We demonstrate that NMR/DNP (Dynamic Nuclear Polarization) allows an unprecedented description of carbonate substituted hydroxyapatite (CHAp). Key structural questions related to order/disorder and clustering of carbonates are tackled using distance sensitive DNP experiments using ¹³C–¹³C recoupling. Such experiments are easily implemented due to unprecedented DNP gain (orders of magnitude). DNP is efficiently mediated by quasi one-dimensional spin diffusion through the hydroxyl columns present in the CHAp structure (thought of as “highways” for spin diffusion). For spherical nanoparticles and ϕ < 100 nm, it is numerically shown that spin diffusion allows their study as a whole. Most importantly, we demonstrate also that the DNP study at 100 K leads to data which are comparable to data obtained at room temperature (in terms of spin dynamics and line shape resolution). Finally, all 2D DNP experiments can be interpreted in terms of domains exhibiting well identified types of substitution: local order and carbonate clustering are clearly favored.

中文翻译：

---

羟基磷灰石：动态核极化的关键结构问题与解答

我们证明，NMR / DNP（动态核极化）可以对碳酸盐取代的羟基磷灰石（CHAp）进行前所未有的描述。与碳酸盐的有序/无序和聚类有关的关键结构性问题通过使用¹³ C– ^13的距离敏感DNP实验得以解决。C耦合。由于空前的DNP增益（数量级），此类实验很容易实现。DNP通过CHAP结构中存在的羟基色谱柱的准一维自旋扩散有效地介导（被认为是自旋扩散的“高速公路”）。对于spherical <100 nm的球形纳米粒子，数值显示自旋扩散使他们的研究成为一个整体。最重要的是，我们还证明了在100 K的DNP研究中得出的数据与在室温下获得的数据（在自旋动力学和线形分辨率方面）可比。最后，所有2D DNP实验都可以根据具有明确识别的取代类型的域进行解释：本地顺序和碳酸盐簇明显受到青睐。