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Cm 3+ / Fluorescence / Laser-induced time-resolved spectroscopy / Nanoparticle / Silicate / Eu 3+ Summary. The complexation of Cm(III) and Eu(III) with dissolved silica was studied by solubility measurement and time resolved laser fluorescence spectroscopy (TRLFS) in basic solutions over a range of total silica concentrations and ionic strengths (NaNO 3 ). In initial experiments on the solubility of Eu(OH) 3 in silicate containing solutions we observed a rapid increase in the soluble Eu(III) concentration under basic conditions. The Eu(III)/Cm(III) silicate complexes that formed caused a significant increase of the hypersensitive 5 D 0 → 7 F 2 band around 615 nm relative to the non-hypersensitive 5 D 0 → 7 F 1 band at 592 nm for Eu(III). Further studies of Eu(III) and Cm(III) containing solutions showed a shift of the fluorescence spectral maximum from 594 nm to up to 607 nm for Cm(III) along with a significant increase of fluorescence intensities. The fluorescence lifetimes for Eu(III) species increased from 115 µs to 1.8 ms in 3.0 M and 5.0 M NaNO 3 , corresponding to full coordination, and from 68 µs to 202 µs for Cm(III) in 0.1 M NaNO 3 , consistent with the removal of 6-7 water molecules upon silicate complexation. The variations of the fluorescence intensity and the concentrations of the monomeric and polymeric silicates suggested that in basic silicate solutions, Eu(III)/Cm(III) mainly complexes with polysilicates.

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