Determination of Technetium and its Speciation by Surface Enhanced Raman Spectroscopy

Abstract

Technetium-99 (Tc) is an important radionuclide of concern, and there is a great need for its detection and speciation analysis in the environment. For the first time, we report that surface-enhanced Raman spectroscopy (SERS) is capable of detecting an inorganic radioactive anion, pertechnetate (TcO4-), at ~10-7 M concentration levels. More importantly, the technique allows the detection of various species of Tc such as oxidized Tc(VII) and reduced or complexed Tc(IV) species using gold nanoparticles as a SERS substrate. The primary Raman scattering band of Tc(VII) occurs at about 904 cm-1, whereas reduced Tc(IV) and its humic and EDTA complexes show scattering bands at about 866 and 870 cm-1, respectively. Results also indicate that Tc(IV)-humic complexes are unstable and re-oxidize to TcO4- upon exposure to oxygen. This study demonstrates that SERS could potentially offer a new tool and opportunity in studying Tc and its speciation and interactions in the environment at low concentrations.