Relating conformation and photophysics in single MEH-PPV chains.

We use a novel fluorescence polarization microscope in combination with molecular dynamics calculations to determine the conformation of individual isolated chains of the conjugated polymer MEH-PPV. We found a narrow distribution of defect cylinder conformations in a poor-solvent matrix and two types of defect coil conformations in a good-solvent matrix. The conformations were related to photophysical properties of MEH-PPV by measuring fluorescence intermittency on the same chains.

Structure-dependent photophysics studied in single molecules of polythiophene derivatives.

We report on the photophysical characterization at the single-molecule level of a graft copolymer consisting of a polythiophene backbone and long polystyrene branches. The presence of the branches prevents the polymer chain from forming a collapsed conformational state. The photophysical properties of the resulting solution-like conformation are studied by measuring single-molecule photobleaching dynamics, emission polarization anisotropy and emission spectra.

A method for determining the absorption ellipsoid of single conjugated polymer molecules and single luminescent nanoparticles.

We propose a simple method for the measurement of the absorption ellipsoid of luminescent nanoparticles. The method is based on a combination of far-field and near-field polarized excitation in a wide-field fluorescence microscope and provides the orientation and axes ratio r of a rotationally symmetric ellipsoid. Potential applications of the method including the study of conjugated polymer conformations are discussed.