Supramolecular photochemistry research group (SPC-group)

The research activity at the SPC-Group, led by Professors Helge Lemmetyinen and Nikolai Tkachenko (since 2008), can be described as a fundamental study of the photochemistry occurring in solutions and in artificial or self-assembled molecular systems. The key issues are the discovery and development of new materials with desired properties. Systems of interest include molecules capable of transmitting energy, charge or electrons, materials exhibiting electrical conductivity, molecules with unusual optical properties, and structures with optical information storage and processing capability.

The strong background of the group in photochemical research has been created by systematic increase of the knowledge on the theory of photochemistry and by technical development of the photochemistry laboratory, since 1994 at TUT. The laboratory has excellent equipments, especially for measuring ultra-fast photochemical processes.

Special attention have been paid on studies of

Photo-induced processes in organized system
Photo-induced generation and transport of charge
Generation and migration of electronic energy
Control and tuning of photochemical and -physical properties of molecular components in organized film structures.

Recently reported climate changes demand that the additional energy must be produced by renewable carbon-neutral energy sources. With the background and strategy of the research described above, it was easy for the SPC-group to direct its energies to more practical and ambitious objective: to learn to understand the functioning of organic solar cells. Since 2000 the aim of the research has been to study and develop, with chemical and physical methods, new organic electro- and photo-active materials and structures, which rely on electron donating and accepting molecules and conductive polymers, supramolecular structures, and compounds (porphyrins, phthlocyanines, fullerenes, carbon nanotubes and organic pigments), and demonstrate the operation of an organic solar cell.

Parallel to solar energy research it is utmost important to reveal the crucial factors which control the rates and efficiencies of electron transfer (ET) mechanisms and to develop a quantitative theory for the reactions on the basis of experimental data obtained by time-resolved spectroscopy. This requires experimental investigation of reaction dynamics to distinguish different ET mechanisms and reveal criteria for domination of each of them. The results of this research are supposed to offer new possibilities to control and accomplish ET reactions and to perform new chemical reactions promoted by ET (proton transfer, bonds rearrangements, etc.). This will provide also the novel approaches to the design of molecular devices and nanotechnologies using fine control of ET processes by microenvironment and weak intermolecular interactions in organized molecular systems.

Statistics and lists of publications

Photochemistry is also part of the Nanophotonic Consortium in TUT, one of the three Leading-Edge Fields of Research of the University. The research strategy of the SPC-group)is based on the following assertion, which was presented in the Introduction of an approved application, entitled "Organic Thin Films with Functional Activity" for the National Programme on Materials and Structure Research of the Academy of Finland 1994:

“The branch of chemistry, which focuses on complex structures of association of several moieties and on the novel chemical properties resulting from this higher complexity is called supramolecular chemistry. Present day’s supramolecular chemistry has two “souls”, one is based upon synthesis of complex organic structures by synthetic chemistry, and one in which the structural complexity is achieved by self-assembling and self-organization of smaller units without the help of covalent bonds. This kind of molecular thinking - often referred to as chemical engineering or nanochemistry - is the basis for the design of molecular devices, namely structures which perform a very specific function. A photon is at the same time a quantum of energy and a bit of information. The interaction of light with matter can therefore be used for energy or information purpose. The results that can be obtained depend on the degree of organization of the receiving matter.”