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Towards the Aqueous Chemistry of Copernicium


This project is focused on developing an aqueous extraction and separation device to perform atom-at-a-time studies of copernicium (Cn). This device will utilize microfluidics to decrease volume and extraction time that will allow for the study of either 285Cn (t¬1/2 = 29 s) or 283Cn(t¬1/2 = 4 s) isotopes. In addition to performing the first aqueous chemistry experiments on Cn, this device will also incorporate a position sensitive detection system allowing for lifetime confirmation of the decaying nucleus. Before Cn can be studied in a chemistry setup, an extraction needs to be developed that will provide meaningful results. To do this, the chemistry of Cn will be compared to its closest homologues: cadmium and mercury. Extractions were developed that would selectively extract each homologue into the organic phase. After finding ideal solution conditions for each homologue, these extractions would be repeated with Cn. The Cn results would then provide insight into its chemical behavior. If Cn extracts under the same conditions as its homologues then it will be said to share similar, metallic properties, and follow group 12 trends.

To understand the homologue extraction behavior, experiments were performed in various solutions to determine the conditions that yielded high extraction along with selectivity for that specific homologue. These extractions were done using radioactive isotopes, 109Cd for Cd and 203Hg for Hg. Several different organic ligands were tested for the selective extraction of these two homologues, with trioctylphosphine oxide (TOPO) being selected as the best ligand. The ideal aqueous conditions found for Cd were 0.5 M NH¬4SCN and an organic phase of 0.25 M TOPO in toluene. The selective extraction conditions for Hg were 0.05 M HCl and 0.25 M TOPO in toluene. These conditions were then used for extractions in a microfluidic setup.

A microfluidic setup was designed and tested to determine the optimum dimensions and flow rates that would eventually be used for atom-at-a-time studies. Parameters including: flow rate, flow ratio, tubing inner diameter, tubing length, membrane separator, and ligand concentration were tested. The only parameter that affected the extraction was the ligand concentration, which decreased separation efficiency in the setup above 0.20 M TOPO in toluene. This meant the microfluidic conditions used for the atom-at-a-time studies of Cn could be altered drastically to prioritize rapid extraction and separation without affecting the chemistry that is being performed.

To determine the position of the probable Cn decay a detector scheme was developed using liquid scintillation counting, photomultiplier tubes (PMT) and liquid lightguides. The nuclear decay would be converted to light by liquid scintillator chemicals. This would occur in a liquid lightguide, which is tubing capable of total internal reflection, and light would travel in both directions to a PMT. Due to light attenuation along the lightguide, the position of the decay can be determined by comparing the PMT pulse heights.

The combination of microfluidics and liquid lightguides was used to develop an aqueous chemistry setup that will eventually be utilized to perform atom-at-a-time aqueous chemistry on Cn. This setup will allow for studying other short-lived transactinide elements beyond Cn and broaden the chemistry knowledge on these rare and difficult to study elements.

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