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Electronic Spectroscopy Laboratory Applications to Supramolecules and Nanostructures
Research Director Permanent Staff e-mail: pistolis@chem.demokritos.gr
Our main experimental methods involve, static and dynamic fluorescence techniques, such as:
Research Activities: Organized Supramolecular Assemblies: non-covalently bonded Nanotubes. Nanotube formation between cyclodextrins and DPP proceeds as a self-associative chain reaction, each step of which consists of the attachment of one DPP/ã-CD unit, to the growing nanotube
From computer simulations it was found that the binding constant required for the completion of the nanotube formation is at least of the order of 108 M-1 Signaling of Molecular and Macromolecular Recognition via Electronic Energy Transfer process. We have studied the simultaneous complexation of pyrene and perylene with ã-cyclodextrin in water, by means of electronic excitation energy transfer. We found evidence that although in the solution there are present three different pyrene:ã-cyclodextrin complexes with stoichiometries 1:1, 1:2 and 2:2, the (perylene)1:(ã-cyclodextrin)2 complex formed, associates exclusively with the excimer emitting (pyrene)2:(ã-cyclodextrin)2 adduct and not at all with the others. Moreover, this effect is not observed when pyrene is replaced by some of its homologues which also form 2:2 excimer emitting complexes with ã-cyclodextrin.
Biomaterials based on Dendritic Structures: Use of dendrimers as media for controlled release of encapsulated active molecules We have examined the possibility of employing ordinary dendrimers as encapsulating media for hydrophobic molecules in aqueous environments, and also ways for controlling such encapsulations, i.e. inducing at will, inclusion of the additive molecule in the dendrimer or its release to the environment. Diaminobutane poly(propyleneimine) was chosen as the dendrimer, because it is a typical dendritic macromolecule readily available commercially.
Photophysics of Photonic Polymers The development of efficient and stable blue light emitting polymeric materials is an important issue of investigation. 
Polychromophoric dendronized rigid-flexible alternating polyethers of main-chain quinquephenyl fluorophores decorated with two second generation Fréchet-type side dendrons as the rigid part, and aliphatic chains of 11 or 12 methylene groups as the flexible one, have been synthesized and investigated. The effect of the aliphatic main-chain length on the photoluminescence of these dendronized polyethers is examined in solution and in thin films. Even a subtle change in the length of the flexible spacer, from 11 to 12 methylene groups, has a strong effect on some fluorescence parameters of these polymers and particularly on the fluorescence quantum yield of thin films, which is of the greatest importance for the potential applications of such ð-conjugated polymers as OLEDs.
General Research Interests Spectroscopy Materials Bioactive Materials Macromolecules Supramolecular systems Organized systems Cyclodextrins Polymers Dendrimes Photopolymerisation Physical chemical Characterization Photonic and Optoelectronic Materials Micro and Nanolithography
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