Heavy ion bath
doi:10.1038/nindia.2010.52 Published online 21 April 2010
Swift heavy ion irradiation could make some conducting polymers antioxidant and biocompatible. Exposure to irradiation reshapes the surface architecture of nanofibers made of polyaniline (PAni), a conducting polymer.
These properties make conducting polymer nanostructures suitable for biomedical applications. PAni nanofibers are known to have antioxidant activity.
To sharpen the antioxidant activity of PAni nanofibers, the researchers doped them with hydrochloric acid and camphor sulphonic acid CSA) and exposed them to swift heavy ion irradiation. Irradiation decreased the diameter of HCl doped nanofibers from 40 nm to about 10 nm and that of CSA doped nanofibers from 50 nm to 15 nm.
To study the antioxidant activity, they were exposed to a radical — 2,2-diphenyl-1 picrylhydrazyl (DPPH). The increasing DPPH scavenging activity coincided with the decrease in nanofiber particle size. The nanofibers also prevented hemolysis (the breaking open of red blood cells) proving that they were biocompatible.
"The irradiation technique can bring about unexpected modifications in polymeric materials," says lead researcher Ashok Kumar. The enhancement in antioxidant activity of PAni nanofibers is due to the reduction in their size which increases their surface to volume ratio and conformational changes in the nanofibers, he adds.