Charge Modulation Research Articles

Fabrication of poly(maleic acid)-grafted cross-linked chitosan/montmorillonite nanospheres for ultra-high adsorption of anionic acid yellow-17 and cationic brilliant green dyes in single and binary systems

In this contribution, poly(maleic acid)-grafted cross-linked chitosan/montmorillonite composite nanospheres (PMAL-CTS/MMT) were synthesized via a facile approach for adsorption of organic dyes. The adsorption capacity of PMAL-CTS/MMT towards anionic acid yellow-17 (AY17) and cationic brilliant green (BG) was compared to PMAL-CTS, CTS/MMT, and MMT to emphasize the role of surface functional groups introduced by poly(maleic acid) and montmorillonite. Interestingly, the adsorption efficiency of PMAL-CTS/MMT nanocomposite towards both dyes in the single and binary systems was extremely high due to plenty of functional groups. The affinity of PMAL-CTS/MMT towards cationic and anionic dyes resulted from the feasible modulation of the surface charges as a function of the solution pH. The PMAL-CTS/MMT nanocomposite exhibited a maximum adsorption capacity of 518 and 1910 mg g–1 for AY17 and BG, respectively, which is higher than most of the adsorbents reported in recent literature studies. The proposed mechanism based on the characterization of PMAL-CTS/MMT after the adsorption highlighted that the adsorption is mainly controlled by electrostatic interaction, π − π interactions, and hydrogen bonding. More importantly, the PMAL-CTS/MMT nanocomposite was successfully applied to separate the AY17 and BG dyes from real-life aquatic environments. Collectively, the simple fabrication and superior adsorption performance reveal that PMAL-CTS/MMT has the potential to treat concomitant organic dyes effectively.

Catching Nucleosome by Its Decorated Tails Determines Its Functional States.

The fundamental packaging unit of chromatin, i.e., nucleosome, consists of ∼147 bp of DNA wrapped around a histone octamer composed of the core histones, H2A, H2B, H3, and H4, in two copies each. DNA packaged in nucleosomes must be accessible to various machineries, including replication, transcription, and DNA damage repair, implicating the dynamic nature of chromatin even in its compact state. As the tails protrude out of the nucleosome, they are easily accessible to various chromatin-modifying machineries and undergo post-translational modifications (PTMs), thus playing a critical role in epigenetic regulation. PTMs can regulate chromatin states via charge modulation on histones, affecting interaction with various chromatin-associated proteins (CAPs) and DNA. With technological advancement, the list of PTMs is ever-growing along with their writers, readers, and erasers, expanding the complexity of an already intricate epigenetic field. In this review, we discuss how some of the specific PTMs on flexible histone tails affect the nucleosomal structure and regulate the accessibility of chromatin from a mechanistic standpoint and provide structural insights into some newly identified PTM–reader interaction.

A Gradient Doped Integrated JFET With Improved Current Capability for HV Start-Up Circuit

The conventional high-voltage (HV) JFET (C-JFET) for HV start-up circuit suffers space charge modulation (SCM) effect especially when high current capability is required. Thus, the trade-off relationship between on-state breakdown voltage (ON-BV) and saturation current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dsat</sub> ) is worthy of analysis. In this work, a gradient doped integrated HV junction field effect transistor (JFET) for HV start-up circuit with high ON-BV and high I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dsat</sub> is proposed. In the resistance region and drift region of the proposed JFET, different slot ratios of deep N-well (DNW) are adopted. Hence, the gradient doped drift region with adjusted injected current and concentration enhanced N-buffer region can be obtained without adding extra mask. Benefit by introducing the gradient doped structure, the dose of DNW can increase. The well- calibrated simulated results indicate that the proposed HV JFET with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$147~\mu $ </tex-math></inline-formula> m device length can obtain 889 V ON-BV and 929 V OFF-BV with 0.152 mA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> m current capability, which is 21.6% better than our previously proposed D-JFET at the same off-state breakdown voltage level with the same device length.

Thermodynamics of Charge Regulation near Surface Neutrality.

The interaction between two adjacent charged surfaces immersed in aqueous solution is known to be affected by charge regulation─the modulation of surface charge as two charged surfaces approach each other. This phenomenon is particularly important near surface neutrality where the stability of objects such as colloids or biomolecules is jeopardized. Focusing on this ubiquitous case, we elucidate the underlying thermodynamics and show that charge regulation is governed in this case by surface entropy. We derive explicit expressions for charge regulation and formulate a new universal limiting law for the free energy of ion adsorption to the surfaces. The latter turns out to be proportional to kBT, and independent of the association energy of ions to surface groups. These new results are applied to the analysis of unipolar as well as amphoteric surfaces such as oxides near their point of zero charge or proteins near their isoelectric point.

Research on the mixed control strategy of the battery energy storage considering frequency modulation, peak regulation, and SOC

AbstractThe battery energy storage system (BESS) is considered as an effective way to solve the lack of power and frequency fluctuation caused by the uncertainty and the imbalance of renewable energy. Based on these, this paper proposes a mixed control strategy for the BESS. First, this paper divides the demand for frequency modulation, peak regulation, and state of charge (SOC) of the battery into different zones. Then the Kuramoto model modulates the frequency, and the self‐recovery strategy is used to optimize the SOC. Meanwhile, the proposed mixed control strategy is used to integrate frequency control, demand control, and SOC optimization. Finally, the simulation results verify the rationality of the strategy.

Structural instability and charge modulations in the kagome superconductor AV3Sb5

Recently, both charge density wave (CDW) and superconductivity have been observed in the kagome compounds $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$. However, the nature of the CDW that results in many novel charge modulations is still under hot debate. Based on the first-principles calculations, we discover two kinds of CDW states in $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$, namely, the trimerized-hexamerized $2\ifmmode\times\else\texttimes\fi{}2$ phase and the dimerized $4\ifmmode\times\else\texttimes\fi{}1$ phase. Our phonon spectrum and electronic Lindhard function calculations reveal that the most intensive structural instability in $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ originates from a combined in-plane vibration mode of V atoms through the electron-phonon coupling, rather than the Fermi surface nesting effect. More importantly, a metastable $4\ifmmode\times\else\texttimes\fi{}1$ phase with the V-V dimer pattern and twofold symmetric bow-tie-shaped charge modulation is revealed in ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$. Further analyses demonstrate that both the in-plane phonon instability and $c$ direction interaction play important roles during the $4\ifmmode\times\else\texttimes\fi{}1$ phase formation, which provides key understanding for the mechanism of the $4\ifmmode\times\else\texttimes\fi{}1$ CDW and relative novel phenomena in ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$.

Electric double layers with modulated surface charge density: exact 2D results

Electric double layers (EDL) with counterions only, say electrons with the elementary charge −e, in thermal equilibrium at the inverse temperature β are considered. In particular, we study the effect of the surface charge modulation on the particle number density profile and the pressure. The mobile particles are constrained to the surface of a 2D cylinder and immersed in vacuum (no dielectric image charges). An EDL corresponds to the end-circle of the cylinder which carries a (fixed) position-dependent line charge density. The geometries of one single EDL and two EDLs at distance d are considered; the particle density profile is studied for both geometries, the effective interaction of two EDLs is given by the particle pressure on either of the line walls. For any coupling constant Γ ≡ βe 2 = 2 × integer, there exists a mapping of the 2D one-component Coulomb system onto the 1D interacting anticommuting-field theory defined on a chain of sites. Using specific transformation symmetries of anticommuting variables, the contact value theorem is generalized to the EDL with modulated line charge density. For the free-fermion coupling Γ = 2 it is shown that, under certain conditions, the matrix of interaction strengths between anticommuting variables diagonalizes itself which permits one to obtain exact formulas for the particle density profile as well as the pressure. The obtained results confirm the previous indications of weak-coupling and Monte Carlo observations that the surface charge inhomogeneity implies an enhancement of the counterion density at the contact with the charged line and a diminution of the pressure between two parallel lines in comparison with the uniformly charged ones (with the same mean charge densities).

Mapping the dispersion of the occupied and unoccupied band structure in photoexcited 1T-TiSe2

Charge density waves (CDW) are states of broken symmetry with a periodic modulation of charge and lattice typically leading to the opening of a gap in the band structure. In the model CDW system 1T-TiSe2 such a gap opens up between its Se4p valence and Ti3d conduction band, accompanied by a change of dispersion. These changes are crucial in understanding the CDW phase, as they provide a measure of the Se4p-Ti3d hybridization strength and characteristic mechanistic features. Using time- and angle-resolved photoelectron spectroscopy (trARPES), the unoccupied band structure is populated with near-infrared (NIR) pump pulses which allows to directly visualize the parabolically-shaped Ti3d conduction band. Furthermore, we observe a transient change of effective mass in the Se4p valence band following photoexcitation. This occurs alongside an overall reduction due to weakening of the CDW phase and is accompanied by an oscillating component with the frequency of the characteristic A1g phonon. These observations, enabled by trAPRES, highlight the importance of the lattice contributions in establishing the CDW order in 1T-TiSe2.

Metal-Organic Frameworks with Assembled Bifunctional Microreactor for Charge Modulation and Strain Generation toward Enhanced Oxygen Electrocatalysis.

Two-dimensional metal-organic frameworks (MOFs) have served as favorable prototypes for electrocatalytic oxygen evolution reaction (OER). Despite promising catalytic activity, their OER reaction kinetics are still limited by the sluggish four-electron transfer process. Herein, we develop a ferrocene carboxylic acid (FcCA) partially substituted cobalt-terephthalic acid (CoBDC) catalyst with a bifunctional microreactor composed of two species of Co active sites and ligand FcCA (CoBDC FcCA). Benefiting from the ultrathin nanosheet structure, CoBDC FcCA catalyst exhibits an excellent OER performance with a low overpotential of 280 mV to reach 10 mA cm-2 and a small Tafel slope of 53 mV dec-1. Structure characterization together with theoretical calculations directly unravel the coordination for two species of Co active moieties with FcCA forming a microreactor of tensile strain, leading to a conversion of the Co spin from a high spin state (t2g5eg2) to an intermediate spin state (t2g6eg1) to regulate antibonding states of Co 3d and O 2p orbital. In situ spectroscopic measurements for mechanistic understanding reveal that this CoBDC FcCA catalyst possesses an optimal OH* adsorption energy for propitious formation of O-O bonds in the OOH* intermediate, thus effectively decreasing the thermodynamic Gibbs free energy of the rate-determining step (O* → OOH*) to accelerate reaction kinetics for the whole OER process. When loaded on an integrated BiVO4 photoanode as a cocatalyst, CoBDC FcCA enables highly active solar-driven oxygen production from water splitting.

Charge Modulation at Atomic-Level through Substitutional Sulfur Doping into Atomically Thin Bi2 WO6 toward Promoting Photocatalytic CO2 Reduction.

Photocatalytic reduction of CO2 has attracted enormous interest as a sustainable and renewable source of energy. In the past decade, numerous bulk‐type semiconductors have been developed, but the existing designs suffer many limitations, namely rapid recombination of charge carriers and weak light absorption ability. Herein, a bottom‐up approach was developed to design atomically thin sulfur‐doped Bi2WO6 perovskite nanosheets (S‐BWO) with improved reduction ability, extended visible light absorption, prolonged lifetime of charge carriers, enhanced adsorption of CO2, and reduced work function. Compared with pristine Bi2WO6 (P‐BWO), S‐BWO nanosheets exhibited a 3‐fold improvement in photocatalytic reduction of CO2 under simulated sunlight irradiation. Experimental studies and density functional theory calculations revealed the synergistic roles of atomically thin nanosheets and S atoms in promoting photocatalytic efficiency.

Interfacial Charge Modulation via in situ Fabrication of 3D Conductive Platform with MOF Nanoparticles for Photocatalytic Reduction of CO2.

Highly-efficient photocatalytic conversion of CO2 into valuable carbon-contained chemicals possesses a tremendous potential in solving the energy crisis and global warming problem. However, the inadequate separation of photogenerated electron-hole pairs and the unsatisfied capture of CO2 stay the chief roadblocks. Herein, we designed a novel photocatalyst for CO2 reduction by assembling three-dimensional graphene (3D GR) with a typical metal-organic framework material UIO-66-NH2 , aiming to construct a built-in electric field for charge separation as well as taking advantage of the typical 3D structure of GR for maximizing the exposed absorption site on the surface. The performance evaluation demonstrated that the photocatalytic activity has been improved for the composite materials compared with that of the pure UIO-66-NH2 . Further mechanism investigations proved that the enhanced photocatalytic performance is attributed to the synergy of enhanced CO2 absorption and inhibited photogenerated charge recombination, which could be owing to the better distribution and exposure of absorption and reaction sites on composites, and the redistribution of photogenerated carriers between 3D GR and UIO-66-NH2 . This study provides a promising pathway to probe nanocomposites based on MOFs in environmental improvement and other relevant fields.

Effect of Device Scaling on Electron Mobility in Nanoscale GaN HEMTs with Polarization Charge Modulation.

We have experimentally investigated the impact of vertical and lateral scaling on low-field electron mobility (µ) in InAlN/GaN high-electron-mobility transistors (HEMTs). It is found that µ reduces as InAlN barrier (TB) and gate length (LG) scale down but increases with the scaled source–drain distance (LSD). Polarization Coulomb Field (PCF) scattering is believed to account for the scaling-dependent electron mobility characteristic. The polarization charge distribution is modulated with the vertical and lateral scaling, resulting in the changes in µ limited by PCF scattering. The mobility characteristic shows that PCF scattering should be considered when devices scale down, which is significant for the device design and performance improvement for RF applications.

Design of Intelligent Wireless Charging System for Electric Vehicle

This design takes stm32h743vit6 chip in STM32 Series MCU as the core controller of the intelligent wireless charging system. The electric vehicle system is composed of wireless charging module, image processing system and intelligent vehicle driving module. It can realize the functions of logistics transportation within the set distance, wireless charging at the stop, returning according to the specified route and so on. This design can be applied not only in daily life, but also in short-distance intelligent logistics transportation environment such as AGV.

Unleashing Insulating Polymer as Charge Transport Cascade Mediator

AbstractCrafting spatially controllable charge transfer channels at the nanoscale level remains an enduring challenge in solar‐to‐chemical conversion technology. Despite the advancements, it still suffers from sluggish interfacial charge transport kinetics and scarcity of strategies to finely modulate charge transport pathways. Herein, this article demonstrates the unexpected charge modulation property of non‐conjugated insulating polymer assisted by a universal layer‐by‐layer self‐assembly tactic. Oppositely charged poly(dimethyl diallyl ammonium chloride) (PDDA) and Ti3C2 MXene quantum dots (MQDs) are periodically attached to the wide bandgap metal oxides (WMOs) to design multilayered heterostructured photoanodes. The intermediate PDDA layer acts as an efficacious charge relay medium to access directional electron flow from WMOs to Ti3C2 MQDs, while Ti3C2 MQDs serve as the electron extractor. Charge transfer cascade is thus stimulated on account of the simultaneous electron‐trapping capabilities of interim PDDA layer and Ti3C2 MQDs, which synergistically favors the conspicuously boosted charge separation over WMOs, affording the WMOs/(PDDA/MQDs)n photoanodes with considerably enhanced photoelectrochemical (PEC) water oxidation performances. Moreover, PEC performances of such photoanodes can be tuned by interface configuration via assembly number and sequence. This work will provide an insightful perspective to craft a directional charge transfer pathway through insulating polymer for solar energy conversion.

Verification Platform of SOC Estimation Algorithm for Lithium-Ion Batteries of Electric Vehicles

As one of the core technologies of electric vehicles (EVs), the state of charge (SOC) estimation algorithm of lithium-ion batteries is directly related to the performance of the battery management system (BMS). Before EVs are put into the market, the SOC estimation algorithm must be tested and verified to ensure the reliability of the BMS and the safe operation of EVs. Therefore, this paper establishes a lithium-ion batteries’ SOC estimation algorithm verification platform for the comprehensive performance evaluation and verification of the new SOC estimation algorithm. In addition, there are two schemes, including real-time SOC estimation verification and offline SOC estimation verification can be selected, which improve the reliability and efficiency of verification. Firstly, the design idea of the verification platform (the research and development purpose, functional requirements, and the overall design scheme) is introduced in detail. Secondly, the modular design idea is used to design the hardware structure of the verification platform, which mainly includes the BMS host module, BMS slave module, battery charger module, and electronic load module. Finally, the software system, including the communication architecture, the SOC reference standard and evaluation indexes of the algorithm, and the upper computer function and implementation is designed to realize the functions of the verification platform.

Ti-Fe2O3/perylene-3,4,9,10-tetracarboxylic acid heterojunction modified with Co(OH)2 as cocatalyst for photoelectrochemical water oxidation

Interface charge modulation by integrating the extraction layer and cocatalyst with semiconductor is closely linked with the photoelectrochemical (PEC) water oxidation performance, which is aimed at the directed transfer of photogenerated holes from semiconductors to electrolyte. Herein, a hybrid photoanode is elaborately designed for PEC water oxidation, which is fabricated by loading perylene-3,4,9,10-tetracarboxylic acid (PTCA) as a extraction layer on Ti-Fe2O3 for Ti-Fe2O3/PTCA heterojunction followed by the deposition of Co(OH)2 as the water oxidation cocatalyst. On the one hand, the band structure at the Ti-Fe2O3/PTCA interface and the PTCA/Co(OH)2 interface is in favor of the formation of successive interfacial electric filed in Co(OH)2/PTCA/Ti-Fe2O3, which in turn accelerates the hole extraction from Ti-Fe2O3 to Co(OH)2. In addition, the passivating role of Co(OH)2 also has contribution to the effective hole extraction. On the other hand, the in situ formed CoOOH from Co(OH)2 motivates the quick hole injection at the photoanode/electrolyte interface. To be brief, the vectorial transfer of photogenerated holes (Ti-Fe2O3→PTCA→Co(OH)2→electrolyte) is achieved by the co-deposition of PTCA and Co(OH)2. As such, Co(OH)2/PTCA/Ti-Fe2O3 exhibits a photocurrent density of 2.48 mA/cm2 at 1.23 V vs. RHE, which is much superior to Ti-Fe2O3.

Research on Active Overbalanced Control Strategy for Lithium-Ion Battery

In order to improve the voltage balancing effect of the lithium-ion power battery pack, a control strategy based on single-cell voltage overbalanced in the battery pack was proposed. In this method, the voltage of each battery is taken as the criterion of energy balance, and the analog switch and the energy storage inductor are used in the energy balance circuit. The PID control strategy of overequalization is proposed, which fully considers the self-recovery of voltage after the end of the charging process. The voltage balanced system of the lithium-ion power battery pack based on the voltage of a single-battery pack is realized, and the voltage maintains a stable equilibrium state after being balanced. The experimental circuit built in this paper verifies the effectiveness of the proposed method and gives the experimental waveform and data of the balanced charging module, which proves the scheme’s feasibility.

Quantum Dot-Embedded Hybrid Photocatalytic Nanoreactors for Visible Light Photocatalysis and Dye Degradation

Utilization of visible light to drive chemical transformations is a fascinating field of research and particularly important in the current socioeconomic context. However, bare photocatalysts often undergo photodegradation or agglomeration, which limits their recyclability. In this regard, designing robust and flexible artificial photocatalytic nanoreactors with embedded catalytic units finds tremendous importance in recent times. Herein, we utilized quantum dot (QD)-embedded coacervate nanodroplets (NDs) as photocatalytic nanoreactors for model chemical transformations, which are otherwise inefficient with bare QDs in bulk aqueous solution. Hybrid NDs fabricated from negatively charged CdTe QDs and positively charged poly(diallyldimethyl) ammonium chloride (PDADMAC) have been exploited as a confined host toward efficient visible light-driven photoredox transformation of ferricyanide (Fe3+) to ferrocyanide (Fe2+) and photocatalytic dye degradation of rhodamine B and methylene blue. The present NDs display excellent recyclability without any appreciable decrease in the conversion yield and reaction kinetics. Our findings suggest the involvement of individual QDs embedded within these NDs as the active photocatalytic site for these transformations. The observed photocatalytic activity of the QD-embedded NDs arises due to the combined effect of surface charge modulation of embedded QDs and nanoconfinement inside the nanoreactor. The present study paves the way for designing next-generation photocatalytic nanoreactors toward a vast array of photochemical conversions involving semiconductor nanoparticles.

Magnetic modulations in bulk α−BiFeO3 described using monoclinic superspace groups

The structural and magnetic properties of the room-temperature multiferroic bulk $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{BiFeO}}_{3}$ are described by using the magnetic superspace group formalism. The antiferromagnetic cycloid with its propagation vector along the hexagonal [1,1,0] direction cannot be described with trigonal magnetic superspace groups derived from $R3c$. This disagreement shows the necessity to replace trigonal symmetry with monoclinic symmetry. Several phenomena observed experimentally in bulk $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{BiFeO}}_{3}$, e.g., antiferromagnetic cycloid, weak ferromagnetic spin-density wave, and hkl-dependent Bragg peaks' broadening can all be described by using the monoclinic magnetic superspace groups $Cc(0\ensuremath{\beta}0)0$ for clockwise magnetic moments rotation and $C{c}^{\ensuremath{'}}(0\ensuremath{\beta}0)0$ for counterclockwise magnetic moments rotation. The proposed monoclinic superspace groups can also describe anharmonic magnetic modulations, charge modulations, atomic position modulations, as well as weak nonmodulated ferromagnetic ordering or ferroelectric polarization in bulk $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{BiFeO}}_{3}$.

Statistical learning of engineered topological phases in the kagome superlattice of AV3Sb5

Recent experimental findings have reported the presence of unconventional charge orders in the enlarged (2 × 2) unit-cell of kagome metals AV3Sb5 (A = K, Rb, Cs) and hinted towards specific topological signatures. Motivated by these discoveries, we investigate the types of topological phases that can be realized in such kagome superlattices. In this context, we employ a recently introduced statistical method capable of constructing topological models for any generic lattice. By analyzing large data sets generated from symmetry-guided distributions of randomized tight-binding parameters, and labeled with the corresponding topological index, we extract physically meaningful information. We illustrate the possible real-space manifestations of charge and bond modulations and associated flux patterns for different topological classes, and discuss their relation to present theoretical predictions and experimental signatures for the AV3Sb5 family. Simultaneously, we predict higher-order topological phases that may be realized by appropriately manipulating the currently known systems.