Flow 1H Dynamic Nuclear Polarization Studies in Normal Liquids and Supercritical Fluid Carbon Dioxide

Flow 1H dynamic nuclear polarization (DNP) experiments of small probe molecules (i.e. chloroform and benzene) were conducted in normal liquids (i.e. neat benzene, deuterated benzene, chloroform) and supercritical fluid CO₂. Initial data collected on the 14N NMR line width of acetonitrile in normal liquids and SF CO₂ resulted in a 2-6 factor increase in the molecular motion of the molecule in the SF--the result of which corresponds to the expected factor increase in DNP signal enhancements in the low viscosity fluid. Observed DNP signal enhancements were 2-5 times greater in the supercritical fluid versus the normal liquids in both the solid-liquid intermolecular transfer (SLIT) and liquid-liquid intermolecular transfer (LLIT) experiments. Significant changes in the electron spin-spin (T1S) and spin-lattice (T2S) relaxation times of the nitroxide radical TEMPO in neat benzene, deuterated benzene, and SF CO₂ were noted; the T1ST2S product (calculated from DNP saturation plots) of the LLIT DNP data were compared. Due to the high pressures and elevated temperatures necessary for optimum flow DNP with SF CO₂ (e.g. P = 2310 psi, T = 313 K), high pressure flow cells were developed (and, also, adapted to a commercially available probe in the NMR regime) using PEEK (polyetheretherketone) material.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2002

Author dc:creator

• Salido, Sandra I.

Chair dc:contributor.committeechair

• Dorn, Harry C.

Committee members dc:contributor.committeemember

• Anderson, Mark R.
• Wightman, James P.
• Taylor, Larry T.
• Tanko, James M.

• Proton
• Polarization
• Supercritical fluid
• Nuclear
• Dynamic

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-03072003-124722

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/26380