Effect of nanoparticle size on the near-surface pH-distribution in aqueous and carbonate buffered solutions
Thomas Stepan, Lisa Tété, Lila Laundry-Mottiar, Elena Romanovskaia, Yolanda S. Hedberg, Herbert Danninger, Michael Auinger
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.