Limitations with solvent exchange methods for synthesis of colloidal fullerenes

Abstract

Listen

Translate article

We have found demonstrated that the use of tetrahydrofuran (THF) as a solvent to produce dispersed, water soluble fullerenes results in significant oxidation and degradation of the fullerene cage, which has not been reported previously. We also report a new finding that the use of N, N-dimethylformamide (DMF) can also generate stabilised fullerene (C60) nanoparticle dispersions in aqueous solutions including water and phosphate buffered saline (PBS) buffer. We compare this new DMF method with the well-known THF method following an extensive chemical and physical analysis of the resulting nanoparticles. The exact mechanism of action behind this oxidation and degradation is unknown, however, the role of peroxides is likely. The method of solvent exchange based on the use of DMF results in the formation of fullerene nanoparticle agglomerates that are highly stable in PBS and water, while the THF agglomerates are only stable in water. However, caution should be applied when using these approaches due to the significant degradation of the fullerene cage observed when using various techniques such as dynamic light scattering (DLS), matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) and cryo transmission electron microscopy (cryo-TEM). Our results show that the solvent exchange technique using THF results in partial oxidation and degradation of C60, interestingly, the DMF evaporative method results in greater oxidation and degradation of C60 but significantly enhanced colloidal stability in buffer.