Kinetics of Cluster Growth in Fullerene Solutions of Different Polarity

摘要

Investigations of aggregation and associated kinetic effects, proceeding in various solutions of fullerenes C_(60) present a general interesting subject of research for the last 20-30 years. Since the discovery of fullerene solubility in liquids of different polarity, and also proposition of several methods for their dispersion in water media, these studies are considered particularly interesting from practical point of view. In this chapter we give a brief review of some experimental facts about kinetics of cluster growth in these systems, and present some theoretical models for their description. Most attention is given to such solvents as toluene, benzene and N-methylpyrrolidone (NMP). Some recent ultraviolet-visible (UV-Vis) spectroscopy studies of kinetics of fullerene dissolution, and C_(60)-NMP complexes formation are presented. While in case of low-polar solvents one can easily extract the kinetic constants by applying simple dissolution equations, for the polar solutions the Bouguer-Lambert-Beer law is not applicable and we propose a model for accounting of the complex formation. This allows, again, to extract the dissolution rate constants, and also the complex formation rates. The kinetic theory of cluster formation and growth is based on the nucleation theory. We develop additional suppositions that are required to account for change of fullerene state after interaction with solvents. For obtaining the evolution of the cluster-size distribution function for any stage of cluster growth in the solution, a specific method is applied. Finally, we propose a general model for describing the critical character of fullerenes clusters decomposition in polar solvent on addition of water. This model is based on the specific dependence of molecules solubility in binary mixture on the amount of added water.