Bulk Nuclear Hyperpolarization of Inorganic Solids by Relay from the Surface

NMR is a method of choice to determine structural and electronic features in inorganic materials, and has been widely used in the past, but its application is severely limited by its low relative sensitivity. We show how the bulk of proton-free inorganic solids can be hyperpolarized with a general strategy using impregnation dynamic nuclear polarization through homonuclear spin diffusion between low-γ nuclei. This is achieved either through direct hyperpolarization or with a pulse cooling cross-polarization method, transferring hyperpolarization from protons to heteronuclei at particle surfaces. We demonstrate a factor of 50 gain in overall sensitivity for the 119Sn spectrum of powdered SnO2, corresponding to an acceleration of a factor >2500 in acquisition times. The method is also shown for 31P spectra of GaP, 113Cd spectra of CdTe, and 29Si spectra of α-quartz.核磁共振（Nuclear Magnetic Resonance，NMR）是测定无机材料结构与电子特征的首选方法，过往已得到广泛应用，但因相对灵敏度较低，其应用受到严重限制。本研究提出一种通用策略，可实现大量无质子无机固体的超极化：通过低旋磁比核（low-γ nuclei）间的同核自旋扩散，结合浸渍式动态核极化技术完成。该策略可通过直接超极化实现，亦可采用脉冲冷却交叉极化方法，将质子的超极化转移至颗粒表面的异核。针对粉末状二氧化锡（SnO₂）的锡-119（¹¹⁹Sn）谱，本方法使整体灵敏度提升50倍，对应采集时间加速超过2500倍。该方法还在磷化镓（GaP）的磷-31（³¹P）谱、碲化镉（CdTe）的镉-113（¹¹³Cd）谱以及α-石英的硅-29（²⁹Si）谱中得到验证。