Poly(vinyl pyrrolidone) Mediated Solubilization and Stabilization of Fullerene C₆₀ in the Form of Nanofluid in an Alcoholic Medium

Abstract

We report on the solubilization and stabilization of C₆₀ molecules in presence of a macroscopic capping agent such as poly(vinyl pyrrolidone) PVP polymer in n-butanol using a sonochemical route. Augmentation in the absorbance value by nearly two times in the π → π* band in the C(sp²) electron transitions of C₆₀ molecules at 328 nm in presence of PVP suggests an increase in the electron charge density on the surface interface via donor-acceptor interaction. A reasonably broad band feature observed in the π → π* transition at 435 nm in PVP moieties in a PVP-surface modified C₆₀ sample indicates that PVP is cross-linking over the C₆₀ surface in specific structure. Quenching of light emission in PVP molecules in n-butanol results from non bonding electrons (n) transfer from C˭O: (PVP) moieties to a C₆₀ nanosurface in a C₆₀:PVP charge transfer (CT) complex. Dynamic light scattering band measures two bands one at 32.0 nm and other one at 8.1 nm with average values of hydrodynamic diameter 9.2 nm and polydispersity index 0.35 apparently in two types of distinct structures. The zeta plot in the 4.63 μM C₆₀ with PVP measures a zeta band with full width at half maximum ∼14.4 mV with average values of zetapotential ξ (−) 12.4 mV and surface conductivity of 0.074 mS/cm. The negative ξ-value describes that of O-atom of PVP molecules accumulate on the C₆₀ surface via a chemisorptions process. Raman and Fourier transform infrared bands show that CT complex made in n-butanol presents a poor donation of the C˭O n-electrons from PVP moiety to the C₆₀ molecules owing to adverse steric effect. High resolution transmission electron images in C₆₀-PVP nanofluids illustrates a core-shell structure which consists of a C₆₀ core covered by a shell of nearly 2.0 nm thickness of an amorphous PVP layer of a whitish contrast.

Keywords:

• Nanofluids
• core-shell structure
• chemisorptions
• Quenching of light
• Hydrodynamic diameter

Acknowledgements

This work was supported by Silicon Institute of Technology, Bhubaneswar, India.