Publications [#328156] of Warren S. Warren

Journal Articles
  1. Zhou, Z; Yu, J; Colell, JFP; Laasner, R; Logan, A; Barskiy, DA; Shchepin, RV; Chekmenev, EY; Blum, V; Warren, WS; Theis, T, Long-Lived 13C2 Nuclear Spin States Hyperpolarized by Parahydrogen in Reversible Exchange at Microtesla Fields., The Journal of Physical Chemistry Letters, vol. 8 no. 13 (July, 2017), pp. 3008-3014 [doi] .

    Parahydrogen is an inexpensive and readily available source of hyperpolarization used to enhance magnetic resonance signals by up to four orders of magnitude above thermal signals obtained at ∼10 T. A significant challenge for applications is fast signal decay after hyperpolarization. Here we use parahydrogen-based polarization transfer catalysis at microtesla fields (first introduced as SABRE-SHEATH) to hyperpolarize 13C2 spin pairs and find decay time constants of 12 s for magnetization at 0.3 mT, which are extended to 2 min at that same field, when long-lived singlet states are hyperpolarized instead. Enhancements over thermal at 8.5 T are between 30 and 170 fold (0.02 to 0.12% polarization). We control the spin dynamics of polarization transfer by choice of microtesla field, allowing for deliberate hyperpolarization of either magnetization or long-lived singlet states. Density functional theory calculations and experimental evidence identify two energetically close mechanisms for polarization transfer: First, a model that involves direct binding of the 13C2 pair to the polarization transfer catalyst and, second, a model transferring polarization through auxiliary protons in substrates.