Molecular Dynamics of Ionic Transport and Electrokinetic Effects in Realistic Silica Channels

Abstract

Silica is one of the most widely used inorganic materials in experiments and applications involving aqueous solutions of biomolecules, nanoparticles, etc. In this paper, we construct a detailed atomistic model of a silica interface that captures the essential experimentally known properties of a silica interface. We then perform all-atom molecular dynamics simulations of a silica nanochannel subjected to either an external pressure or an electric field and provide an atomistic description of ionic transport and both electro-osmotic flow and streaming currents for a solution of monovalent (0.4 M NaCl) as well as divalent (0.2 and 1.0 M CaCl 2 ) salts. Our results allow a detailed investigation of ζ-potentials, Stern layer conductance, charge inversion, ionic mobilities, as well as continuum theories and Onsager relations. We conclude with a discussion on the implications of our results for silica nanopore experiments and micro-and nanofluidic devices.

Molecular dynamics for ion-tuned wettability in oil/brine/rock systems

“…41,42 This model charges α-quartz by deprotonation of some surface hydroxyls, consistent with electrokinetics theories such as Basic Stern model 43 and triple layer model. 44,45 It also fully defines harmonic bonds and angles, so flexible surface can be produced.…”

“…In our simulations, we construct five layers of α-quartz lattice, with crystal orientation [ value is close to the sum of van der Waals radius of H of a hydroxyl (0.11 nm) 46 and the bond length of a hydroxyl (0.096 nm), 42 so that the brine/α-quartz interface is approximately located at z = 0.…”

“…41,42. We consider two surface charge densities of α-quartz: σ 0,qz = 0 C m 2 and σ 0,qz = 0.067 C m 2 .…”

Aqueous electrolytes confined within functionalized silica nanopores

“…Most notably are those oriented to the analysis of fluids within model hydrophobic nanotubes [38][39][40][41][42][43][44] and in slit-shaped silica and carbon nanopores. [45][46][47][48][49] Our motivation in performing this new set of simulations was to analyze pore size and wallfunctionalization effects on the equilibrium solvation structures and the dynamics of the solute species within the pores. Special care was taken to model the confined liquid phase under realistic conditions, i.e., in contact with a bulk solution.…”

Modeling the Interface between Biological and SyntheticComponents in Hybrid Nanosystems

“…In the case of a highly charged surfaces, we expect to observe an electric double-layer near the surface and streaming currents arising from the water flow [80]. In each system, the proteins were placed in a random orientation with respect to the surface of the channel, representing a unique initial condition.…”