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Abstract
The treatment of sp2 carbon materials, including micrographite, nanographite, HOPG, onion-like-carbon, and single-walled carbon nanotubes, in a 3:1 sulfuric to nitric acid mixture produced photoluminescent reaction solutions. These colloidal, aqueous solutions appeared photoluminescently stable under a UV lamp and ranged in color from red to blue. The photoluminescent wavelength shifted to shorter wavelength with increasing reaction time or increasing reaction temperature. Raman spectroscopy showed evidence of defect structures in graphitic residue, and transmission electron microscopy showed unusual structures present in the supernatant including graphitic balls.
Acknowledgments
S. H. and O. S. are thankful for the support by the Space and Naval Warfare Systems Centers under Grant N66001-04-1-8933. S. T. gratefully acknowledges the financial support from the Fund for Scientific Research Flanders (FWO).