Project description:Certain industrially relevant performance metrics of CO2 electrolyzers have already been approached in recent years. The energy efficiency of CO2 electrolyzers, however, is yet to be improved, and the reasons behind performance fading must be uncovered. The performance of the electrolyzer cells is strongly affected by their components, among which the gas diffusion electrode is one of the most critical elements. To understand which parameters of the gas diffusion layers (GDLs) affect the cell performance the most, we compared commercially available GDLs in the electrochemical reduction of CO2 to CO, under identical, fully controlled experimental conditions. By systematically screening the most frequently used GDLs and their counterparts differing in only one parameter, we tested the influence of the microporous layer, the polytetrafluoroethylene content, the thickness, and the orientation of the carbon fibers of the GDLs. The electrochemical results were correlated to different physical/chemical parameters of the GDLs, such as their hydrophobicity and surface cracking.
Project description:The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels' structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli.
Project description:This article describes novel composite thin films consisting of GaN, C, and Ga (termed "GaCN", as an analogue to BCN and other carbonitrides) as a prospective material for future optical applications. This is due to their tunable refractive index that depends on the carbon content. The composites are prepared by introducing alternating pulses of trimethylgallium (TMG) and ammonia (NH3) on silicon substrates to mimic an atomic layer deposition process. Because the GaCN material is hardly reported to the best of our knowledge, a comprehensive characterization is performed to investigate into its chemical nature, primarily to determine whether or not it exists as a single-phase material. It is revealed that GaCN is a composite, consisting of phase-segregated, nanoscale clusters of wurtzitic GaN polycrystals, in addition to inclusions of carbon, nitrogen, and gallium, which are chemically bonded into several forms, but not belonging to the GaN crystals itself. By varying the deposition temperature between 400 and 600 °C and the NH3 partial pressure between 0.7 × 10-3 and 7.25 mbar, layers with a wide compositional range of Ga, C, and N are prepared. The role of carbon on the GaCN optical properties is significant: an increase of the refractive index from 2.19 at 1500 nm (for carbon-free polycrystalline GaN) to 2.46 (for GaCN) is achieved by merely 10 at. % of carbon addition. The presence of sp2-hybridized C=N clusters and carbon at the interface of the GaN polycrystals are proposed to determine their optical properties. Furthermore, the formation of the GaN polycrystals in the composite occurs through a TMG:NH3 surface-adduct assisted pathway, whereas the inclusions of carbon, nitrogen, and gallium are formed by the thermal decomposition of the chemisorbed TMG species.
Project description:Conventionally, only two states are assumed to exist in water: well-dispersed gas monomers and gas bubbles. Rarely is this paradigm explored experimentally. To close this gap, here we used transmission electron microscopy (TEM) to study degassed water, deionized water, and gas-supersaturated water encapsulated in graphene liquid cells. While neither degassed water nor deionized water yielded specific features, two major microscopic structures were evident in gas-supersaturated water: (1) polycrystalline nanoparticles formed of gas molecules and (2) a high density of tiny cells. Dark-field TEM imaging revealed that water molecules surrounding each cell form crystalline structures-a surprising discovery of a clathrate state in gas-supersaturated water that may help resolve several long-standing puzzles. Overall, this study suggests that water may form a matrix that actively interacts with gas molecules in complex and subtle ways.
Project description:DNA nanotechnology facilitates the synthesis of biomimetic models for studying biological systems. This work uses lipid bilayers as platforms for two-dimensional single-particle tracking of the dynamics of DNA nanostructures. Three different DNA origami structures adhere to the membrane through hybridization with cholesterol-modified strands. Their two-dimensional diffusion coefficient is modulated by changing the concentration of monovalent and divalent salts and the number of anchors. In addition, the diffusion coefficient is tuned by targeting cholesterol-modified anchor strands with strand-displacement reactions. We demonstrate a responsive system with changing diffusivity by selectively displacing membrane-bound anchor strands. We also show the programmed release of origami structures from the lipid membranes.
Project description:The blood gas and biochemical reference range established with i-STAT clinical analyzer in avian has become common, however, the reference value for various laying hen lines is limited. Therefore, blood gas and biochemical reference intervals will be established for Lohmann Silver layers in the pre- and post-laying periods. The blood sample was collected at a 4-wk interval. A total of 230 Lohmann Silver layers including 80 pullets (5-17 wk) and 150 laying hens (21-37 wk) were collected for whole blood measurement with the i-STAT clinical analyzer. The CG8+ cartridge provides values of the following 13 parameters: sodium (Na mmol/L), potassium (K mmol/L), ionized calcium (iCa mmol/L), glucose (Glu mg/dL), hematocrit (Hct% Packed Cell Volume [PCV]), pH, partial pressure carbon dioxide (PCO2 mm Hg), partial pressure oxygen (PO2 mm Hg), total concentration carbon dioxide (TCO2 mmol/L), bicarbonate (HCO3 mmol/L), base excess (BE mmol/L), oxygen saturation (sO2%), and hemoglobin (Hb g/dL). The correlation of these parameters and the effect of physiological status were investigated. The reference value interval was established with a reference value advisor for pre-laying and post-laying birds. Correlations were found to be statistically significant, especially between BE and HCO3 and TCO2. Besides, values in Na, iCa, K, Hct, Hb, sO2 differed significantly between the pre- and post-laying periods. Data in this study might serve as important information for facilitating the genetic selection and assessing the health of Lohmann Silver laying hens.
Project description:Magnetic skyrmions, topologically-stabilized spin textures that emerge in magnetic systems, have garnered considerable interest due to a variety of electromagnetic responses that are governed by the topology. The topology that creates a microscopic gyrotropic force also causes detrimental effects, such as the skyrmion Hall effect, which is a well-studied phenomenon highlighting the influence of topology on the deterministic dynamics and drift motion. Furthermore, the gyrotropic force is anticipated to have a substantial impact on stochastic diffusive motion; however, the predicted repercussions have yet to be demonstrated, even qualitatively. Here we demonstrate enhanced thermally-activated diffusive motion of skyrmions in a specifically designed synthetic antiferromagnet. Suppressing the effective gyrotropic force by tuning the angular momentum compensation leads to a more than 10 times enhanced diffusion coefficient compared to that of ferromagnetic skyrmions. Consequently, our findings not only demonstrate the gyro-force dependence of the diffusion coefficient but also enable ultimately energy-efficient unconventional stochastic computing.
Project description:A one-step synthesis of magnetic nickel nanowires (NiNWs) with tunable characteristics is reported. The method is simple and easy to be conducted, leading to high compatibility with scaling-up. It is discovered that the size and morphology of NiNWs can be adjusted by tuning the reaction temperature, time length, as well as surfactant concentration. It is found that the products have shown high purity which remained after being stored for several months. A remarkable enhanced saturation magnetization of the product was also observed, compared to that of bulk nickel. By providing both practical experimental details and in-depth mechanism, the work introduced in this paper may advance the mass production and further applications of NiNWs.
Project description:Hydrogenases, which catalyze H(2) to H(+) conversion as part of the bioenergetic metabolism of many microorganisms, are among the metalloenzymes for which a gas-substrate tunnel has been described by using crystallography and molecular dynamics. However, the correlation between protein structure and gas-diffusion kinetics is unexplored. Here, we introduce two quantitative methods for probing the rates of diffusion within hydrogenases. One uses protein film voltammetry to resolve the kinetics of binding and release of the competitive inhibitor CO; the other is based on interpreting the yield in the isotope exchange assay. We study structurally characterized mutants of a NiFe hydrogenase, and we show that two mutations, which significantly narrow the tunnel near the entrance of the catalytic center, decrease the rates of diffusion of CO and H(2) toward and from the active site by up to 2 orders of magnitude. This proves the existence of a functional channel, which matches the hydrophobic cavity found in the crystal. However, the changes in diffusion rates do not fully correlate with the obstruction induced by the mutation and deduced from the x-ray structures. Our results demonstrate the necessity of measuring diffusion rates and emphasize the role of side-chain dynamics in determining these.
Project description:Clays and clay rocks are considered good natural and engineered barriers for deep geological disposal of nuclear waste worldwide. Metal corrosion and organic waste degradation in underground repositories generate significant amounts of gas that should be able to migrate through the multibarrier system to avoid potential pressure buildup, which could be compromising the integrity of the barriers and host rocks. The gas is expected to accumulate in larger pores and eventually form an interconnected network. Under such conditions, the migration of gas molecules takes place both in pore water films and gas-filled macropores. Therefore, mass fluxes depend on the distribution of gas molecules between the water-rich and gas-rich phases and their mobility in both compartments. Classical molecular dynamics (MD) simulations were employed to investigate the mobilities of He, H2, CO2, Ar, and CH4 in a Na-montmorillonite mesopore as a function of the degree of saturation, as well as evaluate the hydrodynamic behavior of the pore fluid in partially saturated clays. The diffusivity of the gas molecules was determined by observing the asymptotic behavior of the mean square displacement in the gas-rich phase and at the gas-water interface. The partition coefficient and Gibbs free energy were analyzed to investigate the transfer of gas molecules between the gas-rich and water-rich phases by observing the molecular trajectories as they cross the vapor-liquid interface. The results revealed that the diffusion coefficient in the gas phase increased with increasing gas-filled pore width and converged asymptotically toward the diffusion coefficient in the bulk state. It could be shown that the diffusion coefficient of gas molecules dissolved in the water films remained constant as long as the interacting water surface was in the bulk-liquid-like phase. This behavior changes in very thin water films. It was observed that the partitioning coefficient of gas molecules at the solid-liquid interface is nearly the same as that in the bulk-liquid-like phase. Partitioning is observed to be strongly dependent on the temperature and gas molecular weights. In the second part of the study, nonequilibrium molecular dynamics (NEMD) simulations were performed to investigate the mobility of gases in pressure-driven decoupled gas-phase dynamics (DGPD) and coupled gas and water phase dynamics (CGWPD) in a partially saturated Na-montmorillonite slit mesopore. The dynamic viscosity of the gas phase was calculated from NEMD simulations and indicated that the viscosity of the gas phase was almost the same in both methods (DGPD and CGWPD). The average slip length for gas molecules at the gas-water interface was also calculated, revealing that the slip-free boundary condition assumed in continuum models is generally invalid for microfluidics and that a slip boundary condition exists at the microscale for specific surface interactions. Finally, a Bosanquet-type equation was developed to predict the diffusion coefficient and dynamic viscosity of gas as a function of the average pore width, gas mean-free path, geometric factor, and thickness of the adsorbed water film.