Quantification of Uncoupled Spin Domains in Spin-Abundant Disordered Solids

Area of Science:

• Materials Science
• Solid-State Chemistry
• Analytical Chemistry

Background:

• Minor heterogeneous phases significantly impact material properties.
• Characterizing these minor phases, especially dilute, uncoupled nuclei, is challenging.
• Existing methods may require impractically long signal averaging times.

Purpose of the Study:

• To develop a Nuclear Magnetic Resonance (NMR) strategy for quantifying minor heterogeneous sample regions.
• To amplify NMR signals from dilute, uncoupled nuclei in complex materials.
• To accurately determine the concentration of residual graphitic carbon in poly(carbon monofluoride).

Main Methods:

• Utilized solid-state NMR with Carr-Meiboom-Purcell-Gill (CPMG) acquisition.
• Dephased NMR signals from coupled nuclei while amplifying signals from uncoupled nuclei.
• Quantified residual graphitic carbon using 13C CPMG NMR in poly(carbon monofluoride) samples.

Main Results:

• Achieved signal amplification of one to two orders of magnitude for uncoupled nuclei.
• Determined the concentration of uncoupled spin regions by estimating CPMG signal amplification.
• Established a detection limit better than 0.05 mol% for graphitic carbon.

Conclusions:

• The developed NMR strategy effectively quantifies minor heterogeneous phases containing dilute, uncoupled nuclei.
• This method allows for accurate determination of low-concentration components, such as residual graphitic carbon.
• The technique offers a significant improvement over conventional methods requiring extensive signal averaging.