Silicon nanoparticles (SiNPs) are intriguing materials and their properties fascinate the broader scientific community; they are also attractive to the biological and materials science sub-disciplines because of their established biological and environmental compatibility, as well as their far-reaching practical applications. While characterization of the particle nanostructure can be performed using ²⁹Si solid-state nuclear magnetic resonance (NMR) spectroscopy, poor sensitivity due to low Boltzmann population and long acquisition times hinder in-depth studies of these potentially game-changing materials. In this study, we compare two dynamic nuclear polarization (DNP) NMR protocols to boost ²⁹Si sensitivity in hydride-terminated SiNPs. First, we assess a traditional indirect DNP approach, where a nitroxide biradical (AMUPol or bCTbk) is incorporated into a glassing agent and transferred through protons (e⁻ → ¹H → ²⁹Si) to enhance the silicon. In this mode, electron paramagnetic resonance (EPR) spectroscopy demonstrated that the hydride-terminated surface was highly reactive with the exogenous biradicals, thus decomposing the radicals within hours and resulting in an enhancement factor, ε, of 3 (T_B = 15 s) for the 64 nm SiNP, revealing the surface components. Secondly, direct DNP NMR methods were used to enhance the silicon without the addition of an exogenous radical (i.e., use of dangling bonds as an endogenous radical source). With radical concentrations <1 mM, ²⁹Si enhancements were obtained for the series of SiNPs ranging from 3 to 64 nm. The ability to use direct ²⁹Si DNP transfer (e⁻ → ²⁹Si) shows promise for DNP studies of these inorganic nanomaterials (ε = 6 (T_B = 79 min) for 64 nm SiNPs) with highly reactive surfaces, showing the sub-surface and core features. These preliminary findings lay a foundation for future endogenous radical development through tailoring the surface chemistry, targeting further sensitivity gains.

硅纳米颗粒（SiNPs）是令人着迷的材料，其性质吸引了更广泛的科学界。由于它们已建立的生物学和环境相容性以及广泛的实际应用，它们对生物和材料科学子学科也很有吸引力。尽管可以使用²⁹ Si固态核磁共振（NMR）光谱对颗粒纳米结构进行表征，但由于玻尔兹曼（Boltzmann）含量低和获取时间长而导致的灵敏度差，阻碍了对这些可能改变游戏规则的材料的深入研究。在这项研究中，我们比较了两种动态核极化（DNP）NMR方案以提高²⁹氢化物封端的SiNP中的Si敏感性。首先，我们评估传统间接DNP方法中，其中氮氧双基（AMUPol或bCTbk）被结合到装配玻璃剂和通过质子转移（E ^- → ¹ ħ→ ²⁹的Si），以提高硅。在这种模式下，电子顺磁共振（EPR）光谱表明，氢化物封端的表面与外源双自由基具有很高的反应性，从而在数小时内分解了自由基，并导致增强因子ε为3（T _B = 15 s）对于64 nm SiNP，揭示了表面成分。其次，直接DNP NMR方法用于增强硅，而无需添加外源自由基（即，使用悬挂键作为内源自由基源）。当自由基浓度<1 mM时，一系列SiNP从3到64 nm可获得^29种Si增强。使用直接²⁹ Si DNP转移（e ⁻ → ²⁹ Si）的能力显示出对这些无机纳米材料（ε= 6（T _B 对于具有高反应活性表面的64 nm SiNPs，= 79分钟），显示了亚表面和核心特征。这些初步发现为未来内源性自由基的发展奠定了基础，方法是定制表面化学，以进一步提高灵敏度为目标。