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Synthèse et caractérisation de matériaux hybrides organiques-inorganiques à base d'architectures pi-conjuguées et de nanocristaux de semi-conducteurs II-VI

Abstract : This work is devoted to the synthesis of organic-inorganic hybrid materials obtained by controlled grafting of thiophene- or aniline-based conjugated oligo- and polymers on the surface of CdSe nanocrystals.
The interaction between both components is assured by a carbodithioate anchor function present in the organic molecules having a high affinity for the nancrystals' surface. There are two ways to perform the grafting: either by exchange of the nanocrystals' surface ligands with pi-conjugated molecules carrying the anchor function, or by the post-functionalisation of nanocrystals capped with bi-functional ligands containing the anchor group as well as a reactive group, such as an aldehyde (e.g. 4-formyldithiobenzoate). The latter case constitutes a rather general method and can be applied for a wide range of oligomers or polymers containing amine groups. It provides also the possibility to co-deposit a mixture of aldehyde-capped nanocrystals and the amine-oligomer or polymer of interest and to perform the coupling reaction in the solid phase by a subsequent annealing step.
Both organic ligands and inorganic nanocrystals retain their electrochemical activity upon the grafting reaction. Spectroelectrochemical studies allow monitoring the processes induced by potential changes, such as the doping of the conjugated capping molecules, which occurs via the same mechanisms as in the non-grafted molecules.
The relative position of the energy levels of the conjugated ligands and the nanocrystals should allow a charge transfer upon photo-excitation, which leads to an efficient quenching of the photoluminescence of both constituents of the hybrid. Time-resolved photoluminescence measurements, on the picosecond level, show a clear correlation between the conjugation length of the ligands and the transfer efficiency. In the case of aniline tetramer as the capping ligand no photoluminescence at all is detectable indicating charge transfer on a timescale shorter than mesurable. Also in the case of thiophene-dithiobenzoate the transfer occurs very rapidly. Preliminary measurements of photoconductivity show promising results in terms of photocurrent.
Therefore, the developed strategy for the grafting of polyconjugated molecules on the surface of semiconductor nanocrystals opens up the way to a new class of hybrid materials with a high potential for applications in optoelectronic devices, such as solar cells.
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Submitted on : Tuesday, February 13, 2007 - 7:56:34 PM
Last modification on : Friday, March 25, 2022 - 11:10:32 AM
Long-term archiving on: : Tuesday, April 6, 2010 - 9:47:04 PM


  • HAL Id : tel-00130789, version 1



Claudia Querner. Synthèse et caractérisation de matériaux hybrides organiques-inorganiques à base d'architectures pi-conjuguées et de nanocristaux de semi-conducteurs II-VI. Autre. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00130789⟩



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