Ion–ion correlation, solvent excluded volume and pH effects on physicochemical properties of spherical oxide nanoparticles

Abstract

One major source of complexity in the implementation of nanoparticles in aqueous electrolytes arises from the strong influence that biological environments has on their physicochemical properties. A key parameter for understanding the molecular mechanisms governing the physicochemical properties of nanoparticles is the formation of the surface charge density. In this article, we present an efficient and accurate approach that combines a recently introduced classical solvation density functional theory for spherical electrical double layers with a surface complexation model to account for ion-ion correlation and excluded volume effects on the surface titration of spherical nanoparticles. We apply the proposed computational approach to account for the charge-regulated mechanisms on the surface chemistry of spherical silica (SiO2) nanoparticles. We analyze theeffects of the nanoparticle size, as well as pH level and electrolyte concentration of the aqueous solution on the nanoparticle’s surface charge density and Zeta potential. We validate our predictions for 580 Å and 200 Å nanoparticles immersed in acid, neutral and alkaline mono-valent aqueous electrolyte solutions against experimental data. Our results on mono-valent electrolyte show that the excluded volume and ion-ioncorrelations contribute significantly to the surface charge density and Zeta potential of the nanoparticle at high electrolyte concentration and pH levels, where the solvent crowding effects and electrostatic screening have shown a profound influence on the protonation/deprotonation reactions at the liquid/solute interface. The success of this approach in describing physicochemical properties of silica nanoparticles supports its broader application to study other spherical metal oxide nanoparticles.

A multi-scale approach to describe electrical impulses propagating along actin filaments in both intracellular andin vitroconditions

“…In this section, we use expressions (12), (15), (17), (19), (37), (40) and (41) to investigate the impact of different electrolyte solutions and voltage stimulus on the physicochemical properties of G-actins and electrical signal propagation along F-actins. We investigate two electrolyte solutions, one representing an intracellular biological environment in physiological solution conditions (140mM K + , 4mM Cl − , 75mM HP O 2− 4 , and 012mM N a + at 310 K), 51 whereas the other represents in vitro conditions 5 (0.1M K + and 0.1M Cl − at 298 K).…”

Electrical double layer properties of spherical oxide nanoparticles

“…We use the solvent particle model to characterize the electrolyte 34 . Each ionic species i is represented by bulk Molar concentration [ ${\rho }_i^0$], a charged hard sphere of diameter d i , and total charge q i = ez i , where e is the electron charge and z i is the corresponding ionic valence (see Fig.…”

“…In this work, we utilize the same parameters used in our previous work 34 . We consider silica oxide nanoparticles with total density number of active functional group N total = 2*10 −6 mol / m 2 and equilibrium constants pK A = − log ( K A ) = 6.8 (protonation) and pK B = − log ( K B ) = 1.7 (deprotonation).…”

“…A novel approach named classical solvation density functional theory (CSDFT) has been recently introduced to study the influence that biological environments at neutral pH may have on the physicochemical properties of spherical nanoparticles of different sizes while under a variety of electrolyte conditions 32 . A more recent formulation of this approach combines CSDFT and surface complexation model (SCM) 33 to account for ion-ion correlation and particle crowding effects on the surface titration of spherical oxide nanoparticles 34 . The results, successfully validated against experiments, show that the particle crowding and electrostatic screening effects have a profound influence on the SCD and ZP of the nanoparticle.…”

A java application to characterize biomolecules and nanomaterials in electrolyte aqueous solutions

“…In this article, we present a free, multi-platform and portable Java software which provides both experts and non-experts in the field an easy and efficient way to get an accurate molecular characterization of the EDL properties for biomolecules and nanomaterials at infinite dilution. The application is based on the so-called Classical Solvation Density Function Theory (CSDFT) and its modifications, which have been shown to be particularly useful in studying multiple environmental scenarios for a variety of rod-like [12,13] and spherical [14][15][16] rigid-like macroions without computational restriction. CSDFT extends the capabilities of NLPB formalism, eliminating the extremely high computational demands of full atomistic simulation calculations without losing important structural features of complex EDL properties (see Figure 1).…”