Orientation of molecular probes in latent ion tracks

Abstract

By using polarized fluorescence spectroscopy, the orientation properties of special molecular probes deposited in the ion tracks were investigated. Foils of poly(ethylene terephthalate) (PET) were used as a matrix for the ion tracks wherein fluorescence probes such as aminostyryl-derivatives can be incorporated using a suitable solvent e.g. N, N'-dimethylformamide (DMF) as transport medium. The diffusion of a small amount of probes into the virgin material and the high sensitivity of fluorescence methods allows the comparison of probe properties in ion tracks with that in virgin material. 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 inter-diffusion into the track surrounding material. The breakdown of the orientation at high areal doses can be correlated with the increasing multiple overlapping of the ion tracks.