Termodinâmica de sistemas fullerênicos em soluções / Thermodynamic systems fullerenic solutions


IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia




In this work, we present a computational study of the solvation process of the C60 fullerene and its hydroxylated derivate, the fullerenol C60(OH)24, in aqueous environment and organic solvents, using classical molecular dynamics simulations. Diverse sets of parameters to the Lennard-Jones interaction potential have been utilized in simulations of fullerenes in solutions and biological environments, however, none of these sets of parameters were assessed and critically validated until the moment. Molecular dynamics simulations combined with thermodynamic integration methods were employed to simulate the transference of the fullerene molecule between two organic liquids (benzene and ethanol) by using different atomistic models of potentials. We observed that the analysis of the structural and dynamical properties is not decisive to choose of potential model to reproduce the thermodynamic properties of C60 in a realistic way. Thus, we calculated the free energy of transfer in order to validate what the sets of atomistic potentials are more appropriate to reproduce the thermodynamic properties by comparing the obtained results with the experimental measurements of solubility of C60 in organic solvents. In the second part of this work, we investigate the structural, dynamical and thermodynamical properties of the hydroxylated derivate of the C60 fullerene, the C60(OH)24 fullerenol. There are no computational investigations in condensed medium. For this system, we compared the obtained results through the analysis of the local structure change of solvent for the two solutes from the radial distribution function where we found an average value of 63 and 48 water molecules in the first hydration shell of C60 and C60(OH)24, respectively. We also analyzed the formation of hydrogen bonds between the surface of fullerenol and water as well as the lifetime of these bonds in the interface with the solute and in the liquid bulk. The dynamical properties were investigated from the diffusion coefficient and its velocity auto correlation function. Finally, we obtained the standard Gibbs free energy of transfer which allowed us compare the thermodynamical behavior of the fullerenol with its corresponding fullerene.


dinâmica molecular energia livre solvatação fullerenóis fullerenos engenharia de materiais e metalurgica fullerenes fullerenols solvation free energy molecular dynamics

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