engleski

Single-Molecule Spectroscopy of Organic Dendrimers

We present a study of the photophysical properties of two model dendrimer molecules composed of two identical branches of D-A-D (S-2) and D-A (TOZ-2) type. Sequential photobleaching of the ICT branches has been demonstrated on the single-molecule level using time-resolved confocal laser microscopy. The lifetime decrease in the highly emissive levels in TOZ-2 reflects the fluorescence from the delocalized ICT excited state. In contrast, no change in fluorescence lifetime with sequential photobleaching of the branches was observed in S-2. The results show that single-molecule (SM) spectroscopy can be a powerful technique for studying exciton-like ICT coupling dynamics in dendritic systems. The strong coupling and stepwise photobleaching of the ICT branches in the dendrimers, which depends on torsional disorder, have been demonstrated. The fluorescence from the delocalized ICT state over two branches in push-pull molecules has been observed at the single-molecule level, which cannot be distinguished by means of conventional experiments probing the average behavior of large ensembles of molecules.

single-molecule spectroscopy; organic dendrimer

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