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Fluorescence-based spectroscopic sensor development for technetium in harsh environments

Branch, Shirmir D
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521192977626836

Abstract Details

2018, PhD, University of Cincinnati, Arts and Sciences: Chemistry.
The remediation of technetium-99 (99Tc) is an ongoing effort at many nuclear sites around the United States. A significant fraction of 99Tc in waste storage tanks at the Hanford Site in southeastern Washington is believed to exist as non-pertechnetate [Tc(CO)3]+. This fraction has impacted remediation efforts as they do not behave similarly to pertechnetate. Spectroscopy-based sensors provide rapid and economic techniques that would allow for the in situ detection of these [Tc(CO)3]+ species. These quantification techniques provide useful information for 99Tc speciation at nuclear sites. A fluorescence-based sensing platform was demonstrated for the quantification of [Tc(CO)3]+ in Hanford tank 241-AN-102. These species lack a spectroscopic signature distinguishable from other constituents in tank waste. To address this challenge, the [Tc(CO)3]+ species were converted into luminescent complexes containing a sensitizing ligand which can be measured using optical spectroscopy. Preliminary studies using this method, referred to as the pretreatment protocol, used [Re(CO)3]+ species as non-radioactive analogues. Several [Re(CO)3]+ complexes were synthesized and characterized in order to understand the spectroscopic behavior of the target species within the protocol. The pretreatment protocol involves diluting a simulated waste sample containing the non-emissive [Re(CO)3]+ species in a developer solution, which contains a high concentration of sensitizing ligand. The developer solution was designed to accomplish several things simultaneously, including rapid conversion of the [Re(CO)3]+ species into a luminescent complex and reducing matrix effects of the waste sample. After conversion to the luminescent complex, the emission was measured. The concentration of [Re(CO)3]+ in the simulated waste sample determined using the standard addition method was within 2.01% of the actual concentration. The pretreatment protocol was then used for the in situ quantification of [Tc(CO)3]+ in real waste samples. Several [Tc(CO)3]+ complexes were synthesized and characterized using spectroscopic techniques in order to understand the spectroscopic behavior of the target species converted within the real waste samples. The pretreatment protocol used for the [Re(CO)3]+ was tested using lab-synthesized [Tc(CO)3]+ in a simulated waste sample. The concentration determined by the protocol was within 27.7% of the actual concentration. The protocol was used for the in situ quantification of [Tc(CO)3]+ in a sample from tank AN-102. The concentration of [Tc(CO)3]+ was determined to be 1.84 × 10-5 M. Pathways for a more sensitive sensor can involve multimode detection techniques. The incorporation of electrochemistry and spectroscopy into one sensing platform was explored for its potential of detecting target species in environments with interfering species, such as [Tc(CO)3]+ in tank waste. An optically transparent electrode (OTE) chip was investigated for this purpose. The working electrode was composed of indium tin oxide (ITO); and the auxiliary and quasi-reference electrodes were composed of platinum. The quasi-reference platinum electrode was stabilized by plating the surface with Ag/AgCl. The electrochemical properties of the chip were characterized using cyclic voltammetry and Randles-Sevcik analyses. For spectroelectrochemical measurements, the chip was assembled into a thin-layer OTE (OTTLE) cell, which was characterized using absorption-based coulometry, and luminescence-based spectroelectrochemical modulation. The modulation of the analyte, [Ru(bpy)3]2+, yielded a detection limit of 3.6 × 10-8 M.
William Heineman, Ph.D. (Committee Chair)
Samuel A. Bryan, Ph.D. (Committee Member)
Thomas Ridgway, Ph.D. (Committee Member)
Laura Sagle, Ph.D. (Committee Member)
133 p.
Analytical Chemistry
technetium; fluorescence; spectroelectrochemistry; rhenium

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Citations

  • Branch, S. D. (2018). Fluorescence-based spectroscopic sensor development for technetium in harsh environments [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521192977626836

    APA Style (7th edition)

  • Branch, Shirmir. Fluorescence-based spectroscopic sensor development for technetium in harsh environments. 2018. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521192977626836.

    MLA Style (8th edition)

  • Branch, Shirmir. "Fluorescence-based spectroscopic sensor development for technetium in harsh environments." Doctoral dissertation, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521192977626836

    Chicago Manual of Style (17th edition)

ucin1521192977626836
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This open access ETD is published by University of Cincinnati and OhioLINK.