Single molecule spectroscopy

This technique has the following projects (and possibly other techniques) related to it:

• 2D polarisation single-molecule spectroscopy
• Time-resolved single molecule spectroscopy
• Excitonic processes in molecular antennas
• Simulations of conjugated polymer chain conformations and interchain energy transfer
• Single molecule spectroscopy of bioobjects
• Single molecule spectroscopy of conjugated polymers
• Single polymer molecule fluorescence in electric field

Single Molecule Spectroscopy group of Ivan Scheblykin

SMS team with colleagues in March 2012 (from left to right): Yi Hu, Dheerendra Yadav, Rafael Camacho, Ji-Eun Lee (visitor from Korea), Ivan Scheblykin, Aboma Merdasa, Sumera Tubasum. The image at the screen shows fluorescent impurities in a PMMA matrix.

Our group in June 2009. Hongzhen demostrates his Swedish national team football t-shirt.

Recent development of nano- and molecular electronics requires the knowledge of properties of materials at the scale of nanometers. It is necessary to know not only the topology of molecular systems at such scale, which can be done by different microscopy methods, but also their individual functional characteristics such as e.g. exciton transfer, charge separation and fluorescence efficiencies. This knowledge could be obtained by optical spectroscopy methods. However, traditional spectroscopy deals with bulk samples (solutions or films), where all these individual "fingerprints" appear to be completely lost due to contribution of many molecules probed in the sample. It is usually called "ensemble averaging effect". To understand the intrinsic properties hidden in such "collective" response, methods of Single Molecule Spectroscopy (SMS) should be used. The current level of detector sensitivity and light collection efficiency allows carrying out steady state and time-resolved (with nanosecond time resolution) spectral, intensity and polarization analysis of the fluorescence of a single molecule.

"How an ordinary Nikon digital camera shows individual molecules of MEH-PPV. Without any spectrometer one can see a large diversity of spectral properties of individual chains. Exposure time was several seconds. Excitation power - 100W/cm²; oil objective lens with NA1.25

Single Molecule Spectroscopy group is the youngest entity of the Department. It has started at in the beginning of 2003. Today we have in operation a wide set of single molecule spectroscopy techniques based on a wide-field microscope allowing studying of single molecule fluorescence at room and cryogenic temperatures. We can do time resolved fluorescence measurements with 50 ps time resolution (time correlated single photon counting) and 2-dimensional (2D) polarization single molecule imaging . The latter is a new technique recently developed by us.

The general focus of our research group is to apply methods of single molecule spectroscopy to "non-standard" objects, which cannot really be considered as single chromophores because of large size and complicated internal structure. Examples of such systems are conjugated polymers, light harvesting antenna complexes, fluorescent biomolecules, J-aggregates.

List of collaborators

Prof. Frank Wuerthner (Wuerzburg, Germany)

Prof. Olle Inganäs (Linköping, Sweden)

Prof. Arvi Freiberg, (University of Tartu, Estonia)

Prof. Harry Anderson, (Oxford University, UK)

Prof. Alfred R. Holzwarth (Mülheimer Max-Planck-Institute, Germany)

Single molecule spectroscopy group is sponsored by:
Vetenskapsrådet, Crafoord foundation, Knut&Alice Wallenberg foundation, Kungliga Fysiografiska Sälskapet, Wenner-Gren foundation, FP6 (Marie Curie Incoming International Fellowship)