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Single Molecule Spectroscopy

Recent development of nano- and molecular electronics requires knowledge of material properties at the nanometer scale. It is not sufficient to achieve information only on 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 have to be investigated.

Such information might 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 contributions from many molecules probed in the sample. This usually is called "ensemble averaging effect." To understand the intrinsic properties hidden in such "collective" response, Single Molecule Spectroscopy (SMS) methods should be used. The current level of detector sensitivity and light collection efficiency allows to carry 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 has started in the beginning of 2003. Today we have in operation a wide set of single molecule spectroscopy techniques based on wide-field microscopy, which allows for studies of single molecule fluorescence at room and cryogenic temperatures. The temporal resolution of our  fluorescence measurements reaches down to 50 ps (time correlated single photon counting). Recently we developed a new technique: two-dimensional polarization single molecule imaging (2D POLIM)

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.


Ivan Scheblykin

People involved: Aboma Merdasa, Daniela Täuber

Formerly involved: Rafael Camacho Dejay, Dheerendra Yadav, Yi Hu,  Matthias Meyer, Dibakar Sahoo

Single Molecule Group is Sponsored by

Vetenskapsrådet, Crafoord foundation, Knut&Alice Wallenberg foundation, Kungliga Fysiografiska Sälskapet, Wenner-Gren foundation, FP6 (Marie Curie Incoming International Fellowship)