Surface-Mediated Hyperpolarization of Liquid Water from Parahydrogen

This article reports the discovery of surface-mediated parahydrogen-induced alignment of the proton magnetic moments in liquid water as well as methanol and ethanol. In this SWAMP (surface waters are magnetized by parahydrogen) effect, the spin polarization of the solvent protons is enhanced simply by the bubbling of parahydrogen through a suspension of Pt3Sn intermetallic nanoparticles (iNPs) encapsulated within a protectective mesoporous silica shell (Pt3Sn@mSiO(2)). The conversion of singlet spin order into magnetization is mediated by symmetry-breaking interactions on the surface of the iNPs. Stimulated emission NMR signals of the exchangeable hydroxy protons are observed. Non-exchangeable methyl or methylene protons are also hyperpolarized, an observation that provides insight into the molecular mechanism. SWAMP has a myriad of potential applications, ranging from low-field MRI to drug discovery.