Mesoporous Silica Colloids: Wetting, Surface Diffusion, and Cationic Surfactant Adsorption

Abstract

We have investigated the wetting and surface diffusion of mesoporous colloidal silica particles at the water surface; and the adsorption of cationic cetyltrimethylammonium (CTA +) surfactant on these particles. Porous silica colloids diffuse at the surface of water and in the volume, interacting with cationic surfactants that can adsorb inside the pores of the particles. We observed that surfactant adsorption on mesoporous silica depends dramatically not only on the particle pore size but also on specific counterion effects. We measured striking differences both on a macroscopic property of the interface, i.e. surface tension, and also at a single particle level by evaluating the translational diffusion of partially wetted particles at the fluid interface. We varied the pore size from 2 to 7 nm and explored the effects of ions owing different hydration number and kosmotropic/chaotropic character. At concentrations lower than the critical micellar concentration, we evidence that cationic surfactants adsorb on silica as surface micelles and surfactant adsorption inside the pores occurs only if the pore diameter is larger than the size of surface micelles. With a view to understand the surprising different adsorption behavior of CTA + OH  and CTA + Br  on porous silica particles, we investigated the effect of counterions on the surfactant adsorption on porous silica colloids by tuning the pH and the counterion properties.

Motion of micro- and nano- particles interacting with a fluid interface

“…Preliminary calibrations of the colloidal probe on bare interfaces may be not sufficient to evaluate the contact line dynamics contribution to the translational drag, since the latter depends also on the interfacial tension and local viscosity. Secondly, the interaction between the probe particle and the surface active species at the contact line may significantly perturb the probe boundary conditions, the interface structure and properties, which may render this method highly perturbative [83].…”

Shape Deformation in Ion Beam Irradiated Colloidal Monolayers: An AFM Investigation

“…Interfacial self-assembly has been used for the fabrication of colloidal monolayers due to its effectiveness and versatility for the assembly of very diverse materials and has been widely investigated theoretically [1,3,[45][46][47][48][49][50][51][52][53][54][55][56]. In particular, air/water interface self-assembly based on surface confinement and water discharge has been adopted [45].…”

Performance Evaluation of an Octadecyltrimethyl Ammonium Chloride–Dimethyl Silicone Oil as a Waterproof Locking Agent in Low-Permeability Reservoirs

“…The D 50 values at 20 and 70 °C were 325 and 470.8 nm, respectively, owing to an increase in the Brownian motion of the oil-in-water droplets in the waterproof locking agent; as a result of increased temperature, there is a consequent increase in the number and probability of collisions between droplets, leading to an increase in particle size. The average diameter of the low-permeability pore throat is larger than that of the waterproof locking agent at 0.15–4.18 μm, 19 allowing the waterproof locking agent to enter the pore throat of the low-permeability reservoir and reduce water lock damage.…”

“…The use of a single surfactant in low-permeability reservoirs is restricted by high costs stemming from its high adsorption and injection characteristics. Meanwhile, complex binary systems have good application prospects owing to their superior emulsification ability, wettability, and low cost. − …”