Correlation analysis of fluorescence intensity and fluorescence anisotropy fluctuations in single-molecule spectroscopy of conjugated polymers.

Single-molecule spectroscopy techniques are used to investigate time fluctuations of the fluorescence properties of two different types of conjugated polymer, a polythiophene derivative (PDOPT) and a phenylene vinylene derivative (MEH-PPV), at 100 and 293 K. Linear correlation coefficients between fluorescence intensity and polarization are used to characterize fluctuations. We are able to distinguish between different blinking and bleaching effects on the polarization. Furthermore, the polarization data reveal clear differences in the topology of these two polymers, which is related to the ordered conformation of the MEH-PPV. Plots of correlation coefficients appear to be very different for the two polymers and are also very sensitive to temperature. These observations prove that correlation analysis is a useful tool to understand fluorescence fluctuations in multi-chromophoric systems.