Functional bisimide dyes bound via electrostatic interactions to oxide nanostructures generated by AFM lithography

Abstract Silicon oxide nanostructures have been functionalized by selective binding of a positively charged bisimide dye derivative. The structures were prepared by AFM nanolithography via local anodic oxidation (LAO) of dodecyl-terminated silicon and are negatively charged due to the production process. Therefore cationic spermine-functionalized perylene bisimide (sf-PBI) molecules can be bound to the structures by electrostatic interactions. The assembly of the sf-PBI units on the LAO nanostructures is verified by AFM height measurements and means of fluorescence microscopy. Emission spectra from the dye-functionalized oxide show that the molecules are able to form excimers. These excimers are characterized by a broad and featureless red-shifted emission band and an increased excited state life time. In contrast to the emission of sf-PBI films on uncharged silicon oxide, the excimer emission was found to decrease strongly low temperatures. This might be explained by a very tight binding due to the electrostatic attraction of the molecules to the LAO oxide.