Modeling Zeta Potential for Nanoparticles in Solution: Water Flexibility Matters

Paulo Siani; Giulia Frigerio; Edoardo Donadoni; Cristiana Di Valentin

doi:10.1021/acs.jpcc.2c08988

Modeling Zeta Potential for Nanoparticles in Solution: Water Flexibility Matters

J Phys Chem C Nanomater Interfaces. 2023 May 9;127(19):9236-9247. doi: 10.1021/acs.jpcc.2c08988. eCollection 2023 May 18.

Authors

Paulo Siani^{1

2}, Giulia Frigerio^{1

2}, Edoardo Donadoni^{1

2}, Cristiana Di Valentin^{1

2}

Affiliations

¹ Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, via R. Cozzi 55, 20125 Milano, Italy.
² BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20126 Milano, Italy.

Abstract

Nonequilibrium molecular dynamics simulations were performed to study the electrokinetic properties of five mainstream TIPxP water models (namely, TIP3P-FB, TIP3Pm, TIP4P-FB, TIP4P-Ew, and TIP4P/2005) in NaCl aqueous solutions in the presence of a negatively charged TiO₂ surface. The impact of solvent flexibility and system geometry on the electro-osmotic (EO) mobility and flow direction was systematically assessed and compared. We found that lack of water flexibility decelerates the forward EO flow of aqueous solutions at moderate (0.15 M) or high (0.30 M) NaCl concentrations, in some special cases to such an extent that EO flow reversal occurs. Zeta potential (ZP) values were then determined from the bulk EO mobilities using the Helmholtz-Smoluchowski formula. The straight comparison against available experimental data strongly suggests that water flexibility improves the ZP determination of NaCl solutions adjacent to a realistic TiO₂ surface under neutral pH conditions.