Single polymer molecule fluorescence in electric field

This project is related to the following Fields, Subjects and Techniques:

How does a single conjugated polymer molecule respond to an electric field?

Experimental arrangement for observation of SM response to an electric field

Constant voltage

Fluorescence blinking and degradation induced by a constant electric field. The right panel shows a cartoon to illustrate different types of responses on switching on the electric field.

P.R.Hania and I.G.Scheblykin, Electric field induced quenching of the fluorescence of a conjugated polymer probed at the single molecule level, Chem.Phys.Lett, 2005, 414, 127

AC voltage

An electric field oscillating at a frequency ~1 Hz is found to induce strong modulation of the fluorescence intensity of single MEH-PPV molecules embedded in a poly(methyl methacrylate) matrix. Strong qualitative variation in the modulation from chain to chain reflects large anisotropy in the chain packing and/or matrix cage. In a polystyrene matrix, fluorescence intensity modulations are on average much less pronounced; this can be explained in terms of lower field-induced exciton dissociation rates originating from either a lack of suitable acceptor sites in the matrix or more open conformations of the MEH-PPV chains. A pure exciton dissociation mechanism is however insufficient to explain our observations: effects of energy transfer to long-living on-chain hole polarons have to be included. Moreover, it is likely that the modulations of some molecules arise from triplet as well as singlet quenching by hole polarons.

Individual fluorescence modulation of 2 different molecules of MEH-PPV induced by application of a sinusoidal voltage. Sample thickness was 300 nm.

D.Thomsson, P.R.Hania, I.G.Scheblykin, submitted to JPCB, 2006