Application of the Edwards Model to Steric Stabilization of Nanoparticles

2003 ◽  
Vol 17 (15) ◽  
pp. 2791-2820 ◽  
Author(s):  
Jiunn-Ren Roan
Keyword(s):  
Large Particle ◽  
Colloidal Particles ◽  
Particle Separation ◽  
Colloidal Dispersion ◽  
Colloidal Dispersions ◽  
Repulsive Force ◽  
Steric Stabilization ◽  
Conformational Entropy ◽  
Standard Picture ◽  
Edwards Model

The Edwards model for polymers with excluded-volume interaction has been used to study steric stabilization of colloidal dispersions since Dolan and Edwards' work in 1975. Following the standard picture of steric stabilization since 1950s, Dolan and Edwards solved the model by treating the surfaces of colloidal particles as plane surfaces. Consequently, their result was also consistent with the standard picture: Reduction of conformational entropy of the adsorbed homopolymers results in a purely repulsive force that stabilizes the colloidal dispersion. Recently the Edwards model was solved without treating the spherical particle surfaces as plane surfaces. It was found that, contrary to the standard picture, the conformational entropy indeed increases and the force between particles may be either purely attractive or attractive at large particle-particle separation, repulsive at intermediate separation, and again attractive at small separation. Thus, the standard picture of steric stabilization was challenged. This review summarizes this recent progress in the theory of steric stabilization of colloidal dispersions. Reconciliation between the standard picture and the recent result, and possible directions for further research are also discussed.

scholarly journals Tailoring the Morphology of Supraparticles by Primary Colloids with Different Shapes, Sizes and Dispersities

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 79
Author(s):  
Wonmi Shim ◽  
Chan Sik Moon ◽  
Hyeonjin Kim ◽  
Hyun Su Kim ◽  
Haoxiang Zhang ◽  
...  
Keyword(s):  
Composite Material ◽  
Colloidal Particles ◽  
Colloidal Dispersion ◽  
Colloidal Dispersions ◽  
Single Component ◽  
Promising Method ◽  
Shell Structures ◽  
Core Shell ◽  
Different Shapes ◽  
Shape And Size

Surface-templated evaporation driven (STED) method is a promising method to fabricate supraparticles with various sizes, porosities, and shapes by drying colloidal dispersion drops on liquid repellent surfaces. Until now, for the method, only spherical shaped colloidal particles have been used as primary colloids. Here, we introduce six different shapes of nano-colloidal dispersions for the STED method: nanocubics, nanoplates, nanosheets, coffin-shaped nanoparticles (NPs), spherical NPs, and aggregates of NPs. It is confirmed that the shape and size of the primary colloids have little effect for drying the dispersion drop when a single component colloidal dispersion is dried. For heterogeneous supraparticles with composite material assembly, still the shape of the colloids has no influences, while the size and dispersity play roles for tuning the morphology of the supraparticles. From the results, we propose a way to fabricate homogeneous mixture, core/shell, and Janus core/shell structures of the supraparticles depending on the size and dispersity of the mixture colloidal dispersion. Indeed, knowledge on the effects of types of colloids would be of great importance for tailoring supraparticles.

Synthesis of Vanadium Oxide Colloidal Dispersions for Antistatic Coatings

1996 ◽  
Vol 432 ◽  
Author(s):  
Eric.D. Morrison
Keyword(s):  
Vanadium Oxide ◽  
Conduction Mechanism ◽  
Colloidal Particles ◽  
Small Polaron ◽  
Electronic Conductivity ◽  
Colloidal Dispersions ◽  
Thin Layers ◽  
Properties Of Coatings ◽  
Polaron Hopping ◽  
Dispersed Particles

AbstractVanadium oxide deposited in thin layers from aqueous colloidal dispersions exhibits electronic conductivity by a small polaron hopping conduction mechanism. Conductivity and static dissipative properties of coatings are unaffected by changes in humidity. Because vanadium oxide is highly colored, the deposition of effective antistatic coatings which are transparent and colorless requires that the percolative (networking forming) properties of the colloidal particles be maximized. The percolative properties of the colloid are strongly influenced by morphology of the dispersed particles and the extent to which they are well dispersed in the aquasol. These properties are determined by the synthetic route to the colloid. Vanadium oxide is the most potent antistatic agent known and has been found to provide antistatic properties even when as little as 1 milligram per square meter is used.

PARTICLE MOTIONS IN SHEARED SUSPENSIONS III.: FURTHER OBSERVATIONS ON COLLISIONS OF SPHERES

1955 ◽  
Vol 33 (5) ◽  
pp. 763-773 ◽  
Author(s):  
R. St. J. Manley ◽  
S. G. Mason
Keyword(s):  
Particle Separation ◽  
Colloidal Dispersions ◽  
Mirror Image ◽  
Equal Size ◽  
Air Bubbles ◽  
Rigid Spheres ◽  
Glass Spheres ◽  
Velocity Gradients ◽  
Image Separation ◽  
Sheared Suspensions

Two-body interactions between glass spheres of diameters a1 and a2 caused by velocity gradients vary with a1/a2. When 1 < a1/a2 < 2, well-defined collisions similar to those previously reported for spheres of equal size can be observed. Fair agreement is found between the experimentally observed and calculated collision frequencies over a range of particle concentrations and velocity gradients. When a1/a2 > 2 the particles are separated at all times and the phenomena of interaction are more complex. Single air bubbles rotate at the same angular velocity as rigid spheres. When two air bubbles of equal size are brought into collision a doublet is formed; instead of the mirror-image separation observed with neutral rigid spheres, the doublet continues to rotate for as many as 60 rotations before coalescence occurs. Less frequently a doublet with distinct particle separation is observed. Periods of rotation of both types of doublet and certain details of the rotational orbit of a doublet of touching air bubbles have been measured and compared with values predicted from Jeffery's theoretical equations for rigid ellipsoids. Apart from their intrinsic interest, the phenomena described are of importance in theories of viscosity and coagulation of suspensions and colloidal dispersions.

Framboid Self-Assembly and Self-Organization

2021 ◽  
pp. 262-282
Author(s):  
David Rickard
Keyword(s):  
Self Assembly ◽  
Energy Minimization ◽  
Short Range ◽  
Colloidal Particles ◽  
Repulsive Force ◽  
The Self ◽  
Icosahedral Symmetry ◽  
Entropy Maximization ◽  
Close Packed Structure ◽  
Packed Structure

The formation of framboids involves two distinct processes. First, pyrite microcrystals aggregate into spherical groups through surface free energy minimization. The self-assembly of framboid microcrystals to form framboids is consistent with estimations based on the classical Derjaguin-Landau-Verwey-Overbeek (DVLO) theory, which balances the attraction between particles due to the van der Waals forces against the interparticle electrostatic repulsive force. Second, the microcrystals rearrange themselves into ordered domains through entropy maximization. Icosahedral symmetry tends to minimize short-range attractive interactions and maximize entropy. The physical processes which facilitate this rearrangement are Brownian motion and surface interactions. Curved framboid interface enforce deviation from the cubic close packed structure. In the absence of a curved surface, weakly interacting colloidal particles preferentially self-assemble into a cubic close packed structure, and this is observed in irregular, non-framboidal aggregates of pyrite micro- and nanocrystals.

scholarly journals Biosynthesis of Self-Dispersed Silver Colloidal Particles Using the Aqueous Extract of P. peruviana for Sensing dl-Alanine

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Mohd Rashid ◽  
Suhail Sabir
Keyword(s):  
Electron Microscopy ◽  
Aqueous Extract ◽  
Colloidal Particles ◽  
Chemical Sensor ◽  
Colloidal Dispersion ◽  
Single Step ◽  
Transmission Electron ◽  
Particle Size And Morphology ◽  
Uv Visible ◽  
Size And Morphology

We report the biosynthesis of silver nanoparticles (AgNPs) in a single step using edible fruit aqueous extract of P. peruviana that essentially involved the concept of green chemistry. Yellowish-brown color appeared upon adding the broth of P. peruviana to aqueous solution of 1 mM AgNO3 which indicates the formation of AgNPs. The maximum synthesis of these nanoparticles was being achieved in nearly 2 hrs at 28°C. The synthesis of AgNPs was followed by AgNPs UV-visible spectroscopy. Particle size and morphology of AgNPs were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. These studies revealed that the AgNPs characterized were spherical in shape with diameter ranging from 31 to 52 nm. The energy dispersive X-ray spectroscopy showed that the AgNPs present are approximately 63.42 percent by weight in the colloidal dispersion. The absorption spectra of the AgNPs in absence and presence of dl-alanine show a distinguish shift in surface plasmon resonance (SPR) bands. Thus, these nanoparticles may be used as a chemical sensor for dl-alanine present in the human blood.

The Role of Nanoscale Forces in Colloid Dispersion Rheology

MRS Bulletin ◽  
2004 ◽  
Vol 29 (2) ◽  
pp. 100-106 ◽  
Author(s):  
Norman J. Wagner ◽  
Jonathan W. Bender
Keyword(s):  
Colloidal Particles ◽  
Colloidal Dispersions ◽  
Stable Complex ◽  
Structure Property ◽  
Colloidal Forces ◽  
Structure Property Relationships ◽  
Fundamental Understanding ◽  
Colloid Dispersion ◽  
And Control

AbstractAdvances in our fundamental understanding of and control over interparticle colloidal forces have enhanced our ability to formulate stable, complex fluids with colloidal and/or nano-sized particles with specific rheological properties. This understanding stems from advances in experimental methods that probe these forces, either directly or indirectly, as well as theoretical treatments and simulation methods linking macroscopic suspension properties to the dynamics and interactions between colloidal particles. This article highlights recent experimental developments in the structure—property relationships for colloidal dispersions, with emphasis on the sensitivity of colloid rheology to nanometer-scale interactions. Examples of applications are used to illustrate these relationships.

Surface modification of bentonites: I. Betaine montmorillonites and their rheological and colloidal properties

Clay Minerals ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 447-458 ◽  
Author(s):  
C. U. Schmidt ◽  
G. Lagaly
Keyword(s):  
Network Formation ◽  
Relative Viscosity ◽  
Colloidal Dispersion ◽  
Dlvo Theory ◽  
Colloidal Dispersions ◽  
A Value ◽  
Yield Value ◽  
Yield Values ◽  
Na Ions ◽  
Silicate Layers

AbstractMontmorillonite was modified by replacing the exchangeable cations with betaines(CH3)3N+ - (CH2)n - COO-M+ (n = 3, 5, 7, 10)The betaine derivatives delaminated in water and formed a colloidal dispersion. Air-drying of this material yielded hard pieces which were difficult to redisperse. The dried material became redispersible in water when the Na ions (counterions to the carboxyl groups) were replaced by Li ions. Colloidal dispersions of this material were more stable against salts than Li+- or Na+ - montmorillonite. Extremely high LiCl concentrations (>1 mol/l) were needed to coagulate the betaine derivatives (n>5) in the presence of diphosphate. The increased salt stability resulted from lyospheres around the silicate layers or thin packets of them which reduced the van der Waals attraction. Addition of organic solvents destabilized the dispersion by compressing the diffuse ionic layer (DLVO theory). The delaminated particles then aggregated to small flocs which settled very slowly. Neither band-type structures nor cardhouses were formed at conditions comparable to network formation and stiffening of Li- and Na-montmorillonite dispersions. Rheological measurements revealed the liquefying action of the betaines. Dispersions of butyrobetaine montmorillonite (15 g solid/l) revealed a relative viscosity (related to the dispersion medium water) ηrel ≈ 2. The longer chain derivatives showed a value slightly >1 whereas Li+-montmorillonite had ηrel = 8. Yield values were not formed at pH ≈ 7. Only at acidic conditions did the butyrobetaine montmorillonite dispersion showed a small yield value (<200 mPa).

scholarly journals Effect of Capillary Number on the Residual Saturation of Colloidal Dispersions Stabilized by a Zwitterionic Surfactant

2021 ◽  
Vol 11 (2) ◽  
pp. 524
Author(s):  
Han Am Son ◽  
Taewoong Ahn
Keyword(s):  
Oil Recovery ◽  
Capillary Number ◽  
Colloidal Dispersion ◽  
Colloidal Dispersions ◽  
Particle Aggregation ◽  
Water Interface ◽  
Residual Oil ◽  
Zwitterionic Surfactant ◽  
Anionic Polymer ◽  
Oil Water

We investigated oil recovery from porous rock using nanoscale colloidal dispersions, formed by adsorption of an anionic polymer [poly-(4styrenesulfonic acid-co-maleic acid); PSS-co-MA] and a zwitterionic surfactant [N-tetradecyl-N, N-dimethyl-3-ammonio-1-propanesulfonate, TPS] onto silica nanoparticles. In an emulsion, colloidal dispersion enhanced the stability of the oil-water interface in the absence of particle aggregation; the hydrophobic alkyl chains of TPS shifted into the oil drop, not only physiochemically, stabilizing the oil-water interface, but also promoting repulsive particle-to-particle interaction. Core flooding experiments on residual oil saturation as a function of capillary number, at various injection rates and oil viscosities, showed that the residual oil level was reduced by almost half when the zwitterionic surfactant was present in the colloidal dispersion. Consequently, the result revealed that this colloidal dispersion at the interface provides a mechanically robust layer at the oil-water interface without particle aggregation. Thus, the dispersion readily entered the pore throat and adhered to the oil-water interface, lowering the interfacial tension and improving oil recovery.

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