Enhanced single molecule fluorescence of conjugated polymer poly(3-hexylthiophene) on silver-nanocubes

• A simple method was used to fabricate a nanostructure for PL enhancement.
• To enhance the single molecule fluorescence of P3HT ∼7 folds by silver nanocubes.
• PL enhancement of P3HT was due to the radiative decay rates and enhanced local field.

We investigate the enhancement of poly(3-hexylthiophene) (P3HT) single molecule fluorescence using silver-nanocube as substrates. Results show that the silver nanocube substrate enhances the single molecule fluorescence of P3HT by about 7 folds and effectively improves the photophysical stabilities of individual P3HT molecules by delaying the photobleaching process. We find that the increase of the radiative decay rates, resulted from the coupling between photogenerated excitons and surface plasmon, is directly related to the observed fluorescence enhancement of P3HT. The enhanced local field provided by the silver-nanocube substrate also contributes to fluorescence enhancement via coupling. This coupling depends on the overlap between the emission frequency of the fluorophore and the surface plasmon field provided by the substrate. As the emission wavelength of the fluorophore gets closer to the surface plasmon resonance of silver nanocubes, the coupling becomes stronger, leading to greater fluorescence enhancement.

The single molecule fluorescence enhancement of poly(3-hexylthiophene) (P3HT) on silver-nanocubes film substrates is due to the coupling between photogenerated excitons and surface plasmon depending on the overlap between the emission frequency and surface plasmon field.Figure optionsDownload as PowerPoint slide