Diffusion Separation of Fullerenes in Solution
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tion of Fullerenes in Solution Alexander V. Eletskii, Michael V. Okun and Eugene V. Stepanov MRS Proceedings / Volume 359 / 1994 DOI: 10.1557/PROC359567
Link to this article: http://journals.cambridge.org/ abstract_S1946427400350515 How to cite this article: Alexander V. Eletskii, Michael V. Okun and Eugene V. Stepanov (1994). Diffusion Separation of Fullerenes in Solution. MRS Proceedings,359, 567 doi:10.1557/PROC359567 Request Permissions : Click here
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DIFFUSION SEPARATION OF FULLERENES IN SOLUTION Alexander V. Eletskii, Michael V. Okun and Eugene V. Stepanov* Russian Research Center "KurchatovInstitute ", Kurchatov Sq. 1, Moscow 123182, Russia
ABSTRACT The diffusion of fullerenes in solution is studied taking into account the recently established fact of the formation of clusters containing some number of aggregated fullerene molecules. Based on a droplet model of a cluster, the distribution function of fullerene clusters by size is obtained for various concentrations of solution. It is shown that dissolved fullerene is present mainly in the form of clusters at saturation conditions, but the contribution of clusters decreases as concentration drops down. Since the diffusion mobility of clusters is much less than that of molecules, it leads to the dependence of an effective diffusion coefficient on concentration, which is computed for the case of fullerene C60 . The feasibility of the use of this dependence as a basis for a diffusion method of the separation and enrichment of the fullerene extract with a small addition of higher fullerenes is analyzed. Possible schemes for enrichment are discussed. INTRODUCTION An exciting interest in the study of the behavior of fullerenes in solution is mainly due to the wide use of methods for the preparation, separation and purification of fullerenes based upon the application of organic solvents[I-4]. Besides, this interest is stimulated by much of extraordinary physical and chemical properties revealed by fullerenes in solution. So, the temperature dependence of the C60 solubility in some solvents proved to be non-monotone with a maximum at about 280 K [5]. The optical spectra of C70 dissolved in the mixture of toluene and acetonitrile dramatically depend on the percentage composition of the mixture undergoing a sharp transformation at the acetonitrile concentration around 60% [6]. The dependence of the non-linear optical susceptibility of C60 dissolved in benzene on the C60 concentration also significantly changes its character at concentration approaching to saturation [7]. All these facts are explained by the phenomenon of the formation of clusters containing some number of fullerene molecules [8,9]. Recently the clusters of C60 in benzene solution were directly observed by the light scattering method [10]. A thermodynamic approach to the analysis of fullerene clustering in solution utilizing a droplet model of a cluster is developed in [8,9]. As shown in those studies, a
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