Electrostatic Repulsive Forces Research Articles

Reducing Lithium‐Diffusion Barrier on the Wadsley–Roth Crystallographic Shear Plane via Low‐Valent Cation Doping for Ultrahigh Power Lithium‐Ion Batteries

AbstractRapid‐charging niobium–tungsten oxide Nb14W3O44 (NbWO) anodes with a Wadsley–Roth crystallographic shear (WRCS) structure possess 3D interconnected open tunnels. However, the anisotropic Li+ diffusion paths lead to a high lithium‐diffusion barrier of hooping between window sites across edge‐shared octahedrons, as the rate‐limiting step of hooping. To improve the rate capability of NbWO, doping it with low‐valent cations (with valences lower than W6+) to reduce the high lithium‐diffusion barrier is proposed. Electron energy loss spectroscopy reveals that low‐valent V5+, V4+, Tb4+, and Ce4+ tend to distribute on the crystallographic shear plane under electrostatic repulsion forces. The reduction in steric hindrance resulting from the increased long bond length ratio of doped edge‐shared octahedrons, coupled with coordination environment modification of [LiO5] on the crystallographic shear plane due to the low energy level of V5+, enhances Li+ diffusion kinetics and cyclic stability. V5+‐ and Tb4+‐doped NbWOs achieve rate capacities of 83 and 63 mAh g−1, at 200 C (1C = 0.178 Ag−1) and retain 75.42% and 86.79% of their capacities, respectively, after 3700 cycles at 20 C. Thus, the proposed doping strategy is promising for preparing WRCS‐type niobium‐based oxides for ultrafast lithium storage.

Enhanced Electrostatic Dust Removal from Solar Panels Using Transparent Conductive Nano-Textured Surfaces.

Dust accumulation on solar panels is a mjor operational challenge faced by the photovoltaic industry. Removing dust using water-based cleaning is expensive and unsustainable. Dust repulsion via charge induction is an efficient way to clean solar panels and recover power output without consuming any water. However, it is still challenging to remove particles of ≈30µm and smaller because Van der Waals force of adhesion dominates electrostatic force of repulsion. Here, the study proposes nano-textured, transparent, electrically conductive glass surfaces to significantly enhance electrostatic dust removal for particles smaller than ≈30µm. We perform atomic force microscopy pull-off force experiments and demonstrates that nano-textured surfaces reduce the force of adhesion of silica micro-particles by up to 2 orders of magnitude compared to un-textured surfaces from 460 to 8.6 nN. We show that reduced adhesion on nano-textured surfaces results in significantly better dust removal of small particles compared to non-textured or micro-textured surfaces, reducing the surface coverage from 35% to 10%. We fabricate transparent, electrically conductive, nano-textured glass that can be retrofitted on solar panel surfaces using copper nano-mask based scalable nano-fabrication technique and shows that 90% of lost power output for particles smaller than ≈10µm can be recovered.

Electrostatic Interaction of Dielectric Particles in an Electrolytic Solution

On the basis of the Poisson-Boltzmann equation the electrostatic interaction between two charged dielectric spherical particles in a symmetric electrolyte solution is considered. The interaction forces between particles of the same radius under the condition of uniform charge distribution on their surfaces in the absence of an external field have been calculated by the finite element method. The dependence of the electrostatic repulsion forces between the particles on the magnitude of the particle charges and the dielectric permittivities of the particle materials and the surrounding medium has been analyzed.

Manipulating Aggregate Electrochemistry for High‐Performance Organic Redox Flow Batteries

Organic molecule in solutions is the energy storage unit in the organic redox flow batteries (ORFBs), of which the aggregation is acknowledged pivotal but has been rarely investigated. By establishing a pyridinium library, the manipulation over the aggregation in solutions is investigated at the molecular level. Both theoretical calculations and physiochemical methods are used to characterize the aggregate’s structure, and salient findings are as follows. First, the singly‐reduced monoradicals simultaneously aggregate in a concentrated solution, which is driven by the solvation effect, orbital overlap and dispersion interaction. Second, the aggregation can be manipulated by the molecular engineering strategy and counteracted by introducing either electrostatic repulsive force or twisted geometry. Third, the monoradical’s aggregation yields a decrease in the molecular singly occupied molecular orbital energy level and a linear scaling relationship with its thermodynamic potential. As a result, the increase in the concentration lowers the battery’s voltage, which counteracts its effort to increase the battery’s energy density. The anti‐aggregation is proven effective in breaking the scaling relationship and accordingly, a molecular strategy to manipulate aggregate electrochemistry is developed. This work provides physical insights into the electrolytic solution and chemical strategy for optimizing the flow battery.

Effect of background ions and physicochemical factors on the cotransport of microplastics with Cu2+ in saturated porous media

Microplastics (MPs) in subsurface environments are migratory and can carry heavy metals, increasing the extent of MP and heavy metal pollution. This study used quartz sand-filled column experiments to investigate the adsorption and cotransport behaviours of PS-MPs, O3, UV-aged PS-MPs, and Cu2+ at different MP concentrations, ionic strengths, and ionic valences in a saturated porous medium. The results showed that when MPs migrate alone in the absence of an ionic background, higher concentrations have increased mobility. In contrast, an increase in the background ion concentration or ion valence inhibits the individual transport capacity of PS-MPs. An increase in the concentration of background ions or elevation in the valence state promotes Cu2+ transport because of the action of the double electric layer on the surface of the colloid and the electrostatic repulsive forces combined with the background ions. The adsorption capacity of aged PS-MPs was stronger than that of PS-MPs because of the binding of the aged PS-MPs to Cu2+ through complexation and electrostatic attraction. In the binary system of PS-MPs/Cu2+, PS-MPs promoted Cu2+ transport and the mobility of Cu2+ loaded by PS-MPs decreased with increasing background ion concentration. The cotransport results showed that MPs promote Cu2+ transport in the following order: O3-aged Ps > UV-aged Ps > Ps, as the increasing cation concentration in the MPs and Cu2+ occupies the PS surface adsorption sites. Overall, PS is an effective carrier for Cu2+. These findings offer fresh exploration concepts for the joint migration of MPs and heavy metals in underground settings.

Polypyrrole-bound carbon nanotube conductive polysulfone membranes for self-cleaning of fouling

A novel conductive membrane, polypyrrole carbon nanotubes polysulfone (PPy-CNT-PSF), was successfully synthesized using the membrane phase infiltration in-situ polymerization method (MPIP). The resulting PPy-CNT-PSF, utilized as an anode in the electrochemical filtration reactor, exhibited a chain-like morphology of PPy extending from within to the exterior of the PSF membrane, effectively anchoring the CNT layer on its surface and establishing a stable conductive network with a surface resistance of 0.142 ± 0.052 kΩ/cm. Its electrical conductivity surpasses that of most conductive membranes derived from pyrrole (Py). Furthermore, the structural integrity of this conductive membrane remained intact following exposure to chlorine. Cyclic voltammetry (CV) analysis revealed a subtle redox peak with no significant alteration in surface structure after 50 CV cycles. This reaction can be attributed to a Fenton-like reaction process due to Fe presence detected by EDX on the surface. Current-time curves under constant potential further confirmed that the PPy-CNT-PSF conductive membrane possesses both a stable conductive network and favorable electrode stability. Additionally, self-cleaning occurred when voltage was applied during electrochemical experiments utilizing a conductive membrane anode paired with a Ti cathode due to electrostatic repulsive forces. At an applied voltage of 20 V, removal efficiency and flux restoration achieved values of 97.63 % and 100 %, respectively. This straightforward yet effective approach is believed to hold promise for fabricating conductive membranes characterized by structural stability and electrode reliability for practical applications aimed at mitigating membrane fouling.

Rheological Behavior of Clay Tailings in the Presence of Divalent Cations and Sodium Polyacrylate: Insights from Molecular Dynamics Simulations.

This study analyzes the behavior of sodium polyacrylate (NaPA) as a rheological modifier for clay-based tailings. Special emphasis is placed on the impact of calcium and magnesium ions in industrial water, which are analyzed through rheograms, zeta potential measurements, and molecular dynamics simulations. The results are interpreted as electrostatic interactions, steric phenomena, and cation solvation. This interpretation integrates experimental studies with microscopic analyses, employing molecular dynamics simulations to elucidate the underlying mechanisms. In all cases, a decrease in the yield stress of synthetic slurries is observed as the dosing of NaPA increases due to greater repulsion between tailings particles through an increase in electrostatic repulsion and larger steric forces that hinder agglomeration. However, efficiency is reduced in the presence of divalent cations as zeta potential measurements suggest a reduction in the electrical charges of the particles and the polymer, making its application more challenging. The differences obtained in the presence of calcium compared to magnesium are explained in terms of the solvation of these ions and their impact on the polymer conformation in solution and adsorption on the mineral surfaces. This explanation is reinforced by molecular dynamics studies, which indicate that polymer adsorption on minerals depends on the type of mineral and type of ion. Particularly for quartz, the highest adsorption of NaPA occurs in the presence of calcium, whereas for a kaolinite surface, the highest polymer adsorption is obtained in the presence of magnesium. The competitive effect of these phenomena leads to the rheological behavior of the tailings being dominated by the effects originating in the clay.

Significantly enhancing enzymatic saccharification of poplar waste through the effective removal of lignin and hemicellulose by 1-butanol-Na3PO4-water treatment

Na3PO4-H2O-assisted 1-butanol pretreatment was established for changing the structure of poplar waste and improving its enzymatic efficiency. After poplar waste was pretreated at 180 °C for 60 min, 51.3 % of xylan and 52.5 % of lignin were eliminated. After the enzymatic saccharification of treated poplar waste, the yield of reducing sugars reached 75.3 %. A series of characterizations demonstrated that Na3PO4-H2O-assisted 1-butanol pretreatment altered the poplar composition with improved cellulose accessibility from 231.2 to 459.5 mg/g and reduced surface area of lignin from 384.2 to 255.3 m2/g. Molecular simulations, quantum chemical calculations and independent gradient model analysis were performed on the poplar model, and the 1-butanol-Na3PO4-H2O pretreatment resulted in the increase of electrostatic and van der Waals repulsion forces in lignin and xylan, explaining the efficient lignin and xylan removal. A comprehensive interpretation of mass balance and energy flow was applied to assess the entire pretreatment process. This eco-friendly 1-butanol-Na3PO4-H2O pretreatment effectively broken the encapsulation of cellulose by enzyme inhibitors and improve biomass pretreatment effect.

Effect of particle size on the transport of polystyrene micro- and nanoplastic particles through quartz sand under unsaturated conditions

Micro- and nanoplastics (MNPs) are contaminants of emerging concern recently found in soil ecosystems. Their presence in terrestrial environments and their migration to aquatic environments may become a risk for the health of ecosystems and, through them, of humans. Understanding the interaction between particle properties and physicochemical and hydrodynamic factors is crucial to evaluate their fate and their potential infiltration towards groundwater. This study investigates the impact of particle size on MNPs transport through sand under unsaturated conditions. Infiltration column experiments with polystyrene MNPs ranging from 120 to 10,000 nm were conducted and supported by numerical modelling to derive reactive transport parameters. Results show a significant effect of particle size on the transport of MNPs, with higher recovery values observed for smaller particles (120 nm; 95.11%) compared to larger particles (1000 nm; 71.44%). No breakthrough was observed for 10,000 nm particles, indicating a complete retention within the quartz sand matrix. DLVO theory confirmed the dominance of electrostatic repulsive forces between MNPs and sand grains, suggesting an unfavourable environment for MNPs to adhere to quartz sand. Consequently, particle retention in the sand matrix occurs predominantly by physical processes. Equilibrium sorption modelling reveals that larger particles (1000 nm) tend to be immobilized in small pores throats due to straining, resulting in lower recoveries. When they are not trapped, particles tend to travel faster through preferential flows due to a size exclusion effect, evidenced by shorter arrival times at the column outlet compared to tracers. These findings highlight the influence of particle size on the transport and retention of MNPs in quartz sand under unsaturated conditions and contribute to a better understanding of their transport dynamics and environmental fate.

Exploration of the regulatory mechanism of pulsed electric field on the aggregation behavior of soybean protein isolates

As an emerging protein modification technology, pulsed electric field (PEF) technology in modifying soybean protein isolates (SPI) suffers from unclear mechanism and controversial changes in aggregation structure. To address these issues, the effects of PEF treatment with different electric field intensities (5–30 kV/cm) on the aggregation behavior and spatial structure of SPI were investigated. The results showed that the SPI aggregates exhibited a trend of depolymerization followed by reaggregation with the increase of PEF intensity. At 10 and 15 kV/cm, the polarization effect of PEF induced the unfolding of the tertiary structure of SPI, leading to the enhancement of the electronegativity of the side chains, and the electrostatic repulsive force between the molecules promoted the depolymerization of SPI aggregates. However, with the withdrawal of PEF, the structure of the SPI was partially reversible, resulting in a limited depolymerization effect. When the PEF intensity reached 20 kV/cm and above, SPI underwentstructure unfolding, subunit dissociation, continuous exposure of hydrophobic groups and sulfhydryl groups, and ultimately reaggregation mediated by hydrophobic interactions and disulfide bonding, resulting in the formation of high molecular weight soluble and insoluble protein aggregates. In addition, the formation of free radicals under strong electric fields (≥20 kV/cm) accelerated the oxidation of SPI and promoted the rapid formation of disulfide bonds. This study provides a theoretical basis for the targeted regulation of SPI aggregation structure by PEF.

Having their cake and eat it too: Effects of different cations in reduced-salt myofibrillar protein microgel pickering emulsion under high-intensity ultrasound

Health concerns have increased the demand for low-salt emulsified meat products emulsions; however, salt-soluble myofibrillar proteins (MP) are less than optimal emulsifiers under low-salt conditions. In this study, four different cations (Na+, K+, Ca2+, and Mg2+) were added to a Pickering emulsion and high-intensity ultrasound (HIU, 20 kHz, 600 W) was used to determine the quality of the final emulsion. The divalent cation group was found to significantly (P < 0.05) improve the emulsification performance of the emulsion; in particular, the emulsion activity index and emulsion stability index of Mg2+-H group increased to 16.24 ± 1.22 m2/g and 89.66 ± 3.01%, respectively. Measurements of the particle size and zeta potential confirmed that the emulsion particle size of the Mg2+-H group decreased, and the electrostatic repulsion force increased. Based on the surface hydrophobicity and endogenous tryptophan spectra, the particle structure of the MP microgel was determined to be a more stable emulsifier. What's more, the divalent cations promoted the droplets to become evenly dispersed under high-intensity ultrasound. The micrograph confirmed this result: the divalent cation group emulsion was more uniform and stable than the monovalent cation group emulsion. Divalent cations are more suitable than monovalent cations for improving the quality of reduced-salt Pickering emulsions.

Concept of electrons pairing during the formation of covalent chemical bonds

This research studies the forces acting in an electron pair with antiparallel spins participating in forming a covalent chemical bond between atoms. The first is the force of electrostatic repulsion of electrons. The second is the gravitational attraction of these electrons. The third is the force of electromagnetic attraction between the electron pair. From calculations it follows, that the force of gravitational attraction is negligible, and therefore it is not able to withstand the force of electrostatic repulsion between electrons. However, the force of electromagnetic attraction between a pair of electrons with antiparallel spins turned out to be hundreds of times greater than the force of their electrostatic repulsion. As a result, the formation of stable electron pairs in molecular orbitals becomes possible. Thus, valence electrons of neighboring atoms interact with each other like femto-electromagnets, as a result of which a stable bond is formed between these electrons. Calculations have shown that in hydrogen molecule the force of electrostatic attraction between nuclei and paired electrons of a molecular orbital significantly exceeds the force of electrostatic repulsion of nuclei, which ensures the formation of a strong covalent chemical bond. To form covalent bonds in other molecules, the force of electrostatic attraction between the nuclei and paired electrons of the molecular orbitals must be much greater than the forces of electrostatic repulsion between both the positively charged nuclei and the negatively charged electrons of the atomic orbitals of different atoms.

Continuous Focusing of Particles by AC-Electroosmosis and Induced Dipole Interactions.

Continuous particle focusing by using microfluidics is an effective method for separating particles, cells, or droplets for analytical purposes. Previously, it was shown that an alternating current across rectangular microchannels with slightly deformed side walls results in vortex flow patterns caused by alternating current electroosmosis (AC-EOF) and could lead to particle focusing. In this work, we explore this mechanism by experimentally studying the particle focusing behavior for various fluid flow velocities through a microchannel. Since it is unlikely that the particles are kept in their focused position solely by convection, a theoretical force balance between the hydrodynamic and the induced dipole force was determined. In our experiments, it was found that there is no substantial effect of the pressure-driven fluid velocity on the particle focusing velocity within the studied range. From the theoretical force balance calculations, it was determined that while the addition of the induced dipole force can still not completely describe the experimentally observed particle focusing, the induced dipole can be strong enough to overcome the hydrodynamic force. Finally, it is hypothesized that under specific circumstances, including a repulsive electrostatic force between a particle and electrode wall can complete the theoretical particle focusing force balance. Alternative phenomena that could also play a role in particle focusing are proposed.

Interaction of charged magnetic nanoparticles with surfaces

The behavior of magnetic nanoparticles covering the surface with positive charges (MN), suspended in a continuous medium, was simulated by Brownian dynamics. Then, we studied the behavior of the MN in an aqueous-like suspension and their adsorption on a negatively charged surface, mimicking a mica surface. After several microseconds, particles are deposited onto the charged surface. Experimental results of ordered magnetic nanoparticles in surfaces are compared with the present simulation results of MN in two dimensions. We also demonstrate the effect of charged MN on the hexagonal structure when electrical repulsions dominate against magnetic dipole-dipole and van der Waals attractions. On one hand, the adsorption of MN on the surface depends on the electrostatic attraction force with the surface, while the surface organization of MN results from balancing electrostatic repulsion forces and magnetic attraction forces among particles. In magnetic nanoparticles simulated with a non-charged surface or weakly charged surface, dipole-dipole interactions dominate the particle-particle interactions, and the interactions between particles and a mica-like surface are conducted by van der Waals forces.

Divergent responses of aggregate breakdown by slaking to nitrogen forms in solution for contrasting soil types

Aggregate stability strongly affects many soil processes and is critical to maintain sustainable agriculture. Aggregate breakdown is controlled by the interaction between soil intrinsic properties and solution characteristics. Nitrogen fertilization including different forms is well known to influence aggregate stability; however, relative to their long-term effects, there is little recognition on the rapid response of aggregate breakdown to nitrogen solutions. This study aimed to examine the effects of nitrogen form and concentration on aggregate stability for different types of soils. Aggregate breakdown against slaking of three soil types (Phaeozem, Luvisol, and Acrisol) and three horizons (organo-mineral (A), illuvium (B), and parent material horizons (C)) was determined subjected to nitrogen solutions of three forms (CO(NH2)2, NH4+, NO3–) and five concentrations (0.05 ∼ 1.0 mol/L). Among nitrogen forms, urea solution almost had non-significant effect irrespective of soil type and horizon (p > 0.05); for NH4+ and NO3– solutions, aggregate stability showed little variations (MWD of 0.19 ∼ 0.26 mm) with electrolyte concentration for Phaeozem in B and C horizons, overall increased for Luvisol and Phaeozem in A horizon, and decreased first and then reached a steady state for Acrisol. The effects of nitrogen forms on aggregate breakdown were dependent on soil aggregation status or cementing agents (mainly organic matter, clay mineralogy). Electrolyte nitrogen solutions (NH4+ and NO3–) inhibited aggregate breakdown mainly through reducing electrostatic repulsive forces for moderately developed soils rich in swelling clays, and promoted aggregate breakdown by both weakening particle cohesion and enhancing compression pressure of entrapped air for highly developed soils rich in non-swelling clays and Fe/Al oxides. These results facilitate an improvement of fertilizer management and irrigation to improve soil quality on different soil types.

Evaluating the operational properties of concrete admixtures containing molecularly modified polycarboxylate superplasticizers

The objective of this study focused on the design and preparation of a molecularly modified polycarboxylate superplasticizer to develop concretes with enhanced engineering features. For this purpose, polyethylene glycol was chemically modified with maleic anhydride to give the mono polyethylene glycol maleate (MPEGM). Then, polycarboxylate superplasticizer comprising of isoprenyl oxy polyethylene glycol (TPEG) and acrylic acid (AA, PCE-1), and the synthesized MPEGM with TPEG and AA (PCE-2) were prepared through solution radical polymerization. Subsequently, concrete mixtures with different dosages (0, 0.1, 0.15, 0.2, 0.25, 0.3 wt%) of PCE-1 and PCE-2 were prepared. Chemical structure of the synthesized MPEGM and superplasticizers together with their copolymer composition were identified by FTIR and 1HNMR analyses. The molecular weights (Mw) and molecular weight distributions (PDI) of PCE-1 (8.74 × 104, 1.36) and PCE-2 (8.74 × 104, 2.19) were studied by GPC analysis, respectively. The zeta potential of cement particles (2.8 mV) becomes negative in the presence of 0.6 g/L of PCE-1 (− 7.8) and PCE-2 (− 9.5). This implies that electrostatic and steric hindrance forces of adsorbed superplasticizers synergistically provide a situation for appropriate dispersion of cement particles. The results of water-reducing percentage, fluidity, air content, bleeding water rate, initial and final setting times, wet density, flexural and compressive properties, and ultrasonic pulse velocity analyses exhibit significant enhancement on the features of concrete mixtures made of polycarboxylate superplasticizer. The superiority of PCE-2 to PCE-1 was connected to its adsorption-dispersibility potent induced by stronger electrostatic and steric repulsion forces, which result in quality and continuity enhancement in concretes.

Electrodynamic dust shield efficiency characterisation under UV in vacuum for lunar application

Dust mitigation is one of the most crucial aspects of extraterrestrial exploration. This paper presents a series of experiments on the electrodynamic dust shield (EDS) and how UV radiation affects its efficiency on selected lunar simulants (LHS-1 and LMS-1) across a range of particle sizes, quantities, and surface materials. In this experimental study, VUV is used with a 1500 V AC electric field to mobilise the dust particles resting on either glass, Kapton, or Beta cloth inside a vacuum chamber at ∼10-6 mbar. The dust removal efficiency is characterised by two quantifying methods: weighing and solar array light transmission. The experimental results show that EDS activation under continuous UV exposure on the simulant particles improves the dust removal rate by 40 to 80 percentage points across all surfaces, with the exception of certain particle size ranges on Beta cloth. The primary force facilitating particle mobilisation was identified as the repulsive electrostatic force, enhanced by ionising mechanisms such as photoemission.

Crosslinking and Swelling Properties of pH-Responsive Poly(Ethylene Glycol)/Poly(Acrylic Acid) Interpenetrating Polymer Network Hydrogels.

This study investigates the crosslinking dynamics and swelling properties of pH-responsive poly(ethylene glycol) (PEG)/poly(acrylic acid) (PAA) interpenetrating polymer network (IPN) hydrogels. These hydrogels feature denser crosslinked networks compared to PEG single network (SN) hydrogels. Fabrication involved a two-step UV curing process: First, forming PEG-SN hydrogels using poly(ethylene glycol) diacrylate (PEGDA) through UV-induced free radical polymerization and crosslinking reactions, then immersing them in PAA solutions with two different molar ratios of acrylic acid (AA) monomer and poly(ethylene glycol) dimethacrylate (PEGDMA) crosslinker. A subsequent UV curing step created PAA networks within the pre-fabricated PEG hydrogels. The incorporation of AA with ionizable functional groups imparted pH sensitivity to the hydrogels, allowing the swelling ratio to respond to environmental pH changes. Rheological analysis showed that PEG/PAA IPN hydrogels had a higher storage modulus (G') than PEG-SN hydrogels, with PEG/PAA-IPN5 exhibiting the highest modulus. Thermal analysis via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated increased thermal stability for PEG/PAA-IPN5 compared to PEG/PAA-IPN1, due to higher crosslinking density from increased PEGDMA content. Consistent with the storage modulus trend, PEG/PAA-IPN hydrogels demonstrated superior mechanical properties compared to PEG-SN hydrogels. The tighter network structure led to reduced water uptake and a higher gel modulus in swollen IPN hydrogels, attributed to the increased density of active network strands. Below the pKa (4.3) of acrylic acid, hydrogen bonds between PEG and PAA chains caused the IPN hydrogels to contract. Above the pKa, ionization of PAA chains induced electrostatic repulsion and osmotic forces, increasing water absorption. Adjusting the crosslinking density of the PAA network enabled fine-tuning of the IPN hydrogels' properties, allowing comprehensive comparison of single network and IPN characteristics.

Enhanced assembly stability for amine-based cationic glycolipid

Glycolipids incorporating positive charges, mediated by an imidazolium cation, have shown potential for effective formulation of vesicular drug carriers, reflecting repulsive electrostatic forces, promoting the formation of nanosized assemblies and preventing unwanted Oswald ripening (Goh et al. (2019), ACS Omega 4, 17,039). Our continuous development of an assembly-based drug delivery system prompted us to investigate a pH-sensitive analogue, leading to the synthesis of a 6-amino-Guerbet glycoside. However, in contrast to the imidazolium counterpart, the amine-mediated charge increased the intermolecular cohesions, furnishing bigger assemblies instead, which further increased upon introduction of acid. Moreover, assemblies exhibited a significantly reduced positive charge density. It is concluded that strong proton-initiated hydrogen bonding between amino groups provide cohesive head group interactions overcompensating possible repulsive charge interactions. While this behavior invalidates the application of the amino-glucoside as dispersing agent for the formulation of small vesicles, it potentially paves a route towards enhanced vesicle stability.

The decisive role of filtration reducers’ surface charge in affecting drilling fluid filtration performance

To elucidate the effects of filtration reducers’ surface charge on drilling fluid filtration performance, three kinds of SiO2@polymer nanoparticles with different surface charges are prepared. When these nanoparticles are added into bentonite-based drilling fluids as filtration reducers, the negatively charged nanoparticles show the best filtration reduction performance while the positively charged nanoparticles show the most inferior filtration reduction performance. Moreover, more negative charges induce better filtration reduction performance. Conversely, more positive charges induce more inferior filtration reduction performance. The filtration performance of drilling fluids is decided by the compactness of the filter cake. And the interactions among the particles in the drilling fluids play an important role in affecting the compactness of filter cake. The electrostatic attraction forces between the positively charged nanoparticles and negatively charged bentonite particles promoted the aggregation before the formation of incompact filter cake, and the electrostatic repulsion forces between the negatively charged nanoparticles and negatively charged bentonite particles slowed down the aggregation of particles to form more compact filter cakes. These findings demonstrate the decisive role of surface charge of filtration reducers, which could provide guidance for searching suitable filtration controlling additives for drilling fluids in the future.