Adsorption Behavior of α-SiO2 Nanoparticles at Oil-Water Interface Based on Molecular Dynamics Simulation
The adsorption and self-assembly of nanoparticles at fluid interfaces are widely applied in various fields such as oil recovery,foam flotation,drug delivery,and novel functional materials.However,nanoparticles may not spontaneously adsorb to oil-water interfaces due to various interactions,such as solvation forces and electrostatic repulsion,which create an adsorption barrier.In this study,the dynamic characteristics of the adsorption of α-SiO2 nanoparticles at the oil-water interface are investigated,including an in-depth analysis of the effect of both hydration layer structure and ionic concentration on the adsorption behavior of nanoparticles using the molecular dynamics simulation method.Surface modification using hydrophilic/hydrophobic groups has been utilized to achieve diverse adsorption characteristics of α-SiO2 nanoparticles.The nanoparticles undergo three distinct processes upon spontaneous diffusion to the sub-interface:relaxation adsorption to the interface,rapid adsorption,and a period of relaxation in the interfacial region before reaching dynamic equilibrium.The analysis aims to quantify and compare the structure of the hydrated layer and hydrogen bond network near the surface of the nanoparticles.This was achieved by using radial distribution functions,angular distribution functions,as well as hydrogen bonds density distribution.The dynamic properties of the hydrated layer and hydrogen bond structure were analyzed using the residence autocorrelation function of water molecules and hydrogen bond lifetime.The study reveals that the structure of the hydration layer is influenced by the surface properties of the interacting particles.Water molecules exhibit greater orientation and mobility on hydrophobic surfaces compared to hydrophilic surfaces.Surface-water hydrogen-bond interactions and special hydrogen-bond structures within the hydration layer play a crucial role in particle adsorption.Different ionic effects can also interfere with the hydrogen-bonding structure,promoting adsorption at the phase interface of the nanoparticles.This study provides a reference for understanding the kinetic properties of nanoparticle phase-interface adsorption and the formation mechanism of adsorption barriers.It can be of significant guidance for the controllable adsorption of nanoparticles at phase-interfaces in the fields of petroleum recovery and new functional materials.
molecular dynamicsamorphous silicafunctionalized nanoparticleoil-water interfacephase-interfaces adsorptionhydrogen bond lifetimehydrogen bond interactionhydration layer
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