Charging and aggregation processes were studied in aqueous dispersions of halloysite nanotubes (HNTs) in the presence of monovalent inorganic electrolytes and ionic liquid (IL) constituents. The same type of co-ion (same sign of charge as HNT) was used in all systems, while the type of counterions (opposite sign of charge as HNT) was systematically varied. The affinity of the inorganic cations to the HNT surface influenced their destabilizing power leading to an increase in the critical coagulation concentration (CCC) of HNT dispersions in the Cs+ < K+ < Na+ order. This trend agrees with the classical Hofmeister series for negatively charged hydrophobic surfaces. For the IL cations, the CCCs increased in the order BMPY+ < BMPIP+ < BMPYR+ < BMIM+. An unexpectedly strong adsorption of BMPY+ cations on the HNT surface was observed giving rise to charge neutralization and reversal of the oppositely charged outer surface of HNT. The direct Hofmeister series was extended with these IL cations. The main aggregation mechanism was rationalized within the classical theory developed by Derjaguin, Landau, Verwey, and Overbeek, while ion specific effects resulted in remarkable variation in the CCC values. The results unambiguously proved that the hydration level of the surface and the counterions plays a crucial role in the formation of the ionic composition at the solid–liquid interface and consequently, in the colloidal stability of the HNT particles in both inorganic salt and IL solutions.

The preparation of an antioxidant hybrid material by controlled heteroaggregation of manganese oxide nanoparticles (MnO2 NPs) and sulfate-functionalized polystyrene latex (SL) beads was accomplished. Negatively charged MnO2 NPs were prepared...

The charging and aggregation properties of boron nitride nanospheres (BNNSs) were investigated in the presence of electrolytes of different compositions and valences in aqueous suspensions. The influence of mono- and multivalent cations (counterions) and anions (coions) on the colloidal stability of the negatively charged particles was studied over a wide range of salt concentrations. For monovalent ions, similar trends were determined in the stability and charging of the particles irrespective of the salt composition, i.e., no ion-specific effects were observed. Once multivalent counterions were involved, the critical coagulation concentrations (CCCs) decreased with the valence in line with the direct Schulze–Hardy rule. The dependence indicated an intermediate charge density for BNNSs. The influence of the coions on the CCCs was weaker and the destabilization ability followed the inverse Schulze–Hardy rule. The predominant interparticle forces were identified as electrical double-layer repulsion and van der Waals attraction. These findings offer useful information to design stable BNNS dispersions in various applications, where mono- and multivalent electrolytes or their mixtures are present in the samples.

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Ion specific effects of ionic liquid (IL) constituents on charging and aggregation phenomena of two types of particles (positively charged amidine (AL) and polyimidazolium-functionalized sulfate (SL-IP-2) latexes) were investigated in...

Chemobrionics is an emerging scientific field focusing on the coupling of chemical reactions and different forms of motion, that is, transport processes. Numerous phenomena appearing in various gradient fields, for example, pH, concentration, temperature, and so on, are thoroughly investigated to mimic living systems in which spatial separation plays a major role in proper functioning. In this context, chemical garden experiments have received increased attention because they inherently involve membrane formation and various transport processes. In this work, a noninvasive external magnetic field was applied to gain control over the directionality of membrane structures obtained by injecting one reactant solution into the other in a three‐dimensional domain. The geometry of the resulted patterns was quantitatively characterized as a function of the injection rate and the magnitude of magnetic induction. The magnetic field was proven to influence the microstructure of precipitate tubes by diminishing spatial defects.

The colloidal stability of sulfate (SL) and polyimidazolium-modified sulfate (SL-IP-2) latex particles was studied in an ionic liquid (IL) of ethylammonium nitrate (EAN) and its water mixtures. Aggregation rates were found to vary systematically as a function of the IL-to-water ratio. Repulsive electrostatic interactions between particles dominated at low IL concentrations, while they were significantly screened at intermediate IL concentrations, leading to destabilization of the dispersions. When the IL concentration was further increased, the aggregation of latex particles slowed down due to the increased viscosity and finally, a striking stabilization was observed in the IL-rich regime close to the pure IL solvent. The latter stabilization is due to the formation of IL layers at the interface between particles and IL, which induce repulsive oscillatory forces. The presence of the added salt in the system affected differently the structure of the interfaces around SL and SL-IP-2 particles. The sign of the charge and the composition of the particle surfaces were found to be the most important parameters affecting the colloidal stability. The nature of the counterions also plays an important role in the interfacial properties due to their influence on the structure of the IL surface layers. No evidence was observed for the presence of long-range electrostatic interactions between the particles in pure ILs. The results indicate that the presence of even low concentrations of water and salt in the system (as undesirable impurities) can strongly alter the interfacial structure and thus, the aggregation mechanism in particle IL dispersions.

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