Surface Charge Distribution Research Articles

Numerical simulation of electromagnetically induced transparency in composite metamaterial

Abstract In high-refractive-index dielectric nanostructure, the Mie resonance become evident, and the destructive interference of the radiation fields from electric and toroidal dipole moments results in the excitation of anapole state, which has the unique optical properties of a dark state and can support the excitation of more diverse optical phenomena, such as the electromagnetically induced transparency (EIT) effect. In this study, we performed numerical simulations of a composite metamaterial consisting of Si nanocubes and gold nanorods. The Au-Si composite structure produces an electromagnetically induced transparency spectrum based on the coupling of the optical dark channel (i. e. anapole state) and bright channel (i. e. localized surface plasmon resonance). By tailoring the surface structure of the dielectric Si cube, the surface charge and current distributions can be modified, and finally, the nonradiative anapole state may be influenced and manipulated. The results show that the modified metal/dielectric metamaterial can realize an electromagnetically induced transparency effect with a transmission of up to 95% and a refractive index sensitivity of 170 nm RIU−1.

A Native LH1–RC–HiPIP Supercomplex from an Extremophilic Phototroph

Halorhodospira (Hlr.) halophila strain BN9622 is an extremely halophilic and alkaliphilic purple phototrophic bacterium and has been widely used as a model for exploring the osmoadaptive and photosynthetic strategies employed by phototrophic extreme halophiles that enable them to thrive in hypersaline environments. Here we present the cryo-EM structures of (1) a unique native Hlr. halophila triple-complex formed from light-harvesting (LH1), the reaction center (RC), and high-potential iron–sulfur protein (HiPIP) at 2.44 Å resolution, and (2) a HiPIP-free LH1–RC complex at 2.64 Å resolution. Differing from the LH1 in the Hlr. halophila LH1–LH2 co-complex where LH1 encircles LH2, the RC-associated LH1 complex consists of 16 (rather than 18) αβ-subunits circularly surrounding the RC. These distinct forms of LH1 indicate that the number of subunits in a Hlr. halophila LH1 complex is flexible and its size is a function of the photocomplex it encircles. Like LH1 in the LH1–LH2 co-complex, the RC-associated LH1 complex also contained two forms of αβ-polypeptides and both dimeric and monomeric molecules of bacteriochlorophyll a. The majority of the isolated Hlr. halophila LH1–RC complexes contained the electron donor HiPIP bound to the surface of the RC cytochrome subunit near the heme-1 group. The bound HiPIP consisted of an N-terminal functional domain and a long C-terminal extension firmly attached to the cytochrome subunit. Despite overall highly negative surface-charge distributions for both the cytochrome subunit and HiPIP, the interface between the two proteins was relatively uncharged and neutral, forming a pathway for electron tunneling. The structure of the Hlr. halophila LH1–RC–HiPIP complex provides insights into the mechanism of light energy acquisition coupled with a long-distance electron donating process toward the charge separation site in a multi-extremophilic phototroph.

Effect of voltage polarity on reaction mechanism of air atmospheric surface dielectric barrier discharge: A numerical study

This study establishes a two-dimensional fluid model of nanosecond surface dielectric barrier discharge (nSDBD) at atmospheric air to investigate the effects of positive and negative sinusoidal nanosecond pulsed voltages on the discharge characteristics. Key discharge parameters are studied, including discharge current, distribution of major active particles, surface charge distribution on the dielectric, energy deposition density distribution, and gas temperature. The numerical simulation results indicate that the plasma streamers excited by positive and negative bipolar pulses exhibit markedly different discharge characteristics, with the discharge characteristics in the first half-cycle largely determining those of the entire cycle. Positive bipolar pulsed streamer discharges exhibit greater discharge currents and stronger local electric fields, with faster propagation speeds but also more pronounced declines. The energy deposition of positive bipolar pulse is higher than that of negative bipolar pulse. The discharges driven by negative bipolar pulses exhibit a more pronounced temperature rise effect, primarily due to their higher efficiency in converting electrical energy into thermal energy, leading to stronger localized thermal release. Consequently, the pressure waves generated by negative bipolar pulsed discharges are more intense. These numerical simulation data provide theoretical explanations and references for understanding and optimizing the physical mechanisms of nSDBD.

Investigating the impact of crystal face on SnO2/GO-A humidity sensor via adsorption kinetics and DFT calculations

Ranging from monitoring indoor air quality to controlling processes in the food, pharmaceutical, and electronics industries, humidity-sensitive sensors play a pivotal role in various industrial and environmental applications. The crystallographic orientation of their surfaces is one of the key factors influencing the performance of metal oxide-based humidity sensors. However, the study of different crystal faces of metal oxides is rarely discussed, such as surface energy, charge distribution and reactivity, which can significantly affect their water absorption behavior and thus affect the sensitivity and response time of the humidity sensor. Hence, the present study introduces a meticulously designed SnO2/GO-A sensor that not only validates the successful fabrication of SnO2/GO-A sensor featuring optimized crystal alignment but also delves into the intricate water absorption mechanisms operative across various SnO2 crystal faces. The First-principles results show that (110) face of SnO2 is more sensitive to the water molecule than others. Consequently, due to the (110) crystal surface growth with annealing process, the SnO2/GO-A sensor demonstrates significant performance enhancements, especially in response speed, recovery time, linearity, and repeatability. In particular, the SnO2/GO-A sensor exhibiting faster response and recovery times of 20s and 18s, respectively, which is higher than SnO2 and SnO2/GO sensor. This advantage makes SnO2/GO-A sensor a potential candidate for humidity sensing applications.

Activation of the Complement Lectin Pathway by Iron Oxide Nanoparticles and Induction of Pro-inflammatory Immune Response by Macrophages

Aims: Nanoparticles are important agents for targeted drug delivery to tissues or organs, or even solid tumour in certain instances. However, their surface charge distribution makes them amenable to recognition by the host immune mechanisms, especially the innate immune system, which interferes with their intended targeting, circulation life, and eventual fate in the body. We aimed to study the immunological response of iron oxide nanoparticles (Fe-NPs) and the role of the complement system in inducing an inflammatory cascade. Background: The complement system is an important component of the innate immune system that can recognise molecular patterns on the pathogens (non-self), altered self (apoptotic and necrotic cells, and aggregated proteins such as beta-amyloid peptides), and cancer cells. It is no surprise that clusters of charge on nanoparticles are recognised by complement subcomponents, thus activating the three complement pathways: classical, alternative, and lectin. Objective: This study aimed to examine the ability of Fe-NPs to activate the complement system and interact with macrophages in vitro. Methods: Complement activation following exposure of macrophage-like cell line (THP-1) to Fe-NPs or positive control was analysed by standard protocol. Real-time PCR was used for mRNA-level gene expression analysis, whereas multiplex cytokine array was used for proteinlevel expression analysis of cytokines and chemokines. Results: Fe-NPs activated all three pathways to a certain extent; however, the activation of the lectin pathway was the most pronounced, suggesting that Fe-NPs bind mannan-binding lectin (MBL), a pattern recognition soluble receptor (humoral factor). MBL-mediated complement activation on the surface of Fe-NPs enhanced their uptake by THP-1 cells, in addition to dampening inflammatory cytokines, chemokines, growth factors, and soluble immune ligands. Conclusion: Selective complement deposition (via the lectin pathway in this study) can make pro-inflammatory nanoparticles biocompatible and render them anti-inflammatory properties.

Strong electrostatic attraction drives milk heteroprotein complex coacervation

Coacervates of oppositely charged milk proteins are used in functional food development, mainly to encapsulate bioactives. To uncover the driving forces behind coacervates formation, we study the association of lactoferrin and β−lactoglobulin at amino-acid level detail, using molecular simulations. Our findings show that inter-protein electrostatic interactions dominate and are, surprisingly, equally divided between an isotropic part, due to monopole-monopole attraction of the oppositely charged proteins, and an anisotropic part due to uneven surface charge distributions. In good agreement with recent experimental association constants, the calculated protein-protein interaction free energy is strongly dependent on pH and salt concentration. In addition to thermodynamics, we also investigate amino acid contacts in microstates of trimeric and pentameric protein complexes, and identify interaction hot-spots that drive heteroprotein complex coacervation process.

Evolutions of surface charge distribution on DC GIL insulators under under electro-thermal coupling field

Evolutions of surface charge distribution on DC GIL insulators under under electro-thermal coupling field

Influence of Composition on the Patterns of Electrokinetic Potential of Thermosensitive N-(Isopropyl)Acrylamide Derivatives with Poly(Ethylene Glycol) Dimethacrylate and N-(2-Hydroxyethyl)Acrylamide.

The synthesis of poly(N-isopropyl acrylamide) (pNIPA)-based polymers via the surfactant-free precipitation polymerization (SFPP) method produced thermosensitive nanospheres with a range of distinctive physicochemical properties. Nano- and microparticles were generated using various initiators, significantly influencing particle characteristics, including the hydrodynamic diameter (DH), which varied from 87.7 nm to 1618.1 nm. Initiators, such as potassium persulfate and 2,2'-azobis(2-methylpropionamidine) dihydrochloride, conferred anionic and cationic functionalities, respectively, impacting the electrokinetic potential (EP) of the particles. Notably, certain particles with cationic initiators exhibited negative EP values at 18 °C, attributed to residual initiator components that affected the surface charge distribution. The presence of hydrophilic N-(2-hydroxyethyl)acrylamide (HEAA) segments also influenced solubility and phase transition behaviors, with critical dependencies on the HEAA/NIPA (N-isopropyl acrylamide) molar ratios. EP measurements taken at 18 °C and 42 °C revealed substantial differences, primarily governed by the initiator type and polymer composition. Observed variations in particle stability and size were associated with the choice of crosslinking agents and comonomer content, which affected both DH and EP in distinct ways. This study provides insights into key factors influencing colloidal stability and electrostatic interactions within thermosensitive polymer systems, underscoring their potential applications in biomedical and industrial fields.

Machine Learning-Assisted SERS Reveals the Biochemical Signature of Enhanced Protein Secretion from Surface-Modified Magnetic Nanoparticles.

This study introduces a novel investigation of the interaction between Komagataella phaffii cells and iron oxide-based magnetic nanoparticles (Fe3O4 MNPs) via protein secretion and machine learning (ML)-assisted surface-enhanced Raman scattering (SERS). For the first time, we produced Fe3O4, Fe3O4@PEG, Fe3O4@PEI10kDa, and Fe3O4@PEI25kDa MNPs by a one-pot coprecipitation reaction. The addition of polymers to the reaction conditions significantly affected the shape, surface charge, size, and size distribution of the MNPs. The surface modification of MNPs is effectively accomplished using polyethylenimine (PEI), and the ζ-potential values of the MNPs exceed +25 mV under the NH4OH control. The homogeneity of MNPs synthesized with NH4OH is more pronounced according to transmission electron microscopy (TEM) pictures. All MNPs exhibited excellent immobilization efficiency (>92%) when we used 250 ppm Fe-containing MNP solutions. Smaller MNPs uniformly encapsulated the surface of K. phaffii cells, whereas larger MNPs exhibited irregular accumulation. K. phaffii cells exhibited excellent viability in all MNP solutions at up to 1000 ppm of Fe concentrations. Finally, the highest recombinant azurin protein secretion rate was obtained in Fe3O4@PEI10kDa MNP-immobilized cells (about 1.3 times). The ML-assisted SERS analysis revealed that MNP interactions with K. phaffii cells were mediated by proteins such as mannoproteins and membrane transporter proteins as well as N-acetylglucosamine (i.e., chitin). These findings revealed the effect of the size and surface properties of MNPs on the immobilization of K. phaffii cells and the enormous potential of magnetic immobilization for protein secretion.

One-Click to 3D: Helical Carbon Nanotube-Mediated MXene Hierarchical Aerogel with Layer Spacing Engineering for Broadband Electromagnetic Wave Absorption.

MXenes are 2D materials known for their unique electromagnetic wave absorption (EMWA) properties arising from their varied composition and structure. In this study, a one-step ice-assisted process is utilized to directly transform 2D MXene into 3D single-layer MXene aerogels (SMAs). Furthermore, the interlayer spacing of the SMAs is optimized by incorporating helical carbon nanotubes (HCNTs). Because of the van der Waals interaction between the MXene nanosheets and HCNTs, the assembled HCNT@MXene aerogels (HMAs) exhibited a regular porous structure and moderate conductivity, leading to significantly enhanced electromagnetic responses, as demonstrated by finite element simulation. The HMAs showed an exceptional EMWA, with a minimum reflection loss of -51.45 dB and an effective absorption bandwidth of 6.48 GHz at 3.0 wt.% filler ratio. Additionally, visualization of surface charge distribution and power loss density characteristics clarified the underlying EMWA mechanisms. By employing a hollow structure gradient metamaterial design, the effective EMWA bandwidth is further expanded to 13.98 GHz. Additionally, HMAs exhibited the maximum radar cross-section reduction values with 27.08 dBm2. Moreover, the HMAs exhibited excellent thermal insulation capability. This paper presents a straightforward yet effective method for fabricating MXene aerogels and offers valuable insights for the development and application of MXene-aerogel-based EMW absorbers.

Surface engineering activation of mixed valence copper selenide: A high-performance anode for long life zinc-ion rock-chair batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) are an attractive alternative to lithium-ion batteries (LIBs) for large-scale energy storage, which offer high ionic conductivity and environmental advantages. However, challenges such as dendrite growth and limited coulombic efficiency (CE) limit electrochemical performance of AZIBs thus hindering their practical application. This study designs a polypyrrole (PPy)-coated copper selenide composite (CuxSey@PPy) that works via Zn2+ insertion/extraction mechanism. Density Functional Theory (DFT) calculations reveal the PPy layer modifies the surface charge distribution of CuxSey, introducing additional electrochemical active sites. Consequently, the novel composite anode achieving specific capacity of 308.2 mAh g−1 at 100 mA g−1 and capacity retain of 96 %after 10,000 cycles at 2000 mA g−1, in half cell configuration. In full cell configuration, the rock-chair batteries with a ZnMn2O4 cathode retained 65.4 % capacity after 20,000 cycles, maintaining a CE consistently above 99 %.

Regulating the electronic modulation configuration of MnxFeCoNiCu high entropy alloy for reliable sulfur redox kinetics

Current research on sulfur redox catalysis primarily focuses on the adsorption and catalytic conversion of lithium polysulfides (LiPSs). However, it often neglecting the modulation of the catalysts' electronic structure, which includes charge transfer and orbital interactions that significantly affect adsorption and catalytic properties. In this work, multi-channel carbon nanotubes modified with high entropy alloy nanoparticles (MnxFeCoNiCu/MCCFs) are elaborately synthesized as hosts to reveal the relationship between the catalytic activity and surface electronic configuration for reliable sulfur electrochemistry. Combining density functional theory (DFT) calculations with detailed experimental investigations, we demonstrate that modulating the electron consumption center of this intrinsic electron transfer-replenishment mechanism, the surface charge distribution is reestablished, thereby improving the performance of multi-electron reactions. Achieving a balance between adsorption and desorption significantly enhance the catalytic efficiency for LiPSs conversion. Consequently, the as-prepared Mn1.00/MCCFs with an optimized electronic structure as sulfur host can deliver a high capacity of 938 mAh g−1, corresponding to an ultralow capacity decay of 0.013 % per cycle over 500 cycles at 1.0 C.

Synthesis of a sustainable material based on pecan nutshell for the elimination of diclofenac in aqueous solution: Characterization and adsorption studies

In the present study, activated carbons were synthesized from pecan nutshells (Carya illinoinensis) using two physicochemical methods: steam (CAVA) and phosphoric acid (CAAF). Their capacity to remove diclofenac from aqueous solution, as well as their textural, morphological, and physicochemical properties, were evaluated. N2 physisorption analysis revealed the microporous nature of the carbons, with specific surface areas of 1123.5 and 375.6 m2 g−1 for CAAF and CAVA, respectively. Scanning electron microscopy showed a heterogeneous morphology, with evident roughness caused by the irregularity of the surfaces resulting from the activation method used. The point of zero charge was 2.9 for CAAF and 8.9 for CAVA. Surface charge distribution analysis indicated that the surface of CAAF is predominantly negative, while that of CAVA is predominantly positive, which reflects the difference in active sites between the two materials. Infrared spectroscopy allowed for the identification of the functional groups present on the surfaces of the materials generated by the activation methods. Thermogravimetric analysis demonstrated that CAAF is more hydrophilic than CAVA, and both carbons exhibited low ash content (7 % for CAVA and 6 % for CAAF). The maximum adsorption capacity for DCF was achieved at a pH of 7, with values of 49.0 mg g−1 for CAVA and 230.8 mg g−1 for CAAF, decreasing as the pH increased from 7 to 10. Increasing the solution temperature from 15 to 35 °C, the adsorption capacity of CAVA and CAAF increased 1.2 and 1.5 times, respectively. Adsorption increased by 1.7 times for CAVA and 1.2 times for CAAF when the ionic strength was raised with a NaCl concentration from 0.001 to 0.01 M. The proposed mechanism for diclofenac adsorption on CAVA involved electrostatic interactions (pH < pHPZC), whereas the predominant mechanism in CAAF was π-π interactions (pH > pHPZC).

Self-adaptive reconstructed high-entropy sulfide catalysts with optimized surface electronic structure for lithium-oxygen batteries

Nonaqueous lithium-oxygen batteries have attracted immense attention owing to their high theoretical energy density. High-entropy based materials, encompassing both high-entropy alloys and high-entropy oxides (sulfides), have emerged as promising candidates for cathode catalysts. However, current fabrication methods for high-entropy materials, particularly high-entropy sulfides, remain complex and expensive. And the catalytic mechanism of high-entropy sulfides under oxygen-mediated reactions remains elusive and warrants further investigation. Herein, we propose a novel synthesis method for high-entropy sulfides, involving a hydrogel-xerogel conversion followed by a duplex treatment (low-temperature sulfuration and high-temperature calcination) processes. The synthesized (CoFeNiMnCu)9S8 high-entropy sulfide catalyst achieves elemental equilibrium and exhibits an optimized surface charge distribution. During oxygen-based battery reactions, the catalyst undergoes self-adaptive surface reconstruction, resulting in the formation of a nanoscale polycrystalline layer. This surface modification facilitates charge transfer between Co and Ni elements, and further modulates the localized electronic structure. Benefiting from the reconstructed (CoFeNiMnCu)9S8 cathode catalysts, lithium-oxygen batteries exhibit high reversible specific capacity (15100 mAh g−1), good rate capability, and enhanced long-term cycling stability.

Toward an Enhanced Hydrophilic TiO2 Nanoparticles Adsorption at Air-Liquid Interface Through Ion Regulation.

This study investigates the dynamic properties of air-liquid interfacial tension for hydrophilic TiO2 P25 utilizing the pendant drop method. Additionally, it examines the interfacial adsorption mechanism of hydrophilic TiO2 particles, considering the characteristics of particle surface charge distribution in relation to ion regulation to enhance particle interface adsorption. Experimental results reveal that in the absence of ion addition, the TiO2 P25 suspension system exhibits limited interfacial adsorption due to its superhydrophilicity, regardless of particle concentration. The addition of NaCl increases the surface charge density of the particles, strengthens the electrostatic attraction between particles and the interface, and enhances particle adsorption. Specifically, at a low NaCl concentration (0.01 wt %), the increased surface charge density and contact angle of the particles elevate particle activity and high interfacial packing density. At a higher NaCl concentration (0.1 wt %), while NaCl further increases the particle contact angle, the increased effective cross-sectional area of the air-liquid interface occupied by individual particles leads to a reduction in surface free energy. Despite the enhanced electrostatic attraction, this results in a lower packing density.

In Situ Transformation of Hybrid Bismuth Halide into Rhombohedral Bismuth for Electrochemical CO2 Reduction to Formate

AbstractBi‐based electrocatalysts have attracted high attention due to their high selectivity for formate, low cost, and high biocompatibility. Surface modification with halides can adjust the surface charge distribution of metal catalysts, thereby regulating the binding force of the intermediate. Organic‐inorganic hybrid bismuth halides provide an alternative, especially low dimensional structures. Herein, zero‐dimensional hybrid bismuth halides containing Bi4I16 units (denoted as Bi4I16) was recommended as pre‐catalyst due to the Bi ⋅ ⋅ ⋅ Bi spacing in Bi4I16 is 4.760 Å, nearly equaling to the Bi ⋅ ⋅ ⋅ Bi spacing in rhombohedral Bi (4.750 Å). The equal spacing may be more beneficial for the electricity‐driven in situ conversion and rearrangement of Bi atoms in the catalytic process. As a contrast, zero‐dimensional bismuth halide containing Bi2I9 units (denoted as Bi2I9) with shorter Bi ⋅ ⋅ ⋅ Bi spacing (4.2415 Å) was prepared. The working electrode prepared by Bi4I16 ink was measured for CO2RR, and the partial formate current density can reach 8.2 mA cm−2 at −1.1 V vs RHE. The Bi4I16 catalyst delivers a maximum Faradaic Efficiency (FE, ~80 %) for formate at −0.86 V vs RHE and maintain a FE higher than 78.5 % after 16 h.

Nitrogen-doped carbon nanosheet confined PtNi alloy for efficient acidic electrocatalytic hydrogen evolution reaction

Low intrinsic electrocatalytic activity and inferior conductivity limit the application of Ni/NC in acidic electrocatalytic hydrogen evolution reaction (HER). Herein, we prepared nitrogen-doped carbon nanosheet confined PtNi alloy electrocatalysts (PtNi/NC-10) using PtCl62− electrostatic adsorption coupling melamine pyrolysis nitriding strategy. PtNi alloying was confirmed by the crystallinity decrease and lattice expansion of Ni/NC. The alloying and confinement effect of Metal-Organic Frameworks (MOFs) suppresses the oxidation and agglomeration of metal nanoparticles during pyrolysis, thus significantly reducing particle size, increasing specific surface area, and promoting the exposure of active sites. The strong electronic interaction between Pt and Ni optimizeds the surface charge distribution, enhancing the adsorption of H species on electron-rich Pt sites, thereby improving reaction kinetics. In addition, PtNi alloying improves the conductivity of the material, accelerating charge transfer and proton transport. Consequently, the prepared PtNi/NC-10 exhibits superior HER performance than Ni/NC in 0.5 M H2SO4 solution, even comparable to commercial 20 wt% Pt/C, with the overpotentials of 35 mV at 0.01 A cm−2. Furthermore, the electrocatalysts assembled PtNi/NC-10-CP‖RuO2-TFF proton exchange membrane (PEM) electrolyzer only requires 2.32 V cell voltage to achieve 1 A cm−2, presenting practical application prospects. Our work provides a novel idea for designing efficient and stable MOFs confined to alloy-based HER electrocatalysts.

Ionic liquid meets ZnIn2S4: Synergistically tuning coordination environment of ZnIn2S4 grown on porous carbon by N, F doping and S-vacancies to load high concentration of single-atom Sb for efficient flexible Zn-Air batteries

Currently, the improvement in energy efficiency of catalysts for Zn-air batteries (ZABs) is seriously hindered by kinetic retardation. In this study, an ionic liquid was employed to generate sulfur vacancies, nitrogen/fluorine atoms, and a high concentration of single-atom Sb on a layered ZnIn2S4 substrate via a one-step synthesis process. These components were uniformly loaded onto porous carbon (SbSANF-ZnIn2S4-x/PC). The sulfur vacancies and nitrogen/fluorine atoms altered the surface charge distribution of ZnIn2S4-x and created an ideal coordination environment for the adsorption of single-atom Sb, enhancing the reactions in oxygen evolution/reduction reactions (OER/ORR) and ZABs. During testing, SbSANF-ZnIn2S4-x/PC demonstrated a half-wave potential of 0.892 V in ORR and an overpotential of 0.319 V in OER. When assembled into ZABs, it showed a specific capacity of 812.1 mAh g⁻¹ and a power density of 186.2 mW cm⁻². Overall, this study presents a promising one-step synthesis approach for creating a highly efficient electrocatalyst with single-metal atoms, non-metal atoms, and vacancies.

Efficient remediation of cadmium and lead contaminated soil in coal mining areas by MICP application in hydrothermal carbon-based bacterial agents: Nucleation pathways and mineralization mechanisms

The development of industrial mining has resulted in a large amount of Cd and Pb polluting the soil in mining areas, and leads to adverse health effects on the life of both plants and animals. Here, a soft template method was conducted to prepare hydrothermal carbon (HC) with regular morphology, which assisted with Bacillus pasteurii to induce calcite precipitation for decontamination of mining soil. Soil remediation experiments over 30 days of remediation with an HC microbial agent (HCMA) resulted in 89.4% and 87.8% decrease in the amount of leached Cd and Pb, respectively. The content of exchangeable Cd and Pb decreased by 76.1% and 81.0%, respectively. At the same time, soil fertility significantly improved. The electrostatic potential and surface charge distribution of extracellular polymeric substances (EPS) and sodium citrate (NaCit) were analyzed using DFT simulations, their nucleophilic and electrophilic regions were determined, and the nucleation mechanism was determined. The DFT results indicated that the oxygen-containing groups of EPS and NaCit had strong negative electrostatic potential and electronegativity, which could cause Cd2+, Pb2+, and Ca2+ to aggregate on their surfaces. They also combined with CO32− produced by urease during the decomposition of urea, resulting in Cd2+ and Pb2+ being encapsulated by calcium carbonate to form a coprecipitate. X-ray diffraction analyses revealed that the precipitate was mainly calcite calcium carbonate, which is more stable and less prone to secondary leaching of HMs. The gathered data prove the significant role of HCMA in remediation of mining soil contaminated with Cd and Pb.

Study on Coalescence Characteristics and Mechanisms of Salt-laden Droplets Under Electric-magnetic Coupling Field

Abstract Electric-magnetic coupling dehydration technology is a novel method that can significantly improve the efficiency of water-oil separation in water-in-oil (W/O) emulsions. However, the electric-magnetic coupling mechanisms and its influence on droplet coalescence have not been understood from a microscopic perspective, which has become a bottleneck restricting the progress of this technology. In this study, the high-speed microscopic experiment and molecular dynamics (MD) simulation were combined to study the kinetic properties of droplets coalescence under an electric-magnetic coupling field, and the potential mechanisms of electric-magnetic coupling field strengthening droplet coalescence were articulated from the perspective of salt ions migration and energy evolution. The results show that the experiment and simulation have excellent qualitative consistency. As water molecules polarise and migrate, the contact interface between adjacent droplets forms a cone tip during the approach process. The contact point of the droplet forms hydrogen bonds due to the mutual attraction of water molecules, which are then transformed into a continuously expanding liquid bridge. The salt ions in the droplet undergo migration deflection by the electric-magnetic coupling effect, which may affect the surface charge distribution of the droplets. During the process of droplet coalescence, strong electrostatic attraction occurs between molecules, leading to a significant increase in coulomb potential and dominating the overall potential energy variation. However, excessively small molecular spacing induces exchange repulsion, thereby reducing the van der Waals potential. The study results are of guiding significance for sounding droplet dynamics theory and guiding the research and development of electric-magnetic dehydration equipment.