Ion Activity Research Articles

Ion sensors based on organic semiconductors acting as quasi-reference electrodes

Thin-film devices that transduce the chemical activity of ions into electronic signals are essential components in various applications, including healthcare diagnostics and environmental monitoring. Combinations of organic semiconductors (OSCs) and ion-selective materials have been explored for developing solution-processable ion sensors. However, the necessity of reference electrodes (REs) and operational stability in ion-permeable OSCs have posed questions regarding whether reliable measurements with thin-film components are attainable with OSCs. Herein, we report electric double-layer transistors (EDLTs) with OSCs in single-crystal forms for ion sensing. Our EDLTs demonstrated high operational stability, with a one-to-one relationship between the source electrode potential and device resistance, and served as quasi-REs (qRE). When our EDLT is served as qRE, its drift was as small as 0.5 mV/h and comparable to that of commonly employed REs. In our system, the semiconductor-electrolyte interface is self-passivated by the alkyl chains of OSCs in single-crystal structures, with the two-dimensional transport layer appearing unaltered upon gating. EDLT arrays with ion-selective and nonselective liquid junctions enable ion concentration sensing without a conventional RE. These findings provide opportunities to develop thin-film devices based on OSCs for easy integration and reliable measurements.

Evaporated Copper‐Based Perovskite Dynamic Memristors for Reservoir Computing Systems

AbstractDynamic memristors are considered as the optimal hardware devices for reservoir computing (RC) enabled by their nonlinear conductance variations. This significantly reduces the extensive training workload typically required by traditional neural networks. Lead halide perovskites, with their tunable band structure and active ion migration properties, have emerged as highly promising materials for developing dynamic memristors. However, large‐scale and consistently stable production remains a challenge for perovskite functional films, while lead elements' toxicity and environmental impact also partly restrict their practical device utilization. In this work, lead‐free copper‐based perovskite (i.e., CsCu2I3) films are prepared by thermal evaporation for constructing dynamic memristors. The effective conductivity modulation of CsCu2I3‐based memristor can be utilized in artificial neural networks, achieving a high handwritten digit recognition accuracy of 91.2%. In addition, the RC system is also constructed based on the dynamic behavior of the devices, by which a letter recognition accuracy of 98.2% with simple training is achieved. This technology provides a feasible pathway to construct copper‐based perovskite dynamic memristors for future neural network information processing.

Bidentate Substrate Binding Mode in Oxalate Decarboxylase.

Oxalate decarboxylase is an Mn- and O2-dependent enzyme in the bicupin superfamily that catalyzes the redox-neutral disproportionation of the oxalate monoanion to form carbon dioxide and formate. Its best-studied isozyme is from Bacillus subtilis where it is stress-induced under low pH conditions. Current mechanistic schemes assume a monodentate binding mode of the substrate to the N-terminal active site Mn ion to make space for a presumed O2 molecule, despite the fact that oxalate generally prefers to bind bidentate to Mn. We report on X-band 13C-electron nuclear double resonance (ENDOR) experiments on 13C-labeled oxalate bound to the active-site Mn(II) in wild-type oxalate decarboxylase at high pH, the catalytically impaired W96F mutant enzyme at low pH, and Mn(II) in aqueous solution. The ENDOR spectra of these samples are practically identical, which shows that the substrate binds bidentate (κO, κO') to the active site Mn(II) ion. Domain-based local pair natural orbital coupled cluster singles and doubles (DLPNO-CCSD) calculations of the expected 13C hyperfine coupling constants for bidentate bound oxalate predict ENDOR spectra in good agreement with the experiment, supporting bidentate bound substrate. Geometry optimization of a substrate-bound minimal active site model by density functional theory shows two possible substrate coordination geometries, bidentate and monodentate. The bidentate structure is energetically preferred by ~4.7 kcal/mol. Our results revise a long-standing hypothesis regarding substrate binding in the enzyme and suggest that dioxygen does not bind to the active site Mn ion after substrate binds. The results are in agreement with our recent mechanistic hypothesis of substrate activation via a long-range electron transfer process involving the C-terminal Mn ion.

Dependence of oxygen evolution reaction catalysis at thin cathodically-deposited nickel-iron-selenide on Fe in the alkaline electrolyte vs. codeposited Fe

This study interrogated the role of Fe co-deposited in films versus Fe included from traces in the electrolyte on the electrochemical dynamics and kinetics for the oxygen evolution reaction (OER) in alkaline at a nickel-iron selenide OER pre-catalyst. Iron was co-included in the bulk of nickel selenide (NixSey) during cathodic deposition and is termed bulk-Fe (Febulk), and/or was included on its surface post-deposition by conditioning at anodic bias in alkaline with Fe traces and is termed surface-Fe (Fesurface). The electrochemical dynamics, OER kinetics, and sustainability of catalysis were studied in 1 M KOH stripped of Fe (Fe-free KOH) or containing Fe traces (KOH). The selenides transformed into a selenide/hydroxide with a few monolayers of surface hydroxide during the hours of conditioning and electrokinetic measurements at anodic bias in both solutions. Bulk-Fe did not enhance OER catalysis at nickel selenide, while surface-Fe promoted OER catalysis. Tafel slopes of ca. 40 mV/dec were recorded at (NiFebulk)xSey-Fesurface and NixSey-Fesurface in KOH, while Tafel-slopes of ca. 100 mV/dec were recorded at (NiFebulk)xSey in Fe-free KOH. Tafel slopes of 60–80 mV/dec were recorded in Fe-free KOH at (NiFebulk)xSey-Fesurface and NixSey-Fesurface that had been conditioned in KOH. OER catalysis at Fesurface-activated electrocatalysts was not sustained in alkaline stripped of Fe, neither at anodic bias nor subjected to potential cycling. The electrochemical data is consistent with a mechanism involving a low-coordination surface-Fe in the thin hydroxide layer of not more than few monolayers formed in-situ on the selenide. Surface-Fe is pictured as part of a dynamic catalytic site whose equilibrium density, to ensure sustainable catalysis, requires a greater than a threshold activity of Fe ions and lower than a threshold of activity of Ni, otherwise Fe will be in an inactive high-coordination state.

Intraventricular haemorrhage in premature infants: the role of immature neuronal salt and water transport.

Intraventricular haemorrhage is a common complication of premature birth. Survivors are often left with cerebral palsy, intellectual disability and/or hydrocephalus. Animal models suggest that brain tissue shrinkage, with subsequent vascular stretch and tear, is an important step in the pathophysiology, but the cause of this shrinkage is unknown. Clinical risk factors for intraventricular haemorrhage are biomarkers of hypoxic-ischaemic stress, which causes mature neurons to swell. However, immature neuronal volume might shift in the opposite direction in these conditions. This is because immature neurons express the chloride, salt and water transporter NKCC1, which subserves regulatory volume increases in non-neural cells, whereas mature neurons express KCC2, which subserves regulatory volume decreases. When hypoxic-ischaemic conditions reduce active ion transport and increase the cytoplasmic membrane permeability, the effects of these transporters are diminished. Consequentially, mature neurons swell (cytotoxic oedema), whereas immature neurons might shrink. After hypoxic-ischaemic stress, in vivo and in vitro multi-photon imaging of perinatal transgenic mice demonstrated shrinkage of viable immature neurons, bulk tissue shrinkage and blood vessel displacement. Neuronal shrinkage was correlated with age-dependent membrane salt and water transporter expression using immunohistochemistry. Shrinkage of immature neurons was prevented by prior genetic or pharmacological inhibition of NKCC1 transport. These findings open new avenues of investigation for the detection of acute brain injury by neuroimaging, in addition to prevention of neuronal shrinkage and the ensuing intraventricular haemorrhage, in premature infants.

Enhanced CO2 conversion through confinement of cross-linked ionic polymer within the pores of porous carbon materials

It is crucial to employ an integrated catalyst to avoid the complications of the recovery process. This work reports the fabrication of porous carbon@ionic liquid (PC@IL) composites with readily accessible active ion sites, achieved by confining cross-linked ionic liquid (IL) within the channels of porous carbon (PC). The incorporation of porous carbon not only confines the IL within its framework, creating microsites for CO2 adsorption and conversion, but also simplifies catalyst recovery. The results indicate that PC@IL composites exhibit excellent cycloaddition activity towards CO2 in a co-catalyst- and solvent-free environment. Notably, PC@IL(C)-24 demonstrates remarkable catalytic performance across various epoxides under 1 bar of CO2, with yields above 90 % at 90 °C for 12 h, and achieving a remarkable styrene carbonate yield of up to 92.8 % under a CO2 pressure of 1 bar (at 100 °C for 12 h). Control experiments confirm that the confinement effect exerted by N,S co-doped carbon on cross-linked IL plays a pivotal role in enhancing both stability and activity of PC@IL composites, thereby providing novel insights for designing functionalized porous carbon catalysts for CO2 cycloaddition conversion.

A sorbent modified with melatonin and lithium: in vitro investigation of the effect on hemostatic reactions

Aim of the study was to evaluate the effect of lithium- and melatonin-containing sorbent based on aluminum oxide and polydimethylsiloxane on changes in the number of platelets during hemosorption modeling and on the features of the hemostatic response during dosed contact of the sorbent with blood in an in vitro experiment. Material and methods. An analysis of the effect of the porous sorbent modified with melatonin (MT, 0.15 %) and lithium (0.5 %) based on aluminum oxide and polydimethylsiloxane (Al2O3@PDMS/MT-Li) was carried out in comparison with sorbent without modifiers (Al2O3@PDMS) and modified with MT (Al2O3@PDMS/MT) on a number of donor blood clotting parameters under in vitro hemosorption conditions. Studies of the hemostatic system included assessment of platelet count, chronometric parameters, fibrinogen concentration, antithrombin activity and plasminogen content. For integral assessment, calibrated thrombography and computer thromboelastometry were used. Results and discussion. Contact of all studied sorbents with blood causes a moderate decrease in the number of platelets (by 5.3–10.1 % from initial). Comparison sorbents reduce fibrinogen concentration by 7.1–7.7 %, Al2O3@PDMS/MT-Li – by 2.6 times, which is likely due to the methodology for determining this protein against the background of the independent anticoagulant activity of lithium ions. Al2O3@PDMS and Al2O3@PDMS/MT cause the development of a hypercoagulable shift, as evidenced by a shortening of kaolin time (by 27.5 and 22.1 %, respectively) and of activated partial thromboplastin time (APTT) by 7.1 % for both sorbents. At the same time, when lithium was included in the sorbent, not only did the hypercoagulation shift not occur, but blood clotting was also inhibited, as evidenced by an increase in kaolin time and APTT by 1.2 and 1.6 times, respectively, as well as in silicone time. Conclusions. Modifying sorbents with biologically active substances, lithium and MT, makes it possible to obtain an original hemosorbent with new properties. The presented results demonstrated the absence of a hypercoagulable shift in donor blood after contact with a lithium-, MTcontaining sorbent in vitro and indicate the potential for its using as a basis for the development of safe drugs.

Passivation characteristics and corrosion behavior of S32202 duplex stainless steel in different temperatures polluted phosphoric acid

The passivation characteristics of S32202 duplex stainless steel in different temperatures polluted phosphoric acid were studied by electrochemical technology and X-ray photoelectron spectroscopy, and its corrosion behavior was studied through immersion corrosion and electrochemical corrosion. The results indicate that as the temperature increases, the open-circuit potential of the sample in polluted phosphoric acid moves forward, and the surface exhibits a rapid passivation process. The main phases of the passivation film are Fe2O3, Fe3O4, Cr2O3, Cr(OH)3, and corresponding phosphates and polyphosphates. The passivation film of the sample in polluted phosphoric acid exhibits n-p-n composite semiconductor properties. As the temperature increases, the electron density and number of defects in the passivation film increase, and the vulnerability of the passivation film increases. The increase in temperature promotes the formation of a porous thick film. The corrosion types of the sample in polluted phosphoric acid are total corrosion, phase boundary corrosion, and intergranular corrosion, accompanied by pitting corrosion in local areas. The corrosion current density and passivation current density of the sample gradually increase with increasing temperature, while the counter-passivation potential and passivation index decrease, the density and protective properties of the passivation film decrease. The doping of phosphate can alleviate the dissolution process of metals, but the increase in temperature increases the solution ionic activity and accelerates the rate of charge transfer at the interface. At the same time, FePO4, CrPO4 and other phosphates are poorly protected, and their large presence is not conducive to the stability of the passivation film structure, resulting in a decrease in the corrosion resistance of the material.

A Practical Zinc Metal Anode Coating Strategy Utilizing Bulk h‐BN and Improved Hydrogen Redox Kinetics

Achieving high‐performance aqueous zinc‐ion batteries requires addressing the challenges associated with the stability of zinc metal anodes, particularly the formation of inhomogeneous zinc dendrites during cycling and unstable surface electrochemistry. This study introduces a practical method for scattering untreated bulk hexagonal boron nitride (h‐BN) particles onto the zinc anode surface. During cycling, stabilized zinc fills the interstices of scattered h‐BN, resulting in a more favorable (002) orientation. Consequently, zinc dendrite formation is effectively suppressed, leading to improved electrochemical stability. The zinc with scattered h‐BN in a symmetric cell configuration maintains stability 10 times longer than the bare zinc symmetric cell, lasting 500 hours. Furthermore, in a full cell configuration with α‐MnO2 cathode, increased H+ ion activity can effectively alter the major redox kinetics of cycling due to the presence of scattered h‐BN on the zinc anode. This shift in H+ ion activity lowers the overall redox potential, resulting in a discharge capacity retention of 96.1% for 300 cycles at a charge/discharge rate of 0.5 A g−1. This study highlights the crucial role of surface modification, and the innovative use of bulk h‐BN provides a practical and effective solution for improving the performance and stability.

Field-Driven Solid-State Defect Control of Bilayer Switching Devices.

We develop a framework for controlling and investigating reversible ionic transfer between two solid metal oxides layers by examining field-driven changes in electrical properties of the thin film bilayer oxide system Pr0.1Ce0.9O2/La1.85Ce0.15CuO4 (PCO/LCCO). We show that we can reversibly redistribute oxygen ions by applied voltage in a highly controlled and reversible fashion near ambient temperatures over large oxygen ion activity limits, which, for the first time, is directly interpretable by defect chemical models. This allowed us to determine how defect concentrations in each layer systematically varied with voltage and the subsequent impact on each film's conductance. These results showcase the relevance and applicability of defect chemical models, traditionally considered only at elevated temperatures, to the development of bilayer devices of importance to neuromorphic memory applications. This allows for a more systematic approach for studying and understanding the solid-solid exchange process in electrochemically controlled microelectronic devices. Moreover, our work sets the foundation for the development of large-area field-driven defect-controlled bilayer switching devices with potential application to a broad array of functionally modulated devices.

Tailoring surface terminals of Ti3C2Tx MXene microgels via interlayer domain-confined polyphosphate ammonium for flexible supercapacitor applications

The MXene material shows potential for flexible energy storage devices due to its high pseudocapacitance and mechanical flexibility. However, MXene nanosheet self-stacking and –F terminal functional groups can hinder active site and ion dynamics, thus affecting the energy storage performance. Herein, we present an interlayer domain-confined strategy that involves the introduction and crosslinking of ammonium polyphosphate (APP) confined to the interlayer of Ti3C2Tx MXene sheets, which induces gelation of the MXene to form a 3D network structure and enlarge their interlayer spacing. And then the cross-linked APP is converted into nitrogen and phosphorus terminals on Ti3C2Tx MXene via thermal treatment. The nitrogen terminals in the form of the pyrrole nitrogen and pyridine nitrogen, and phosphorus terminals of P–O bonds enhance the activity of the redox reaction and the dynamics of the ions, resulting in the boosted energy storage capacity of MXene. The density functional theory (DFT) calculations reveal that nitrogen-phosphorus co-doping modulates the surface electronic states of MXene and contributes to the increase of the electrical conductivity of Ti3C2Tx MXene. As a supercapacitor electrode, Ti3C2Tx MXene with N/P terminals exhibits a higher specific capacitance of 597.8 F/g (1777F cm−3) than the raw Ti3C2Tx MXene (384 F/g). In addition, the quasi-solid state flexible symmetric supercapacitor assembled by Ti3C2Tx MXene with N/P terminals can achieve an energy density of 12.5 Wh kg−1 at a power density of 250 W kg−1. Therefore, this work provides a new strategy for terminal modification of MXene and high-performance MXene supercapacitors.

Manganese octahedral point-constructed oxygen defects realize highly stable lithium-rich cathode materials

Lithium-rich layered oxides (LLOs) are highly favored by researchers for their high specific capacity and low cost. However, the severe voltage and capacity degradation of the material have become the biggest obstacle to commercial application. In this work, the construction of oxygen vacancies on the surface of Li-rich cathode and SiO44- gradient doping have been used in Li-rich materials to improve its performance. The presence of oxygen defects in MnO6 octahedra stabilizes its structure and enhances the electrochemical activity of TM ions. This also serves to reduce the energy level and intensity of the unhybridized O 2p orbitals, as well as decrease the release of lattice oxygen. The "localization effect" of SiO44− on TM ions also inhibits their irreversible migration. After modification, the electrochemical performance of the material has been significantly improved. The initial Coulombic efficiency increased to 89.46 % (82.68 % for LLO), while the specific capacity discharge at 5C reached 178.8 mAh g−1 (139.2 mAh g−1 for LLO). Additionally, the capacity rate after 500 cycles at 1C was 74.1 % (54.5 % for LLO). Therefore, this work provides valuable insights for designing oxygen-deficient lithium-rich cathode materials.

Optimization of CdSe Thin-Film Photoelectrochemical Cells: Effects of NaOH/Na2S/S Redox Couple Concentration and Activity on Cell Efficiency

This study investigates the relationships among redox couple activity, electrolyte concentration, and efficiency in CdSe thin-film photoelectrochemical solar cells. A CdSe photo-electrode was prepared using the electro-depositing technique to produce well-staged layering of CdSe, followed by chemical bath deposition to produce a layer with an acceptable thickness to absorb enough photons to create a suitable amount of photocurrent. The CdSe photo-electrochemical cell was tested under various concentrations of a NaOH/Na2S/S electrolyte solution. The results showed that the activity of the redox couple greatly affected the efficiencies of the solar cells. Correlation plots between ionic strength and PEC efficiency with the Debye–Hückel equation yielded an R² value of 0.96, while those between ionic strength and photocurrent density had an R² value of 0.92. The correlation between concentration and PEC efficiency was much weaker. This paper highlights how optimal ionic activity increases the performance of photoelectrochemical solar cells, which consequently improves the conversion efficiency of solar energy.

Deciphering the SAM- and metal-dependent mechanism of O-methyltransferases in cystargolide and belactosin biosynthesis: A structure–activity relationship study

Cystargolides and belactosins are natural products with a distinct dipeptide structure and an electrophilic β-lactone warhead. They are known to inhibit proteases such as the proteasome or caseinolytic protease P, highlighting their potential in treating cancers and neurodegenerative diseases. Recent genetic analyses have shown homology between the biosynthetic pathways of the two inhibitors. Here, we characterize the O-methyltransferases BelI and CysG, which catalyze the initial step of β-lactone formation. Employing techniques such as crystallography, computational analysis, mutagenesis, and activity assays, we identified a His-His-Asp (HHD) motif in the active sites of the two enzymes, which is crucial for binding a catalytically active calcium ion. Our findings thus elucidate a conserved divalent metal-dependent mechanism in both biosynthetic pathways that distinguishes BelI and CysG from previously characterized O-methyltransferases.

Ion-channel degeneracy and heterogeneities in the emergence of signature physiological characteristics of dentate gyrus granule cells.

Complex systems are neither fully determined nor completely random. Biological complex systems, including single neurons, manifest intermediate regimes of randomness that recruit integration of specific combinations of functionally specialized subsystems. Such emergence of biological function provides the substrate for the expression of degeneracy, the ability of disparate combinations of subsystems to yield similar function. Here, we present evidence for the expression of degeneracy in morphologically realistic models of dentate gyrus granule cells (GCs) through functional integration of disparate ion-channel combinations. We performed a 45-parameter randomized search spanning 16 active and passive ion channels, each biophysically constrained by their gating kinetics and localization profiles, to search for valid GC models. Valid models were those that satisfied 17 sub- and suprathreshold cellular-scale electrophysiological measurements from rat GCs. A vast majority (>99%) of the 15,000 random models were not electrophysiologically valid, demonstrating that arbitrarily random ion-channel combinations would not yield GC functions. The 141 valid models (0.94% of 15,000) manifested heterogeneities in and cross-dependencies across local and propagating electrophysiological measurements, which matched with their respective biological counterparts. Importantly, these valid models were widespread throughout the parametric space and manifested weak cross-dependencies across different parameters. These observations together showed that GC physiology could neither be obtained by entirely random ion-channel combinations nor is there an entirely determined single parametric combination that satisfied all constraints. The complexity, the heterogeneities in measurement and parametric spaces, and degeneracy associated with GC physiology should be rigorously accounted for while assessing GCs and their robustness under physiological and pathological conditions.NEW & NOTEWORTHY A recent study from our laboratory had demonstrated pronounced heterogeneities in a set of 17 electrophysiological measurements obtained from a large population of rat hippocampal granule cells. Here, we demonstrate the manifestation of ion-channel degeneracy in a heterogeneous population of morphologically realistic conductance-based granule cell models that were validated against these measurements and their cross-dependencies. Our analyses show that single neurons are complex entities whose functions emerge through intricate interactions among several functionally specialized subsystems.

Synergetic effects of S, N co-doping and surface concave-pores rich in lotus-leaf-like carbon nanosheets enabled threefold lithium storage mechanisms

Carbon-based materials based on structural and dimensional optimization are appealing as anode materials in lithium-ion batteries (LIBs). However rational design of high-efficiency low-dimensional carbon-based electrodes is still challenging. Therefore, a synthesis strategy based on Schiff base reaction has been devised for S, N co-doped and surface-enriched concave pores coupled with two-dimensional lotus-leaf-like carbon nanosheets (S, N-SCP/LCN). Experimental and theoretical results disclose that the synergetic effect of S, N co-doping and surface concave pores synergistically contribute to the improved lithium storage efficiency. The numerous concave pores within the defective carbon substrates significantly enhance the specific surface area and boost the quantity of active sites. Furthermore, S, N co-doping induces additional surface and structural defects and widens the crystallographic spacing. Herein, the formed threefold lithium storage mechanisms work synergistically to increase the active lithium storage sites and ion diffusion channels, promoting ion diffusion and charge transfer during lithium storage. As expected, the S, N-SCP/LCN exhibits remarkably high lithium storage capacity (1250 mAh/g at 0.1 A/g) and exceptional rate performance (445.65 mAh/g at a high rate of 10 A/g).

Drosophila HCN mediates gustatory homeostasis by preserving sensillar transepithelial potential in sweet environments.

Establishing transepithelial ion disparities is crucial for sensory functions in animals. In insect sensory organs called sensilla, a transepithelial potential, known as the sensillum potential (SP), arises through active ion transport across accessory cells, sensitizing receptor neurons such as mechanoreceptors and chemoreceptors. Because multiple receptor neurons are often co-housed in a sensillum and share SP, niche-prevalent overstimulation of single sensory neurons can compromise neighboring receptors by depleting SP. However, how such potential depletion is prevented to maintain sensory homeostasis remains unknown. Here, we find that the Ih-encoded hyperpolarization-activated cyclic nucleotide-gated (HCN) channel bolsters the activity of bitter-sensing gustatory receptor neurons (bGRNs), albeit acting in sweet-sensing GRNs (sGRNs). For this task, HCN maintains SP despite prolonged sGRN stimulation induced by the diet mimicking their sweet feeding niche, such as overripe fruit. We present evidence that Ih-dependent demarcation of sGRN excitability is implemented to throttle SP consumption, which may have facilitated adaptation to a sweetness-dominated environment. Thus, HCN expressed in sGRNs serves as a key component of a simple yet versatile peripheral coding that regulates bitterness for optimal food intake in two contrasting ways: sweet-resilient preservation of bitter aversion and the previously reported sweet-dependent suppression of bitter taste.

Wood Ion Pumps Enabled by Light-Responsive MoS2-Decorated Nanocellulosic Channels.

Light-driven active ion transport discovered in nanomaterials (e.g., graphene, metal-organic framework, and MXene) implicates crucial applications in membrane-based technology and energy conversion systems. However, it remains a challenge to achieve bulk assembly. Herein, we employ the scalable wood as a framework for in situ growth of MoS2 nanosheets to facilitate light-responsive ion transport. Owing to the aligned and negatively charged wood nanochannels, the MoS2-decorated wood exhibits an excellent nanofluidic conductivity of 8.3 × 10-5 S cm-1 in 1 × 10-6 M KCl. Asymmetric light illumination creates the separation of electrons and holes in MoS2 nanosheets, enabling ions to move uphill against a wide range of concentration gradients. As a result, the MoS2-decorated wood can pump ions uphill against a 20-fold concentration gradient at a light intensity of 300 mW cm-2. When the illumination is applied to the opposite side, the osmotic current along the 20-fold concentration gradient can be enhanced to 75.1 nA, and the corresponding osmotic energy conversion power density increases to more than 12.6 times that of the nonilluminated state. Based on the light-responsive behaviors, we are extending the use of MoS2-decorated wood as the ionic elements for nanofluidic circuits, such as ion switches, ion diodes, and ion transistors. This work provides a facile and scalable strategy for fabricating light-controlled nanofluidic devices from biomass materials.

Gene expression and protein localization of Cl− transporters, Slc26a6 and Cftr, in the gill ionocytes of rainbow trout

Euryhaline fishes acclimate to various osmotic environments by changing the direction of water and ion transport between body fluids and environmental waters. Ionocytes in the gills are one of the most important cells for the active ion transport. This study aimed to identify the molecules responsible for apical Cl− transport in rainbow trout ionocytes. Tissue distribution and time-course changes after seawater transfer were analyzed for mRNA expression of slc26a6, cftr1, and cftr2. slc26a6 was specifically expressed in the freshwater gills and decreased after seawater transfer. Both cftr genes were expressed in the gills and higher in seawater; however, the magnitude of expression increase after seawater transfer was greater in cftr1 than in cftr2. These results suggest that Cftr1 is mainly functioned in hypo-osmoregulation and that Cftr2 may also be involved in ion transport under freshwater conditions, such as acid–base regulation. Slc26a6 was localized at the apical membrane of Nkcc1-negative ionocytes only in freshwater-acclimated trout. Apical Cftr1 localization was also identified in most of ionocytes in seawater-acclimated fish. These results indicate that Slc26a6 in freshwater and Cftr1 in seawater contribute to osmoregulatory Cl− transport across the apical membrane of ionocytes in rainbow trout.

Leaching phosphorous from the lime mud of kraft pulp mills: Towards sustainability

AbstractThe optimum conditions needed to separate phosphorus from the lime mud generated in kraft pulp mills were identified using different leaching solutions including carbonate, bicarbonate, and green liquor under variety of conditions. Carbonate ions seemed to be the active ion in the phosphorus leaching process. Bicarbonate solution seems to be the most effective leaching agent by removing 84% of phosphorus under the optimum operating conditions of 95°C, 2.92 m, and solution‐to‐ mud mass ratio of 3.6. The shrinking core model was used to determine the leaching mechanism and it showed that the leaching process is controlled by a mix of chemical reaction and diffusion through the particle. Two empirical models were developed to predict the leaching efficiency as a function of carbonate concentration and temperature. Counter‐current leaching was shown to be beneficial in increasing the leaching efficiency with the carbonate solutions.