First observation of spectral fluctuation in a single molecule of a rigid-rod pi-conjugated polymer

The photonic function of the light-emission from a rigid-rod conjugated pol ymer, poly(9, 10-anthracenediyl-ethynylene-1,4-phenylene- ethynylene) [poly (AEPE)], was measured using total internal reflection fluorescence microsco py (TIRFM), which is a single molecule detection technique that is carried out in methanol at room temperature. The light-emission from a single polym er molecule as it slowly and dynamically changes over a cycle lasting a few seconds has been successfully detected using TIRFM with a built-in spectro scope. Special mention must be made of the fact that we were able to observ e for the first time fluctuations in the wavelength of the emission spectra resulting from structural changes in a single polymer molecule. Although p oly(AEPE) had a rigid-rod main chain, these changes occurred very slowly ov er a time-scale of several seconds at room temperature. Thus, single molecu le spectroscopy appears to be a powerful tool for studying the dynamic beha vior of single macromolecules. (C) 2001 Elsevier Science Ltd. All rights re served.