Substituted calcium phosphates (CaPs) are vital materials for the treatment of bone diseases and repairing and replacement of defects in human hard tissues. In this paper, we present some applications of the rarely used pulsed electron paramagnetic resonance (EPR) and hyperfine interaction spectroscopy approaches [namely, electron spin-echo envelope modulation (ESEEM) and electron–electron double-resonance detected nuclear magnetic resonance (EDNMR)] to investigate synthetic CaPs (hydroxyapatite, tricalcium, and octacalcium phosphate) doped with various cations (Li⁺, Na⁺, Mn²⁺, Cu²⁺, Fe³⁺, and Ba²⁺). These resonance techniques provide reliable tools to obtain unique information about the presence and localization of impurity centers and values of hyperfine and quadrupole tensors. We show that revealed in CaPs by EPR techniques, radiation-induced stable nitrogen-containing species and carbonate radicals can serve as sensitive paramagnetic probes to follow CaPs’ structural changes caused by cation doping. The most pulsed EPR, ESEEM, and EDNMR spectra can be detected at room temperature, reducing the costs of the measurements and facilitating the usage of pulsed EPR techniques for CaP characterization.

中文翻译：

---

用各种脉冲 EPR 光谱技术研究掺杂磷酸钙中的电子-核相互作用

取代磷酸钙（CaPs）是治疗骨病、修复和替代人体硬组织缺损的重要材料。在本文中，我们介绍了很少使用的脉冲电子顺磁共振 (EPR) 和超精细相互作用光谱方法的一些应用[即电子自旋回波包络调制 (ESEEM) 和电子-电子双共振检测核磁共振 (EDNMR) ] 研究掺杂各种阳离子（Li ⁺、Na ⁺、Mn ²⁺、Cu ²⁺、Fe ³⁺和 Ba ²⁺）的合成 CaP（羟基磷灰石、三钙和磷酸八钙））。这些共振技术提供了可靠的工具来获取关于杂质中心的存在和定位以及超精细和四极张量值的独特信息。我们表明，通过 EPR 技术在 CaPs 中揭示，辐射诱导的稳定含氮物质和碳酸盐自由基可以作为敏感的顺磁探针来跟踪由阳离子掺杂引起的 CaPs 结构变化。大多数脉冲 EPR、ESEEM 和 EDNMR 光谱可以在室温下检测到，从而降低测量成本并促进使用脉冲 EPR 技术进行 CaP 表征。