Valence Of Ions Research Articles

Ion Partition in Polyelectrolyte Gels and Nanogels.

Polyelectrolyte gels provide a load-bearing structural framework for many macroscopic biological tissues, along with the organelles within the cells composing tissues and the extracellular matrices linking the cells at a larger length scale than the cells. In addition, they also provide a medium for the selective transportation and sequestration of ions and molecules necessary for life. Motivated by these diverse problems, we focus on modeling ion partitioning in polyelectrolyte gels immersed in a solution with a single type of ionic valence, i.e., monovalent or divalent salts. Specifically, we investigate the distribution of ions inside the gel structure and compare it with the bulk, i.e., away from the gel structure. In this first exploratory study, we neglect solvation effects in our gel by modeling the gels without an explicit solvent description, with the understanding that such an approach may be inadequate for describing ion partitioning in real polyelectrolyte gels. We see that this type of model is nonetheless a natural reference point for considering gels with solvation. Based on our idealized polymer network model without explicit solvent, we find that the ion partition coefficients scale with the salt concentration, and the ion partition coefficient for divalent ions is higher than for monovalent ions over a wide range of Bjerrum length (lB) values. For gels having both monovalent and divalent salts, we find that divalent ions exhibit higher ion partition coefficients than monovalent salt for low divalent salt concentrations and low lB. However, we also find evidence that the neglect of an explicit solvent, and thus solvation, provides an inadequate description when compared to experimental observations. Thus, in future work, we must consider both ion and polymer solvation to obtain a more realistic description of ion partitioning in polyelectrolyte gels.

A salt-induced tackifying polymer for enhancing oil recovery in high salinity reservoirs: Synthesis, evaluation, and mechanism

Polymer flooding is an effective method widely applied for enhancing oil recovery (EOR) by reducing the mobility ratio between the injected water and crude oil. However, traditional polymers encounter challenges in high salinity reservoirs due to their salt sensitivity. To overcome this challenge, we synthesized a zwitterion polymer (PAMNS) with salt-induced tackifying property through copolymerization of acrylamide and a zwitterion monomer, methylacrylamide propyl-N, N-dimethylbutylsulfonate (NS). NS monomer is obtained from the reaction between 1,4-butanesultone and dimethylamino propyl methylacrylamide. In this study, the rheological properties, salt responsiveness, and EOR efficiency of PAMNS were evaluated. Results demonstrate that PAMNS exhibits desirable salt-induced tackifying characteristics, with viscosity increasing up to 2.4 times as the NaCl concentration reaches a salinity of 30 × 104 mg L−1. Furthermore, high valence ions possess a much stronger effect on enhancing viscosity, manifested as Mg2+ > Ca2+ > Na+. Molecular dynamics simulations (MD) and fluid dynamics experiment results demonstrate that PAMNS molecules exhibit a more stretched state and enhanced intermolecular associations in high-salinity environments. It is because of the salt-induced tackifying, PAMNS demonstrates superior performance in polymer flooding experiments under salinity ranges from 5 × 104 mg L−1 to 20 × 104 mg L−1, leading to 10.38–19.83% higher EOR than traditional polymers.

Oxygen vacancies and electrical properties of different valence ions (W6+, Nb5+, Zr4+, Cr3+) doped Bi4Ti3O12 ceramics

Numerous literatures have attested that donor doping in BiT ceramics will inhibit the generation of oxygen vacancies to improve electrical properties, but our study detects an originality that acceptor doped into BiT ceramics can also reduce the concentrate of oxygen vacancies and raise the values of Curie temperature and piezoelectric constant. A serious BiT-based ceramics with different valence transition metal dopants of W6+, Nb5+, Zr4+, Cr3+ were prepared via traditional solid phase method, achieving a high Curie temperature of 680–699 °C and a large piezoelectric constant of 7–17 pC/N. To improve the structural and electrical properties of BiT-based ceramics, this paper researched the concentration of oxygen vacancies with charge compensation effect of ions substitution by investigating the phase composition, microstructure, dielectricity, and conductivity systematically. The results show that all transition metal dopants enter the B-site of BiT ceramics to different extent and Cr partially replace the A-site of BiT ceramics, while the relaxation behavior and conduction mechanism of these ceramics are mainly contributed by the migration of oxygen vacancies. Due to the increase in the number of free electrons formed by donor doping W6+ and Nb5+ into BiT ceramics, the reduction in the number of trapped electrons proffered by equivalent doping Zr4+ that occupied the Ti3+ position and the consumption in the vacancies of Bi and O provided by Cr3+ that occupied the A-site after Bi volatilization, the oxygen vacancies defects of the BiT-based ceramics were decreased after ions doped.

Enhanced resistivity and piezoelectric response in BiFeO3-BaTiO3 via two-step sintering

Due to the defects from Bi volatilization and Fe ion valence change during normal sintering (NS), the BiFeO3-BaTiO3 (BF-BT) ceramic is always accompanied by serious leakage current and deteriorated electrical performance, which impeded its further application. In this work, the two-step sintering (TSS) method was applied to the BF-BT ceramics preparation, and numerous microstructures of samples were observed and verified that it can decrease the sintering temperature from 1000 ℃ to 900 ℃ and enhance the relative density to above 96%. This reduced the defects and solved the issue of large leakage current, and the resistivity of TSS samples is an order of magnitude higher than NS samples and reaches the maximum among the already reported. Moreover, the experimental and theoretical results conclude that the TSS samples obtained a stronger intrinsic piezoelectric effect, which increased the strain from 0.13% to 0.19%. The TSS method displayed enormous potential for BF-BT preparation.

Model selection for dynamic interfacial tension of dead crude oil/brine to estimate pressure and temperature effects on the equilibrium tension

Interfacial tension (IFT) measurements using pendant drop techniques are typically time-dependent and embed the underlying physics that can be exploited. A physics-based modeling approach of the time-varying IFT is chosen to estimate the equilibrium IFT and to identify which phenomena are leading the dynamic. This approach is both consistent and reproducible, hence advantageous for routine research and industrial applications because typical approaches are especially challenging when the techniques rely on long-time measurements or detailed characterization of phase composition and transport properties. The approach is applied to the Brazilian pre-salt dead crude oil/brine system when the equilibrium between the phases and between bulk and interface concentrations are not assured initially. Selected models based on a different physical phenomenon, mainly focused on diffusion and sorption, and with a particular time scale behavior are tested on measured data. The model which better fits the data in its full-time range should point out which phenomenon is dominant. The results indicate that the model with t time scale seems preferable for this oil/brine system, which is associated with a diffusion-controlled process in multiple regimes, for instance, bulk-to-interface diffusion of naturally present interface chemicals and their rearrangement at the interface. The effect of pressure (14.7 psi–4000 psi) and temperature (22 °C–60 °C) variations on the equilibrium IFT of the Brazilian pre-salt reservoir dead crude oil/brine at various conditions is characterized and discussed using the consistent physics-based estimate for the equilibrium IFT. The results show that the equilibrium IFT does not change significantly with pressure and increases with temperature, further supporting the identified presence of naturally present interface chemicals in the transient IFT measurements and the brine ionic valence influence. Furthermore, the wettability of carbonate rock samples with different mineralogical compositions to the dead crude oil/formation water is assessed using adhesion tension which embeds both IFT and contact angle contributions. Pressure changes do not affect wettability considerably, while the effects of temperature increase show that every sample tended to be wetter to its respective fluid affinity, following the IFT temperature behavior.

Photoinduced Cuproptosis with Tumor-Specific for Metastasis-Inhibited Cancer Therapy.

Cuproptosis is a novel form of regulated cell death which guarantees to increase the efficacy of existing anticancer treatments that employ traditional apoptotic therapeutics. However, reducing the amount of undesirable Cu ions released in normal tissue and maximizing Cu-induced cuproptosis therapeutic effects at tumor sites are the major challenges. In this study, exploiting the chemical properties of copper ionophores and the tumor microenvironment, a novel method is developed for controlling the valence of copper ions that cause photoinduced cuproptosis in tumor cells. CJS-Cu nanoparticles (NPs) can selectively induce cuproptosis after cascade reactions through H2 O2 -triggered Cu2+ release, photoirradiation-induced superoxide radical (∙O2 - ) generation, and reduction of Cu2+ to Cu+ by ∙O2 - . The generated reactive oxygen species can result in glutathione depletion and iron-sulfur cluster protein damage and further augmented cuproptosis. CJS-Cu NPs effectively suppressed tumor growth and downregulated the expression of metastasis-related proteins, contributing to the complete inhibition of lung metastasis. Ultimately, this study suggests novel avenues for the manipulation of cellular cuproptosis through photochemical reactions.

Emission characteristics, crystalline phase and composition of Er3+/Yb3+ doped LiNbO3 thin films deposited by e-beam evaporation

Er3+/Yb3+ doped LiNbO3 (LN) single crystal films with varying Yb3+ doping level were grown on z-cut LiTaO3 bulk single crystals via using e-beam evaporation method. The crystallographic orientation, elemental distribution, fluorescence properties, ionic valence states, Er3+ concentration, Yb3+ concentration and Li2O content of films were carefully studied. Results from XRD, SEM and Raman scattering conclude that the predominant phase of these films is LN and they are oriented along (006). The results of energy dispersive spectroscopy indicate that constituent elements are uniformly distributed over the entirety of the films. The visible and near-infrared luminescence intensities rise with increasing Yb3+-doping concentration. The Li2O content of films remains constant at 48.8 mol% with growing Yb3+-doping level based on the optical birefringence method, which is consistent with the Raman results. XPS results suggest that the Er3+ and Yb3+ concentrations in the films are lower than that in the polycrystalline powder since e-beam evaporation has a low efficiency of heavy Er3+ and Yb3+ ions.

Crystallization behavior and properties of quartz glass-ceramics synthesized from desert sand

Quartz glass-ceramics were synthesized with desert sand as the main raw material. The effects of pretreatment technology of desert sand and various cations on the glass stability (GS) parameters (KH, KLL,KW, KZW, KLX), crystallization kinetic parameters (crystallization activation energy (Ec), reaction rate (k), the effective frequency factor(ν) and the Avrami parameter (n)), phase transition, microstructure and properties of glass-ceramics were investigated. The results show that the chemical composition of desert sand is greatly changed by sieving and magnetic separation, and the glass stability, phase transition and crystallization ability of glass are controlled by the mixed mobile ion effect (MMIE), in which the ionic field intensity determined by ionic valence and radius plays a major role. Finally, the crystallization of glass is dominated by the surface crystallization mechanism, and the obtained glass-ceramics mainly consist of α-quartz, β-cristobalite and glass phases, which have excellent comprehensive properties.

Regularities of Manganese Charge State Formation and Luminescent Properties of Mn-Doped Al2O3, YAlO3, and Y3Al5O12 Single Crystalline Films

In this work, three sets of single crystalline films (SCF) of Al2O3:Mn sapphire, YAlO3:Mn perovskite (YAP:Mn), and Y3Al5O12:Mn garnet (YAG:Mn), with a nominal Mn content of 0.1%, 1%, and 10 atomic percent (at.%) in the melt-solutions, were crystallized by the liquid phase epitaxy (LPE) method onto sapphire, YAP and YAG substrates, respectively. We have also calculated the average segregation coefficient of Mn ions for Al2O3:Mn, YAP:Mn and YAG:Mn SCFs with Mn content in the melt-solution in the 0.1–10% concentration range, which was equal to 0.1, 0.14 and 0.2, respectively. The main goal of the conducted research was the spectroscopic determination of the preferable valence states of manganese ions which were realized in the SCFs of sapphire, perovskite and garnet depending on the Mn content. For this purpose, the absorption, cathodoluminescence (CL), photoluminescence (PL) emission/excitation spectra and PL decay kinetics of Al2O3:Mn, YAP:Mn and YAG:Mn SCFs with different Mn concentrations were studied. Based on the CL and PL spectra, we showed that Mn ions, depending on the Mn content in the melt-solution, are incorporated in Al2O3:Mn, YAP:Mn and YAG:Mn SCFs in the different charged states and are located in the different crystallographic positions of the mentioned oxide lattices. We have observed the presence of the luminescence of Mn4+, Mn3+ and Mn2+ valence states of manganese ions in CL spectra in all SCFs under study with 0.1 and 1% Mn concentrations. Namely, the Mn4+ ion valence state with the main sharp emission bands peaked at 642 and 672 nm, related to the 2E → 4A2 transitions, was found in the luminescence spectra of the all studied Al2O3:Mn SCFs. The luminescence of the Mn2+ valence state was found only in YAP:Mn and YAG:Mn SCFs, grown from melt solution with 1% Mn content, in the emission bands peaked at 525 and 560 nm, respectively, related to the 4T1 → 6A1 transitions. The PL and CL spectra of YAP:Mn and YAG:Mn SCFs with the Mn content in the 0.1–1% range show that the main valence state of manganese ions in these films is Mn3+ with the main emission bands peaking at 655 and 608 nm, respectively, related to the 1T2 → 5E transitions. Meanwhile, higher than 1% Mn content in the melt solution causes a strong concentration quenching of luminescence of all Mn centers in Al2O3:Mn, YAP:Mn and YAG:Mn SCFs.

Broadband La2LiSbO6: Cr3+ Phosphors with Double Luminescent Centers for NIR pc-LEDs.

The La2LiSbO6: xCr3+ phosphors were synthesized by means of a high-temperature solid-phase method. Based on the differences in ionic radius, valence state, and formation energy, the substitution sites of Cr3+ ions are discussed in detail. The optimized doping concentration of Cr3+ is determined to be 0.01. Under 517 nm excitation, the La2LiSbO6: 0.01Cr3+ phosphor presents a wide emission band (from 700 to 1350 nm) with a peak centered at 952 nm. Additionally, its corresponding full width at half-maximum is 155 nm, and the internal quantum efficiency reaches 62.4%. Meanwhile, the emission intensity of the La2LiSbO6: 0.01Cr3+ phosphor at 373 K is about 63.7% of that at room temperature, exhibiting good thermal stability. Aiming to fabricate a near-infrared phosphor-converted light-emitting diode device, the La2LiSbO6: 0.01Cr3+ phosphor is mixed with epoxy adhesive and cured on a green light-emitting diode chip. Under the irradiation of the fabricated light-emitting diode device, fruits and writing in the dark environment can be captured by a near-infrared camera. Hence, the La2LiSbO6: 0.01Cr3+ phosphor is promising for night vision.

Interaction, Adhesion and Aggregation of Microplastic/Nanoplastic Particles: Effects of Plastic Polymer Type

Microplastics (MP; <5 mm) and nanoplastics (NP; <1000 nm) are now ubiquitous in nature as they have been released into inland water, lakes, rivers, and marine water through direct discharge, runoff from upland watersheds, and other terrestrial environments. To understand the aggregation of MP and NP in the last decade, surveys and analytical efforts were undertaken. The MP and NP particles in the soil and water environments interact with other natural and engineered nanoparticles, which in turn form aggregates. These plastic particles could form homoaggregates and/or heteroaggregates depending on pH, ionic type, ionic valence, salt concentration, shape and size of the plastic particles, and the polymer type of MP. Differences in MP aggregation due to differences in plastic polymer type are not yet well documented. This review is conducted to investigate the effect of polymer type on the aggregation of MP and NP particles in the presence of various aggregation conditions.

Chemical Composition of Lithiated Nitrodonickelates Li3-xyNixN: Evidence of the Intermediate Valence of Nickel Ions from Ion Beam Analysis and Ab Initio Calculations.

Lamellar lithiated nitridonickelates have been investigated from both experimental and theoretical points of view in a wide range of compositions. In this study, we show that the nickel ion in lamellar lithiated nitridonickelates adopts an intermediate valence close to +1.5. This solid solution can therefore be written Li3-1.5xNixN with 0 ≤ x ≤ 0.68. Attempts to introduce more nickel into these phases systematically lead to the presence of the endmember of the solid solution, Li1.97Ni0.68N, with metallic nickel as an impurity. The LiNiN phase has never been observed, and first-principles calculations suggested that all the structural configurations tested were mechanically unstable.

The size dependence and defect induced room temperature ferromagnetism of ZnO and Zn 1-x-y AlxZyO (Z=Mg/Ni) nanocomposites

In the current research, Al-Mg-ZnO and Al-Ni-ZnO nanocomposites were synthesized by using simple soft chemical route. Prepared nanocomposites of Al-Mg-ZnO and Al-Ni-ZnO with capsule shape distributed magnetite nanostructured were carried out under the calcinated at 120 C for 12 h in furnace. The structural morphology and characterization analysis of as prepared nanocomposites was analyzed by XRD, UV–vis. FTIR, PL, TEM, VSM studies. XRD analysis confirmed the highly pure crystallized cubic phases. The XRD peaks show that the crystalline sizes are of the order of 22 nm, 19 nm, and 11nm. Magnetic property of the prepared nanocomposites was discussed in room temperature using VSM measurement. In spite of a number of researchers reporting the effect of codoping ZnO nanoparticles (NPs) with two different metals was modify the properties of the entire system such as enrich in room-temperature ferromagnetism. In this research we tried to by experimentally observed the magnetic properties of a series of soft chemical synthesized Zn1-x-yAlxZyO (Z=Mg/Ni) nanocomposites. Interestingly, it was found that in comparison to un-doped ZnO NPs and co-doped with two different metals. The ferromagnetic signal changes in a co-doped system in which one of the Mg/Ni ions increases the concentration of defects mechanism when Mg/Ni ions exhibited only one oxidation state. The potential role of charge transfer ferromagnetism is involving Mg2+ and Ni2+ ions substituted into ZnO lattice, The origin of magnetism in the nanocomposites is due to exchange interaction between local spin polarized electrons and the conduction electrons. The potential role of charge transfer ferromagnetism involving mixed valence ions and effects defect mechanism was used to explain the room temperature ferromagnetism.

Optimization of the electrical transport properties of La0.7Ca0.3MnO3 films by sintering temperature adjustment

With the development of the radiation thermometers, perovskite manganites have been fallen into the focus of highly sensitive infrared bolometers due to its metal-insulator transition properties. In this study, La0.7Ca0.3MnO3 (LCMO) films were prepared on (l00) LaAlO3 substrates using sol-gel spin-coating technology by adjusting different sintering temperatures (Ts, 1000 °C ≤ Ts ≤ 1400 °C). The analysis of the microstructure, surface morphology, ion valence state, and electrical transport properties revealed that the crystalline quality enhanced and the concentration of Mn4+ increased with the increasing of sintering temperature, promoting the DE effect and improving the electrical properties of the LCMO films. At Ts = 1200 °C, the temperature coefficient of resistivity (TCR) value of the LCMO film reached the maximum value (22.95% K−1) and corresponding peak TCR temperature of 246.85 K indicating that the LCMO film has great potential in infrared bolometers.

Field-scale zero liquid discharge of coking wastewater - Operating efficiency and environmental impact

Coking wastewater is typical industrial wastewater produced in the process of coal coking. The notion of Zero Liquid Discharge (ZLD) presents a paradigm aimed at mitigating waste generation and optimizing resource recovery. However, the implementation of ZLD in the realm of industrial wastewater treatment remains inadequately investigated and researched. We undertook an investigation into a ZLD treatment system applied to coking wastewater within a steel plant, which had been in operation for a span of four years, where the core steps are membrane concentration separation and thermal crystallization. The treatment efficiency of each unit was studied using the method of on-site sampling and detection. In comparison to the initial phase, the separation effectiveness of NF unit on different valence ions demonstrated sustained stability, the average rejection rate of SO42− was approximately 96%, whereas the rejection rate of Cl− was near 0. Conversely, under the influence of long-term operation and membrane fouling, the efficiency of the membrane concentration unit had a downward trend, with problems such as the deterioration of membrane, loss of ion rejection capability, and degradation of reclaimed water. The water recovery rate has decreased to 48.9% and the average ion retention rate has decreased to 85% in the membrane concentration unit. Nonetheless, the resultant by-products continued to align with the steel plant's recycling requirements. In addition, the Life cycle Assessment (LCA) method was used to assess environmental impact during operation. Subsequent analysis led to that reagents and electricity consumed in pretreatment and advanced treatment had a significant impact for negative EI. The impact of pretreatment on ODP accounted for 27.64%, and the impact on ADP accounted for 20.72%. The impact of advanced treatment on ADP accounted for 16.25%, the impact on EP accounted for 21.74%, and the impact on ET accounted for 27.06%. Meanwhile, the recovered water and salt during operation generate considerable environmental benefits and dominate the evaluation of the entire operating process. This work furnishes a valuable point of reference for pertinent ZLD investigations, while unveiling the pronounced capacity of ZLD to contribute substantially to waste management and the betterment of environmental consequences.

Alkali metal ion-mediated ice nucleation

Understanding the effects of ion specificities on ice nucleation is essential for atmospheric science and biology. Although valence and concentration changes of ions can regulate ice nucleation, it is unclear if alkali metal ions of different species with the same valence can regulate ice nucleation. This study investigated the behavior of ice nucleation on alkali metal ion-modified surfaces with atomic-scale roughness and (sub)nanometer thickness to decouple the effect of alkali metal ions on ice nucleation. The results showed that modulating the type of alkali metal ion could regulate ice nucleation. Additionally, it was found that different hydration shells of alkali metal ions may influence the structure of interfacial water and the thermodynamic phase transition to play a key role in regulating ice nucleation. This study shed light on a long-standing problem of the mechanism of alkali metal ions in ice nucleation and provided a strategy for effectively regulating ice nucleation .

Coeffect of Co-Mn in bimetallic oxide catalyst for ultrafast electrochemical reduction of nitrate: Insight into ion interaction

Co3O4 has been considered as promising catalysts for electroreduction of nitrate (ERN), which is an emerging tactic to close the nitrogen cycle on earth. However, the nitrate reduction efficiency of Co3O4 is less than satisfactory, which could be enhanced by assistance of Mn element. Herein, we synthesized Co3O4, Mn2O3 and Mn1.5Co1.5O4 nanoparticles for electrodes via a simple sol–gel method using metal nitrates. Moreover, a special electrode 3-Mn/Co was fabricated by physical mixed Co3O4 and Mn2O3. Mn1.5Co1.5O4 and 3-Mn/Co electrodes presented 78.6 % and 64.09 % nitrate removal efficiency after 3 h, 115.46 % and 75.68 % higher than that of Co3O4, proving the existence of Co-Mn coeffect. The optimum Mn1.5Co1.5O4 endures operating parameters experiments of applied potential, level of NO3– concentration, pH value and Cl- concentration and maintains solid stability through ten batches of reaction. Eventually, the ion valence changes of electrodes before and after electrocatalysis verifies that both Co and Mn function in the reaction. The ERN performance variation between electrodes, doped and physically mixed with Mn, and Co3O4 further elucidates that Mn3+ takes major effect in ERN process, while Mn4+ would blocks the electrons transferred to NO3–. In general, a novel process of Co3+/Mn3+- Co2+/Mn4+ reaction cycle in Co and Mn bimetallic and monometallic oxides for ERN performance is proposed as a clue for electrode fabrication.

Deposition behaviors of carboxyl-modified polystyrene nanoplastics with goethite in aquatic environment: Effects of solution chemistry and organic macromolecules

The ubiquitous nanoplastics (NPs) in the environment are emerging contaminants due to their risks to human health and ecosystems. The interaction between NPs and minerals determines the environmental and ecological risks of NPs. In this study, the deposition behaviors of carboxyl modified polystyrene nanoplastics (COOH-PSNPs) with goethite (α-FeOOH) were systematically investigated under various solution chemistry and organic macromolecules (OMs) conditions (i.e., pH, ionic type, humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA)). The study found that electrostatic interactions dominated the interaction between COOH-PSNPs and goethite. The deposition rates of COOH-PSNPs decreased with an increase in solution pH, due to the enhanced electrostatic repulsion by higher pH. Introducing cations or anions could compress the electrostatic double layers and compete for interaction sites on COOH-PSNPs and goethite, thereby reducing the deposition rates of COOH-PSNPs. The stabilization effects, which were positive with ions valence, followed the orders of NaCl ≈ KCl < CaCl2, NaNO3 ≈ NaCl < Na2SO4 < Na3PO4. Specific adsorption of SO42− or H2PO4− caused a potential reversal of goethite from positive to negative, leading to the electrostatic forces between COOH-PSNPs and goethite changed from attraction to repulsion, and thus significantly decreasing deposition of COOH-PSNPs. Organic macromolecules could markedly inhibit the deposition of COOH-PSNPs with goethite because of enhanced electrostatic repulsion, steric hindrance, and competition of surface binding sites. The ability for inhibiting the deposition of COOH-PSNPs followed the sequence of SA > HA > BSA, which was related to their structure (SA: linear, semi-flexible, HA: globular, semi-rigid, BSA: globular, with protein tertiary structure) and surface charge density (SA > HA > BSA). The results of this study highlight the complexity of the interactions between NPs and minerals under different environments and provide valuable insights in understanding transport mechanisms and environmental fate of nanoplastics in aquatic environments.

(Invited) Structure and Dynamics of Interfacial Species in Electrical Double Layer

Understanding electrochemical processes is of importance for many industrial and scientific fields. Especially, interfacial species, such as electrolyte ions and solvent significantly affect electrochemical reaction activity. Surface oxide species also promote or inhibit various electrode reactions; therefore, the oxidation processes of metal electrode have been investigated using in situ vibrational spectroscopy. Infrared (IR) spectroscopy is an important tool because it can detect the complementary vibrational modes of surface oxide species. However, observation of the low-frequency mode is restricted by infusible IR windows such as CaF2, that are generally used in the IR reflection absorption spectroscopy (IRAS). We developed a complementary IR method that can be used to avoid contamination by dissolved ions from window material. The fusible low-pass IR window can be applied to in-situ IRAS measurements [1,2]. The adsorbed hydroxide was observed on the single crystal Pt electrodes depending on the surface orientation, its coverage was correlated with the decrease in oxygen reduction reaction activity [3]. Recent time resolved X-ray diffraction measurements revealed that there is a delay in the approach of alkali metal cations to surface because the interfacial water causes a blocking effect [4]. Therefore, the kinetics of approaching step in the EDL is significantly different from that of migration in the bulk phase, and the adsorption rate depends on the hydration structure, ionic valence, and ionic size. Although X-ray diffraction provides a distribution of interfacial species, it does not provide sufficient information about species identification and molecular orientation. We investigated the coadsorption dynamics of metal cation and (bi)sulfate anion using time resolved IR measurement [5]. Boron doped diamond (BDD) is a promising material of which properties are significantly different from those of metals and other carbon materials. However, the complex atomic arrangement and oxidation state of the polycrystalline BDD surface inhibit an atomic level study on the relationship between the electrochemical response and surface structure. More detailed surface analyses are necessary for the investigation of the electrode surface of BDD. We applied in situ ATR−IR spectroscopy to reveal the oxidative species and dopamine oxidation on the BDD electrode [6,7].[1] M. Nakamura, Y. Nakajima, N. Hoshi, H. Tajiri, O. Sakata, ChemPhysChem, 14, 2426 (2013).[2] M. Nakamura, Y. Nakajima, K. Kato, O. Sakata, N. Hoshi, J. Phys. Chem. C, 119, 23586 (2015).[3] T. Kumeda, H. Tajiri, O. Sakata, N. Hoshi, M. Nakamura, Nat. Commun., 9, 4378 (2018).[4] M. Nakamura, H. Kaminaga, O. Endo, H. Tajiri, O. Sakata, N. Hoshi, J. Phys. Chem. C, 118, 22136 (2014).[5] M. Nakamura, T. Banzai, Y. Maehata, O. Endo, H. Tajiri. O. Sakata, N. Hoshi, Sci. Rep., 7, 914 (2017).[6] T. Ogose, S. Kasahara, N. Ikemiya, N. Hoshi, Y. Einaga, M. Nakamura, J. Phys. Chem. C, 122, 27456 (2018).[7] R. Hosoda, N. Kamoshida, N. Hoshi, Y. Einaga, M. Nakamura, Carbon, 171, 814 (2021).

Charging Metal‐Organic Framework Membranes by Incorporating Crown Ethers to Capture Cations for Ion Sieving

AbstractProtein channels on the biofilm conditionally manipulate ion transport via regulating the distribution of charge residues, making analogous processes on artificial membranes a hot spot and challenge. Here, we employ metal–organic frameworks (MOFs) membrane with charge‐adjustable subnano‐channel to selectively govern ion transport. Various valent ions are binded with crown ethers embedded in the MOF cavity, which act as charged guest to regulate the channels’ charge state from the negativity to positivity. Compared with the negatively charged channel, the positive counterpart obviously enhances Li+/Mg2+ selectivity, which benefit from the reinforcement of the electrostatic repulsion between ions and the channel. Meanwhile, theoretical calculations reveal that Mg2+ transport through the more positively charged channel needed to overcome higher entrance energy barrier than that of Li+. This work provides a subtle strategy for ion‐selective transport upon regulating the charge state of insulating membrane, which paves the way for the application like seawater desalination and lithium extraction from salt lakes.