060) facet with Fe sites exhibited a lower theoretical overpotential for the OER, which was attributed to a moderately strong interaction between the active sites and the reaction intermediates; this interaction was reinforced by the strong electron-withdrawing behavior of fluoride ions. This finding offers new insights for developing efficient electrocatalysts based on oxyfluorides, leveraging the high electronegativity of fluorine to optimize the electronic states at active sites for the OER, without relying on precious metals.

Stimuli-responsive star polymers are promising functional materials whose aggregation, adhesion, and interaction with cells can be altered by applying suitable stimuli. Among several stimuli assessed, the potassium ion (K + ), which is known to be captured by crown ethers, is of considerable interest because of the role it plays in the body. In this study, a K + -responsive star copolymer was developed using a polyglycerol (PG) core and grafted copolymer arms consisting of a thermo-responsive poly( N -isopropylacrylamide) unit, a metal ion-recognizing benzo-18-crown-6-acrylamide unit, and a photoluminescent fluorescein O -methacrylate unit. Via optimization of grafting density and copolymerization ratio of grafted arms, along with the use of hydrophilic hyperbranched core, microsized aggregates with a diameter of 5.5 μm were successfully formed in the absence of K + ions without inducing severe sedimentation (the lower critical solution temperature (LCST) was 35.6 °C). In the presence of K + ions, these aggregates dispersed due to the shift in LCST (47.2 °C at 160 mM K + ), which further induced the activation of fluorescence that was quenched in the aggregated state. Furthermore, macrophage targeting based on the micron-sized aggregation state and subsequent fluorescence activation of the developed star copolymers in response to an increase in intracellular K + concentration were performed as a potential K + probe or K + -responsive drug delivery vehicle., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the most critical reactions that limit the efficiency of fuel cells, water electrolyzers, and metal-air batteries. Therefore, a need exists to develop cost-effective and highly active alternative electrocatalysts for ORR and OER. This study investigates the influence of metal coordination fashion on electrocatalytic ORR and OER activities among three types of Co-Mn bimetallic oxides (CMOs): tunnel-type (CMO_T), layer-type (CMO_L), and spinel-type (CMO_S) structures. An electrochemical evaluation for CMOs verifies that CMO_L has the highest ORR and OER specific activities, which is relatively better than the previously reported bifunctional metal oxides. Additionally, atomic configuration analysis for the oxides suggests that the excellent ORR and OER activities of CMO_L result from the difference in Co and Mn coordination states. This paper not only presents an excellent electrocatalyst for alkaline fuel cells and water electrolyzers but also provides an important guideline for the design of oxygen electrocatalysts., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

Nitrogen containing mesoporous carbon obtained by the pyrolysis of graphene oxide (GO) wrapped ZIF-8 (Zeolitic Imidazolate Frameworks-8) micro crystals is demonstrated to be an efficient catalyst for the oxygen reduction reaction (ORR). ZIF-8 synthesis in the presence of GO sheets helped to realize layers of graphene oxide over ZIF-8 microcrystals and the sphere-like structures thus obtained, on heat treatment, transformed to highly porous carbon with a nitrogen content of about 6.12% and surface area of 502 m 2 /g. These catalysts with a typical micromeso porous architecture exhibited an onset potential of 0.88Vvs RHE in a four electron pathway and also demonstrated superior durability in alkaline medium compared to that of the commercial Pt/C catalyst. The N-doped porous carbon derived from GO sheathed ZIF-8 core-shell structures could therefore be employed as an efficient electrocatalyst for fuel cell applications.

Design of Pt alloy catalysts with enhanced activity and durability is a key challenge for polymer electrolyte membrane fuel cells. In the present work, we compare the durability of the ordered intermetallic face-centered tetragonal (fct) PtFeCu catalyst for the oxygen reduction reaction (ORR) relative to its counterpart bimetallic catalysts, i.e., the ordered intermetallic fct-PtFe catalyst and the commercial catalyst from Tanaka Kikinzoku Kogyo, TKK-PtC. Although both fct catalysts initially exhibited an ordered structure and mass activity approximately 2.5 times higher than that of TKK-Pt/C, the presence of Cu at the ordered intermetallic fct-PtFeCu catalyst led to a significant enhancement in durability compared to that of the ordered intermetallic fct-PtFe catalyst. The ordered intermetallic fct-PtFeCu catalyst retained more than 70% of its mass activity and electrochemically active surface area (ECSA) over 10 000 durability cycles carried out at 60 °C. In contrast, the ordered intermetallic fct-PtFe catalyst maintained only about 40% of its activity. The temperature of the durability experiment is also shown to be important: the catalyst was more severely degraded at 60 °C than at room temperature. To obtain insight into the observed enhancement in durability of fct-PtFeCu catalyst, a postmortem analysis of the ordered intermetallic fct-PtFeCu catalyst was carried out using scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX) line scan. The STEM-EDX line scans of the ordered intermetallic fct-PtFeCu catalyst over 10 000 durability cycles showed a smaller degree of Fe and Cu dissolution from the catalyst. Conversely, large dissolution of Fe was identified in the ordered intermetallic fct-PtFe catalyst, indicating a lesser retention of Fe that causes the destruction of ordered structure and gives rise to poor durability. The enhancement in the durability of the ordered intermetallic fct-PtFeCu catalyst is ascribed to the synergistic effects of Cu presence and the ordered structure of catalyst.

A bioinspired geometric templating of an electrospun PVDF substrate with hexagonal platelets of Mg-Al layered double hydroxide (LDH), an intrinsic anion conductor, is presented. The distinctive morphology restructures the internal pore geometry and modulates the dynamic wetting profile of PVDF, transforming it into a highly functional substrate for SAFC anion conducting membranes. The membrane fabricated with PVDF-LDH substrate exhibited exceptionally high durability (>140 °C), high anionic conductivity, ion exchange capacity (IEC), restricted swelling, and improved tensile strength, overcoming critical challenges associated with PVDF electrospun substrates and validating its immense potential as a high-temperature-stable and durable substrate for advanced fuel cell membrane applications.

Available methods to analyze proton conduction mechanisms cannot distinguish between two proton-conduction processes derived from the Grotthuss mechanism. The two mechanistic variations involve structural diffusion, for which water movement is indispensable, and the recently proposed "packed-acid mechanism," which involves the conduction of protons without the movement of water and is typically observed in materials consisting of highly concentrated (packed) acids. The latter mechanism could improve proton conductivity under low humidity conditions, which is desirable for polymer electrolyte fuel cells. We proposed a method with which to confirm quantitatively the packed-acid mechanism by combining (2)H and (17)O solid-state magic-angle-spinning nuclear magnetic resonance (MAS-NMR) measurement and (1)H pulsed-field gradient (PFG)-NMR analysis. In particular, the measurements were performed below the water-freezing temperature to prevent water movement, as confirmed by the (17)O-MAS-NMR spectra. Even without water movement, the high mobility of protons through short- and long-range proton conduction was observed by using (2)H-MAS-NMR and (1)H-PFG-NMR techniques, respectively, in the composite of zirconium sulfophenylphosphonate and sulfonated poly(arylene ether sulfone) (ZrSPP-SPES), which is a material composed of highly concentrated acids. Such behavior contrasts with that of a material conducting protons through structural diffusion or vehicle mechanisms (SPES), in which the peaks in both (2)H and (17)O NMR spectra diminished below water-freezing temperature. The activation energies of short-range proton movement are calculated to be 2.1 and 5.1 kJ/mol for ZrSPP-SPES and SPES, respectively, which indicate that proton conduction in ZrSPP-SPES is facilitated by the packed-acid mechanism. Furthermore, on the basis of the mean-square displacement using the diffusivity coefficient below water-freezing temperature, it was demonstrated that long-range proton movement, of the order of 1.3 μm, can take place in the packed-acid mechanism in ZrSPP-SPES.

Molecular collisions, which are the microscopic origin of molecular diffusive motion, are affected by both the molecular surface area and the distance between molecules. Their product can be regarded as the free space around a penetrant molecule defined as the "shell-like free volume" and can be taken as a characteristic of molecular collisions. On the basis of this notion, a new diffusion theory has been developed. The model can predict molecular diffusivity in polymeric systems using only well-defined single-component parameters of molecular volume, molecular surface area, free volume, and pre-exponential factors. By consideration of the physical description of the model, the actual body moved and which neighbor molecules are collided with are the volume and the surface area of the penetrant molecular core. In the present study, a semiempirical quantum chemical calculation was used to calculate both of these parameters. The model and the newly developed parameters offer fairly good predictive ability., (© 2011 American Chemical Society)

A controlled-release device that responds to a specific molecular signal is an ideal goal in drug delivery and tissue engineering. A molecular recognition ion gating membrane, in which a copolymer of N-isopropylacrylamide and benzo[18]-crown-6-acrylamide was grafted onto the surface of the porous polyethylene film, was used to control the permeability of vitamin B12 and lysozyme in response to a specific ion signal. The observed response depended on the amount of grafted copolymer. When the grafting ratio was below 15%, the membrane pores opened by Ca2+ and closed by Ba2+. The permeability of model drugs became higher by opening of the pores. On the other hand, when the grafting ratio was above 15%, the properties of the membrane changed. The permeability of model drugs became lower by Ca2+ due to dehydration of the grafted copolymer. The opposite responses were observed at different grafting ratios.

We developed a rapidly regenerable cell culture system in which the cell culture substrate detects cell death and selectively releases the dead cells. This culture material was achieved by combining a detector that responds to the signal from the dead cells and an actuator to release the dead cells. Benzo-18-crown-6-acrylamide (BCAm) with a pendant crown ether receptor was used as the sensor to recognize cellular signals and N-isopropylacrylamide (NIPAM) was used as the actuator. This copolymer of NIPAM and BCAm can respond to potassium ions and change its nature from hydrophobic to hydrophilic at the culture temperature of 37 degrees C. Living cells concentrate potassium ion internally; when cells die, potassium ions are released. The polymer surface recognizes the potassium ions released from the dead cells, the NIPAM hydrates, and the dead cells are selectively detached. This in vitro culture system is a novel one in which artificial culture materials work cooperatively with cellular metabolism by responding to this signal from the cells, thereby realizing in vitro tissue regeneration partly mimicking the mechanisms of in vivo homeostasis.