Nuclear spin polarization transfer across an organic-semiconductor interface

Abstract

Motivated by Tycko’s proposal to harness optically pumped nuclear spin polarization for the enhancement of nuclear magnetic resonance (NMR) signals from biological macromolecules, we investigate the transfer of thermal nuclear spin polarization between H1 or F19 in an organic overlayer and P31 at the surface of micron-sized InP particles by Hartmann–Hahn cross polarization. Comparison with analytic and numerical models indicates that the total quantity of polarization transferred across the semiconductor-organic interface is limited by the relatively short room-temperature H1 T1ρ (11 ms) and the slow diffusion of nuclear spin polarization in the semiconductor. Models and spin-counting experiments indicate that we are able to transfer approximately 20% of the total nuclear spin polarization originating in the organic overlayer to the semiconductor, supporting the feasibility of transferred optically pumped NMR.