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The synthesis of a series of lanthanide trifluoroacetic acid (H-TFA) derivatives which contain only the TFA and its conjugate acid has been developed. From the reaction of Ln(N(SiMe3)2)3 with an excess amount of H-TFA, the products were identified as: [Ln(μ-TFA)3(H-TFA)2]n (Ln = Y, Ce, Sm, Eu, Gd, Tb, Dy), [Ln(μ-TFA)3(μ-H-TFA)]n·solv (Ln·solv = Pr·2 H-TFA, H3O+, Ho·2py, Er·py, Yb·py, H-TFA), 3[H][(TFA)La(μ-TFA)3La(TFA)(μ-TFA)2(μc-TFA)2]n ½(H2O) ½(H2O, H-TFA) (La·½(H2O) ½(H2O, H-TFA)), [(k2-TFA)Nd(μ-TFA)3]n·H-py+ (Nd·H-py+), [(py)2Tm(μ-TFA)3]n (Tm), or [Lu(μ-TFA)4Lu(μ-TFA)3·H3O+]n (Lu·H3O+). The majority of samples formed long chain polymers with 3 or 4 μ-TFA ligands. Tm was isolated with py coordinated to the metal, whereas Ho, Er, and Yb were isolated with py located within the lattice. Select samples from this set of compounds were used to generate nanomaterials under solvothermal (SOLVO) conditions using pyridine (py) or octylamine at 185 °C for 24 h. The SOLVO products were isolated as: (i) from py: La – fluocerite (LaF3, PDF 98-000-0214, R = 9.64%, 35(0) nm), Tb – terbium fluoride (TbF3, PDF 00-037-1487, R = 4.76%, 21(2) nm), Lu lutetium oxy fluoride (LuOF, PDF 00-052-0779, R = 8.24%, 8(2) nm); (ii) from octylamine: La – fluocerite/lanthanum oxide carbonate (LaF3, PDF 98-000-0214, R = 7.47%, 5(0) nm; La2O2(CO3), PDF 01-070-5539, R = 12.32%, 12(0) nm), Tb – terbium oxy fluoride (TbOF, PDF 00-008-0230, R = 7.01%, 5(0) nm); Lu – lutetium oxide (Lu2O3, PDF 00-012-0728, R = 6.52%, 6(1) nm).

A series of hydrated hexafluoro-iso-propoxide (hfip) lanthanide complexes was synthesized from the amide-alkoxide exchange reaction of the lanthanide bis-trimethylsilyl amide dissolved in toluene and an excess amount of H-hfip. The products were isolated and identified by single crystal X-ray diffraction as: [cis-(H2O)2(hfip)2Ln(μ-hfip)]2 (Ln = Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y), [trans-(H2O)2(hfip)2Sc(μ-hfip)]2 (Sc), [(H2O)2(hfip)2La2(μ-hfip)3(μ3-OH)]2 (La-OH), and [(H2O)(hfip)2Sc(μ-hfip)(μ-OH)(μ3-OH)Sc(H2O)(hfip)]2 (Sc-OH). All species were found to have bound H2O molecules thought to be present in the hfip. For the non-oxo species, dinuclear species were formed with one bridging and two terminal hfip ligands. The waters were cis-oriented for all samples but the smallest derivative, Sc, where they were located in trans arrangement. Oxo species were formed by ‘aged’ hfip and generated tetranuclear species (La-OH and Sc-OH) that possessed different ligand sets. Initial efforts to determine these compounds utility for LnF3 nanomaterial production were undertaken using amine solvent in solvothermal (SOLVO) or solution precipitation (SPPT) routes. LnF3 phases were noted but often this was mixed with the Ln(O,F) or Ln2O3 phases.

For enhanced or Engineered Geothermal Systems (EGS) geothermal brine is pumped to the surface via the production wells, the heat extracted to turn a turbine to generate electricity, and the spent brine re-injected via injection wells back underground. If designed properly, the subsurface rock formations will lead this water back to the extraction well as heated brine. Proper monitoring of these geothermal reservoirs is essential for developing and maintaining the necessary level of productivity of the field. Chemical tracers are commonly used to characterize the fracture network and determine the connectivity between the injection and production wells. Currently, most tracer experiments involve injecting the tracer at the injection well, manually collecting liquid samples at the wellhead of the production well, and sending the samples off for laboratory analysis. While this method provides accurate tracer concentration data at very low levels of detection, it does not provide information regarding the location of the fractures which were conducting the tracer between wellbores. Sandia is developing a high-temperature electrochemical sensor capable of measuring tracer concentrations and pH downhole on a wireline tool. The goal of this effort is to collect real-time pH and ionic tracer concentration data at temperatures up to 225 °C and pressures up to 3000 psi. In this paper, a prototype electrochemical sensor and the initial data obtained will be presented detailing the measurement of iodide tracer concentrations at high temperature and pressure in a newly developed laboratory scale autoclave.