Solubility of large fullerenes in concentrated sulfuric acids

PRES 59

Pradeep Rai1, A. Nicholas G. Parra-Vasquez, alario33@rice.edu1, Haiqing Peng, hpeng@rice.edu2, Robert Hauge, Hauge@rice.edu2, and Matteo Pasquali, mp@rice.edu3. (1) Department of Chemical Engineering, Rice University, 6100 Main St. MS-362, Houston, TX 77005, (2) Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main St. MS100, Houston, TX 77005, (3) Chemical and Biomolecular Engineering Department, Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main St. MS-362, Houston, TX 77005
We present the solubility of large fullerenes (LFs) in concentrated sulfuric acids. We employ a centrifugation technique in conjunction with UV-Vis-nIR spectroscopy to quantify solubility. The UV-Vis-nIR absorbance of large fullerenes in concentrated sulfuric acids between 400 to 1400 nm wavelengths follows Beer's Law behavior enabling calibration curves for measuring LFs concentration in acids be constructed. Centrifugation of concentrated dispersions of LFs in concentrated sulfuric acids results in a clear phase separation where the isotropic phase is supernatant. UV-Vis-nIR absorbance measurement on the top phase yields true solubility of LFs. Large fullerenes exhibit an unusually high solubility in sulfuric acids concentrated in the range of 85-96%. We find that the solubility of large fullerenes increases with acid strength as expected for solubilization by protonation mechanism. This is the first time, the solubility of LFs is being reported and the solubility of large fullerenes in 96% sulfuric acid is higher than the solubility of smallest fullerene (C60) in many organic solvents.