Abstract
An analytical solution for the effect of particle size on the current density and near-surface ion distribution around spherical nanoparticles is presented in this work. With the long-term aim to support predictions on corrosion reactions in the human body, the spherical diffusion equation was solved for a set of differential equations and algebraic relations for pure unbuffered and carbonate buffered solutions. It was shown that current densities increase significantly with a decrease in particle size, suggesting this will lead to an increased dissolution rate. Near-surface ion distributions show the formation of a steep pH-gradient near the nanoparticle surface (<6 μm) which is further enhanced in the presence of a carbonate buffer (<2 μm). Results suggest that nanoparticles in pure electrolytes not only dissolve faster than bigger particles but that local pH-gradients may influence interactions with the biological environment, which should be considered in future studies.
Highlights
Nanoparticles have gained an immense interest during the past decades
Results are discussed for the specific case of a carbonate buffer and agglomeratefree nanoparticle suspensions
The spherical geometry leads to a change of the local ion distributions, which become steeper for smaller particles, resulting in higher current densities
Summary
Nanoparticles (i.e. particles in the nanometre size range) have gained an immense interest during the past decades. The high surface-to-volume ratio of these particles has led to applications in the area of heterogeneous catalysis [1], especially for electrochemical reactions involving the oxygen reduction/evolution reaction (ORR/OER) and CO2 reduction [2,3,4], to enhance mechanical properties of alloys [5,6] and for biomedical applications [7] such as nanosheets and nanozymes for catalytic use [8,9] Due to their small size, nanoparticles can be absorbed by the human body and engulfed by cells (endocytosis) through a variety of exposure routes, such as inhalation, ingestion, injection, and dermal exposure [10,11,12,13].
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