Janus colloids with one attractive patch on an otherwise repulsive particle surface serve as model systems to explore structure formation of particles with chemically heterogeneous surfaces such as ...proteins. While there are numerous computer studies, there are few experimental realizations due to a lack of means to produce such colloids with a well-controlled variable Janus balance. Here, we report a simple scalable method to precisely vary the Janus balance over a wide range and selectively functionalize one patch with DNA. We observe, via experiment and simulation, the dynamic formation of diverse superstructures: colloidal micelles, chains, or bilayers, depending on the Janus balance. Flexible dimer chains form through cooperative polymerization while trimer chains form by a two-stage process, first by cooperative polymerization into disordered aggregates followed by condensation into more ordered stiff trimer chains. Introducing substrate binding through depletion catalyzes dimer chains to form nonequilibrium rings that otherwise do not form.
We study experimentally the effect of added salt in the phoretic motion of chemically driven colloidal particles. We show that the response of passive colloids to a fixed active colloid, be it ...attractive or repulsive, depends on the ionic strength, the ζ potential, and the size of the passive colloids. We further report that the direction of self-propulsion of Janus colloids can be reversed by decreasing their ζ potential below a critical value. By constructing an effective model that treats the colloid and ions as a whole subjected to the concentration field of generated ions and takes into account the joint effect of both generated and background ions in determining the Debye length, we demonstrate that the response of the passive colloids and the velocity of the Janus colloids can be quantitatively captured by this model under the ionic diffusiophoresis theory beyond the infinitely-thin-double-layer limit.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
In this Review, we describe the synthesis of high‐quality colloidal nanoparticles in organic solvents, the mechanisms by which they can be transferred into aqueous solution, and some of their ...applications in biology. In particular, we will place emphasis on the creation of multifunctional nanoparticles or nanoparticle assemblies.
The nanomaterials of the future will be designed with the aim of performimg specific functions, as dictated by their synthetic manufacture. This Review examines one particular type of material, colloidal nanoparticles, whose potential in a number of medical and biological applications is already beginning to be realized (the image shows MDA‐MB‐43s and MCF‐7 cells labeled with green and red fluorescent silica‐coated CdSe/ZnS nanocrystals, respectively).
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper examines the critical role of surface roughness (both nano- and micro-scale) on the processes of colloid retention and release in porous media under steady-state and transient chemical ...conditions. Nanoscale surface roughness (NSR) in the order of a few nanometers, which is common on natural solid surfaces, was incorporated into extended-DLVO calculations to quantify the magnitudes of interaction energy parameters (e.g. the energy barrier to attachment, ΔΦa , and detachment, ΔΦd , from a primary minimum). This information was subsequently used to explain the behavior of colloid retention and release in column and batch experiments under different ionic strength (IS) and pH conditions. Results demonstrated that the density and height of NSR significantly influenced the interaction energy parameters and consequently the extent and kinetics of colloid retention and release. In particular, values of ΔΦa and ΔΦd significantly decreased in the presence of NSR. Therefore, consistent with findings of column experiments, colloid retention in the primary minimum was predicted to occur at some specific locations on the sand surface, even at low IS conditions. However, NSR yielded a much weaker primary minimum interaction compared with that of smooth surfaces. Colloid release from primary minima upon decreasing IS and increasing pH was attributed to the impact of NSR on the values of ΔΦd . Pronounced differences in the amount of colloid retention in batch and column experiments indicated that primary minimum interactions were weak even at high IS conditions. Negligible colloid retention in batch experiments was attributed to hydrodynamic torques overcoming adhesive torques, whereas significant colloid retention in column experiments was attributed to nano- and micro-scale roughness which would dramatically alter the lever arms associated with hydrodynamic and adhesive torques.
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•Density and height of nanoscale roughness significantly influenced colloid retention and release processes.•Colloid retention in the primary energy minimum occurred at low solution ionic strength.•Fractional colloid release from primary minima upon decreasing ionic strength and increasing pH was observed.•Microscopic roughness caused significant colloid retention in column experiments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Microplastics (MPs) can act as vectors for various contaminants in the aquatic environment. Although some research has investigated the adsorption characteristics and influencing factors of ...metals/organic molecules on MPs, the effects of dissolved organic matter (DOM) (which are ubiquitous active species in ecosystems) on metal oxyanions such as Cr(VI) capture by MPs are largely unknown. This study explored the adsorption behaviors and mechanisms of Cr(VI) oxyanions onto polystyrene (PS) MPs using batch adsorption experiments and multiple spectroscopic methods. The effects of representative DOM components (i.e., humic acid (HA), fulvic acid (FA) and tannic acid (TA)) on Cr(VI) capture by PS were particularly studied. Results revealed a significantly enhanced adsorption of Cr(VI) on PS in the presence of TA. The Cr(VI) adsorption capacity was increased from 2876 μg g−1 to 4259 μg g−1 and 5135 μg g−1 when the TA concentrations raised from 0 to 10 and 20 mg L−1, respectively. Combined microscopic and spectroscopic investigations revealed that Cr(VI) was reduced to Cr(III) by TA and formed stable Cr(OH)3 colloids on PS surfaces. Contrarily, HA and FA inhibited Cr(VI) adsorption onto PS, especially at pH > 2.0 and higher DOM concentrations, due to site competition and electrostatic repulsion. Increase in pH was found to reduce zeta potentials of MPs, resulting in inhibited Cr(VI) adsorption. The adsorbed Cr(VI) declined with increasing ionic strength, implying that outer-sphere surface complexation affected the adsorption process in the presence of DOM. These new findings improved our fundamental understanding of the fate of Cr(VI) and MPs in DOM-rich environmental matrices.
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•Dissolved organic matter had different roles on Cr(VI) capture by PS microplastics.•TA promoted Cr(VI) adsorption while HA/FA inhibited its adsorption on PS.•Increase in pH and salinity hindered Cr(VI) adsorption on PS.•Cr(VI) was reduced to Cr(III) by TA and precipitated as Cr(OH)3 on PS surface.•SEM observation and XPS spectrum confirmed the deposition of Cr(OH)3 on PS surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Active particles such as swimming bacteria or self-propelled colloids spontaneously self-organize into large-scale dynamic structures. The emergence of these collective states from the motility ...pattern of the individual particles, typically a random walk, is yet to be probed in a well-defined synthetic system. Here, we report the experimental realization of tunable colloidal motion that reproduces run-and-tumble and Lévy trajectories. We utilize the Quincke effect to achieve controlled sequences of repeated particle runs and random reorientations. We find that a population of these random walkers exhibit behaviors reminiscent of bacterial suspensions such as dynamic clusters and mesoscale turbulentlike flows.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Background
Critically ill people may lose fluid because of serious conditions, infections (e.g. sepsis), trauma, or burns, and need additional fluids urgently to prevent dehydration or kidney ...failure. Colloid or crystalloid solutions may be used for this purpose. Crystalloids have small molecules, are cheap, easy to use, and provide immediate fluid resuscitation, but may increase oedema. Colloids have larger molecules, cost more, and may provide swifter volume expansion in the intravascular space, but may induce allergic reactions, blood clotting disorders, and kidney failure. This is an update of a Cochrane Review last published in 2013.
Objectives
To assess the effect of using colloids versus crystalloids in critically ill people requiring fluid volume replacement on mortality, need for blood transfusion or renal replacement therapy (RRT), and adverse events (specifically: allergic reactions, itching, rashes).
Search methods
We searched CENTRAL, MEDLINE, Embase and two other databases on 23 February 2018. We also searched clinical trials registers.
Selection criteria
We included randomised controlled trials (RCTs) and quasi‐RCTs of critically ill people who required fluid volume replacement in hospital or emergency out‐of‐hospital settings. Participants had trauma, burns, or medical conditions such as sepsis. We excluded neonates, elective surgery and caesarean section. We compared a colloid (suspended in any crystalloid solution) versus a crystalloid (isotonic or hypertonic).
Data collection and analysis
Independently, two review authors assessed studies for inclusion, extracted data, assessed risk of bias, and synthesised findings. We assessed the certainty of evidence with GRADE.
Main results
We included 69 studies (65 RCTs, 4 quasi‐RCTs) with 30,020 participants. Twenty‐eight studied starch solutions, 20 dextrans, seven gelatins, and 22 albumin or fresh frozen plasma (FFP); each type of colloid was compared to crystalloids.
Participants had a range of conditions typical of critical illness. Ten studies were in out‐of‐hospital settings. We noted risk of selection bias in some studies, and, as most studies were not prospectively registered, risk of selective outcome reporting. Fourteen studies included participants in the crystalloid group who received or may have received colloids, which might have influenced results.
We compared four types of colloid (i.e. starches; dextrans; gelatins; and albumin or FFP) versus crystalloids.
Starches versus crystalloids
We found moderate‐certainty evidence that there is probably little or no difference between using starches or crystalloids in mortality at: end of follow‐up (risk ratio (RR) 0.97, 95% confidence interval (CI) 0.86 to 1.09; 11,177 participants; 24 studies); within 90 days (RR 1.01, 95% CI 0.90 to 1.14; 10,415 participants; 15 studies); or within 30 days (RR 0.99, 95% CI 0.90 to 1.09; 10,135 participants; 11 studies).
We found moderate‐certainty evidence that starches probably slightly increase the need for blood transfusion (RR 1.19, 95% CI 1.02 to 1.39; 1917 participants; 8 studies), and RRT (RR 1.30, 95% CI 1.14 to 1.48; 8527 participants; 9 studies). Very low‐certainty evidence means we are uncertain whether either fluid affected adverse events: we found little or no difference in allergic reactions (RR 2.59, 95% CI 0.27 to 24.91; 7757 participants; 3 studies), fewer incidences of itching with crystalloids (RR 1.38, 95% CI 1.05 to 1.82; 6946 participants; 2 studies), and fewer incidences of rashes with crystalloids (RR 1.61, 95% CI 0.90 to 2.89; 7007 participants; 2 studies).
Dextrans versus crystalloids
We found moderate‐certainty evidence that there is probably little or no difference between using dextrans or crystalloids in mortality at: end of follow‐up (RR 0.99, 95% CI 0.88 to 1.11; 4736 participants; 19 studies); or within 90 days or 30 days (RR 0.99, 95% CI 0.87 to 1.12; 3353 participants; 10 studies). We are uncertain whether dextrans or crystalloids reduce the need for blood transfusion, as we found little or no difference in blood transfusions (RR 0.92, 95% CI 0.77 to 1.10; 1272 participants, 3 studies; very low‐certainty evidence). We found little or no difference in allergic reactions (RR 6.00, 95% CI 0.25 to 144.93; 739 participants; 4 studies; very low‐certainty evidence). No studies measured RRT.
Gelatins versus crystalloids
We found low‐certainty evidence that there may be little or no difference between gelatins or crystalloids in mortality: at end of follow‐up (RR 0.89, 95% CI 0.74 to 1.08; 1698 participants; 6 studies); within 90 days (RR 0.89, 95% CI 0.73 to 1.09; 1388 participants; 1 study); or within 30 days (RR 0.92, 95% CI 0.74 to 1.16; 1388 participants; 1 study). Evidence for blood transfusion was very low certainty (3 studies), with a low event rate or data not reported by intervention. Data for RRT were not reported separately for gelatins (1 study). We found little or no difference between groups in allergic reactions (very low‐certainty evidence).
Albumin or FFP versus crystalloids
We found moderate‐certainty evidence that there is probably little or no difference between using albumin or FFP or using crystalloids in mortality at: end of follow‐up (RR 0.98, 95% CI 0.92 to 1.06; 13,047 participants; 20 studies); within 90 days (RR 0.98, 95% CI 0.92 to 1.04; 12,492 participants; 10 studies); or within 30 days (RR 0.99, 95% CI 0.93 to 1.06; 12,506 participants; 10 studies). We are uncertain whether either fluid type reduces need for blood transfusion (RR 1.31, 95% CI 0.95 to 1.80; 290 participants; 3 studies; very low‐certainty evidence). Using albumin or FFP versus crystalloids may make little or no difference to the need for RRT (RR 1.11, 95% CI 0.96 to 1.27; 3028 participants; 2 studies; very low‐certainty evidence), or in allergic reactions (RR 0.75, 95% CI 0.17 to 3.33; 2097 participants, 1 study; very low‐certainty evidence).
Authors' conclusions
Using starches, dextrans, albumin or FFP (moderate‐certainty evidence), or gelatins (low‐certainty evidence), versus crystalloids probably makes little or no difference to mortality. Starches probably slightly increase the need for blood transfusion and RRT (moderate‐certainty evidence), and albumin or FFP may make little or no difference to the need for renal replacement therapy (low‐certainty evidence). Evidence for blood transfusions for dextrans, and albumin or FFP, is uncertain. Similarly, evidence for adverse events is uncertain. Certainty of evidence may improve with inclusion of three ongoing studies and seven studies awaiting classification, in future updates.
A two-dimensional imine-linked covalent organic framework bearing pyrene has been prepared and exfoliated in water as nanosheets to produce a stable water colloid. As a proof-of-concept, this COF ...colloid has been used to detect the presence of several organic dyes and polynitro-aromatic derivatives. These results show the high potential of these nanomaterials for applications in chemical sensing of pollutants directly in water.
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•LAL allows preparing stable and highly active water-ethanol colloids of CuOx NPs.•Ethanol provides phase composition and morphology stability of CuOx NPs in colloids.•Water provides ...electrostatic stabilization of the water-ethanol colloids.•Ethanol shows inhibitory effect on 4-nitrophenol reduction with NaBH4.•Inhibitory effect of ethanol is well describing by the Langmuir-Hinshelwood model.
Colloidal nanoparticle catalysts play a decisive role both in the implementation of a number of important industrial processes, including the hydrogenation of nitro compounds, and in fundamental studies of catalytic reactions on nanoparticles. The laser ablation in liquid (LAL) is a promising method to prepare nanoparticle colloids, and the use of mixed solutions as a medium can be attractive for both preparation of stable colloids and their application in catalysis. While using the LA in water-ethanol solutions, the stable colloids of CuOx NPs demonstrating high catalytic activity in the 4-nitrophenol (4-NP) hydrogenation were prepared. The reasons for the instability of colloids obtained in water and alcohol as well as the stabilization of colloids in water-ethanol solutions were considered. The results obtained contribute to the understanding of the lower catalytic activity of the studied CuOx catalyst in ethanol and other non-aqueous solvents. The presence of ethanol in the reaction medium was found to have an inhibitory effect on the 4-NP reduction kinetics due to the alcohol adsorption on the catalyst surface that is well described within the framework of the Langmuir-Hinshelwood model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Clear understanding of pore-scale mechanisms that control transport and retention of colloids in porous media at different physicochemical conditions is critical to improve design and efficient ...cleanup methodologies of filter beds. The objective of this work was to investigate the impact of hydrophobicity, solution ionic strength, and pH on colloid retention mechanisms in single-phase and two-phase flow in porous media systems. A series of experiments were conducted using a geometrically representative micromodel. Hydrophilic and hydrophobic colloids were dispersed in water at different solution ionic strength and pH conditions. Findings indicate that hydrophilic colloids exhibit high filtration efficiency as the colloids interact attractively with other colloids and solid-water-interface irrespective of the solution chemistry. However, for hydrophobic colloids, changes in solution chemistry significantly increase colloid retention where the colloid interaction become attractive with the increase in ionic strength and decrease in pH values. Colloids attached to the collector surfaces mobilized by the strong capillary forces induced by the moving gas-water interface and transported along with the interface. However, hydrophilic colloids redeposited on gas-water-solid interfaces or thin water films because of their greater capillary potential. Therefore, greater filtration efficiency is achieved with the hydrophilic colloids compared to the hydrophobic colloids for which the efficiency can be improved by changing the solution chemistry. Moreover, the removal efficiency by the moving gas-water interface was observed to be more for hydrophobic colloids compared to hydrophilic colloids for which the efficiency can be improved by lowering the ionic strength or increasing the pH value. This study indicates that the coupled effects of solution chemistry and colloid hydrophobicity should be taken into account while investigating efficient filtration and cleaning practices for the filter beds.
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•Applying a geometrically representative micromodel to study colloid retention mechanisms.•The filtration of hydrophobic colloids has been improved by altering solution chemistry.•Use of moving gas-water interface to clean filter beds with hydrophobic colloids.•Impact of solution chemistry differ for hydrophilic and hydrophobic colloids.•Incorporating coupled effects of ionic strength and pH on colloid transport mechanisms.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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