Mechanism of Solubilizing Fullerene C₆₀in Presence of Poly(Vinyl pyrrolidone) Molecules in Water

Abstract

In this article, a possible mechanism of solubilizing C 60 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   * band in the C(sp 2 ) electron transitions of C 60 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 C 60 -PVP nanofluids clearly show adsorption of an amorphous PVP surface layer (35-37 nm thickness) on the C 60 nanosurface. An intense dynamic light scattering band measuring an average hydrodynamic length of 306 nm attributes to PVP encapsulated C 60 molecules. An average zetapotential (-) 17.8 mV at 6.5 pH describes PVP molecules aided accumulation of n-electrons on the C 60 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 C 60 molecule as a result of a charge transfer coupling of PVP functional groups with the C 60 nanosurface. A nearly 11% decrease in emission band intensity in the n  n* band of the PVP molecules at 393 nm upon addition of Downloaded by [University of Leeds] at 01:36 06 July 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 4.0 µM C 60 molecules exhibit n-electrons transfer from O-atom of pyrrolidone ring to electron deficient carbon nanosurface in surface modified C 60 molecules.

Poly(vinyl pyrrolidone) Mediated Solubilization and Stabilization of Fullerene C60in the Form of Nanofluid in an Alcoholic Medium

“…This mechano-chemical process was then followed by an ultrasonic irradiation at 50 0 C for 15 min (at 20 kHz frequency and 250 W power). As reported earlier (20,21), the ultrasonic irradiation is critical in producing exfoliated PVP molecules with abundance of active "O=C-N<" head groups to bond with the C 60 molecules. In order to prepare samples free from toxic toluene solvent, the nanofluid was kept in a vacuum oven (1-3 kPa pressure) that was maintained at 100 ± 10 0 C over a period of 10 h so that all the solvents were evaporated leaving behind the solid C 60 :PVP sample.…”

“…A small red-shift in the lactam C=O stretching band frequency of PVP from 1667 cm -1 in the PVP solution to that at 1662 cm -1 in the C 60 -PVP complex reveals only a weak exchange interaction between the PVP and C 60 structures in a steric factor (20,21,24,25,33,34). Like the FTIR bands in Fig.…”

“…1A, the spectrum in sample-A consists of a sharp p ® p* absorption band, with absorbance maximum α max = 0.114 cm −1 lying at 330 nm, followed by a weak band with absorption maximum wavelength λ max 406 nm. The prominent 330 nm band is characteristic of a spin allowed 1 A 1g ® 1 T 1u (3) (p ® p*) transition in C(sp 2 ) electrons of the C 60 molecules which are dispersed in nbutanol molecules, while the weak band is characteristic of an orbital forbidden singlet-singlet 2 1 H u ® 1 1 A g transition in C(sp 2 ) electrons of the C 60 molecules (20,21,23). An inset in Fig.…”

“…The 345 nm band arises in the 1 8 (p ® p*) transition in the C(sp 2 ) electrons from the PVP surface-modified C 60 in small molecular assemblies whereas the extremely weak band shown at 435 results in a charge transfer band. Low intensity in these bands indicates that a local symmetry of C 60 molecules retains either on a charge transfer of n-electrons from a ">N-C=O" moiety (PVP) to a C 60 molecule or an electron transfer due to a steric congestion (20,21,24,25). A reasonably broadened band feature observed in the p ® p* transition in PVP moieties in a PVP-surface modified C 60 sample indicates that the PVP is cross-linking over the C 60 surface and the later appear in joint C 60 -PVP assemblies in Fig.…”

“…Among the various solubilizing and stabilizing agents, a biocompatible macroscopic stabilizing agent like poly (vinyl pyrrolidone) PVP is gaining much interest to scientific and academia (7)(8)(9)(16)(17)(18)(19)(20)(21). The various advantages of using such agent are: (i) induces excellent In the present article, we report on the enhancement in both solubilization and stabilization of C 60 molecules in n-butanol in presence of PVP polymer.…”