Para-hydrogen perspectives in hyperpolarized NMR

Abstract

The first instance of para-hydrogen induced polarization (PHIP) in an NMR experiment was serendipitously observed in the 1980s while investigating a hydrogenation reaction (Seldler et al., 1983; Bowers and Weitekamp, 1986, 1987; Eisenschmid et al., 1987) [1-4]. Remarkably a theoretical investigation of the applicability of para-hydrogen as a hyperpolarization agent was being performed in the 1980's thereby quickly providing a theoretical basis for the PHIP-effect (Bowers and Weitekamp, 1986) [2]. The discovery of signal amplification by a non-hydrogenating interaction with para-hydrogen has recently extended the interest to exploit the PHIP effect, as it enables investigation of compounds without structural alteration while retaining the advantages of spectroscopy with hyperpolarized compounds [5]. In this article we will place more emphasis of the future applications of the method while only briefly discussing the efforts that have been made in the understanding of the phenomenon and the development of the method so far.

Keywords: ALTADENA; Atomic magnetometers; Catalysis; Earth field; Gas phase imaging; Hyperpolarization; Immobilized catalysts; Inhomogeneous fields; Long-lived coherences; Low magnetic fields; MRI contrast; Metabolic imaging; Molecular imaging; NMR spectroscopy; Nanoparticles; PASADENA; PHIP; Para-hydrogen; Reaction monitoring; Remote detection; SABRE; Singlet states; Trace detection; Zero-field.