Molecular orientation in heavy ion tracks

Abstract

By using polarized fluorescence methods the orientation properties of molecular probes incorporated in heavy ion tracks were investigated. For the investigations poly(ethylene-terephthalate) (PET) was chosen as a polymer with well characterized fluorescence properties. Fluorescence probes such as aminostyryl-derivatives were incorporated in heavy ion tracks by using a suitable solvent, e.g. N,N′-dimethylformamide (DMF) as transport medium. By means of polarized fluorescence spectroscopy it is shown that deposited molecular probes with a high aspect ratio have a preferential orientation parallel to the ion track axis. The orientation of the molecular probes indicates that molecules can be aligned in ion tracks without interdiffusion into the surrounding material. It can be shown that this orientation is sensitive to an overlapping of the tracks. By this a track radius of about 18 nm can be determined. The orientation of the fluorophores correlates with the amount of overlapping tracks.