In the geochemical field, the chemical speciation of hexavalent uranium (U(VI)) has been widely investigated by performing measurements to determine its luminescence properties, namely the excitation, emission, and lifetime. Of these properties, the excitation has been relatively overlooked in most time-resolved laser fluorescence spectroscopy (TRLFS) studies. In this study, TRLFS and continuous-wave excitation–emission matrix spectroscopy are adopted to characterize the excitation properties of U(VI) surface species that interact with amorphous silica. The luminescence spectra of U(VI) measured from a silica suspension and silica sediment showed very similar spectral shapes with similar lifetime values. In contrast, the excitation spectra of U(VI) measured from these samples were significantly different. The results show that distinctive excitation maxima appeared at approximately 220 and 280 nm for the silica suspension and silica sediment, respectively.

1. Introduction
2. Material and Experimental
    2.1 Material
    2.2 Spectroscopic instruments
3. Results and Discussion
    3.1 Time-resolved luminescence and lifetimeproperties
    3.2 Excitation properties
4. Conclusion
Acknowledgement
REFERENCES

• Euo Chang Jung(Korea Atomic Energy Research Institute) Corresponding Author
• Tae-Hyeong Kim(Korea Atomic Energy Research Institute)
• Hee-Kyung Kim(Korea Atomic Energy Research Institute)
• Hye-Ryun Cho(Korea Atomic Energy Research Institute)
• Wansik Cha(Korea Atomic Energy Research Institute)