Charge Regulation Research Articles

Bio-MIL-100(Fe) Heterostructure Construction and Charge Regulation: Iron Redundancy Breakthrough in a Fenton-like System

Bio-MIL-100(Fe) Heterostructure Construction and Charge Regulation: Iron Redundancy Breakthrough in a Fenton-like System

Nitrogen-doped carbon quantum dot-decorated In2O3 synaptic transistors for neuromorphic computing

Nitrogen-doped carbon quantum dots (N-CQDs) are promising materials for electronic devices due to their variable bandgap and structural stability. Here, we integrate N-CQDs into In2O3 synaptic transistors with electrolyte gating, resulting in a hybrid structure. The surface functional groups and defects of N-CQDs empower the charge trapping mechanism, permitting controlled conduction and charge regulation, which are crucial for emulating linear and symmetric artificial synaptic devices. Devices incorporating N-CQDs demonstrate enhanced stability and memory characteristics, low energy consumption, consistent retention, and a significant hysteresis window across multiple voltage cycles. Finally, the study emulates biological synapses and cognitive functions, achieving an energy consumption of 10 fJ per synaptic event and a pattern recognition accuracy of 91.2% on the MNIST dataset in hardware neural networks. This work demonstrates the potential of well-manipulating charge trapping in N-CQDs to develop high-performance, nonvolatile synaptic devices.

MEDOC: A fast, scalable and mathematically exact algorithm for the site-specific prediction of the protonation degree in large disordered proteins.

Intrinsically disordered regions are found in most eukaryotic proteins and are enriched in positively and negatively charged residues. While it is often convenient to assume these residues follow their model-compound pK a values, recent work has shown that local charge effects (charge regulation) can upshift or downshift sidechain pK a values with major consequences for molecular function. Despite this, charge regulation is rarely considered when investigating disordered regions. The number of potential charge microstates that can be populated through acid/base regulation of a given number of ionizable residues in a sequence, N , scales as ∼2 N . This exponential scaling makes the assessment of the full charge landscape of most proteins computationally intractable. To address this problem, we developed MEDOC (Multisite Extent of Deprotonation Originating from Context) to determine the degree of protonation of a protein based on the local sequence context of each ionizable residue. We show that we can drastically reduce the number of parameters necessary to determine the full, analytic, Boltzmann partition function of the charge landscape at both global and site-specific levels. Our algorithm applies the structure of the q -canonical ensemble, combined with novel strategies to rapidly obtain the minimal set of parameters, thereby circumventing the combinatorial explosion of the number of charge microstates even for proteins containing a large number of ionizable amino acids. We apply MEDOC to several sequences, including a global analysis of the distribution of pK a values across the entire DisProt database. Our results show differences in the distribution of predicted pK a values for different amino acids, in agreement with NMR-measured distributions in proteins.

The hostile environment in primary care: Qualitative analysis of a cross sectional survey of health care professionals in primary care

BackgroundIn 2014 the UK government rolled out the then called hostile environment as a series of punitive policies designed to disenfranchise undocumented migrants from living in Britain. As part of these measures upfront charging was introduced in 2017 which saw patients being denied treatment without prior full payment based on their immigration status. AimAssess the knowledge of the charging regulations in a sample of primary care practitioners. Assess the impact of the regulations on both patients and practitioners in a primary care setting. MethodsBuilding on a previous survey by the RCPCH, a cross sectional survey was circulated through the RCGP faculties and GP training groups within England. Demographic information and likert responses were collected from over 300 responses. Thematic analysis of over 120 white space questions was undertaken to create themes and sub-themes. ResultsResults showed an overall poor knowledge of the regulations. Thematic analysis was split into two main categories, (i) human impact of the policies and (ii) the economic and political impact of the policies. Key points were (i) lack of knowledge and awareness of the regulations, (ii) evidence of patient harm through patients’ being denied care, avoiding care or having care delayed, (iii) evidence of clinician harm through burnout, stress, a loss of faith in practice and concerns over extra work and (iv) concerns over implicit bias and structural racism within primary care and (v) concerns over lack of economic analysis. ConclusionCharging of overseas visitors is poorly understood within primary care despite having an impact on both patients and practitioners within this setting. Recommendations to help tackle this issue and reduce harm include training of staff, systematic reporting of harm, and a system wide economic analysis.

Mechanism design of EVs fast charging rights for enhanced vehicle-to-grid regulation

With the advancement of policy initiatives and technological developments, vehicle-to-grid (V2G) interactions have emerged as a critical focus within power system research. Despite numerous current studies on V2G, the exploration of incentive mechanisms to encourage user participation in these systems remains comparatively underdeveloped. This study proposes an innovative demand response (DR) incentive mechanism for electric vehicles (EVs) grounded in the regulation of fast charging powers via strategically assigning and allocating virtual points defined as fast charging right (FCR). The primary objective of this mechanism is to meet the power regulation requirements of DR while simultaneously balancing the grid’s response costs and accommodating the charging demands of EV users. Through simulation and comparative analysis with the existing pilot DR incentive mechanisms, the results demonstrate that the proposed mechanism outperforms the current model in three critical aspects: power regulation efficacy, cost-effectiveness, and user experience. In addition, this paper investigates the performance of the incentive mechanisms in both online and offline scheduling environments. The findings reveal that the FCR mechanism maintains robust power regulation performance even under online scheduling conditions.

Surface Charge Regulation of Graphene by Fluorine and Chlorine Co-Doping for Constructing Ultra-Stable and Large Energy Density Micro-Supercapacitors.

Settling the structure stacking of graphene (G) nanosheets to maintain the high dispersity has been an intense issue to facilitate their practical application in the microelectronics-related devices. Herein, the co-doping of the highest electronegative fluorine (F) and large atomic radius chlorine (Cl) into G via a one-step electrochemical exfoliation protocol isengineered to actualize the ultralong cycling stability for flexible micro-supercapacitors (MSCs). Density functional theoretical calculations unveiled that the F into G can form the "ionic" C─F bond to increase the repulsive force between nanosheets, and the introduction of Cl can enlarge the layer spacing of G as well as increase active sites by accumulating the charge on pore defects. The co-doping of F and Cl generates the strong synergy to achieve high reversible capacitance and sturdy structure stability for G. The as-constructed aqueous gel-based MSC exhibited the superb cycling stability for 500,000 cycles with no capacitance loss and structure stacking. Furthermore, the ionic liquid gel-based MSC demonstrated a high energy density of 113.9mWhcm-3 under high voltage of up to 3.5V. The current work enlightens deep insights into the design and scalable preparation of high-performance co-doped G electrode candidate in the field of flexible microelectronics.

Deciphering the work function induced local charge regulation towards activating an octamolybdate cluster-based solid for acidic water oxidation.

The advancement of highly robust and efficient electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions is imperative for the sustainable production of green hydrogen. In accomplishing sustainable and sturdy electrocatalysts for oxygen evolution at low pH, the challenge is tough for non-iridium/ruthenium-based electrocatalysts. This study elaborates on the intrinsic alterations in electronic arrangements and structural disorder upon the precise activation of an octamolybdate cluster-based solid [{Cu(pz)4}2Mo8O26]·2H2O through room temperature grinding with rGO (reduced graphene oxide), resulting in enhanced conductivity, stability, and activity of the electrocatalyst towards the acidic OER without employing any benchmark metal ion (Ru or Ir). Additionally, the work function of the composites was found to be low compared to that of pristine polyoxometalates (POMs), indicative of the improved conducive behavior, which is lacking in the POM structure. The catalyst displays a notably reduced overpotential of 185 mV to achieve a current density of 10 mA cm-2, coupled with significant stability lasting 24 hours at a higher current density of 100 mA cm-2. These findings propose the manipulation of crystalline POMs with highly conductive non-metallic elements to facilitate superior water oxidation at lower pH levels which can help in the production of green hydrogen.

Ionic liquid-triggered charge regulation of polydopamine-based surface for antibacterial nanofiltration

The charged surfaces with desirable performance are of high concern in membrane separation but there exist challenges to tailor them over a task-specific range. Herein, we propose an ionic liquid (IL)-triggered charge regulation strategy for polydopamine (PDA)-based surfaces by tuning the number and position of amino groups of ILs. By strategically manipulating the location of amino groups in either the anion, cation, or both, we realize a complete inversion in the surface charge nature of PDA coatings from highly negative to negative and even highly positive (zeta potential: −25 mV to +25 mV). This charge inversion triggered by IL is attributed to both the number of protonable groups and shielding effect provided by counter ions. Such charge flip enhances Donna effect when the PDA/IL coatings serve as the skin layer of nanofiltration membranes, thereby enabling high rejection to both negative and positive target molecules (i.e., chlorogenic acids at various pH). Despite charge regulation, ILs with dual amino groups cross link the PDA aggregates, largely narrowing the pore size distribution of the skin layer. The IL cross-linked PDA skin layer with uniform pores thus shows a nearly 100 % rejection to the target solutes. Meanwhile, the IL synchronously endow the PDA coatings with tunable charge characteristics, imidazolium functional groups and exceptional superoleophobicity, compensating for the originally inferior antibacterial activity of membranes in a wide pH range.

Charge regulation of nanoparticles in the presence of multivalent electrolytes.

We explore the charge regulation (CR) of spherical nanoparticles immersed in an asymmetric electrolyte of a specified pH. Using a recently developed reactive canonical Monte Carlo (MC) simulation method, titration isotherms are obtained for suspensions containing monovalent, divalent, and trivalent coions. A theory based on the modified Poisson-Boltzmann approximation, which incorporates the electrostatic ion solvation free energy and discrete surface charge effects, is used to compare with the simulation results. A remarkably good agreement is found without any fitting parameters, both for the ion distributions and titration curves, suggesting that ionic correlations between coions and hydronium ions at the nanoparticle surface play only a minor role in determining the association equilibrium between hydroniums and the functional sites on the nanoparticle surface. On the other hand, if suspension contains multivalent counterions, we observe a large deviation between theory and simulations, showing that the electrostatic correlations between counterions and hydronium ions at the nanoparticle surface are very significant and must be properly taken into account to correctly describe CR for such solutions.

Mitigating Jahn–Teller effect of MnO2 via charge regulation of Mn-local environment for advanced calcium storage

Manganese dioxide (MnO2) stands out as a prospective cathode material for calcium ion batteries (CIBs) owing to its elevated theoretical capacity and high operating voltage. Nevertheless, MnO2 with Jahn-Teller (J-T) twisted MnO6 octahedra experiences severe Mn dissolution during cycling, leading to the destabilization of the transition metal layer and resulting in poor cycling performance. In this work, Mo-substitution is purposely proposed to suppress the J-T effect in MnO2 for CIBs. The local charge of Mn is regulated by Mo doping, which enhances the electrical conductivity of MnO2 and suppresses the J-T distortion of the MnO6 octahedron. Meanwhile, density-functional theory (DFT) calculations manifest that Mo doping enhances the structural integrity of MnO2, making it difficult for Mn to escape from the MnO6 structure and inhibiting the dissolution of Mn. Accordingly, Mo-MnO2 demonstrates impressive rate capability (112 mAh g−1 at 1 A g−1) and excellent cycling stability, maintaining approximately 93.9 % capacity after 900 cycles at 1 A g−1. As a result, the introduction of heteroatoms through doping offers a novel design approach for the advancement of cathode materials for advanced CIBs.

Three-dimensional hydrogel membranes for boosting osmotic energy conversion: Spatial confinement and charge regulation induced by zirconium ion crosslinking

Ion-exchange membranes have been widely used to harvest osmotic energy in the past decades. However, conventional ion-exchange membranes suffer from low output power and poor conversion efficiency due to their limited pores and high membrane resistance. Herein, a sodium alginate (SA)/3-sulfopropyl acrylate potassium salt (SPAK) hydrogel membrane which has good cationic selectivity and can effectively harvest osmotic energy is designed, yielding a maximum power density of 16.44 W/m2 under a 50-fold NaCl concentration gradient and 36.85 W/m2 with ion selectivity of 0.73 at 500-fold. Furthermore, by introducing Zr4+, post-crosslinking reaction was employed to prepare tougher hydrogel membranes at room temperature for breaking a trade-off between selectivity and permeability, boosting a maximum power density up to 25.07 W/m2 under a 50-fold NaCl concentration gradient and 121.66 W/m2 with a high cation selectivity of 0.87 at 500-fold. Importantly, the resultant SA/SPAK/Zr4+ membrane reveals excellent osmotic energy harvesting property with the largest thickness of 500 μm, exceeding other reported porous nanofluidic membranes. Theoretical calculations correlate the enhanced power density of SA/SPAK/Zr4+ membranes with the enriched Cl- and smaller pore size after the introduction of Zr4+. This work paves an avenue to design and develop the 3D hydrogel membranes for high-performance osmotic energy generators.

Unexpected Two-Stage Swelling of Weak Polyelectrolyte Brushes with Divalent Counterions.

We use particle-based, coarse-grained simulations to study the influence of divalent counterions on a weak polyelectrolyte brush. Our simulations show a profound influence of even small concentrations of divalent salt on the titration behavior of the brush, which is shown to be a combined effect of electrostatic interactions and the Donnan effect. Furthermore, we examine the partitioning of mono- and divalent counterions into the brush. We demonstrate the preferred uptake of divalent ions by the brush, which is further enhanced by electrostatic correlation effects. Finally, our simulations reveal a hitherto unobserved two-stage swelling of the brush as a function of the pH in the presence of divalent salt. This phenomenon arises as a consequence of charge regulation and ion partitioning.

A photo-controlled charge regulator improves cancer theranostics.

A photo-controlled charge regulator improves cancer theranostics.

Protein Charge Neutralization Is the Proximate Driver Dynamically Tuning Reflectin Assembly.

Reflectin is a cationic, block copolymeric protein that mediates the dynamic fine-tuning of color and brightness of light reflected from nanostructured Bragg reflectors in iridocyte skin cells of squids. In vivo, the neuronally activated phosphorylation of reflectin triggers its assembly, driving osmotic dehydration of the membrane-bounded Bragg lamellae containing the protein to simultaneously shrink the lamellar thickness and spacing while increasing their refractive index contrast, thus tuning the wavelength and increasing the brightness of reflectance. In vitro, we show that the reduction in repulsive net charge of the purified, recombinant reflectin-either (for the first time) by generalized anionic screening with salt or by pH titration-drives a finely tuned, precisely calibrated increase in the size of the resulting multimeric assemblies. The calculated effects of phosphorylation in vivo are consistent with these effects observed in vitro. The precise proportionality between the assembly size and charge neutralization is enabled by the demonstrated rapid dynamic arrest of multimer growth by a continual, equilibrium tuning of the balance between the protein's Coulombic repulsion and short-range interactive forces. The resulting stability of reflectin assemblies with time ensures a reciprocally precise control of the particle number concentration, encoding a precise calibration between the extent of neuronal signaling, osmotic pressure, and the resulting optical changes. The charge regulation of reflectin assembly precisely fine-tunes a colligative property-based nanostructured biological machine. A physical mechanism is proposed.

Ru-Mn pair-site triggers key oxygen intermediate for enhanced acidic oxygen evolution reaction kinetics

Charge and spin regulation of electrons are identified as a vital factor in improving the oxygen evolution reaction (OER) catalytic activity. Nevertheless, the influence of surface reconstruction on charge and spin structure under complex catalytic reaction conditions has been unintentionally neglected. Correct understanding and targeted regulation of surface reconstruction are the key to prepare high active catalysts. Herein, variable valence states Mn is adopted to regulate Ru-NC, which serves as a model to reduce the localization of Ru 4d structure and stimulate facile charge transfer, achieving accelerated surface reconstruction to generate Ru-O active ingredient with high active to acidic water oxidation. Doping Mn not only accelerates surface reconstruction, but also improves durability by eliminating Ru peroxidation due to Mn-buffered charge compensation. The enhancement of OER activity results from the Mn and O induced Ru spin states to change from intermediate spin to low spin, thereby weakening the interaction with *O intermediates, and promoting *OH adsorption, which benefits the initial step of OER. This study not only provides a strategy to achieve directional reconstruction with the help of metal site asymmetry, but also provides a thorough comprehension of charge and spin dependent acidic OER kinetics.

Nonlinear Poisson-Boltzmann solutions for charged parallel plates: When opposite charges repel.

I present an exact solution of the Poisson-Boltzmann equation for two parallel plates and discuss the solution properties. I discuss in more detail plates with opposite charges: In this case, there are two critical separations, Lc,1 < Lc,2. For separations less than Lc,1, the force between plates is repulsive. It switches to attractive at Lc,1, but with the electric potential having the same signon both plates. For L > Lc,2, the force remains attractive, and the potential at the plates has the same signas the charge on each plate. I also describe charge regulation, determined by pKa, and provide formulas for both the critical distance where oppositely charged plates repel and their charging process. The implications of these results for the nanoparticle assembly, as driven by electrostatic interactions, are also discussed.

MOFs/MXene nano-hierarchical porous structures for efficient ion dynamics

Nature's various hierarchical structures exhibit exceptional performance in enhancing mass transport. However, how to bionic nano-hierarchical structures to enhance ion dynamics and achieve charge regulation is a significant challenge. Herein, a nano-hierarchical porous hybrid membrane inspired by nature was designed by integrating 1D metal-organic frameworks (MOFs) on the 2D MXene substrate utilizing MOF nanoparticles with tailorable positive and negative surface charges. The synergistic effects of the bioinspired nanohierarchical porous structure and surface charge interactions significantly enhance the performance and stability of the nanoconfined membrane, as corroborated by experimental characterizations and theoretical simulations. As a result, the optimized nanohierarchical porous membrane exhibits high a cation selectivity of 0.95, an outstanding power density of 35.04 W m−2, and excellent stability over one month. Synergizing enhanced mass transport and ion dynamics in nano-hierarchically structured materials with tailored charge improves osmotic power generation efficiency and benefits logic circuits with controlled charge transport.

Local charge regulation via selenium vacancies engineering in dielectric cobalt diselenide with enhanced microwave absorption

The weak electromagnetic loss capability of the single semiconductor material is difficult to meet the complicated electromagnetic environment nowadays, so vacancy engineering is employed to optimize the dielectric loss capability of CoSe2. Selenium vacancies are introduced into CoSe2 by re-annealing treatment, and the test results show that the selenium vacancies concentration enlarged with annealing temperature. The formation of selenium vacancies introduces a localized state in CoSe2, which enhances the capability of CoSe2 to trap charge carriers, and the increased conductivity contributes to the enhancement of the dielectric loss capability. Density Functional Theory (DFT) calculations demonstrate that the selenium vacancies disrupt the original charge equilibrium distribution of the CoSe2, and the non-recombined positive and negative charge centers induce a strong electric dipole polarization loss. Benefiting from the optimization of CoSe2 dielectric loss by the selenium vacancies engineering, RLmin of CoSe2-600 reaches −30.73 dB and the effective absorption bandwidth reaches 4.00 GHz at 1.8 mm. This study provides a simple and effective solution to optimize the microwave absorption performance of single-component microwave absorption materials.

Interface Charge Regulation Enhancing Output and Durability of Triboelectric Nanogenerator for Efficient Wastewater Treatment

Interface Charge Regulation Enhancing Output and Durability of Triboelectric Nanogenerator for Efficient Wastewater Treatment

Stabilizing Zn anodes via a binder-free MoS2 interface with charge regulation toward stable Zinc-Ion batteries

Aqueous zinc ion batteries (AZIBs) have been a promising candidate for next-generation batteries. However, the uncontrolled dendrite formation and side reactions of the Zn anode significantly restrict their application. Herein, a binder-free MoS2 protective layer were uniformly deposited on Zn foil by electrochemical deposition. The MoS2 protected Zn anode has a lower nucleation barrier and a uniform electric field distribution, which can effectively alleviate the corrosion and side reactions of Zn metal, thus leading to the fast Zn2+ diffusion kinetics. The results show that the MoS2-Zn anode has low voltage hysteresis, long cycle stability at 0.5 mA cm−2/0.1 mAh cm−2 in symmetrical batteries. The MoS2-Zn//α-MnO2 full cell exhibits an exceptional reversible capacity of 225.8 mAh/g at 1C, while maintaining stable cycling performance over 300 cycles. This work provides a promising strategy to construct a 2D coating to improve the stability of Zn anode in AZIBs.