Coarse-Grained Modeling of the Titration and Conductance Behavior of Aqueous Fullerene Hexa Malonic Acid (FHMA) Solutions

• Published in: The journal of physical chemistry. B Vol. 118; no. 11; pp. 3150 - 3155
• Main Authors: Allison, Stuart A, Wu, Hengfu, Moyher, Avery, Soegiarto, Linda, Truong, Bi, Nguyen, Duy, Nguyen, Tam, Park, Donghyun
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 20.03.2014
• Subjects: Binding; Charge; Coarsening; Fullerenes; Mathematical analysis; Mathematical models; Numerical analysis; Titration
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp500196j

The coarse-grained continuum primitive model is developed and used to characterize the titration and electrical conductance behavior of aqueous solutions of fullerene hexa malonic acid (FHMA). The spherical FHMA molecule, a highly charged electrolyte with an absolute valence charge as large as 12, is modeled as a dielectric sphere in Newtonian fluid, and electrostatics are treated numerically at the level of the non-linear Poisson–Boltzmann equation. Transport properties (electrophoretic mobilities and conductances) of the various charge states of FHMA are numerically computed using established numerical algorithms. For reasonable choices of the model parameters, good agreement between experiment (published literature) and modeling is achieved. In order to accomplish this, however, a moderate degree of specific binding of principal counterion and FHMA must be included in the modeling. It should be emphasized, however, that alternative explanations are possible. This comparison is made at 25 °C for both Na+ and Ca2+ principal counterions. The model is also used to characterize the different charge states and degree of counterion binding to those charge states as a function of pH.