Luminescent Spectroscopy of Uranium(VI) Complexes in Natural Waters

Budylin G. S., Shirshin E. A., Petrov V. G., Kalmykov S. N., Fadeev V. V.

We present the investigation of uranium(VI) complexes using steady-state and time-resolved laser induced fluorescence spectroscopy. Dependences of uranyl complexes’ photophysical parameters on local environmental parameters (i. e. coordination or anion ligands number in the first coordination sphere), global environmental parameters (solution ionic strength, temperature, humic substances concentration) and excitation radiation intensity are investigated. We demonstrate that the dependence of integral luminescence of uranium(VI) complexes on the total concentration of fluoride-anion in solution is not monotonous. Our investigation of uranium solutions with humic and fulvic acids demonstrates that the process of uranyl luminescence quenching is a static quenching process and it can be described by Stern-Volmer equation. We show that the process of uranyl excited state deactivation depends on the laser excitation intensity. This dependence could be explained with diffusion-limited excited state annihilation, which is a process involving interaction of excited ions. Presented results provide a better understanding of uranium(VI) complexes luminescent properties which should be taken into account in the fluorescent diagnostic tools development.

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