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Dispersion State Phase Diagram of Citrate-Coated Metallic Nanoparticles in Saline Solutions

preprint
submitted on 22.04.2020 and posted on 23.04.2020 by Sebastian Franco Ulloa, Giuseppina Tatulli, Sigbjørn Løland Bore, Mauro Moglianetti, Pier Paolo Pompa, Michele Cascella, Marco De Vivo
The fundamental interactions underlying citrate-mediated chemical stability of metal nanoparticles (NPs), and their surface characteristics dictating particle dispersion/aggregation in aqueous solutions, are largely unclear. Here, we used a newly developed theoretical model to estimate the stoichiometry of citrate molecules chemisorbed onto spherical metallic NPs and define the uncovered solvent-accessible surface area of the NP. Then, we exploited two-body free energy calculations and extended coarse-grained molecular dynamics simulations of citrate-capped metallic NPs in saline solutions to explore an experimentally relevant range of NP charge, as well as the electrolytic medium’s ionic strength, a known trigger for aggregation. In this way, we define dispersion state phase diagrams of citrate-capped metal nanocolloids. UV-vis spectroscopy experiments validated our predictions and extended our results to NPs up to 35 nm. Altogether, our results disclose a complex interplay between the particle size, its surface charge density, and the ionic strength of the medium, which ultimately clarifies how these variables impact colloidal stability.

Funding

Associazione Italiana per la Ricerca sul Cancro (IG 23679)

Research Council of Norway (262695)

Norwegian Supercomputing Program NOTUR (NN4654K)

History

Email Address of Submitting Author

sebastian.franco@iit.it

Institution

Istituto Italiano di Tecnologia

Country

Italy

ORCID For Submitting Author

0000-0001-6128-0630

Declaration of Conflict of Interest

The authors declare that they have no conflicts of interest with the contents of this article.

Exports