Multi-Scale Modelling of Aggregation of TiO2 Nanoparticle Suspensions in Water

Abstract

Titanium dioxide nanoparticles have risen concerns about their possible toxicity and the European Food Safety Authority recently banned the use of TiO2 nano-additive in food products. Following the intent of relating nanomaterials atomic structure with their toxicity without having to conduct large-scale experiments on living organisms, we investigate the aggregation of titanium dioxide nanoparticles using a multi-scale technique: starting from ab initio Density Functional Theory to get an accurate determination of the energetics and electronic structure, we switch to classical Molecular Dynamics simulations to calculate the Potential of Mean Force for the connection of two identical nanoparticles in water; the fitting of the latter by a set of mathematical equations is the key for the upscale. Lastly, we perform Brownian Dynamics simulations where each nanoparticle is a spherical bead. This coarsening strategy allows studying the aggregation of a few thousand nanoparticles. Applying this novel procedure, we find three new molecular descriptors, namely, the aggregation free energy and two numerical parameters used to correct the observed deviation from the aggregation kinetics described by the Smoluchowski theory. Ultimately, molecular descriptors can be fed into QSAR models to predict the toxicity of a material knowing its physicochemical properties, enabling safe design strategies.

Heat Transfer and Thermal Energy Storage Enhancement by Foams and Nanoparticles

“…Finally, focusing on alumina nanoparticle, the overall thermal properties of nanofluids were estimated using cluster analysis and, thus, not relying upon prior assumptions about the shape and size of the resulting NP aggregates, with the goal to predict the thermal conductivity of the nanofluids and, more generally, to pave the way toward new design strategies of nanofluids. Subsequently, the above approach was further extended to titania nanoparticles in [65]. Here, the coordinates of the atoms forming the NPs were retrieved from quantum calculations.…”

Representing and describing nanomaterials in predictive nanoinformatics

“…At the same time, whereas in most cases the reduction in a specific surface area leads to reduced nano-cell interactions, some studies report increased adverse effects 47 . New specific descriptors for the aggregation state have recently been proposed: the aggregation free energy and two numerical parameters used to correct for the observed deviation from the aggregation kinetics described by the Smoluchowski theory 49 . These descriptors are generated as a result of a coarsening strategy combining ab initio density functional theory and molecular and Brownian dynamics.…”

Advanced Computational Modelling of Interface Properties

“…Moreover, the free energy of solvation (water) including the vibrational entropy of the materials consists of a novel descriptor [5], and is examined through molecular dynamics simulations on the semi-empirical tight binding density functional theory level [6]. The interaction energies of aggregated nanoparticles in water [3,7] and the dissolution of ions from a metal (oxide) surface are significant interface descriptors in the quest for safe materials. Latter descriptors are obtained through calculations of the free energy of the material with an atomic vacancy on the surface layer [5].…”