Speciation of europium (III) surface species on monocrystalline alumina using time-resolved laser-induced fluorescence-scanning near-field optical microscopy.

The aim of this work was to perform highly localized spectroscopic surface measurements by combining time-resolved laser spectroscopy and scanning near-field optical microscopy. The final purpose of that was to study surface sorption at the molecular level of trivalent ions in the framework of nuclear waste disposal assessment. Time-resolved laser spectroscopy presents the advantages of being selective, sensitive, and noninvasive and scanning near-field optical microscopy is a promising technique for high resolution surface speciation.

Local heterogeneity for a Eu3+-doped glass evidenced by time-resolved fluorescence spectroscopy coupled to scanning near-field optical microscopy.

Time-resolved fluorescence spectroscopy (TRFS) was applied to an aluminate glass sample doped with Eu3+ cation as a fluorescent probe of the chemical environment and local symmetry. Conventional far-field experiments revealed the presence of two different phases: an amorphous phase featured by a highly disordered environment surrounding the Eu3+ cation and a more ordered polycrystalline phase that exhibits a significant increase in the Eu3+ fluorescence decay time compared to that of the amorphous phase. Near-field fluorescence spectra and decay kinetics were recorded in the frontier region between the two phases using a home-built scanning near-field optical microscope.