Ion Structure Near a Core-Shell Dielectric Nanoparticle

A generalized image charge formulation is proposed for the Green’s function of a core-shell dielectric nanoparticle for which theoretical and simulation investigations are rarely reported due to the difficulty of resolving the dielectric heterogeneity. Based on the formulation, an efficient and accurate algorithm is developed for calculating electrostatic polarization charges of mobile ions, allowing us to study related physical systems using the Monte Carlo algorithm. The computer simulations show that a fine-tuning of the shell thickness or the ion-interface correlation strength can greatly alter electric double-layer structures and capacitances, owing to the complicated interplay between dielectric boundary effects and ion-interface correlations.

Figure 1

Self-energy of a cation (a) and interaction energy between a cation and an interfacial anion (b) which are collinear with the NP center, in the presence of a HCP for different shell thicknesses. Energy unit $({\ell }_B/R)k_{B}T$.

Figure 2

With a given surface charge density $\sigma =-10e/(4\pi R^2)$ and correlation strength $\nu =0.1$, RDFs of counterions versus dimensionless positions with different shell thicknesses are shown in (a) for the HCP and (b) for the LCP.

Figure 3

Scaled differential capacitances versus dimensionless surface potentials with different shell thicknesses $\theta =0–0.05$ and a fixed correlation strength $\nu =0.1$ are shown in (a) for the HCP and (b) for the LCP; the relative enhancements of differential capacitance from $\nu =0.1–0.5$ versus dimensionless surface densities with different shell thicknesses $\theta =0–0.05$ are shown in (c) for the HCP and (d) for the LCP.