Solubilization and stabilization of fullerene C60 in presence of poly(vinyl pyrrolidone) molecules in water

Abstract

Solubilizing C60 molecules in an aqueous medium is highly imperative in processing them in different forms of ionic or nonionic liquids, nanofluids, films and other derivatives. In this investigation, we report a facile chemical route using polymer molecules of poly(vinyl pyrrolidone) (PVP) which mediate C60 molecules dissolving in water in a stable solution at room temperature. Poly(vinyl pyrrolidone) molecules, soluble in water as well as many organic liquids such as n-butanol, ethanol, or DMF, can be useful for transferring C60 molecules from a non-aqueous to an aqueous system. A broad optical absorption arises over 270–520 nm when C60 molecules are dissolved in water, 0.001–0.065 g/L in presence of 20–120 g/L PVP molecules. It consists of a strong π → π* absorption band (relatively sharp) lying at 294 nm in C(sp2) electrons from PVP-surface modified C60 molecules followed by a broad charge transfer band which extends up to 520 nm. Upon a suitable surface modification, the C60 molecules conquer enhanced optical absorption in both kinds of the bands. Dynamic light scattering reveals an average hydrodynamic length 181.5 nm and a polydispersity index 0.506 after a typical loading 0.065 g/L C60. A zeta potential −8.3 mV with a surface conductivity 0.064 mS/cm at 6.5 pH describes a negatively charged surface structure, showing an n-electron transfer from C=O (PVP) to a nanosurface in surface modified C60 molecules in a weak donor–acceptor complex. Water soluble C60 in presence of a biocompatible compound like PVP is useful for biological, medicinal, and other applications.