Exact form of the short-range acid–base repulsive potential at the cell–nanorod interface

Determine the exact functional form of the short-range, highly repulsive acid–base interaction potential between bacterial cell surfaces and gold nanorod surfaces required in the extended DLVO framework used to model their interactions.

Background

The paper models interactions between gold nanorods and bacteria using an extended DLVO approach that includes electrostatic double-layer forces, van der Waals forces, an acid–base short-range repulsive term, and steric repulsions from surface biopolymers. The acid–base (AB) term is introduced as a short-range repulsive potential to capture interactions not accounted for by classical DLVO theory.

The authors explicitly state that the precise functional form of this short-range potential is unknown. In their calculations, they adopt a commonly used exponential form parameterized by a strength term (denoted AGAB in the text) to represent this interaction. Resolving the exact form of the short-range AB repulsion specific to bacterial cell surfaces and gold nanorods would improve quantitative accuracy of the interaction energy profiles and predicted equilibrium separations relevant to SERS enhancement.