Particles In Aqueous Solution Research Articles

Liquid Metal Nanoparticles Physically Hybridized with Cellulose Nanocrystals Initiate and Toughen Hydrogels with Piezoionic Properties.

Liquid metal (LM) particles can serve as initiators, functional fillers, and cross-linkers for hydrogels. Herein, we show that cellulose nanocrystals (CNCs) stabilize LM particles in aqueous solutions, such as those used to produce hydrogels. The CNC-coated LM particles initiate free-radical polymerization to form poly(acrylic acid) (PAA) hydrogel with exceptional properties─stretchability ∼2000%, excellent toughness ∼1.8 MJ/m3, mechanical resilience, and efficient self-healing─relative to cross-linked PAA networks polymerized using conventional molecular initiators. FTIR spectroscopy, rheology, and mechanical measurements suggest that physical bonds between PAA and both Ga3+ and LM-CNC particles contribute to the excellent mechanical properties. The gels are used to sense a wide range of strains, such as those associated with human motion, via changes in resistance through the gel. The sensitivity at low strains enables monitoring subtle physiological signals, such as pulse. Without significantly compromising the toughness, soaking the gels in salt solution brings about high ionic conductivity (3.8 S/m), enabling them to detect touch via piezoionic principles; the anions in the gel have higher mobility than cations, resulting in significant charge separation (current ∼30 μA, ∼10 μA/cm2) through the gel in response to touch. These attractive properties are promising for wearable sensors, energy harvesters, and self-powered ionic touch panels.

Roles of Hydrogen Bonds and Alignment in Oriented Attachment of Gibbsite Nanoparticles: Insights from Molecular Dynamics

Oriented attachment (OA) of nanoparticles is an important crystal growth pathway in the synthesis of hierarchical structures. Although a significant understanding of OA has been made, the effect of atomistic misalignment and the roles of solvent/particle and particle/particle interactions on the structure–energy relationship during an OA remain elusive. In this study, we perform molecular dynamics simulations to calculate the potential of mean force (PMF) profile for gibbsite particle translation on a gibbsite slab with 1 or 2 intervening water layers (1W or 2W). The structures of the gibbsite surfaces and the confined water are analyzed to determine how the number and type of hydrogen bonds (H-bonds) influence the free energy profile during the translation. The PMF profile exhibits a periodicity of length 5.078 Å, consistent with the gibbsite unit cell size along the translation direction. The changes in the surface–water and water–water hydrogen bond network and water and surface OH groups’ orientations during the translation are strongly coupled with the changes in the PMF profile in the 1W case. However, when increasing the number of intervening water layers from 1W to 2W, the particle/slab misalignment becomes a dominant factor controlling the behavior of the PMF profile. We also establish a method to quantify misalignment between the particle and the slab, which exhibits a strong correlation with the free energy for the 2W case. These results shed more light into the roles of particle/slab misalignment and hydrogen bond network in the OA of mineral particles in aqueous solution.

Colloidal Rod-Like Particles with Temperature-Driven Tunable Interactions.

Temperature-sensitive rod-like colloidal particles were synthesized by grafting a temperature-responsive polymer, poly(2-(dimethylamino)ethyl methacrylate) (PDMA), on the surface of high aspect ratio silica rods by surface-initiated atom transfer radical polymerization. The stability of the grafted polymer on the surface of the particles in aqueous solutions was found to deteriorate with time, leading to a gradual decrease of the polymer content of the hybrid colloids, which was attributed to the mechanically activated hydrolysis of the labile bonds at the polymer-silica interface. The polymer degrafting was significantly suppressed by first growing a hydrophobic poly(methyl methacrylate) block onto the particle surface to act as a barrier layer for the penetration of water molecules at the polymer-particle interface, followed by chain-extension with the hydrophilic PDMA chains. Dynamic light scattering, microscopy, and rheological measurements revealed that the PDMA block conferred a temperature-responsive behavior to the rod-like particles, which formed aggregates at temperatures above the lower critical solution temperature (LCST) of the polymer. However, in contrast to their spherical counterparts, the polymer-grafted rod-like particles did not exhibit complete thermo-reversibility upon lowering the solution temperature below the LCST of PDMA, which was reflected by different values of the diffusion coefficient for the heating and cooling cycles, indicating an irreversible rod particle aggregation upon increasing the temperature.

Newly engineered alumina quantum dot-based nanofluid in enhanced oil recovery at reservoir conditions

In this work, a newly engineered alumina quantum dot-based nanofluid (α-AQDs; D ~ 4 nm; amorphous solid) and one commercial alumina nanoparticle-based nanofluid (γ-ANPs; D ~ 20 nm; crystalline type) with the capability of strong colloidal dispersion at reservoir conditions, such as, high salinity, divalent ions (Ca2+) and high temperature was compared. The main goal of this research was to study the crude oil displacement mechanisms of alumina suspensions as a function of variety in size and particle morphology in aged carbonate rocks. The strong interaction potential between the particles was achieved by the citric acid and a special composition of a carboxylate-sulfonate-based polyelectrolyte polymer as an effective dispersant compound on the surface, leading to a negative particle charges and an additional steric and electrostatic repulsion. Wettability alteration upon exposure to fluids using the contact angle and the Amott cell were performed on saturated carbonate plug samples and rock slices. While, dynamic core displacements were conducted to test the water/nanofluid/oil flow and nanoparticle retention behavior thorough typical pore throats underground the reservoir conditions. The stability results revealed that PE-polymer was able to create a long-term colloidal fluid during 30 days. It was found that mass concentration of nanofluid increased with decreasing in particle size. The optimal amount of particles in aqueous solution was obtained 0.05 wt% for ANPs, increased up to 0.1 wt% for AQDs. Analysis of experiments showed that wettability alteration was the main mechanism during nanofluid injection. Laboratory core-flooding data proved that the enhanced oil recovery due to a less concentration state by ANPs was consistent with AQDs at higher concentrations. In addition, permeability-impairment-behavior study was discussed in terms of possible mineral scale deposition and alumina release on the rock surface. Results showed that a large extent of permeability damage caused by mineral scale (55–59%). Alumina quantum dot-based nanofluids were found a minimum impairment (2–4%) and a significant reduction of ~ 10% in permeability was observed for ANPs-based nanofluid.

Metal-ion inserted vanadium oxide nanoribbons as high-performance cathodes for aqueous zinc-ion batteries

The current energy and environmental crises are driving the burgeoning demand for efficient and reliable energy storage devices. Aqueous zinc-ion batteries (ZIBs) are currently considered to be promising candidates because of their excellent safety in operation and low cost. However, the real-world application of ZIBs has been impeded by a lack of cost effective cathode materials with the requisite high capacities and stability. Here we report the preparation and relevant properties of a special class of layered materials, which can be described as metal ion-inserted vanadium oxide (MVO, M = Zn, K, Na, and Ca) nanoribbons, as cathode materials for ZIBs. Metal ions are inserted into vanadium oxide by mixing the respective metal chloride with V2O5 particles in aqueous solution at room temperature, resulting in layered MVOs with expanded interlayer spaces. When used as the cathode material for ZIBs, ZnVO nanoribbons delivered specific capacities of 414.8, 368.6, 318.2, 271.2, 225.8 and 163.5 mAh g−1 at current rates of 0.1, 0.2, 0.5, 1, 2 and 5 A g−1, respectively. Also, a capacity of 409.6 mAh g−1 was retained after current rate was returned to 0.1 A g−1. After cycling at 2 A g−1 for 1500 cycles, 84.4% of the initial capacity was retained, much higher than that possible using pristine V2O5. The synthesis strategy can be easily scaled up to a 10-liter reaction scale, demonstrating its potential for the large scale production of cathode materials for high-performance aqueous ZIBs.

Long-Range Ionic and Short-Range Hydration Effects Govern Strongly Anisotropic Clay Nanoparticle Interactions.

The aggregation of clay particles in aqueous solution is a ubiquitous everyday process of broad environmental and technological importance. However, it is poorly understood at the all-important atomistic level since it depends on a complex and dynamic interplay of solvent-mediated electrostatic, hydrogen bonding, and dispersion interactions. With this in mind, we have performed an extensive set of classical molecular dynamics simulations (included enhanced sampling simulations) on the interactions between model kaolinite nanoparticles in pure and salty water. Our simulations reveal highly anisotropic behavior, in which the interaction between the nanoparticles varies from attractive to repulsive depending on the relative orientation of the nanoparticles. Detailed analysis reveals that at large separation (>1.5 nm), this interaction is dominated by electrostatic effects, whereas at smaller separations, the nature of the water hydration structure becomes critical. This study highlights an incredible richness in how clay nanoparticles interact, which should be accounted for in, for example, coarse-grained models of clay nanoparticle aggregation.

Insight into the self-aggregation behavior of lignite and anthracite in water: Atomic-level research using experiments and molecular dynamics simulations

To enable effective treatment of coal slime and prevent its release as an environmental pollutant, the interaction between coal particles in aqueous solutions must be well understood to enhance flocculation and sedimentation of the coal. In this study, the interaction between coal particles was explored using experiments and molecular simulations, which revealed the self-aggregation behavior of lignite and anthracite at different coalification levels in water. Atomic force microscopy results indicated that the anthracite–anthracite adhesion force is greater than that of lignite–lignite, and the adhesion force dominates particle interactions. The surface electrostatic potential range of lignite (-85.57–87.67 kcal/mol) is much higher than that of anthracite (-63.68–59.60 kcal/mol) and the lignite surface provides more polar regions for adsorbing water molecules. Lignite and anthracite rely on π–π accumulation to form a dimer skeleton structure. The dispersion interaction, dominated by π–π interactions, is key to promoting cluster formation and maintaining a stable cluster. The coal molecules proceed through three stages of movement, forming a cluster structure by dissipating the surrounding water molecules. The hydrophobic surface of the cluster molecules is exposed, gradually concealing the hydrophilic groups, which maintains the stability of coal self-aggregates. This process affects the water-molecule distribution, damaging the water bridge structure formed between the water molecules in coal molecule interlayers. This results in a decrease in the average number of water molecules surrounding a single lignite or anthracite molecule, and a change in the water-molecule orientation. Therefore, to enhance the flocculation of coal particles in slime water, it is necessary to increase the hydrophobicity of low-rank coal particles.

Characteristic curves and relationships for surface charging parameters of nonelectrolyte-immersed aqueous cavities

Most properties of charged particles’ dispersions are closely related to the amount of charge residing on the surface of particles. Very few works have been done so far to investigate curvature-dependence of surface potential and charge density of dispersed charged particles. Although there are some experimental studies in the literature on this subject, only a few of them have examined the mathematical relationship between particle size and surface charging parameters, resulting in contradictory findings. Indeed, a universal behavior is yet to be inferred from analysis of the outcomes of these studies since they reported either a roughly constant or decreasing trend of surface charge density with increasing particle radius. Unfortunately, the majority of the limited research efforts on surface charging have focused on dispersion of charged particles in aqueous solutions, but there are systems in biological and engineering worlds where an electrolyte solution is encapsulated in the core of charged particles and immersed in a background non-electrolyte medium. In an attempt to fill this scientific gap and gain a better understanding of surface charging, analytical models are developed in the present work for prediction of surface potential, surface charge, and surface charge density for cylindrical and spherical particles in such systems.First, the problem under investigation is non-dimensionalized to facilitate the modeling process, consider the simultaneous effects of key variables, and generalize the results and behaviors. Then, the mutual relationship between every pair of variables is extracted by employing Gauss's law and combining it with the electro-neutrality condition in an aqueous cavity. Afterwards, the resulting generalized seemingly simple, but inherently complex, integral equations are solved to build the characteristic curves and regressed to derive explicit characteristic equations. Finally, the derived characteristic equations are transformed into a dimensional form to obtain simple formulas for explicit calculations of charging parameters on the surface of electrolyte-encapsulating charged particles in terms of easily measurable properties of the electrolyte solution, the size of the cavity, and thermodynamic conditions. This predictive capability of the new models will significantly reduce the time, costs, and efforts required to simultaneously characterize the size and charging parameters of particles because it removes the need for such a challenging measurement as charging parameters are explicitly related to particle size through thermodynamic conditions, as well as available or easy-to-measure properties of the solution.

Self-assembly of berberine and a boron cluster for antibacterial regulation

B12H122−and BBR can quickly form rod-shaped particles in aqueous solution with enhanced reactive oxygen species (ROS) generation ability.

A deeper exploration of the relation between sulfonation degree and retanning performance of aromatic syntans

It is well-known that the sulfonation degree (DS) of aromatic syntan is an important factor affecting its retanning performances. But the quantitative relation between DS and syntan property and the influencing mechanism of DS on syntan property are not clarified. In this work, five phenolic formaldehyde syntans (PFSs) with the same polymerization degree but varying DS were prepared to investigate the effect of DS on the properties of syntan and crust leather. It was found that the absolute value of zeta potential and the particle size of PFS decreased with increasing DS in aqueous solution. Molecular dynamic simulation results proved that the DS of PFS was a major contributor to electrostatic interaction and hydrogen bonding in the PFS–water system and greatly affected the aggregation and dispersion of PFS in aqueous solution. The PFS with a low DS was prone to aggregate to large particles in aqueous solution because of low intermolecular electrostatic repulsion and less hydrogen bonds and therefore can be used to increase the thickness and tightness of leather. The PFS with a high DS presented a small particle size with more anionic groups in aqueous solution, thereby sharply decreasing the positive charge of leather surface and facilitating the penetration of the post-tanning agents into the leather. These results might be scientifically valid for rational molecular design of syntans and more productive use of syntans in leather making.Graphical

Role of pH and substrate on drying patterns of Laponite® droplet

Disc shaped Laponite® particles in aqueous solution have a net negative charge on the faces and a positive charge along the rim. The charge on the rim of these particles changes to negative around a pH of 12. The pH of the aqueous Laponite® solution thus determines whether the Laponite® particles arrange themselves in a repulsive glass phase or form a cage-like gel structure as they gel during drying. When droplets of Laponite® solution having different pH are allowed to evaporate, the arrangement of the particles during drying is further perturbed by currents of mass transfer due to uneven evaporation flux from the droplet surface. In this work we report the interesting patterns left by drying droplets of aqueous Laponite® with different pH, dried on substrates of different hydrophobicity. On hydrophobic substrate, in highly acidic pH, a prominent coffee-ring was observed , while in a strong basic pH, salt crystals on Laponite® particles gathered at the centre of the dried droplet. Similar studies were done on hydrophilic substrates and quite different dried patterns obtained. Further in the case of very acidic pH of the aqueous Laponite® droplet drying on a hydrophobic substrate, the dried pattern revealed collapsed cavities whose walls showed rings of salt crystallites. We offer an explanation of the different patterns on the basis of particle-substrate electrostatic interactions in tandem with the role of pH, in the determination of the final pattern.

Adsorption characteristics of Eu(III) on colloidal bentonite particles in aqueous solution: impact of colloid concentration, pH, foreign ions, and temperature

Adsorption characteristics of Eu(III) on colloidal bentonite particles in aqueous solution: impact of colloid concentration, pH, foreign ions, and temperature

Synthesis of a Ga-doped La5Ti2Cu0.9Ag0.1O7S5 photocatalyst by thermal sulfidation for hydrogen evolution under visible light

Ga-doped La5Ti2Cu0.9Ag0.1O7S5 absorbs visible light up to 710 nm and can serve as a H2 evolution photocatalyst in Z-scheme water splitting systems. This material is typically obtained in the form of rod-like particles that exhibit one-dimensional conductivity along their long axis. However, these relatively long particles (10–20 µm) require charge carriers migrate over significant distances to participate in photocatalytic reactions, which limits reaction efficiency. In the present study, Ga-doped La5Ti2Cu0.9Ag0.1O7S5 particles approximately 2 µm in length were prepared by thermal sulfidation. The as-formed particles had rod-like morphology but contained a lot of burrs that could be eliminated by annealing in the presence of sulfur vapor. Rh cocatalyst particles could be deposited on the tips of these particles in a dense, widely dispersed manner by stepwise impregnation-reduction and post-photodeposition. These treatments enhanced the photocatalytic H2 evolution activity of the Ga-doped La5Ti2Cu0.9Ag0.1O7S5 particles in aqueous solutions containing electron donors by a factor of seven and increased the apparent quantum efficiency of the process to 3.1% at 420 nm. This work demonstrates that thermal sulfidation is an effective approach to reducing the particle size of an oxysulfide photocatalyst. With appropriate post-treatment and cocatalyst loading processes, such photocatalysts can efficiently evolve hydrogen from aqueous solutions.

Trichloroethylene dechlorination rates, pathways, and efficiencies of ZVMg/C in aqueous solution

The removal mechanism from the reductive dechlorination of trichloroethylene (TCE) by zero valent magnesium (ZVMg) in aqueous solution is systematically studied. Following the preparation and characterization of ball-milled micro ZVMg with graphite (ZVMg/C) particles, this paper evaluated the TCE reaction rates, pathways, utilization rates and aging effects of ZVMg/C particles in aqueous solution under uncontrolled pH conditions. Overall, 38 μM of TCE was transformed by 10 g/L of ZVMg/C to methane (62.51%) and n-hexane (11.86%) and ethane (7.40%) and other alkene and alkyne products through the catalytic hydrogenation pathway. The measured surface area normalized pseudo-first order rate constants (KSA) were up to 9.31 × 10−2 L/m2/h and the utilization rate of Mg0 accounted for around 60%. The KSA were decreased to 1.90 × 10−2 L/m2/h in case of ZVMg/C being exposed in the atmosphere for 6 days due to 7.3% reduction in the utilization rate of Mg0 from the initial 85.2%, and 5.11 × 10−2 L/m2 h in case of ZVMg/C aged in water for one day. The removal efficiencies of approximately 56%, 58% and 87% by 10 g/L of ZVMg/C were achieved in the contaminated groundwater comprising 38 μM of TCE, 43 μM of 1,2-dichlorobenzene and 8.12 μM of trichlormethane. Therefore, it is concluded that ZVMg/C is viewed as a potential and effective remediation reagent for the groundwater remediation.

Controlled Growth of Strontium Sulfate Particles in Aqueous Solution: Inhibition Effects of a Bubble Column Evaporator

In the oil industry, strontium sulfate (SrSO4) scale deposits have long plagued oilfield and gas production operations. This remains an unsolved problem. We here show how the bubble column evaporator (BCE) can be used to control aqueous precipitation from salt solutions. Mixtures of strontium nitrate and sodium sulfate in the BCE system were used to precipitate strontium sulfate at different degrees of supersaturation. The effectiveness of the BCE system was compared to standard mechanical stirring. The precipitation of strontium sulfate in both processes was monitored through turbidimeter, particle counting, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). The results show that the BCE system has a significant inhibition effect and so can be used to control precipitation growth rate, even from supersaturated solutions. This remarkable effect also provides new insights into mechanisms of crystallisation, of bubble interactions and mineral flotation.

A Novel Approach to Fabricate Carbon Nanomaterials\u2013Nanoparticle Solids through Aqueous Solutions and Their Applications

A better understanding of the bonding and aggregation processes occurring between carbon nanomaterials and metal oxide particles in aqueous solutions is important in the development of novel nanosolids for applications in the areas of sensor development, highly conductive paint, nanotube alignment, polymer composites, Li-ion batteries, and many other areas. The current investigation reviews these processes and presents a detailed description of the aggregation processes occurring between carbon nanomaterials and metal oxide particles (metals) in various aqueous solutions. The results indicate that the charge attraction between the particles results in a strong homogeneous bonding that occurs within the aqueous solution and for the first time demonstrate and describe the aggregation process of these nanoparticles. The relative importance of many parameters that impact the aggregation process is identified and discussed, and guidelines for controlling the aggregation process are presented. This is a simple and cost-effective process to manufacture a novel nano-solid based on carbon nano-material and metal oxide. In addition, the process is easy to scale up and optimize. The methodology could lead to many significant applications as well as commercialization.

Heat transfer and thermoregulation within single cells revealed by transient plasmonic imaging

Summary Cells, as the basic unit of life, undergo continuous heat transfer and dissipation during their metabolism, which is related not only to fundamental cellular functions but also massive applications. Unfortunately, thus far, we still know little about the heat transfer properties at the cellular or subcellular levels. Here, we demonstrated a transient microscopic method to measure the heat transfer in single cells. The thermal conductivity of different regions within a single cell shows a wide heterogeneity, and heat transfer in the region near the cell membrane is more active than the central region. However, the median values of thermal conductivity between different individual cells are quite close. A cellular-level heat regulation that responds to environmental temperature is observed in warm-blooded humans and chickens rather than in cold-blooded bullfrogs. According to the temperature-dependent cell metabolism, we proposed a hypothesis for cellular control of heat dissipation, which might be the cellular-level foundation of body thermoregulation.

Optical conveyor belt based on a plasmonic metasurface with polarization dependent hot spot arrays.

In this Letter, we propose a novel metasurface conveyor belt with periodic orientated arrays of gold plasmonic elliptical elements (GPEEs), which can be continuously lit in a relay way by switching the polarization of the excitation beam and can be used to trap, transport, and sort particles. The array of the hot field can provide a larger trapping area and better stiffness. With the incident optical intensity of 0.08mW/µm2, the depth of the potential well could be as high as 10KBT. By setting a narrow interval between plasmonic ellipses in principal axes, it can help further enhance their directional resonant coupling and polarization dependence. Furthermore, based on consideration of the Brownian motion of trapped particles in aqueous solution, we analyzed its time response property of particle manipulation with different applied switching frequencies from a statistical point of view. As confirmed by numerical analysis, our design offers a novel scheme of particle sorting using a scalable hot spot array with better performance, which could be used in many on-chip optofluidic applications.

Multiresponsive Polymer Nanoparticles Based on Disulfide Bonds

A disulfide polymer that is triggerable by ultrasound, UV, and redox in aqueous solution and can self-assemble with ionic probe molecules into again multitriggerable assemblies is presented. It is created by oxidative coupling of a branched insoluble thiol to water-soluble ionic thiols. The synthesis via a nanoprecipitation technique results in charged macromolecule particles with adjustable sizes between a few tens and a few hundred nanometers stable in aqueous solution. Macromolecules of different compositions form with pentaerythritol tetrakis(3-mercaptopropionate) as insoluble cross-linkers yielding the polymer backbone, while mercaptopropionic acid, mercaptosuccinic acid, or aminoethane thiol in varying amounts is coupled to the backbone. Molecular and nanoscale switchability of the disulfide macromolecule with UV light, redox potential, and ultrasound is demonstrated. The anionic character of the polymer particles is exploited by electrostatic self-assembly with the tetra-cationic 5,10,15,20-tetrakis-(N-methyl-4-pyridyl)porphyrin and its zinc-metalated derivative, yielding supramolecular composite structures as a model system for delivery. The new type of polymer particles in aqueous solution may pave an alternative way toward multiresponsive and functional materials with potential in medicine and material science.

Investigation on Microparticle Transport and Deposition Mechanics in Rhythmically Expanding Alveolar Chip.

The transport and deposition of micro/nanoparticles in the lungs under respiration has an important impact on human health. Here, we presented a real-scale alveolar chip with movable alveolar walls based on the microfluidics to experimentally study particle transport in human lung alveoli under rhythmical respiratory. A new method of mixing particles in aqueous solution, instead of air, was proposed for visualization of particle transport in the alveoli. Our novel design can track the particle trajectories under different force conditions for multiple periods. The method proposed in this study gives us better resolution and clearer images without losing any details when mapping the particle velocities. More detailed particle trajectories under multiple forces with different directions in an alveolus are presented. The effects of flow patterns, drag force, gravity and gravity directions are evaluated. By tracing the particle trajectories in the alveoli, we find that the drag force contributes to the reversible motion of particles. However, compared to drag force, the gravity is the decisive factor for particle deposition in the alveoli.