Fullerene purification

From Wikipedia, the free encyclopedia

Fullerene purification is the process of obtaining a fullerene compound free of contamination. In fullerene production mixtures of C60, C70 and higher homologues are always formed. Fullerene purification is key to fullerene science and determines fullerene prices and the success of practical applications of fullerenes. The first available purification method for C60 fullerene was by HPLC from which small amounts could be generated at large expense.

A practical laboratory-scale method for purification of soot enriched in C60 and C70 starts with extraction in toluene followed by filtration with a paper filter. The solvent is evaporated and the residue (the toluene-soluble soot fraction) redissolved in toluene and subjected to column chromatography. C60 elutes first with a purple color and C70 is next displaying a burgundy color [1].

[edit] Experimental purification strategies

  • A recent kilogram scale fullerene purification strategy was demonstrated by Nagata et al [2]. In this method C60 was separated from a mixture of C60, C70 and higher fullerene compounds by first adding the amidine compound DBU to a solution of the mixture in 1,2,3-trimethylbenzene. DBU as it turns out only reacts to C70 fullerenes and higher which reaction products separate out and can be removed by filtration. C60 fullerenes do not have any affinity for DBU and are subsequently isolated. Other diamine compounds like DABCO do not share this selectivity.
  • C60 but not C70 forms a 1:2 inclusion compound with cyclodextrin (CD). A separation method for both fullerenes based on this principle is made possible by anchoring cyclodextrin to colloidal gold particles through a sulfur - sulfur bridge [3]. The Au/CD compound is very stable and soluble in water and selectively extracts C60 from the insoluble mixture after refluxing for several days. The C70 fullerene component is then removed by simple filtration. C60 is driven out from the Au/CD compound by adding adamantol which has a higher affinity for the cyclodextrin cavity. Au/CD is completely recycled when adamantol in turn is driven out by adding ethanol and ethanol removed by evaporation. 50 mg of Au/CD captures 5 mg of C60 fullerene.

[edit] References

  1. ^ Purification and Modification of Fullerene C60 in the Undergraduate Laboratory Tracey Spencer, Barney Yoo, and Kent Kirshenbaum Journal of Chemical Education 1218 Vol. 83 No. 8 August 2006
  2. ^ Kilogram-scale [60]Fullerene Separation from a Fullerene Mixture: Selective Complexation of Fullerenes with 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) Koichi Nagata, Eiji Dejima, Yasuharu Kikuchi, Masahiko Hashiguchi Chemistry Letters Vol. 34 2005, No. 2 p.178. Abstract
  3. ^ Thio[2-(benzoylamino)ethylamino]--CD fragment modified gold nanoparticles as recycling extractors for [60]fullerene Yu Liu, Ying-Wei Yang and Yong Chen Chemical Communications, 2005, (33), 4208 - 4210 Graphical abstract Suppl. data Full text
Retrieved from "http://en.wikipedia.org../../../f/u/l/Fullerene_purification.html"