Mechanism of Solubilizing Fullerene C60 in Presence of Poly(Vinyl pyrrolidone) Molecules in Water

Abstract

In this article, a possible mechanism of solubilizing C60 molecules through poly (vinyl pyrrolidone) PVP is described in exploring its diverse biological, cosmetical, and medicinal activities. Markedly enhanced (∼ three times) absorbance, molar extinction coefficient, or oscillator strength in a π → π* band in the C(sp2) electron transitions of C60 molecules at 299 nm confers an effective surface adsorption of chromophoric groups of PVP molecules on the carbon surface. High resolution transmission electron and field emission scanning electron microscopic images in C60-PVP nanofluids clearly show adsorption of an amorphous PVP surface layer (35–37 nm thickness) on the C60 nanosurface. An intense dynamic light scattering band measuring an average hydrodynamic length of 306 nm attributes to PVP encapsulated C60 molecules. An average zetapotential (−) 17.8 mV at 6.5 pH describes PVP molecules aided accumulation of n-electrons on the C60 surface. Raman and Fourier transform infrared bands show distinctly enhanced intensity in the C ˭ O and C‒N stretching vibrations of lactam rings in presence of C60 molecule as a result of a charge transfer coupling of PVP functional groups with the C60 nanosurface. A nearly 11% decrease in emission band intensity in the n ← nπ* band of the PVP molecules at 393 nm upon addition of 4.0 µM C60 molecules exhibit n-electrons transfer from O-atom of pyrrolidone ring to electron deficient carbon nanosurface in surface modified C60 molecules.