Inflation of the screening length induced by Bjerrum pairs

Abstract

Within a modified Poisson-Boltzmann theory we study the effect of Bjerrum pairs on the typical length scale $1/\bar{\kappa }$ over which electric fields are screened in electrolyte solutions, taking into account a simple association-dissociation equilibrium between free ions and Bjerrum pairs. At low densities of Bjerrum pairs, this length scale is well approximated by the Debye length $1/\kappa \propto 1/\sqrt{{\rho }_{\mathrm{s}}}$, with ${\rho }_{\mathrm{s}}$ the free ion density. At high densities of Bjerrum pairs, however, we find $1/\bar{\kappa }\propto \sqrt{{\rho }_{\mathrm{s}}}$ which is significantly larger than $1/\kappa$ due to the enhanced effective permittivity of the electrolyte, caused by the polarization of Bjerrum pairs. We argue that this mechanism may explain the recently observed anomalously large colloid-free zones between an oil-dispersed colloidal crystal and a colloidal monolayer at the oil-water interface.

12 pages, 7 figures

Cited by in corpus (14)

• Perspective: Coulomb fluids -- weak coupling, strong coupling, in between and beyond
• Screening length for finite-size ions in concentrated electrolytes
• Theory of Ion Aggregation and Gelation in Super-Concentrated Electrolytes
• Dielectric Constant of Ionic Solutions: Combined Effects of Correlations and Excluded Volume
• Bjerrum Pairs in Ionic Solutions: a Poisson-Boltzmann Approach
• Charge Oscillations in Ionic Liquids: A Microscopic Cluster Model
• Dressed Counterions: Strong Electrostatic Coupling in the Presence of Salt
• Anomalous Underscreening in the Restricted Primitive Model
• Dressed Counterions: Poly- and monovalent ions at charged dielectric interfaces
• Asymmetric Coulomb fluids at randomly charged dielectric interfaces: Anti-fragility, overcharging and charge inversion
• Coupling between bulk- and surface chemistry in suspensions of charged colloids
• Describing screening in dense ionic fluids with a charge-frustrated Ising model
• Theory of electrolytes including steric, attractive, and hydration interactions
• Interaction regimes for oppositely charged plates with multivalent counterions