Dynamic nuclear polarization of spherical nanoparticles
Dynamic nuclear polarization of spherical nanoparticles
复制标题
DOI：
10.1039/c3cp53095g
复制
发表时间：
2013-01-01
影响因子：
3.3
通讯作者：
Oschkinat, Hartmut
中科院分区：
文献类型：
--
作者：
Akbey, Uemit;Altin, Burcu;Oschkinat, Hartmut
采用改进的Stoeber法制备了不同粒径(约10~100 nm)的球形二氧化硅纳米粒子，并用动态核极化(DNP)增强核磁共振(NMR)谱对其进行了表征。这项研究包括对表面结合氨基酸及其痕量超分子结构的超灵敏检测，利用DNP使核磁共振灵敏度提高高达三个数量级。此外，表面上的硅核和芯(亚表面)中的体硅核的性质在原子分辨率下得到了表征。因此，我们对这些纳米粒子的表面化学有了独到的见解，这可能会导致改进它们的合理设计，以满足其作为催化剂或成像造影剂等有前途的应用的需要。测定了氨基酸与表面的非共价结合，这表明氨基酸不仅起到催化剂的作用，而且在形成过程中被结合到纳米颗粒中。结果，从表面和核心区只观察到三种不同的Q型二氧化硅信号。我们观察到DNP增强随着颗粒大小的变化而发生戏剧性的变化，非常小的颗粒(更适合体内应用)以最好的效率被超极化。尺寸为13 nm的纳米颗粒与尺寸为100 nm的纳米颗粒相比，其DNP增强效应几乎高出一个数量级。我们确定了球形纳米粒子从电子到核的极化转移的近似DNP穿透深度(类似于4.2或类似于5.7 nm)。对于较大的纳米颗粒，观察到更快的DNP极化建立。这种纳米粒子的高效超极化，如本工作中所实现的，可用于磁共振成像(MRI)等应用。
Spherical silica nanoparticles of various particle sizes (similar to 10 to 100 nm), produced by a modified Stoeber method employing amino acids as catalysts, are investigated using Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy. This study includes ultra-sensitive detection of surface-bound amino acids and their supramolecular organization in trace amounts, exploiting the increase in NMR sensitivity of up to three orders of magnitude via DNP. Moreover, the nature of the silicon nuclei on the surface and the bulk silicon nuclei in the core (sub-surface) is characterized at atomic resolution. Thereby, we obtain unique insights into the surface chemistry of these nanoparticles, which might result in improving their rational design as required for promising applications, e. g. as catalysts or imaging contrast agents. The non-covalent binding of amino acids to surfaces was determined which shows that the amino acids not just function as catalysts but become incorporated into the nanoparticles during the formation process. As a result only three distinct Q-types of silica signals were observed from surface and core regions. We observed dramatic changes of DNP enhancements as a function of particle size, and very small particles (which suit in vivo applications better) were hyperpolarized with the best efficiency. Nearly one order of magnitude larger DNP enhancement was observed for nanoparticles with 13 nm size compared to particles with 100 nm size. We determined an approximate DNP penetration-depth (similar to 4.2 or similar to 5.7 nm) for the polarization transfer from electrons to the nuclei of the spherical nanoparticles. Faster DNP polarization buildup was observed for larger nanoparticles. Efficient hyperpolarization of such nanoparticles, as achieved in this work, can be utilized in applications such as magnetic resonance imaging (MRI).