mercredi 19 juin 2013 à 16:00
Amphi G. Besse
Although polonium (Po) was discovered in 1898 by Pierre and Marie Curie, little is said about the complexation chemistry of polonium. Most notably, its chemistry in solution is not well understood, and this can be explained by two main reasons.
First, polonium is very rare in nature, being found in uranium ores at approximately 100 mg/ton. Second, all of its isotopes are radioactive. Thus, specific tools are required to investigate its chemistry and the use of spectroscopic methods is limited by the manipulation of trace amounts.
Additionally, polonium is a highly toxic element, with the main hazard from ingestion or inhalation. One of its isotopes, polonium-210 (Po-210) that occurs naturally in the uranium decay, is known for being one of the most toxic radionuclides in natural samples due to its high specific activity (1.66 1014 Bq/g). To illustrate this point, 1 μg of Po-210 emits as many alpha particles as of uranium-238.
Nowadays, polonium-210 is considered as an important component of natural radiation affecting humans. This is particularly true for tobacco plant smokers which can absorb polonium from the soil around them. In the case of individual exposure or contamination, the nature of the present chemical species is far from being understood.
Therefore, fundamental research to understand of polonium behavior in solution can help to develop protocols and strategies to minimize its lethal effects.
Our project intends to perform polonium’s chemistry studies in aqueous solution in order to understand its coordination chemistry. In this work, at the atomic scale, a new methodology for the production and purification of polonium-210 is developed, Via the nuclear reaction Bi-209(α, 2n) At-210 to insure the availability of polonium source. At molecular scale, the speciation and coordination properties of polonium are described. In addition, a novel water soluble “N2S2O2/N4O2” macrocyclic complexing agent is designed and synthesized for complexation with respect to the nature of the interacting sites (soft heteroatoms) and their geometrical arrangement in an octahedral coordination shell. Furthermore, The ability of the ligand to complex Po(IV) at pH=7.4 will be studied.