Search

Automatically finding novel pathways plays an important role in the initial designs of metabolic pathways in synthetic biology and metabolic engineering. Although path-finding methods have been successfully applied in identifying valuable synthetic pathways, few efforts have been made in fusing atom group tracking into building stoichiometry model to search metabolic pathways from arbitrary start compound via Mixed Integer Linear Programming (MILP). We propose a novel method called AFP to find metabolic pathways by incorporating atom group tracking into reaction stoichiometry via MILP. AFP tracks the movements of atom groups in the reaction stoichiometry to construct MILP model to search the pathways containing atom groups exchange in the reactions and adapts the MILP model to provide the options of searching pathways from an arbitrary or given compound to the target compound. Combining atom group tracking with reaction stoichiometry to build MILP model for pathfinding may promote the search of well-designed alternative pathways at the stoichiometric modeling level. The experimental comparisons to the known pathways show that our proposed method AFP is more effective to recover the known pathways than other existing methods and is capable of discovering biochemically feasible pathways producing the metabolites of interest. [Display omitted] • AFP tracks the movement of atom group in stoichiometric model to find pathways. • AFP offers the option of finding pathway from arbitrary compound to given compound. • The results show that AFP is able to uncover biochemically feasible pathway. [ABSTRACT FROM AUTHOR]

The mechanism of gas-melt interactions and the compositions of precursors are key to understanding the formation of chondrules. To shed light on the two enigmas, we studied the petrography, chemistry, and oxygen isotopes of six Al-rich chondrules (ARCs, five glassy and one plagioclase-bearing) in unequilibrated ordinary chondrites (OCs, petrologic subtype: 3.05). The plagioclase-bearing ARC was also investigated with Al-Mg chronology. Elemental zonation and inter-element correlations in glassy mesostasis of two ARCs indicate the condensation of gaseous Mg, SiO, Fe, and Na onto chondrule melt. The plagioclase-bearing ARC appears to display internal mass-independent oxygen isotope fractionation with δ18O increasing following the order of mineral crystallization, suggesting partial oxygen isotope exchange with ambient gas during crystallization. Oxygen isotopes of the six ARCs are distributed along a mixing line of slope = 0.99 ± 0.05, which intersects with calcium-aluminum-rich inclusions (CAIs), consistent with a small portion of OC type IA chondrules, but deviates from other OC ferromagnesium chondrules (FMCs) towards higher δ17O, suggesting that OC ARCs and some IA chondrules were established by interactions between CAI-like melts and 16O-poor ambient gas, rather than simply remelting solid mixtures of CAI and FMC materials. All six ARCs have unfractionated refractory lithophile element patterns with bulk concentrations ranging from ∼7 × CI to ∼15 × CI, indicating ∼ 30–100 % of CAI-like materials in their precursors. Their bulk compositions are linearly evolved toward the Mg: SiO ∼ 3:2 to 2:1 (in atomic) apex, consistent with adding gaseous Mg and SiO to the chondrule bulk via gas–melt interactions. The back-calculated compositions of the recycled CAI-like materials closely overlap with pyroxene-anorthite-rich CAIs, suggesting that extensive interactions between the melt of pyroxene-anorthite-rich CAI-like materials and ambient gas could make OC ARCs. The Al-Mg age of the plagioclase-bearing ARC is ∼2.2 Ma after CAIs, similar to typical OC FMCs, suggesting that the refractory component arrived at the OC reservoirs in the late stage of the chondrule heating events. [ABSTRACT FROM AUTHOR]

Dissolution of calcite in water is fundamental to geochemistry. Laboratory methods generally give consistent dissolution rates under conditions far from equilibrium, but close to equilibrium the measurement of dissolution using isotopes is complicated by poorly understood calcite-fluid isotopic exchange processes. This near-equilibrium isotopic exchange occurs in laboratory experiments at rates of order 10-9 to 10-13 mol/m2/s and decreases with experiment duration approximately as 1/time where time is measured from the start of the experiment. Such rates are fast enough to compete with dissolution in days-long experiments and consequently, net dissolution rates may not be measurable with isotopic tracer methods except in experiments carried out for long enough to allow the background exchange to dissipate sufficiently. To better define what should be expected for isotopic signals during dissolution, we develop a quasi-1D model for calcite dissolution that includes the mechanistically unconstrained isotopic exchange as well as solid state diffusion. We use the model, the observations reported in the literature, and the calcite dissolution rates in seawater reported by Naviaux et al., (2019a) to illustrate ambiguities in measurement of near-equilibrium calcite dissolution rates. The results suggest that the reaction order of calcite dissolution close to equilibrium could be 2 at both room temperature and the lower temperatures of the seafloor. The reaction order of near-equilibrium calcite dissolution is important for understanding calcite mineral surface processes, long-term behavior of dissolution on the seafloor, and alkalinity fluxes from modern seafloor sediments. Distinguishing between net dissolution, which affects fluid saturation state, and "exchange," which doesn't, is important but typically cannot be done with isotopic tracers alone. [ABSTRACT FROM AUTHOR]

This work conducts ablation experiments and multi-scale numerical simulations of C/SiC composite materials under CW laser action. The highest surface temperature, macroscopic and microscopic ablation morphology, and approximate ablation threshold for C/SiC composites at different power densities were obtained. A multi-scale ablation calculation method for C/SiC composite materials under CW laser action was established using the level-set method. At the meso-scale, a macro-mesoscopic cross-scale surface ablation model was established, taking into account factors such as solid heat transfer, heat exchange of chemical reactions, differential temperature rise process between internal fibers and matrix, and differences in ablation behavior of two-dimensional plain weave fabrics. The experimental and microscale simulation results indicate that different ablation behaviors (oxidation and sublimation) occur in different regions, resulting in "shoot tip" fibers and residual matrix pore morphology. This work can provide theoretical and experimental basis for the design and precision machining of C/SiC materials. [ABSTRACT FROM AUTHOR]

The reaction mechanism and kinetics of oxygen isotope exchange between tens of nanometer-sized amorphous silicate grains with forsterite composition (amorphous forsterite) and low-pressure carbon monoxide (CO) gas (P CO) of 0.05–1 Pa at 643–883 K were examined to investigate oxygen isotopic evolution in the protosolar disk that led to the mass-independent oxygen isotopic variation of planetary materials. Both CO gas supply- and diffusion-controlled isotope exchange reactions were observed. At 753–883 K and P CO of 0.05–1 Pa, the supply of CO gas controls the isotope exchange reaction, and its rate is 2–3 orders of magnitude smaller than that of the H 2 O supply-controlled isotope exchange reaction. The diffusion-controlled isotope exchange occurred at 643–703 K and P CO of 0.3 Pa, and the reaction rate of D (m2/s) = (3.1 ± 2.3) × 10−23 exp[−41.7 ± 9.6 (kJ mol−1) R −1 (1/ T − 1/1200)] was obtained. We found that the oxygen isotope exchange rates of amorphous forsterite with CO and H 2 O gases are larger than those of gaseous isotope exchange between CO and H 2 O gases at a wide range of temperatures, wherein amorphous forsterite crystallization does not precede the isotope exchange reaction of amorphous forsterite with these gases. The most sluggish isotope exchange rate between H 2 O and CO in the gas phase suggests that amorphous forsterite would play a role in accelerating gaseous isotopic equilibrium through the isotope exchange of amorphous forsterite with both CO and H 2 O. We found that the oxygen isotopic equilibrium between 0.1 μm-sized amorphous forsterite, CO, and H 2 O would be accomplished through the isotope exchange of amorphous forsterite at temperatures as low as ∼600–700 K in the dynamically accreting protosolar disk, which is significantly lower than expected for the case of gaseous isotope exchange (>∼800 K). [ABSTRACT FROM AUTHOR]

During D-T fusion operations the capture, purification, and recycling of unburned tritium will be crucial, as the formation of tritium containing molecules require additional processing. Removing the tritium can require costly processing to be unbound from the tritium-containing molecules and improvements to these processes will be necessary moving forward. Existing techniques using sorbent material beds to remove tritium-containing molecules from process gas streams undergo repeated high-heat cycling which leads to diminished bed lifespans, necessitating replacement and associated downtime. This work demonstrates the capture and isotopic exchange technique of deuterated ammonia (ND 3), used as a surrogate for tritium, at ambient temperature using a Pt catalyst-loaded 13X molecular sieve. Unmodified 13X molecular sieve is capable of adsorbing and retaining the ND 3 however, incorporation of a catalyst facilitates the isotopic exchange of the hydrogen isotopes. The effluent gas streams were analyzed in conjunction with desorbed ammonia isotopologues post-exchange to verify these results. Isotopically exchanging and removing heavier hydrogen isotopes using this technique provides an alternative to traditional removal methods. • Hydrogen isotopes successfully exchanged at ambient temperature with Pt catalyst present on support material. • Pt-loaded 13X demonstrates higher capacity for ND 3 when compared to 13X • Pt-loaded 13X requires lower temperatures for full desorption of ND 3 when compared to 13X [ABSTRACT FROM AUTHOR]

Nonequilibrium flows of air components behind reflected shock waves are systematically studied on the basis of several theoretical models for the rate coefficients of fully coupled vibrational energy exchanges and chemical reactions. Numerical simulations are performed in the frame of the state-to-state approach under initial conditions corresponding to recent shock-tube experiments in mixtures O 2 /Ar, NO/Ar, NO/N 2 /Ar. The model takes into account partial vibrational relaxation between the incident and reflected shock waves, state-resolved dissociation, recombination, exchange reactions with formation of NO in the vibrationally excited states, as well as vibrational–vibrational and vibrational–translational energy transitions. It is shown that for oxygen, relaxation between the incident and reflected shocks is not frozen, and taking it into account in the most test cases considerably improves the agreement of calculated and experimentally measured pressure. For NO-containing mixtures, the effect of intermediate relaxation is weaker. Average deviation of the number density of molecular species with respect to the experimental one is analyzed for several hundreds of numerical simulations; on the basis of these estimates, recommendations are given for the best choice of model parameters. These recommendations can be used for modeling high-temperature flows, in particular, under reentry conditions. • Recent shock-tube experiments in air species are simulated numerically. • State-to-state models of vibrational–chemical coupling are validated. • Good agreement with experimental data is shown. • Recommendations are given for the best choice of model parameters. [ABSTRACT FROM AUTHOR]

Triple oxygen isotope (Δ′17O) analysis of CO 2 or carbonate is increasingly applied in diverse fields in earth and environmental sciences. One of the widely-used analytical methods for Δ′17O of CO 2 is through Pt-catalyzed oxygen isotope exchange between CO 2 and O 2. However, large inter-laboratory inconsistencies in oxygen isotope fractionation between the two gases have been reported, potentially hindering data comparison across different laboratories. By examining the oxygen isotope fractionations in thermal diffusion experiments for pure O 2 and CO 2 gases as well as CO 2 -O 2 mixtures, we demonstrate that thermal-gradient-induced (TG-induced) isotope fractionation is the main reason for the inconsistencies. The degree of TG-induced oxygen isotope fractionation is affected by temperature contrasts and volume ratios between the hot and cold parts of the extraction line as well as gas composition. Larger thermal contrasts generated larger oxygen isotope fractionations. CO 2 fractionated less than O 2 in the same thermal gradient conditions. For CO 2 -O 2 mixtures, TG-induced oxygen isotope fractionation of O 2 was reduced while that of CO 2 was enhanced, compared with the pure gases. Based on the results of thermal diffusion experiments, we found that the anomalous mass fractionation exponents (0.2 ∼ 0.9) observed in the Pt-catalyzed CO 2 -O 2 isotope exchange experiments can be rationalized quantitatively by a combination of isotopic exchange equilibrium and TG-induced oxygen isotope fractionation. Our model suggests that by weakening TG-induced oxygen isotope fractionation and by increasing the volume fraction of hot zone of a reactor, we can achieve a high precision (<10 per meg) for Δ′17O CO2 through CO 2 -O 2 exchange. Considering the widely existing thermal-gradient conditions in nature, the findings in this study may shed light on the origin of non-mass-dependent isotope fractionation. [ABSTRACT FROM AUTHOR]

The article shows, for the first time, an example of the manifestation of electrocatalytic activity in the hydrogen evolution reaction (HER) in a new class of organic, metal-free electrocatalysts called "organic hydrides." These organic hydrides are derivatives of the compound 4,4′-dihydropyridine - 1,1'-(2,6-dimethyl-1,4-dihydropyridin-3,5-diyl)bis(ethan-1-one). The electrocatalytic activity of the organic hydride was studied in the presence of acetic and trifluoroacetic acid. It has been shown that the pK value of the acid used determines the HER mechanism. Based on kinetic data, isotope exchange data, as well as density functional theory (DFT)-based calculations, it is shown that the formation of molecular hydrogen proceeds through three different mechanisms depending on the nature of the acid: in the case of using acetic acid, the process goes through the stage of bimolecular elimination; when using trifluoroacetic acid at potential E = −1.0 V, it goes through the stage of intramolecular elimination; whereas at E = −1.6 V, it proceeds through a heterogeneous mechanism. The first example of electrocatalytic hydrogen evolution (HER) from organic 'hydrides'. [Display omitted] • HER of new members of the family of metal-free electrocatalysts studied. • The TOF value strongly depends on potential and pK of the acid. • The destruction of the radical as a key factor influencing the HER mechanisms. • The pK value of the acid used determines the HER mechanism. [ABSTRACT FROM AUTHOR]

A comparative Study on the conversion of an energetic H+ beam inside a cell neutralizer filled with hydrogen gas target is conducted by two different methods to determine the maximum beam neutralization efficiency and corresponding optimal gas thickness in terms of beam energy, ranging from 1 keV to 10 MeV. One method analytically solves the equations of particle flux with a deterministic response. The other uses the random collisional probability based on the Monte Carlo simulation with non-deterministic response, which is implemented by COMSOL software. Effective reactions of charge exchange and reionization are commonly considered in both methods with the energy-depended collisional cross section. The results obtained from the two methods are compared, demonstrating good fitness with a mean difference of ±1.5 %. This acceptive difference arises often due to statistical errors that occur in the Monte Carlo calculations. Additionally, a close agreement is found between calculated and measured efficiencies. [Display omitted] • The Monte Carlo simulation agrees with the analytical solution and experiment. • The hydrogen neutralization is influenced by beam energy and gas target thickness. • Increasing the density increases the rate of neutralization, not its maximum value. • Collisional cross section of hydrogen considerably affects the calculational results. [ABSTRACT FROM AUTHOR]

Bismuth oxyhalides (BiOX, X = Cl, Br, I) have been showing promising catalytic activity in various applications due to their electronic properties and unique layered structure. However, their catalytic potential for hydrogen generation from chemical hydrides is unrevealed. Herein, BiOX (X = Cl, Br, I) catalysts were prepared via a simple co-precipitation method. The physical and chemical characteristics of the as-prepared samples were then duly characterized using various techniques such as X-ray diffractometer spectroscopy (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Nitrogen adsorption-desorption, and Scanning electron microscope (SEM). The catalysts were then applied to NaBH 4 methanolysis for the production of hydrogen. Among the BiOX catalysts, BiOCl exhibits excellent performance which is attributed to the highest electronegativity possessed by the Cl− halogens clinging onto the catalytic layers, simply overriding the substitution reactions. Subsequently, superior performances were depicted with rapid generation of hydrogen, High rate of hydrogen generation, HGR = 42,740 mL H 2 g−1min−1, and calculated activation energy of Ea = 43.5 kJ/mol with stability for over 5 successive cycles. Withal, a plausible mechanism based on the exchange reactions promoted by the BiOX catalysts, which comprises interlacing [Bi 2 O 2 ] slabs with double halogen slabs coupled with a strong ionic nature is illustrated in line with the experimental results. [Display omitted] • Bismuth oxyhalides (BiOX) catalysts were synthesized via co-precipitation method. • The effect of X = Cl, Br, I towards NaBH 4 methanolysis was studied in detail. • BiOCl exhibits rapid in situ H+ supply for H 2 generation compared to BiOBr and BiOI. • BiOCl showed superior performance with HGR value of 42,740 mL H 2 g−1 min−1. • High recyclability and stability of BiOCl of without activity drop. [ABSTRACT FROM AUTHOR]

Accurate estimations of Hydrogen/Deuterium (H/D) isotope effects have been a long-standing problem since the beginning of stable isotope geochemistry, primarily due to their strong nuclear quantum effects (NQEs). Currently, the D/H ratio plays a key role in deciphering the origin and evolution of water ice and organics in the solar system. Additionally, the Big-bang origin of Deuterium necessitates that the observed D/H variations be linked to isotope exchange reactions, such as HD + H 2 O ↔ H 2 + HDO. Therefore, an accurate benchmark dataset describing the equilibrium H/D isotope fractionations at low temperatures (≤ 200 K) is essential for interpreting rapidly accumulating astrochemical observation data. In this study, we implemented and compared two methods developed for evaluating the NQEs of H/D isotopes: 1) the Full Partition Function Ratio (FPFR) method and 2) the Path Integral Monte Carlo (PIMC) method. Both were assessed for their accuracy and efficiency in estimating equilibrium isotope effects (EIEs) using 10 common interstellar small molecules (H 2 , HF, HCl, HCN, HNC, H 2 O, H 2 S, NH 3 , HCHO, and CH 4) as examples. Most of them are calculated at high precision for the first time. For the FPFR method, several higher-order corrections to the Urey-Bigeleisen-Mayer model were considered, including anharmonicity, quantum mechanical rotation with nuclear-spin statistics, and corrections to the Born-Oppenheimer approximation. For the PIMC method, four different actions related to the thermal density matrix are used. These include the primitive and three fourth-order actions (Takahashi and Imada, Suzuki-Chin and Chin approximations), based on the direct scaled-coordinates transformation. Three main conclusions are obtained: 1) Under the framework of Born-Oppenheimer approximation, the PIMC method holds the same and even slightly better accuracy (more comprehensive descriptions of quantum anharmonicities) in estimating EIEs for H/D isotopes as the FPFR method. However, both methods suffer from the neglection of the DBOC when using the Born-Oppenheimer potential energy surfaces. For the PIMC method, additional corrections for particle distinguishability must be considered when nuclear spin statistics exhibit its effects at low temperatures (e.g., < 160 K for H 2). 2) Among the four actions, three fourth-order actions show better convergence and efficiency (2.2 to 26.5 times speedups at 50 K) than the primitive action, making them superior candidates for PIMC simulations at super-cold (≤ 200 K) conditions. 3) A combination of accurate potential energy surface with the PIMC method serves as an alternative way for theoretical estimations of H/D isotope effects. [ABSTRACT FROM AUTHOR]

Malleability and reprocessability of cross-linked polymers can be achieved via exchange reactions of the boronic ester crosslinking. Herein, we report a facile strategy to fabricate and modulate vitrimers by introducing intermolecular boron-nitrogen coordinated boronic ester crosslinking. Using a one-pot reaction, a series of boronic ester vitrimers based on polybutyl acrylate (PBA) was synthesized. The nitrogen containing monomer dimethylaminoethyl methacrylate (DMAEMA) was successfully copolymerized in the backbone to generate intermolecular boron-nitrogen (B–N) coordination. The presence of B–N coordination increases intermolecular interactions, leading to a denser crosslinked network structure and an elevated glass transition temperature. With the formation of B–N coordination, PBA-xB-yN samples at the same crosslinking density exhibit higher elongation at break and tensile strength. These samples dissipate more energy at the same strain and show a more pronounced strain rate dependency, highlighting the sacrificial role of the B–N coordination bonds. Stress relaxation experiments reveal that the intermolecular B–N coordination promotes faster relaxation of PBA-xB-yN compared to PBA-xB due to accelerated exchange dynamics of boronic ester. Mechanical reinforcement after recycling is observed in PBA-1B–2N, indicating that structural optimization of chemical and physical crosslinking occurs during thermal reprocessing. This study will provide a new strategy to fabricate boronic ester based vitrimeric materials with mechanical reinforcement and toughness enhancement. [Display omitted] • A facile strategy to fabricate and modulate vitrimers by intermolecularly B–N coordinated boronic ester was reported. • PBA-xB-yN samples dissipate more energy , highlighting the sacrificial role of the B–N coordination. • Mechanical reinforcement after recycling indicates that structural optimization of chemical and physical crosslinking. [ABSTRACT FROM AUTHOR]

Reprocessable, repairable, and recyclable ("3R") vitrimers have experienced rapid development over the past decade and demonstrate significant potential for diverse applications. The creep performance of vitrimers is crucial for their dimensional stability under load-bearing conditions at relatively low temperatures and serves as a key metric for evaluating their reprocessability at high temperatures. However, the impact of dynamic covalent polymer networks (DCPNs) on vitrimer mechanics, particularly creep properties, remains debated. Systematic experimental studies on the creep of vitrimers across a wide temperature range are lacking. We use the classic epoxy vitrimer as a model system to investigate the impact of DCPNs on vitrimer mechanics, especially focusing on the creep and recovery behavior across a wide temperature range, spanning from room temperature to the glass transition temperature (T g) and further to the topology freezing transition temperature (T v). We systematically examined the effects of temperature, stress, and catalysts on vitrimer creep, revealing the influence of DCPNs. Our findings demonstrate significant thermo-chemo-mechanical coupling effects in the creep mechanics of vitrimers, a facet not comprehensively acknowledged in existing studies. In addition, at temperatures below T g , vitrimers exhibit superior creep resistance compared to pure epoxy resin due to metal coordination, ensuring excellent dimensional stability under load-bearing conditions. Conversely, at high temperatures, active bond exchange reactions in vitrimers accelerate creep and result in greater residual deformation, highlighting exceptional reprocessability. This study provides new insights into the materials and mechanics of vitrimers. [Display omitted] • Impact of dynamic covalent polymer networks on mechanical properties. • Creep and recovery of vitrimers across a broad temperature range. • Influence of temperature, constant stress and catalyst on vitrimer creep. • Thermo-chemo-mechanical coupling effects in vitrimer mechanics. [ABSTRACT FROM AUTHOR]

• 1-Heteroatom-substituted alkylmagnesium chlorides act as carbanions or carbenoids. • DFT and experimental characterization of 1-heteroatom-substituted alkylmagnesiums. • The carbene characteristics increased in the order of N, S < O < F, Cl, and Br. In addition to exhibiting nucleophilic reactivity, some alkylmagnesium chlorides that possess a heteroatom substituent at the 1-position can exhibit carbene-like reactivity. Herein, DFT calculations and experiments were performed to study the reactivity of several 1-heteroatom-substituted alkylmagnesium chlorides. The carbene character of 1-heteroatom-substituted 2-methylpropylmagneisum chlorides was evaluated using the geometric parameters in their DFT-optimized structures and the activation energies for the 1,2-hydrogen shift estimated by DFT calculations. 1-Heteroatom-substituted alkylmagnesium chlorides were generated from 1-heteroatom-substituted alkyl p -tolyl sulfoxides and isopropylmagnesium chloride via a sulfoxide/magnesium exchange reaction, and the reactivity of these species was evaluated based on the product ratio. The results revealed that 1-amino- and 1-thioalkylmagnesium chlorides were carbanions because the reaction yielded protonated products. In contrast, 1-haloalkylmagnesium chlorides were magnesium carbenoids because the reaction yielded alkene and cyclopropane without haloalkanes. Lastly, 1-pivaloxyalkylmagnesium chloride was a hybrid between carbanions and magnesium carbenoids. The order of carbene character estimated based on the theoretical results was consistent with the experimental results. Graphical abstract synopsis: The reactivity of a series of 1-heteroatom-substituted alkylmagnesium chlorides was studied by DFT calculations and experiments. 1-Amino- and 1-thioalkylmagnesium chlorides, 1-haloalkylmagnesium chlorides, and 1-oxyalkylmagnesium chlorides were determined to be carbanions, magnesium carbenoids, and a hybrid between the two, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

• Reconfigurable light-responsive LCE actuators were fabricated with CNTs and allyl sulfide bonds. • CNTs dispersed in the LCE with amphiphilic dispersants induced high photothermal effects. • Allyl sulfide incorporated in the main chain showed excellent dynamic exchange reaction ability. • MLCE/CNT functionalized allyl disulfide widens the design ability with high performance. Monodomain liquid crystal elastomers (MLCEs), exhibiting a light-induced dynamic exchange reaction (DER) and light-triggered actuation abilities, were prepared using dispersed multiwalled carbon nanotubes (MWCNTs) and allyl sulfide linkages incorporated in the MLCE matrix. MWCNTs were dispersed in the MLCE matrix using a newly synthesized dispersant, poly(4-cyanobiphenyl-4′-oxyundecylacrylate-co-pyrene methyl acrylate); this dispersant exhibited amphiphilic properties of π–π interactions with the MWCNT fillers (attributed to the pyrene moieties) and miscibility with the MLCE matrix (attributed to the cyanobiphenyl mesogenic moieties). A low amount of well-dispersed MWCNTs (≤0.05 wt%) in the MLCE matrix induced excellent photothermal effects under near-infrared (NIR) light irradiation, leading to considerable reversible contraction/extension actuation (∼40 % change in length). The bilayer film comprising the MLCE and PLCE (PLCE: polydomain LCE) composite films bonded via DER without glue exhibited excellent bending actuation under NIR light irradiation and was configured into several actuators such as a flower-shaped actuator, a weightlifter, a circular rolling band, an oscillator mimicking a hummingbird, and a casting catapult. Therefore, this novel MLCE/CNT composite film enhances the design ability for the arbitrary shaping and functionalization of NIR light-triggerable LCE actuators, which can be applied to several interesting soft robots. [ABSTRACT FROM AUTHOR]

A target-induced multiregion MNAzyme nanowire system is designed for the ultrasensitive and homogeneous detection of microRNAs (miRNAs). miRNA-21 and miRNA-375 are chosen as analytes, and a miRNA-induced primer exchange reaction (PER) is utilized to construct a long DNA strand with repetitive sequences. This innovative design enables the efficient anchoring of numerous MNAzymes. This unique architecture significantly boosts the effective local concentration of MNAzymes, thereby enhancing the sensitivity and efficiency of miRNA detection. Notably, the limit of detection (LOD) achieved with our target-induced multiregion MNAzyme nanowire approach is over an order of magnitude lower than most other MNAzyme-based methods, while the MNAzyme reaction time is reduced from several hours to 50 min. The method has demonstrated successful applications in quantitatively determining the expression levels of two miRNAs in cell lysates of MCF-7, HeLa and MCF-10 A cells, highlighting its potential for assaying miRNA biomarkers in clinical samples. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the preparation of some isotopically selected targets by ion implantation is described. The selected isotopes to be implanted over graphite matrices described in the present work were 127I and 81Br. These isotopes were chosen for their similarity with the xenon and krypton isotopes of interest for the study of Double Charge Exchange reactions in the NUMEN project (Nuclear Matrix Elements for the Neutrino-less double beta decay). The characterization of the resulting targets after implantation was carried out using Rutherford Back Scattering Spectroscopy (RBS) with 1H, 12C, 28Si beams at different energies and scattering angles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tuning the A-site deficient concentration and constructing surface-active structure NiO can efficiently enhance the oxygen permeability. • Optimal oxygen permeability was achieved 2.36 mL min−1 cm−2 at 900 °C, which is 1.87 times higher than that of the famous BSCF. • The membrane can operate stably for 400 hours without any degradation which shows the application potential for oxygen separation. The A-site deficient perovskites bring more space for materials design and surface engineering in many fields. In this work, a series of (Ba 0.5 Sr 0.5) 1-x Co 0.7 Fe 0.2 Ni 0.1 O 3-δ (BSCFN) membranes with Ni-substitution and different A-site deficient concentrations were designed to improve the oxygen permeability. The influence of A-site deficient concentration and sintered temperature on the microstructure, oxygen permeability, and stability of BSCFN were investigated. The results show that NiO aggregation happens on the membrane surface which surprisingly accelerates the surface exchange reactions of oxygen. Among the series of BSCFN membranes, BSCFN-2–1140 exhibits the highest oxygen permeation flux of 2.36 mL min−1 cm−2 at 900 °C, which is 1.87 times higher than that of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF). Furthermore, the long-term stability test lasted over 400 h without degradation. Our work demonstrates the feasibility of the A-site deficient strategy and surface nanostructure engineering for oxygen separation and catalytic membrane reactors. [ABSTRACT FROM AUTHOR]

Sensitive monitoring of luteinizing hormone (LH), a glycoprotein that regulates the synthesis of regulatory steroid hormones, can facilitate the diagnosis of various reproductive diseases. In this work, a new and highly catalytic Sulfur-doped and bimetal-coordinated CoFe(CN) 5 NO (denoted as S–CoFe(CN) 5 NO) nanoparticles are synthesized. Such material is further used to construct high performance sensing interface and coupled with primer exchange reaction (PER) and hybridization chain reaction (HCR) amplification cascades for sensitive electrochemical aptamer-based LH assay. Target LH molecules bind aptamer sequences in DNA duplex probes to liberate ssDNA strands, which initiate subsequent PER/HCR amplification cascades for the capture of many ferrocene (Fc)-tagged DNAs on sensing interface. S–CoFe(CN) 5 NO subsequently leads to catalytic oxidation of these Fc tags for yielding substantially magnified currents for realizing ultrasensitive assay of LH with the detection limit of 0.69 pM in range from 5 pM to 10 nM. Owing to the high specificity of aptamer, such sensor has high selectivity and can achieve low levels of LH assay in diluted serum samples. With the successful demonstration for detecting trace LH, such sensor can be easily extended as a universal aptamer-based electrochemical sensing method for monitoring various target analytes in the biomedical and biological fields. [ABSTRACT FROM AUTHOR]

Garnet-group minerals, with their wide range of compositions, play a significant role in Earth's crust and upper mantle, participating in various petrological and geochemical processes. Oxygen isotope fractionation factors between garnets and other minerals hold crucial implications in these contexts. In this work, vibration frequencies were measured via Raman spectra on five garnet mineral samples in the pyrope-almandine-spessartine ternary system and four synthetic pyrope-grossular solid solutions at temperatures up to 1000 °C and pressures up to 17 GPa. Isobaric (γ iP) and isothermal (γ iT) mode Grüneisen, as well as anharmonic (a i) parameters, were determined for the observed modes. Our study shows that the vibration bands tend to shift to lower frequencies with increasing temperature and to higher frequencies with increasing pressure. Moreover, the anharmonic correction has been found to contribute positively to equilibrium oxygen isotope fractionation β factors in garnets, typically within 0.5 ‰ above 1000 K. The 103∙ln β (T) factors calculated from vibration spectra (considering Г points only) align closely with those from theoretical calculations (including all frequencies in the Brillouin zone). Contributions from phonon dispersion (including none- Г points) are typically smaller than the uncertainties propagated from frequency measurements. Additionally, the pressure effect on the oxygen isotope fractionation in garnet, evaluated from the isothermal Grüneisen parameters, is found to be insignificant under crustal and upper mantle conditions, consistent with thermodynamic expectations. Using published oxygen isotope fractionation β factors for quartz and calcite, the equilibrium oxygen isotope fractionation factors (103∙ln α) are calculated between garnets of diverse compositions and any of these phases as functions of temperature, pressure and fraction of garnet endmembers. Considering composition effects helps to reduce the discrepancies among experimental and empirical calibrations of oxygen isotope fractionation factors between garnet and quartz. As an example application, oxygen isotope fractionation factors 103∙ln α (P , T) between garnets and forsterite were calculated under upper mantle conditions. Our findings suggest that these fractionation factors are predominantly dependent on temperature and garnet compositions, with minor influence from pressure. Compared with our calculated fractionation factors between garnet and olivine, the oxygen isotope exchange equilibrium may have been reached in some in kimberlite and mantle xenolith samples between garnet and olivine. However, in other samples, the fractionation factors cannot be explained solely by the composition effect, likely due to metasomatism. Our results underscore the importance of considering garnet compositions when interpreting their oxygen isotope compositions. • Equilibrium 18O 16O β factors for garnets are derived from vibration frequencies. • The calculated β factors are strongly dependent on temperature and composition. • Pressure effect is marginal on 18O 16O fractionation between garnet and olivine. [ABSTRACT FROM AUTHOR]

[Display omitted] • One-pot, cascade conversion of cellulose to 2,5-DMF and 2,5-HDN was investigated. • "All" heterogeneous ZrO 2 -doped bimetallic Cu–Pd/HY(5.1) catalyst was designed. • High-yields of 2,5-DMF (33.8%) and 2,5-HDN (17.2%) were achieved. • Oxygen-vacant ZrO x (O v –ZrO x) sites absorbed reaction intermediates. • The hydroxyl hydrogen of MeOH participated in the HD and HDO reactions. The direct conversion of cellulose to targeted chemicals remains challenging owing to its recalcitrant nature and highly oxygenated structure. Herein, we report a strategy to selectively produce 2,5-dimethylfuran (2,5-DMF) and 2,5-hexadione (2,5-HDN) directly from cellulose, with yields of 33.8% and 17.2%, respectively, over multifunctional heterogeneous ZrO 2 -doped bimetallic Cu–Pd nanoparticles supported on the HY(5.1) catalyst (CuPdZr/Y) under supercritical methanol (scMeOH) conditions. Acidic and metallic sites on the catalyst are involved in sequential cascade reactions, including solvolysis, dehydration, hydrogenation (HD), and hydrogenolysis (HDO). The preferential adsorption of reaction intermediates on the oxygen vacant sites of ZrO x located near the metallic sites promoted HD and HDO. H–D exchange reactions revealed that the hydroxyl hydrogens of methanol were the active hydrogen atoms participating in HD and HDO. The yields of 2,5-DMF and 2,5-HDN decreased marginally after the third run, indicating that CuPdZr/Y was highly robust under the scMeOH reaction conditions. [ABSTRACT FROM AUTHOR]

• Deep transect of dissolved neodymium (Nd) concentrations [Nd] and Nd isotope compositions across the oligotrophic South Pacific. • Extended Optimum Multiparameter Analysis (eOMPA) was performed to quantify conservative and non-conservative effects on the Nd concentrations and isotope compositions. • The dissolved Nd isotope signal is dominated by conservative water mass mixing. • Dissolved Nd is removed from the water column by scavenging of hydrothermal particles originating from the Southeast Pacific Rise. The isotope composition of dissolved neodymium (Nd) in seawater, expressed as ε Nd , serves as a valuable geochemical tracer for the provenance and mixing of water masses in the ocean. However, challenges arise in the application due to additional Nd sources and isotope exchange at ocean boundaries and suspended particles of hydrothermal and lithogenic origin, which are not fully understood. In this study, we present seawater Nd concentrations [Nd] and ε Nd obtained from a deep-water (>1500 m water depth) zonal transect across the oligotrophic South Pacific gyre sampled during R/V Sonne cruise SO245, GEOTRACES process study GPpr09. Across 8 stations, dissolved [Nd] range from 10.8 to 31.1 pmol/kg with a characteristic pattern of increasing [Nd] at all stations, while our ε Nd results from -3.9 to -8.5 show pronounced zonal differences between the eastern and western part of the transect. We compare our measured data with values predicted from optimum multiparameter analysis (OMPA) of water masses to quantify the non-conservative influence on ε Nd and [Nd] along our transect. Our detailed analysis demonstrates that the deep water ε Nd distribution is dominated by conservative mixing of Upper and Lower Circumpolar Deep Water, Pacific Deep Water and Antarctic Intermediate Water, with 66% of all samples falling within ±0.6 epsilon units (i.e., the propagated uncertainty range derived from endmember compositions and analytical uncertainty) of the ε Nd predicted from conservative water mass mixing. In contrast, our [Nd] results reveal a pronounced deficit relative to concentrations predicted from water mass mixing (up to ∼10 pmol/kg). By excluding other influencing factors such as surface particle rain and boundary scavenging, we ascribe the [Nd] deficit to enhanced scavenging by hydrothermal particles in particular in PDW. This is consistent with the striking similarity of the [Nd] deficit and the distribution of δ3He as an indicator of hydrothermal activity along our transect. These findings highlight the decoupling of [Nd], modulated heavily by non-conservative processes, from the mainly conservative behaviour of ε Nd in the deep South Pacific. [ABSTRACT FROM AUTHOR]

• Acidification to pH = 2.0 resulted in the dissociation of ∼73 % Al from PAC in sludge. • Adsorption capacity of cation resin for Al depends on the dissociated Al species. • A pH of 2.0 prompted the breakdown of Al–FA complexes in the acidic sludge leachate. • Preferential adsorption on resin promotes Al separation from coexisting HM and FA. • The water treatment performance of recovered Al is comparable to those of fresh PAC. To recycle aluminum (Al) from waterworks sludge resulting from polyaluminum chloride (PAC) used as coagulants, this study proposed an innovative strong acidic cation (SAC) exchange resin treatment strategy for Al separation from coexisting fulvic acid (FA) and heavy metals (HMs) in the H 2 SO 4 leachate of PAC sludge. Fluorescence titration confirmed the breakdown of the Al-FA complex at pH 2.0, which facilitated Al separation from FA in the acidic leachate. The species distribution of the dissociated Al (i.e. Al a , Al b , and Al c) significantly influenced the adsorption of Al onto the cation exchange resin. The continuous release of H+ during the cation exchange reaction greatly promoted the transformation of dissociated Al c and Al b into Al a , thereby improving the adsorption of total Al. Moreover, the SAC resin column successfully separated the codissolved HMs from the Al in the leachate even at an influent pH of 2.8, which was attributed to the greater selectivity of the sulfonate groups on the cation exchange resin for free Al3+. The Al eluted from the exhausted resin with 1.1 M H 2 SO 4 was collected as the recycled coagulant after proper pH adjustment. The Al adsorption capacity of the SAC resin decreased by approximately 5 % with each operation cycle and was regained by complete regeneration with 1.8 M H 2 SO 4 after 5 cycles. Overall, the integrated efficiency of Al recovery from PAC sludge by H 2 SO 4 acidification and SAC resin separation/purification reached 70.10 %. The recycled Al from sludge has a water treatment performance comparable to that of fresh PAC coagulant. [Display omitted] [ABSTRACT FROM AUTHOR]

Taking inspiration from natural surfaces known for their ability to adaptively remodel their shape, we fabricated stimuli-responsive microstructures by using UV-induced nanoimprint lithography. For this, a fully bio-based dynamic thiol-ene photopolymer was synthetized by the radical mediated addition of a trifunctional eugenol-based thiol (SH 3 E) crosslinker across an allylated linseed oil (ALELO). To catalyze the bond exchange reactions between the hydroxyl and ester groups within the network, a bio-based eugenol phosphate ester was introduced as a transesterification catalyst. Pure eugenol was further added as a reactive diluent to increase the number of hydroxyl groups and thus, accelerate the thermo-activated bond exchange reactions. Once cured by UV exposure, the dynamic photopolymer is thermally stable up to 250 °C and is able to relax 63% of the original stress within 62 min at 160 °C. Subsequently, films with micropillars, having an aspect ratio of 1:2.5 were prepared by using nanoimprint lithography. The macroscopic reflow capability of the dynamic network enabled a reorientation of the imprinted structures during a thermal reshaping step. The imprints were characterized by 2D/3D optical microscopy, μCT imaging and static water contact angle measurements. Based on the orientation of the micropillars, the water contact angle was varied between 118° and 95°, giving rise to a possible application in microfluidic devices. [Display omitted] • Bio-based monomers and catalysts for nanoimprint lithography were synthesized to fabricate switchable microstructures. • Based on the orientation of the micropillars, the water contact angle was varied between 118° and 95°. [ABSTRACT FROM AUTHOR]

After the Fukushima Daiichi nuclear power plant accident, the terrestrial environment became severely contaminated with radiocesium. Consequently, the river and lake water in the Fukushima area exhibited high radiocesium levels, which declined subsequently. The partition coefficient of 137Cs between the suspended sediment (SS) and dissolved phases, K d , was introduced to better understand the dynamic behavior of 137Cs in different systems. However, the K d values in river water, ranging from 2 × 104 to 7 × 106 L kg−1, showed large spatiotemporal variability. Therefore, the factors controlling the 137Cs partition coefficient in natural water systems should be identified. Herein, we introduce a chemical model to explain the variability in 137Cs K d in natural water systems. The chemical model includes the complexation of Cs+ with mineral and organic binding sites in SS, metal exchange reactions, and the presence of colloidal species. The application of the chemical model to natural water systems revealed that Cs+ is strongly associated with binding sites in SS, and a major chemical interaction between 137Cs and the binding sites in SS is the isotope exchange reaction between stable Cs and 137Cs, rather than metal exchange reactions with other metal ions such as potassium ions. To explain the effect of the SS concentration on K d , the presence of colloidal 137Cs passing through a filter is significant as the dominant dissolved species of 137Cs in river water. These results suggest that a better understanding of stable Cs dissolved in natural water is important for discerning the geochemical and ecological behaviors of 137Cs in natural water. [Display omitted] • Partition coefficients of 137Cs between water and sediment are useful parameter to understand behaviors of 137Cs in environment. • Chemical model was applied to partitioning of 137Cs between natural water and suspended sediment. • Chemical model was based on concepts of isotope exchange equilibrium and mass balance including multi-reaction sites and colloidal forms. • Chemical model could confirm that the K d in fresh waters is inversely related to stable cesium (133Cs) concentrations. • 133Cs concentrations are one of the most important factors to control the K d in natural water systems. [ABSTRACT FROM AUTHOR]

Wetlands are crucial for maintaining biodiversity in ecosystems. The reversible chemical reactions can significantly affect the pollutant reduction capacity in wetland flow. The spatial transport of contaminants in wetlands is further complicated by phase exchange kinetics due to reversible reactions in the wetland bed. This paper provides an analytical solution for studying the multi-dimensional concentration distribution of solutes in wetland flow, considering both reversible and irreversible boundary reactions. Unlike previous one-dimensional studies (Jiang et al. (2022), Zhan et al. (2024)), our approach offers a comprehensive view of wetland contaminant transport, accounting for complex interactions between different phases and environmental factors. The solute may undergo reversible sorptive phase exchange between the immobile (wetland bed phase) and the mobile phase (fluid phase). Multi-scale homogenization methods are used to determine the dispersion coefficient, mean concentration, longitudinal and vertical real concentration distributions, rate of variation of vertical concentration distribution under the influence of vegetation force, and reversible and irreversible reactions at a stationary wetland bed. The effects of retention parameter (θ), Damkohler number (D a), vegetation effect (α), dispersion time (τ), and first-order irreversible boundary reaction (β ′) on solute mixing are thoroughly analyzed. The study's analytical results are validated by numerical results obtained using the finite difference method with a Shishkin mesh, and other comparisons are made with the limiting case of Taylor dispersivity. Results show that an increase in Damkohler number and vegetation force weakens contaminant transport in wetland flow, but an increase in D a enhances contaminant concentration in the mobile phase. The presence of reversible phase exchange kinetics causes non-uniform vertical concentration variation across the wetland cross-section. Critical values where the multi-scale homogenization technique may fail are suggested as θ ≤ 0.5 and D a ≥ 1. The study's findings have potential applications to pollution control in wetlands. • Innovative study of reactive contaminant transport in wetland flows with novel multiscale methods. • Comprehensive analysis of reversible and irreversible reactions on wetland contaminant dynamics. • Detailed examination of vegetation effects on solute dispersion and concentration distributions. • Analytical and numerical validation using a unique layer-adapted mesh for enhanced result accuracy. • Findings applicable to effective wetland management and pollution control strategies. [ABSTRACT FROM AUTHOR]

This study investigated the origins of CO 2 selectivity in the oxidative coupling of methane over MnO x –Na 2 WO 4 /(SiO 2 , TiO 2 , or ZrO 2) by means of steady-state isotopic transient kinetic analysis. The kind of support affects the concentration of surface intermediates leading to CO 2. The lowest concentration was determined for the MnO x –Na 2 WO 4 /SiO 2 catalyst exhibiting the lowest CO 2 selectivity, while the most CO 2 -producing MnO x –Na 2 WO 4 /ZrO 2 catalyst has the highest concentration. The lifetime of the intermediates is less sensitive to the kind of support. Employing different isotopes (18O 2 or 13CH 4) led to different lifetimes, suggesting the involvement of secondary exchange reactions with surface oxygen. [Display omitted] • Steady-state isotopic kinetic analysis of OCM over supported MnNaW-based catalysts. • Kinetic parameters of surface intermediates leading to CO 2 and H 2 O were determined. • High CO 2 selectivity over MnNaW/ZrO 2 due to high concentration of surface intermediates. • Significant impact of oxygen exchange between 18O 2 and lattice 16O was observed. [ABSTRACT FROM AUTHOR]

• The surface structure of molybdenum (Mo) oxide catalysts was altered by the reduction conditions. • On the Mo oxide catalyst with oxygen vacancies (O v), NH 3 is formed by a dissociative mechanism, whereas on the catalyst with nitrogen vacancies (N v), NH 3 is formed by an associative mechanism. • The abundant O v in the Mo oxide catalyst enhanced N 2 activation during dissociative NH 3 synthesis. • The catalyst with O v resulted in an NH 3 synthesis rate of 5.6 mmol g Mo −1 h−1, thus outperforming the catalyst with N v (0.3 mmol g Mo −1 h−1). The synthesis of NH 3 from N 2 and H 2 is a significant chemical process, because essential products such as fertilizers and industrial chemicals can be obtained from NH 3. In the catalytic synthesis of NH 3 , N 2 activation is generally considered a kinetically relevant step (KRS). Therefore, advanced heterogeneous catalysts that promote N 2 conversion have been extensively investigated. In this study, the roles of O and N vacancies (O v and N v) of Mo oxide formed during reduction were kinetically evaluated and compared using structural characterization, isotope experiments, kinetic studies, and density functional theory calculations. On the Mo oxide catalyst with O v , NH 3 was formed by a dissociative mechanism, and the surface reaction involving the adsorbed N* and H* was considered the KRS. However, on the catalyst with N v , NH 3 was formed by an associative mechanism, and N–N dissociation of N 2 H 2 * species by H* to produce NH 3 was considered the KRS. The catalyst with O v resulted in an NH 3 synthesis rate of 5.6 mmol g Mo −1 h−1 under relatively mild conditions (1.0 MPa and 400 °C), thus outperforming the catalyst with N v (0.3 mmol g Mo −1 h−1). These results provide insight into the importance of anionic vacancies in reducible metal oxides for NH 3 synthesis. [Display omitted] [ABSTRACT FROM AUTHOR]

Casein microparticles from milk are important carrier materials for bioactive substances with stability and swelling properties that can be influenced by heat treatment. Microparticles produced by depletion flocculation and film drying remain stable in acidic media but swell and disintegrate under slightly alkaline conditions. Heat treatment after formation can stabilize the microparticles via a disulfide bridge network and newly formed hydrophobic contacts. Temperatures >60 °C are required so that denatured whey protein initiate formation of disulfide bridges via thiol exchange reactions. The particles then swell in a two-step process and exhibit an overshooting effect. If formation of disulphide bridges is prevented during heat treatment by adding N -methylmaleimide, overshooting swelling disappears and microparticles continue to expand instead. The analysis with parallel system dynamics models is based on the swelling of uncross-linked caseins, which is limited by the expansion capacity of cross-linked caseins. [Display omitted] • Disulfide bonds stabilizes casein microparticles (CMPs) after heat treatment. • Network formation can be controlled by thiol group blocker NEM. • Discussion of the complex swelling kinetics based on dynamic model simulations. • Heat treatment with blocked thiol groups leads to strongly swelling and stable CMPs. [ABSTRACT FROM AUTHOR]

Vitrimers based on block copolymers give access to adaptable polymer networks where the resulting properties can be adjusted not only by the vitrimer chemistry itself but also can be influenced by the structure of the block copolymer. In this work, linear AB, ABA, and BAB block copolymers are introduced as backbones in vinylogous urethane vitrimers to produce crosslinked materials that are reprocessable and have a wide range of tunable mechanical properties. The narrow-disperse block copolymers were synthesized by photoiniferter reversible addition-fragmentation chain transfer polymerization (photoRAFT). Two different types of hydrophobic A blocks, poly(methyl methacrylate) and poly(ethyl methacrylate) with a higher glass transition temperature compared to the hydrophilic B block, poly(2-hydroxyethyl methacrylate), were chosen. The B block carries the functional groups for further modification to obtain acetoacetylated side groups, which are then transformed to vinylogous urethane crosslinks. It has been found that the architectures of backbones as well as the alkyl substituents in the side groups of the A block influence the final performance of the vitrimers. By adjusting block sequences, the mechanical properties can be varied from hard to tough to elastic materials corresponding to BAB, ABA, and AB block copolymer vitrimers, respectively. These materials are reprocessable and have self-healing as well as shape-memory properties. Vinylogous urethane vitrimers from different block copolymers (i.e. , AB, ABA, BAB) show a broad range of physical, thermomechanical, and mechanical properties. Besides the topological structure of the block copolymer also the size of side groups and the number of crosslinking points affect to properties of materials. The transamination exchange reaction allows reprocessing and results in self-healing materials showing shape-memory. [Display omitted] • Covalent dynamic block copolymer networks show tunable properties. • Block sequence, alkyl substituent, and crosslinking density influence materials properties. • Materials show self-healing and shape-memory properties. • Well-controlled block copolymers synthesis via photoiniferter reversible addition-fragmentation chain transfer polymerization. [ABSTRACT FROM AUTHOR]

[Display omitted] • (Ni x Co 3− x)S 4 NPs were synthetized through cation exchange started from spinel Co 3 S 4 NP. • Composition-catalytic activity relation of (Ni x Co 3− x)S 4 NPs were established. • Structural modulation induced by ionic diffusion provided additional active sites. • Disordered structure facilitated continuous phase transformation into Co/NiOOH. • (Ni 1.2 Co 1.8)S 4 NPs with tailored chemical and structural properties enhanced OER activity. Transition metal spinels are promising oxygen evolution reaction (OER) catalysts; however, their rational design has been impeded by their inherent elemental and structural complexities. To alleviate these issues, this paper describes the role of cation exchange in developing active OER catalysts whose chemical and structural features are tailored while their morphology and crystal structure are maintained for enabling a systematic comparison. Through cation exchange, pre-synthesized Co 3 S 4 spinel nanoparticles (NPs) transform into (Ni x Co 3− x)S 4 NPs with compositions ranging from Co-rich to Ni-rich phases. Apart from stoichiometry, the atomic disorder and chemical state of the metal cations are amended through excessive interdiffusion and interstitial site preference of the cations, evidently helping boost the catalytic activity. Specifically, (Ni 1.2 Co 1.8)S 4 —which exhibits an optimal Ni/Co ratio, high structural disorder, and distinct surface chemical states—shows excellent OER performance (overpotential at 10 mA/cm2: 298 mV). In-depth analyses including in situ Raman spectroscopy and DFT calculations indicate that (Ni 1.2 Co 1.8)S 4 gradually transforms into OER-active Co/NiOOH—which has a unique electronic structure with strong reaction-intermediate-adsorbing characteristics—during the OER cycles. Overall, the study findings underscore the potency of cation exchange as a tool for controlling structural and chemical features, thereby helping explore complex catalyst materials while enhancing their activity. [ABSTRACT FROM AUTHOR]

• The 1.89 Ga Frere granular Fe formation was deposited on a redox stratified shelf. • Trend in whole-rock and magnetite δ 56Fe data tracks changes in sea level. • The δ 56Fe of iron formations are a robust tracer for Paleoproterozoic ocean circulation. • (Ce/Ce*) PAAS holds a primary seawater signature in spite of terrestrial input. • Primary δ 18O values of minerals were overprinted by diagenesis. The Paleoproterozoic (ca.1.89 Ga) Frere Formation is a ca. 300-m-thick sedimentary succession of five stacked, Fe- and silicate-rich shallowing upwards cycles or parasequences that were deposited during marine transgression. Deposition in an oxygen-stratified water column is supported by the occurrence of magnetite-rich mudstones (anoxic and distal) beneath shallower, hematite- and chert-rich grainstones (suboxic and proximal). Minor (LREE/HREE) PAAS depletion and positive Ce anomalies in grainstones support this interpretation. Sequence stratigraphic relationships suggest that the Frere Formation accumulated on an unrimmed continental shelf associated with coastal upwelling of Fe. Large variations in oxygen isotope ratios (δ 18O) of magnetite (–0.6 ‰ ≤ δ 18O ≤ +2.8 ‰, n = 12) and quartz (+8.8 ‰ ≤ δ 18O ≤ +20.1 ‰, n = 11) from lithofacies composing the Frere Formation indicate that pristine δ 18O of minerals were overprinted by diagenesis. Highly variable δ 18O values calculated at 200 °C in equilibrium with quartz (–3.0 to + 8.3 ‰) and magnetite (+8.0 to + 12.7 ‰) suggest that fluids with heterogeneous δ 18O evolved through oxygen isotope exchange between minerals and porewater in accumulating sediment during diagenesis. The Fe isotope ratios (δ 56Fe) of bulk rock (–0.50 ‰ ≤ δ 56Fe ≤ +1.55 ‰, n = 20) and magnetite separates (–0.09 ‰ ≤ δ 56Fe ≤ +2.06 ‰, n = 11) from deeper anoxic and shallow suboxic paleoenvironments define a decreasing trend through stratigraphically stacked parasequences. The high δ 56Fe values of magnetite (+0.7 ‰ to + 2.06 ‰) characterizing the base of the Frere Formation is interpreted to reflect equilibrium isotopic fractionation between dissolved Fe2+ aq and freshly precipitated Fe-(oxyhydr)oxide (Fe(OH) 3) resulting from sluggish recharge of Fe2+ aq from deeper shelf environments. These high δ 56Fe values of magnetite from shallow paleoenvironments may also reflect microbial dissimilatory Fe reduction at the seafloor. As sea level rose, continued deepening and encroachment of a well-mixed water mass increased the oxidation of Fe2+ aq , which ultimately increased the influence of kinetic isotopic fractionation between Fe2+ aq and Fe(OH) 3. Such a process produced δ 56Fe compositions of magnetite that gradually decrease through the stratigraphic thickness of the Frere Formation (+2‰ to −0.1 ‰). Thus, Fe isotopic data framed in a sequence stratigraphic context provides greater insight into water column processes on Fe-rich, oxygen stratified Paleoproterozoic and Mesoproterozoic shelves, as well as geologically younger restricted basins with a redox gradient. [ABSTRACT FROM AUTHOR]

• Alkali metal fluorides do not react selectively with chlorosilanes and chlorogermanes. • Heavier alkali metal fluorides and silanes or germanes form polymeric anionic species. • LiF and NaF are better suited for halide exchange reactions with silanes and germanes. • New polymeric organofluorogermanates were synthesised with alkali metal fluorides. The reactions of representative organochlorosilanes and organochlorogermanes with alkali metal fluorides (LiF, NaF, KF, RbF, CsF) were investigated by NMR spectroscopy and showed not only the fluorination to organofluorosilanes or organofluorogermanes but also the formation of organofluorosilicates and organofluorogermanates. The synthesis and crystal structures of two new polymeric organofluorogermanates, [K][Ph 2 GeF 3 ]∙0.75 MeCN and [Cs][Ph 2 GeF 3 ]∙THF, are presented. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • SCN and SSA increase while E decreases with Robinia pseudoacacia restoration. • Change in soil charge properties mostly due to clay, silt, and organic matter. • Vegetation restoration increases ion-soil particle electrostatic adsorption energy. • Revegetation and ion concentration determine ion diffusion activation energy. Vegetation restoration is an effective strategy for restoring soil function and improving soil quality in ecologically fragile areas; both soil nutrient conservation and interfacial transport are profoundly affected by it. However, reports elucidating the impacts of this on ion adsorption at the soil-water interface from an electrochemical perspective are scarce. This study selected soils from artificial Robinia pseudoacacia forests of different ages in the loess hilly region, with cropland serving as the control, to investigate changes in soil basic physicochemical properties, surface electrochemical properties, and the adsorption processes of cations (Na+, Ca2+, and Mg2+) at the soil-water interface, as well as the intrinsic relationships among these factors. Results show that soil surface charge number (SCN) and specific surface area (SSA) increase with the planting years of vegetation, while the electric field strength (E) decreases. Clay, silt, and organic matter are the major contributing factors to the changes in soil surface electrochemical properties during vegetation restoration, which in turn drive the response of base-cation interface adsorption kinetics. For a given cation type, the adsorption rate constants and equilibrium adsorption amounts increase with increasing SCN and SSA. The electrostatic adsorption energy between ions and soil surfaces increases with the years of vegetation restoration, with the greatest increase in energy proportion for Na+ (3.037 %), Ca2+ (1.805 %), and Mg2+ (1.670 %). Correspondingly, the diffusion activation energy involved in ion interface adsorption reaction kinetics decreases with the increase in vegetation restoration years, leading to more thorough ion exchange adsorption reactions and larger equilibrium adsorption amounts. The diffusion activation energy sequence for ions is Na+ > Mg2+ > Ca2+, while the observed sequence for cation equilibrium adsorption amounts is Ca2+ > Mg2+ > Na+. This study provides model predictions and scientific references for nutrient conservation and interfacial transport during the vegetation restoration process. [ABSTRACT FROM AUTHOR]

Immersion, percolation and tritium release experiments in peat and vermiculite soil samples were performed to analyze their behavior in this widely used medium for plant cultivation. Samples were immersed in tritiated water for 696 h and the isotope exchange capacity evaluated. A vertical flow regime was also considered with analysis for hydraulic conductivity to understand tritium mobility and therefore its availability. Peat soil showed a high tritium retention after percolation, but vermiculite seem to suppress its retention ability. The high moisture and organic content of peat enhanced its isotope exchange capacity. The falling head method was used to numerically evaluate the saturated hydraulic conductivity and outflow flux. Calculated isotope exchange capacity was 4.95×10-2 mol-T 2 O/g for peat and 3.38×10-2 mol-T 2 O/g for vermiculite. The tritium release experiment showed significant release of tritiated carbons in peat. • Tritium is incorporated in peat and vermiculite through an isotope exchange reaction. • HTO (g) released from peat at high temperatures due to tritium in mineral components. • Isotope exchange reaction rate in vermiculite is slower than that in peat. • Soil with water molecules structurally bonded undergo significant tritium exchange. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple synthesis method has been developed for Ag@ZIF-8, involving controlling the loading and size of Ag NPs. • Ag@ZIF-8 meet the requirements for antibacterial agent used in the melamine-impregnated paper. • The multiple synergistic antibacterial mechanism of Ag@ZIF-8 was verified. • The decorated blockboards with 0.20 wt% Ag@ZIF-8 reached Level Ⅰ antibacterial grade. Melamine-impregnated paper, a decorative material in furniture and interior design, could potentially impede the spread of indoor bacteria if it possesses antibacterial properties. Here, nano Ag-doped ZIF-8 (Ag@ZIF-8) was synthesized using ion exchange and in-situ chemical reduction strategies, followed by incorporating it into melamine-impregnated paper. The ion exchange mechanism of Zn2+ and Ag+ during ion exchange reactions was investigated. The structure of Ag@ZIF-8 was well-defined, with Ag nanoparticles evenly distributed on the surface of ZIF-8. Ag@ZIF-8 showed good thermal stability at 400 °C, meeting the requirements for the hot-pressing process of the melamine-impregnated paper. Ag@ZIF-8 exhibited enhanced ROS generation under visible light compare to ZIF-8, which was attributed to its reinforced light absorption and charge carrier separation facilitated by the localized surface plasmon resonance (LSPR) effect. The antibacterial activity of Ag@ZIF-8 was better than ZIF-8, owing to the multiple-synergistic antibacterial mechanisms of the ion release and ROS generation. Specifically, the 10-Ag@ZIF-8 exhibited MIC of 128 μg/mL and 64 μg/mL against E. coli and S. aureus , respectively. The signal intensity of •O 2 − induced by 10-Ag@ZIF-8 was 4.38 times higher than that of ZIF-8. As the addition of Ag@ZIF-8 increased, the antibacterial performance of melamine-impregnated paper improved. Considering the antibacterial property and economy of melamine-impregnated paper, 0.20 wt% was the optimal amount for 10-Ag@ZIF-8 decorated blockboard. This study proposes a novel approach for synthesizing MOF-based melamine-impregnated paper with antibacterial properties, aiming to reduce bacterial spread, minimize disease risks, and contribute to lowering overall healthcare costs. [ABSTRACT FROM AUTHOR]

Proton NMR experiments on carboxylate-stabilized rhenium(I) tricarbonyl 2,2'-bipyridine-supported complexes indicate that carboxylate ligand substitution is proton catalyzed. The amount of substitution and its product(s) depend on K b for the carboxylate and the matrix for the substitution. The differential cytotoxicity, measured as IC 50 values, for the complexes Re(O 2 CR)(CO) 3 (2,2'-bipyridine) (R = H, CH 3 , or CHF 2) towards HSC-2 oral cancer cells correlates positively with the values of K b for the carboxylate ligand that is replaced. [Display omitted] • Carboxylate-stabilized rhenium(I) cytotoxicity for oral cancer cells. • One-pot prep of carboxylate-stabilized rhenium tricarbonyl complexes. • Chiral-carboxylate rhenium(I) tricarbonyl complex crystal structure. • Proton-catalyzed carboxylate ligand substitution at rhenium(I) center. • Eventual carboxylate ligand substitution by pyridine in water/DMSO. A set of six carboxylate-stabilized rhenium(I) tricarbonyl complexes supported by a 2,2′-bipyridine (bpy) ligand, Re(O 2 CR)(CO) 3 (bpy) (R = H, CH 3 , CHF 2 , R - or S -CHBrCH(CH 3) 2 , and C 5 H 11), were prepared by acidolysis of the complex Re(OCO 2 C 5 H 11)(CO) 3 (bpy) with the appropriate carboxylic acid and characterized by 1H and 13C-{1H} NMR and IR spectroscopy. The crystal structure of the complex, Re[ R -O 2 CCHBrCH(CH 3)2](CO) 3 (bpy), was determined by X-ray crystallography. An alternate one-pot route to the carboxylate-stabilized rhenium(I) complexes Re(O 2 CR')(CO) 3 (bpy) (R' = CH 3 or C 6 H 5) and Re(O 2 CCH 3)(CO) 3 (1,10-pheanthroline), which starts with Re 2 (CO) 10 and in which an ester solvent serves as the source of the carboxylate ligand, was also developed. Cell viability tests on three carboxylate-stabilized rhenium(I) complexes (R = H, CH 3 , or CHF 2), using the HSC-2 oral cancer cell line, found different levels of cytotoxicity for each complex. NMR studies of the carboxylate ligand substitution reaction found that the reaction is catalyzed by protons. In a chloride-rich NMR solution, substitution of the carboxylate ligand leads to either a chloride-stabilized neutral complex (major product) or to a water-stabilized cation (minor product). Cytotoxicity results correlate positively with the K b value of the carboxylate ligand. Apparently, the more substitutionally inert the carboxylate-stabilized complex is in a chloride-rich environment (similar to extracellular fluid) the greater the amount of cytotoxic [Re(CO) 3 (bpy)(H 2 O)]+ that forms in the cytosol. [ABSTRACT FROM AUTHOR]

Structural modeling and adsorption mechanism of Li+ on Zr-doped adsorbent. [Display omitted] Lithium-titanium-zirconium composite oxide Li 4 Ti 4.98 Zr 0.02 O 12 (hereinafter referred to as LZrTO) was successfully prepared by a solvothermal method. The structure and morphology of the LZrTO sample were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The LZrTO samples washed by 0.1 mol/L HCl aqueous solution were converted into lithium-ion sieve H 4 Ti 4.98 Zr 0.02 O 12 (hereinafter referred to as HZrTO). The saturated ion exchange capacity and selectivity, pH titration curves, kinetic parameters, and equilibrium coefficients of the Li+-H+ ion exchange reaction were determined. SEM results showed that the LZrTO samples presented a spherical structure with a diameter of 3 ∼ 6 μm and a porous surface. The saturated exchange capacity of the lithium-ion sieve HZrTO for Li+ was up to 6.99 mmol g−1 and remained at 6.76 mmol g−1 after five cyclic exchange tests. In a mixed solution of Li+, Na+, K+, Mg2+, and Ca2+, the selectivity of Li+ ion exchange by HZrTO was 6.23 mmol g−1, which was higher than that of Na+, K+, Mg2+, and Ca2+. The relationship between adsorption time and adsorption capacity of HZrTO was investigated using pseudo-first-order and pseudo-second-order kinetic models, and the adsorption behavior of Li+ on the ion sieve HZrTO was characterized using Langmuir and Freundlich isotherm equations. The results of kinetic experiments verified that the adsorption behavior of Li+ on HZrTO is chemisorption and monolayer adsorption. [ABSTRACT FROM AUTHOR]

Polyethylene-based covalent adaptable networks (PE CANs) are obtained by reactive extrusion in a micro-compounder of a commercial maleic anhydride-grafted polyethylene (PE- g -MA) with two tailor-made α,ω-diamine cross-linkers carrying either imine or 1,2,3-triazolium groups as dissociative covalent dynamic bonds. Depending on the chemical nature of the exchangeable bonds, drastically different properties are demonstrated by FTIR, swelling/extractible, reactive dissolution and rheological experiments. The imine-containing PE CAN yields a high gel fraction but rheology and reactive dissolution experiments demonstrate the lack of dynamicity due to side-reactions promoting the formation of non-dynamic covalent cross-links. Such undesirable reaction occurs already during the processing stage from the premature cleavage of the imine bonds into amines, and further formation of permanent imide cross-links by reaction with pendent maleic anhydrides. Conversely, the 1,2,3-triazolium-containing PE CAN presents a lower gel fraction but exhibits viscoelastic properties typical of dissociative CANs. While this material is easily reprocessable by compression moulding, the evolution of the rheological properties at high temperatures (160–200 °C) points toward the occurrence of side reactions slowing down the relaxation dynamics which we attribute to the chemical rearrangement of the 1,2,3-triazolium cross-links. These two examples illustrate the difficulty of using amine -functionalized dynamic cross-links in the synthesis of PE CANs by reactive extrusion using PE- g -MA. [Display omitted] • Imine- and 1,2,3-triazolium-containing diamine cross-linkers are synthesized. • Polyethylene-based covalent adaptable networks are prepared by reactive processing. • Amine groups react with pendent anhydrides from a commercial polyethylene. • Orthogonality between grafting and exchange reactions is discussed. [ABSTRACT FROM AUTHOR]

• During the PY-GC/MS of lignin, the activity of hydrogen and hydroxyl radicals in the pyrolysis reaction and the production pathway of products can be inferred through the labeling of stable isotopes and the mass spectrometry information of labeled products. Four major pyrolysis products of lignin in supercritical water (H 2 O, D 2 O, H 2 18O) were investigated using Py-GC/MS technique and isotope tracing using lignin as the basic pyrolysis feedstock: phenol (PH), 2-methoxy-4-vinyl phenol (MV), 2,6-dimethoxyphenol (DP), 4-allyl-2,6-dimethoxyphenol (ADP). Abundance ratios were used to study the location of chemical bond breakage during pyrolysis of the four target compounds based on the characteristic signals of the four compounds labeled by stable isotopes in the mass spectra. Experimental results show that stable isotopes can be labelled into the pyrolysis products by co-pyrolysis and that SIM mass spectrometry can be used to characterise and quantify the isotopes in the products. The method of isotope exchange illustrates that the fundamental reason for different temperatures, pyrolysis times and tracer doses hindering radical exchange is the change in bond energy due to steric hindrance effects, conjugation effects and induction effects, which affect the rate and extent of exchange. For all four compounds, changes in temperature had a greater effect on the rate and extent of free radical exchange. In addition to this, tracer dose and pyrolysis time both had a greater effect on PH. For ADP only the degree of hydroxyl radical exchange was a little greater at high doses of H 2 18O. This work could provide a viable method for isotopic labelling of lignin pyrolysis products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface vacancy induced reverse cation exchange for preparation of CuZnS NBs. • Interfacial Zn-S-Cu covalent bond act as electron transfer bridge. • Hollow structure offers ample active sites and shorter carrier transport distances. • CuZnS NBs follows a visible light-induced interfacial charge transfer mechanism. The cation exchange technology plays a significant role in designing high-performance photocatalysts at atomic scale. However, the chemical kinetic energy barrier greatly limits the application of cation exchange strategies. Herein, an effective surface vacancy engineering powered reverse cation exchange strategy was exploited to realize energy-unfavored cation exchange reactions. Cu vacancies are created on the surface of Cu 2-x S nanoboxs (Cu 2-x S NBs), which are subsequently occupied by Zn2+ ions. A hollow CuZnS nanoboxs (CuZnS NBs) were successfully prepared for photocatalytic hydrogen evolution. The prepared CuZnS NBs has abundant interfacial Zn-S bonds, which promote interfacial charge transfer (IFCT) as a rapidly electron bridge. In particular, the photocatalytic hydrogen evolution rate of CuZnS NBs under visible light is 2.06 mmol·g−1·h−1, which is 5.9 times higher than that of Cu 2-x S. The synthetic mechanism and photocatalytic mechanism of the CuZnS was investigated from experiment and theoretical calculations. The surface vacancy powered reverse cation exchange strategy offers a new opportunity for the rational tailoring new-generation photocatalysts at the atomic scale. [ABSTRACT FROM AUTHOR]

Shock-heated flows of air components are studied using the state-to-state approach taking into account coupled vibrational energy transitions and state-specific chemical reactions. Effects of exchange reactions and vibrational excitation of NO molecules on the fluid-dynamic variables and vibrational distributions are evaluated; the results are compared to experimental data and direct simulations Monte Carlo; satisfactory agreement is obtained. It is shown that the effects are opposite in mixtures with and without initial admixture of NO. Whereas in NO/N 2 /Ar mixture the effect of NO vibrational excitation is important, in air it is negligible. Exchange reactions in air are more important than in NO/N 2 /Ar mixture. [Display omitted] • Shock-tube experiments in air species are simulated numerically. • Exchange reactions considerably alter air kinetics and dynamics in shock waves. • Effect of NO vibrational excitation is important in mixtures with initial NO content. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gluten proteins polymerize mainly by disulfide cross-linking during deep-frying. • Deep-frying results in a denser gluten protein network. • Molecular mobility and protein polymerization contribute to structure expansion. • The gluten network structure does not depend on the initial hydration level. The aim of this work was to investigate wheat gluten protein network structure throughout the deep-frying process and evaluate its contribution to frying-induced micro- and macrostructure development. Gluten polymerization, gluten-water interactions, and molecular mobility were assessed as a function of the deep-frying time (0 – 180 s) for gluten-water model systems of differing hydration levels (40 – 60 % moisture content). Results showed that gluten protein extractability decreased considerably upon deep frying (5 s) mainly due to glutenin polymerization by disulfide covalent cross-linking. Stronger gliadin and glutenin protein–protein interactions were attributed to the formation of covalent linkages and evaporation of water interacting with protein chains. Longer deep-frying (> 60 s) resulted in progressively lower protein extractabilities, mainly due to the loss in gliadin protein extractability, which was associated with gliadin co-polymerization with glutenin by thiol-disulfide exchange reactions. The mobility of gluten polymers was substantially reduced during deep-frying (based on the lower T 2 relaxation time of the proton fraction representing the non-exchanging protons of gluten) and gluten proteins gradually transitioned from the rubbery to the glassy state (based on the increased area of said protons). The sample volume during deep-frying was strongly correlated to the reduced protein extractability (r = –0.792, p < 0.001) and T 2 relaxation time of non-exchanging protons of gluten proteins (r = –0.866, p < 0.001) thus demonstrating that the extent of gluten structural expansion as a result of deep-frying is dictated both by the polymerization of proteins and the reduction in their molecular mobility. [ABSTRACT FROM AUTHOR]

Fluorescence biosensor to detect microRNAs via integrating DNA hairpins transition mediated strand displacement amplification with primer exchange reaction. [Display omitted] Herein, we constructed a fluorescence biosensor for the ultra-sensitive analysis of microRNAs (miRNAs) by combining DNA hairpins transition triggered strand displacement amplification (DHT-SDA) with primer exchange reaction (PER). Target miRNA initiated DHT-SDA to facilitate the generation of multiple single-stranded DNA (ssDNA) as PER primer, which was extended into a long ssDNA. The biosensor is successfully utilized in detecting miRNAs with high sensitivity (limit of detection for miRNA-21 was 58 fM) and a good linear relationship between 100 nM and 100 fM. By simply changing the DNA hairpin sequence, the constructed biosensor can be extended to analyze another miRNAs. Moreover, the biosensor has the feasibility of detecting miRNAs in real samples with satisfactory accuracy and reliability. Therefore, the fluorescent biosensor has great application potential in clinical diagnosis. [ABSTRACT FROM AUTHOR]

Scorodites are commonly used for arsenic immobilization, and it is also the main component of arsenic bearing tailings. Alkali-activated geopolymers are commonly used to landfill arsenic-bearing minerals. However, there no previous studies have explored the interaction between geopolymer molecules and the surface of scorodite. In this paper, Si(OH) 4 as a monomer molecule of geopolymer, the mechanism of adsorption and 'ion exchange' between Si(OH) 4 molecule and the surface of scorodite during alkali-activation is studied. Results show that the Fe-terminated scorodite (010) surface has high stability. Si(OH) 4 are more easily adsorbed on the hollow site of an Fe-terminated scorodite (010) surface, which is described as chemisorption. Compared with Si(OH) 4 , NaOH is easier to adsorb on an Fe-terminated scorodite (010) surface. The co-adsorption of NaOH and Si(OH) 4 on the Fe-terminated scorodite (010) surface was studied, and also belongs to chemical adsorption. When the hydroxyl binds to the As atom, the adsorbed Si(OH) 4 is more likely to undergo an 'ion exchange' reaction with the surface, and the reaction is barrierless. The intermediate As(OH) 4 produced by the 'ion exchange' reaction can be deprotonated to form an arsenate molecule, which can occur spontaneously. This work reveals that the interaction mechanism of geopolymer molecules on surface of scorodite. [Display omitted] • The stability of different surfaces of scorodites was studied. • The adsorption of geopolymer Si(OH) 4 molecules and NaOH on the surface was studied, and the co-adsorption of the two was studied. • The replacement reaction between the surface adsorbed molecules and the surface atoms was studied. • The ion exchange reaction between the coating material and the scorodites was demonstrated. [ABSTRACT FROM AUTHOR]

To reveal the influence of nonadiabatic couplings on the H(2S) + NaH(X1Σ+) reaction, a comparative study on adiabatic and nonadiabatic dynamics is conducted by using the time-dependent wave packet method. The dynamics results show that nonadiabatic couplings reduce the reactivity of H 2 (X1Σ g +) forming channel and vibrational state density of the product, while the exchange reaction channel is almost unaffected. Although the nonadiabatic couplings have a great influence on the product state distribution, it has little influence on the scattering direction of the product. For the H 2 (X1Σ g +) forming channels, products tend to forward scattering. For the exchange reaction channel, the NaH(X1Σ+) product exhibits a maximum scattering peak in the backward direction. The study reveals that the effect of nonadiabatic couplings on the ro-vibration distribution of the H 2 (X1Σ g +) forming channel in the H(2S) + NaH(X1Σ+) reaction is significantly different from the effect in the H(2S) + LiH(X1Σ+) reaction. [ABSTRACT FROM AUTHOR]

Perovskite-type oxygen transport membrane (OTM) has considerable potential in the application of oxygen-enriched combustion, which can prepare low-cost, low-energy, and high-purity oxygen. BaCoO 3- δ -based OTM, as a promising candidate, possesses high oxygen permeability, but poor stability limits its application. In this study, the strategy of Y3+ and W6+ co-doping BaCo 0 · 8 Y 0.2- x W x O 3- δ (BCYW- x) was proposed firstly to control the trade-off effect between oxygen permeability and stability by considering the radius and valence of ions. Y3+ and W6+ co-doping stabilize the perovskite cubic structure to room temperature of the BCYW- x , and the average bond energy of metal-oxygen increases with W6+ doping, enhancing the structure stability. Although oxygen vacancy concentration and critical radius decrease, the migration of oxygen ions is accelerated with the increase of W6+ content at high temperatures. The BCYW-0.1 shows the exceptional oxygen permeation flux of 1.90 mL･cm−2･min−1 at 900 °C and stably operates at 900 °C and 800 °C. Furthermore, the kinetic model calculation indicates that the permeation resistance decreases because of the acceleration of the oxygen surface exchange reaction as W6+ doping, contributing to the oxygen permeation process. This study provides a feasible and effective co-doping strategy to improve the oxygen permeability and stability of perovskite OTMs simultaneously. [Display omitted] • The Y3+ and W6+ co-doped BaCo 0·8 Y 0.2- x W x O 3- δ OTM is used for oxygen separation. • The trade-off effect is suppressed by the co-doped strategy. • Y3+ and W6+ co-doped stabilize the perovskite cubic structure to room temperature. • The migration ability of O2− is accelerated with W-doped at high temperatures. • Co-doped strategy improves oxygen permeability and stability simultaneously. [ABSTRACT FROM AUTHOR]

• A biosensor with high-density aptamer is developed for sensitive thrombin detection. • Primer exchange reaction with simple hairpin design amplifys detection signal. • Label-free analysis of thrombin utilizes electrochemical impedance spectroscopy. We report an electrochemical aptamer-based (E-AB) sensor for label-free quantitative detection of thrombin. In-situ synthesis of high-density aptamer replicas on the electrode is accomplished based on primer exchange reaction (PER), by which a DNA primer is continuously extended with the presence of a catalytic hairpin template and DNA polymerase. The PER enables the synthesis of long single-stranded DNA with replicated aptamer sequence for thrombin binding. The PER products on the surface of a gold electrode increase the density of aptamers on a limited electrode area, which can provide more effective binding sites for thrombin and therefore improve the performance of the sensor based on electrochemical impedance spectroscopy. Compared with the conventional E-AB sensor based on a 15-mer aptamer immobilized on the electrode, our method has a lower detection limit of 0.91 pM, and a wider linear range of 1.0 pM to 50 nM. Therefore, we believe our method is promising for label-free electrochemical detection of biomarkers. [ABSTRACT FROM AUTHOR]