Monitoring the Release of Silver from a Supramolecular Fullerene C60-AgNO3 Nanomaterial

Abstract

Abstract Release of silver from the supramolecular fullerene-silver(I) nitrate complex C60(AgNO3)5 was investigated. Silver(I) nitrate release from the complex on treatment with solvent was monitored using the small molecule organo-supergelator 1-phenyl-3-(quinolin-5-yl)urea, which interacts selectively with AgNO3 yielding a stable gel whose extent (i.e. volume fraction of solvent gelated) and persistence indicate that Ag+ cations are continuously released from the complex when immersed in 2-propanol over extended periods of time. The effect of AgNO3 release on the morphology of the C60(AgNO3)5 complex crystals was evaluated using scanning electron microscopy showing that AgNO3 is concurrently deposited as silver nanoparticles at the crystal-solution interface onto an insoluble C60 crystalline framework. Silver release was also monitored potentiometrically revealing emergence of Ag nanoparticles. Initial intense release of Ag+ (in the form of AgNO3) is followed by reductive fixing of silver in nanoparticulate form for longer term bactericidal activity. The latter was established by observing viability of bacterial colonies in aqueous medium where their growth was essentially arrested when C60(AgNO3)5 crystals were present in the medium in contrast to the case for pristine C60 where colony growth proceeded unhindered. Cell proliferation studies using HeLa cell line revealed that C60(AgNO3)5 crystals also exhibit antiproliferative properties in aqueous media.