Dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR) offers a promising route to studying local atomic environments at the surface of both crystalline and amorphous materials. We take advantage of unpaired electrons due to defects close to the surface of the silicon microparticles to hyperpolarize adjacent ¹H nuclei. At 3.3 T and 4.2 K, we observe the presence of two proton peaks, each with a linewidth on the order of 5 kHz. Echo experiments indicate a homogeneous linewidth of $\sim 150-300$ Hz for both peaks, indicative of a sparse distribution of protons in both environments. The high frequency peak at 10 ppm lies within the typical chemical shift range for proton NMR, and was found to be relatively stable over repeated measurements. The low frequency peak was found to vary in position between −19 and −37 ppm, well outside the range of typical proton NMR shifts, and indicative of a high-degree of chemical shielding. The low frequency peak was also found to vary significantly in intensity across different experimental runs, suggesting a weakly-bound species. These results suggest that the hydrogen is located in two distinct microscopic environments on the surface of these Si particles.

动态核极化（DNP）增强核磁共振（NMR）为研究晶体和非晶态材料表面的局部原子环境提供了一条有希望的途径。我们利用由于靠近硅微粒表面的缺陷而产生的不成对电子来使相邻的¹ H核超极化。在3.3 T和4.2 K处，我们观察到存在两个质子峰，每个质子峰的线宽约为5 kHz。回声实验表明均匀线宽为$〜150-300$两个峰的Hz，表示两种环境中质子的稀疏分布。10 ppm处的高频峰位于质子NMR的典型化学位移范围内，并且在重复测量后发现相对稳定。发现低频峰的位置在-19和-37 ppm之间变化，远远超出典型的质子NMR位移范围，并且指示出高度的化学屏蔽作用。在不同的实验运行中，低频峰的强度也有显着变化，表明存在弱结合物种。这些结果表明，氢位于这些Si颗粒表面的两个不同的微观环境中。