Nanoparticle architecture in carbonaceous matrix upon swift heavy ion irradiation of polymer–metal nanocomposites

Abstract

Distinct nanoparticle self-organization in the nanocomposites (∼100 nm) of Teflon AF containing different metallic clusters is reported upon swift heavy ion irradiation of 120 MeV Au beams at different ion fluences ranging from 1 × 10¹¹ to 3 × 10¹² ions/cm². Two dimensionally distributed Au clusters are found to be transformed into long cluster chains of seemingly helical pattern in the organic matrix like pearls on a string. Comparatively diluted three dimensionally arranged Ag nanoparticles are observed to be concentrated in the formed mesh of carbon-enriched nanoregions upon irradiation. The nanoparticle self-organization in such carbonaceous nanowires (diameter ∼ 25 nm) finally leads to a quasi-one-dimensional distribution at the highest fluence with several particles apparently being aligned. It appears most probable that a high Au cluster concentration in the polymer matrix leads to direct ion–cluster interaction. This probably initiates irradiation-enhanced and thermally assisted diffusion of the clusters coupled with intermixing in the polymer layers. Moving clusters are assumed to be trapped in the ion beam induced additional free volume leading to a long string of helical-type nanoscale configuration. On the other hand, with diluted clusters arrangement, irradiation induced electronically excited inter-cluster organic regions are interpreted to act as trapping centres for the nanoparticles that self-organize along the ion damaged zones. Transmission electron microscopic investigations have been applied to analyse the irradiated and pristine nanocomposites.