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X-Ray Diffraction and Multifrequency EPR Study of Radiation-Induced Room Temperature Stable Radicals in Octacalcium
D V Shurtakova1, B V Yavkin1, G V Mamin1
1Kazan Federal University, Kazan, Russia.
Radiation Research
|December 10, 2020
Summary
Octacalcium phosphate (OCP) irradiated with X- and gamma-rays reveals paramagnetic centers like CO33- and nitrogen-centered radicals. Radiation alters OCP phase composition and crystal structure, offering insights into mineralization and radiation effects.
Area of Science:
- Materials Science
- Solid State Chemistry
- Biomaterials Science
Background:
- Octacalcium phosphate (OCP) is a crucial intermediate in biogenic apatite formation, relevant to bone engineering and pathological calcification.
- Understanding OCP's response to radiation is vital for applications involving mineralization and biomaterial processing.
Purpose of the Study:
- To investigate the effects of X- and gamma-ray irradiation on Octacalcium phosphate (OCP) powders.
- To identify and characterize paramagnetic centers induced by irradiation using electron paramagnetic resonance (EPR).
- To analyze the impact of irradiation on the phase composition and crystal structure of OCP.
Main Methods:
- Synthesis of OCP powders via hydrolysis of dicalcium phosphate dihydrate.
- Irradiation of OCP samples using X-rays and gamma-rays.
- Electron paramagnetic resonance (EPR) spectroscopy at various microwave frequencies (9, 36, and 94 GHz).
- X-ray diffraction (XRD) analysis for phase composition and lattice parameter determination.
Main Results:
- Several paramagnetic centers, including H0, CO33-, CO2-, and nitrogen-centered radicals (likely NO32-), were identified and characterized by their spectroscopic parameters.
- Spectroscopic parameters of the nitrogen-centered radical in OCP differed significantly from those in hydroxyapatite.
- Gamma-ray irradiation led to the disappearance of minor phases, leaving only OCP and hydroxyapatite, and altered OCP crystal lattice parameters.
Conclusions:
- Irradiation of OCP induces distinct paramagnetic centers, providing potential markers for mineralization processes.
- Radiation influences the phase stability and structural integrity of OCP, impacting its suitability for biomaterial applications.
- EPR and XRD analyses offer a comprehensive method for studying radiation effects on calcium phosphates.
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