Single Molecule Spectroscopy

Conjugated organic polymers are photoluminescent materials showing a great variety of technological applications such as OLED displays, solar cells or molecular sensors. The manufacture of efficient devices ultimately relies on a deep understanding of the polymers photophysical behaviour. In particular, chain conformation and its immediate surrounding environment have a large impact on the optical properties of fluorophores. Single molecule techniques are uniquely suited for the elucidation of photophysical mechanisms since they provide insight into distinct molecular populations which otherwise remain hidden in bulk measurements.

Photoluminescent materials
Photoluminescent materials have potential applications in a great variety of technologies, such as OLED displays, solar cells or molecular sensors.

In order to study polymers in different solvents and conditions we have developed, in collaboration with chemists, an approach to immobilize single polymer chains onto glass surface. This covalent anchoring allows monitoring photoluminescence from single molecules for extended periods of time. In combination with our in-house built chamber compatible with organic solvents, we were able to study the molecular conformation of representative conjugated polymers poly-3-hexylthiophene-2,5-diyl (P3HT) and poly-9,9-dioctyl-9H-fluorene-2,7-diyl (PFO) when exposed to different solvents.

Here in our group, we possess state of the art facilities and equipment to successfully carry out different single-molecule experiments:

  • Three laser sources offering a wide coverage of excitation wavelengths and illumination powers
  •  An inverted microscope specially tailored for single-molecule measurements which can be used in different illumination modes
  • A spectrograph that enables us to determine spectrographic properties of fluorophores at the single-molecule level

Examples of Current Publications

Real-time observation of conformational switching in single conjugated polymer chains. F. Tenopala Carmona, S. Fronk, G. C. Bazan, I. D. W. Samuel and J. C. Penedo-Esteiro. Science Advances. 4, 2, 13, eaao5786 (2018).