Förster energy transfer in cholesteric mixtures: a new type of phototunable fluorescent material

Abstract

A new approach to the creation of cholesteric glass‐forming materials with photovariable fluorescent properties is suggested. This approach is based on Förster type energy transfer from a photochemically active donor to a highly fluorescent acceptor. For this purpose, a cholesteric mixture containing two fluorescent dopants based on anthracene (Dianthr) and stilbene (DCM) was prepared and studied. The absorbance peak of DCM molecules overlaps the emission peak of Dianthr. The possibility of using energy transfer in cholesteric mixtures containing a photoactive energy donor capable of photobleaching is demonstrated. It is shown that UV irradiation of planarly oriented films of the mixture leads to photodimerization of the Dianthr dopant. This photoreaction results in a significant decrease in the emission intensity of the DCM dopant. In all cases the emitted light is strongly circularly polarized, and the degree of polarization does not change during photoreaction. Such types of photo‐patternable glass‐forming cholesteric materials combining fluorescent properties, the possibility of energy transfer between two fluorescent dyes and a photoactivity of one fluorescent component, provide new opportunities for optical data recording and storage.

Acknowledgement

This research was supported by the Russian Foundation of Basic Research (Grant 05‐03‐33193) and Federal Scientific‐Technical Program (Contract 02.434.11.2025), Russian Science Support Foundation, and INTAS project (Ref. Nr. 03‐55‐956).The authors wish to thank Drs Armin Bayer and Arndt Reuning for technical assistance. A.B. gratefully acknowledges the research fellowship provided by the Alexander von Humboldt Foundation.