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Published on: December 21, 2017
Host matrix dependent fluorescence intensity modulation by an electric field in single conjugated polymer chains.
P Ralph Hania1, Daniel Thomsson, Ivan G Scheblykin
1Department of Chemical Physics, University of Lund, Box 124, SE-22100 Sweden.
The Journal of Physical Chemistry. B
|December 22, 2006
Summary
Single poly[2-methoxy,5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) molecules show strong fluorescence modulation when exposed to an electric field. This effect, influenced by the surrounding matrix, reveals insights into polymer chain behavior and energy transfer mechanisms.
Area of Science:
- Materials Science
- Polymer Chemistry
- Spectroscopy
Background:
- Poly(2-methoxy,5-(2 eal-hexyloxy)-p-phenylene vinylene) (MEH-PPV) is a conjugated polymer with potential optoelectronic applications.
- Understanding the behavior of single polymer molecules under external stimuli is crucial for designing advanced materials.
- Fluorescence intensity modulation can provide insights into charge dynamics and energy transfer processes within polymers.
Purpose of the Study:
- To investigate the effect of an oscillating electric field on the fluorescence intensity of single MEH-PPV molecules.
- To compare the response of MEH-PPV in different polymer matrices (PMMA and polystyrene).
- To elucidate the underlying mechanisms responsible for the observed fluorescence modulations.
Main Methods:
- Single-molecule fluorescence spectroscopy was employed to monitor fluorescence intensity.
- An oscillating electric field (approx. 1 Hz) was applied to MEH-PPV molecules embedded in PMMA and polystyrene matrices.
- MEH-PPV chains were isolated from electrodes to prevent charge injection effects.
Main Results:
- Strong fluorescence intensity modulation was observed for single MEH-PPV molecules in a PMMA matrix.
- Significantly less pronounced modulations were observed in a polystyrene matrix.
- Differences in modulation depth were attributed to varying field-induced exciton dissociation rates and the presence of acceptor sites.
- Energy transfer from excitons to on-chain hole polarons was suggested as a key mechanism.
- Hysteresis in some molecules indicated conformational switching.
Conclusions:
- The fluorescence intensity of single MEH-PPV molecules is highly sensitive to applied electric fields, with matrix-dependent responses.
- The study highlights the role of exciton dissociation and energy transfer to polarons in electric field-induced fluorescence modulation.
- Variations in molecular response suggest the importance of chain topology and acceptor site distribution.
