Melamine cyanurate and melamine barbiturate self-assembled materials were prepared and studied by the electron paramagnetic resonance (EPR) spectroscopy, optical and scanning electron microscopy, X-ray powder diffraction (XRD). Both optical and electron microscopy show the formation of microscale crystalline particles possessing complex layered structures with a highly stable appearance. Both assemblies tend to form twinned crystals, which in the barbiturate case leads to multiple twinning in every particle. Optical microscopy shows high anisotropy and birefringence of both materials. XRD data represent a high crystallinity of melamine barbiturate and much lower for melamine cyanurate. Studied materials reveal the ability to incorporate radicals that correlate with their crystal structure quality. It is attributed to the structure-dependent stabilization of active radical superoxide species in structure voids or defects. In the example of melamine barbiturate, it is shown that the number of active paramagnetic centers increases at ca. 22% when a substance is irradiated with UV + Vis light. It reaches saturation in approximately 20 min, whereas only ca. 14% decrease was observed in a week.

中文翻译：

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二元三聚氰胺氢键自组装体的自由基活性

制备了三聚氰胺氰尿酸酯和三聚氰胺巴比妥酸酯自组装材料，并通过电子顺磁共振（EPR）光谱、光学和扫描电子显微镜、X射线粉末衍射（XRD）进行了研究。光学和电子显微镜均显示形成具有高度稳定外观的复杂层状结构的微米级结晶颗粒。两个组件都倾向于形成孪晶晶体，在巴比妥酸盐的情况下，这会导致每个粒子中出现多重孪晶。光学显微镜显示两种材料的高各向异性和双折射。XRD 数据表明三聚氰胺巴比妥酸盐的结晶度很高，而三聚氰胺氰尿酸盐的结晶度要低得多。研究的材料揭示了结合与其晶体结构质量相关的自由基的能力。这归因于结构空隙或缺陷中活性自由基超氧化物物质的结构依赖性稳定性。在三聚氰胺巴比妥酸盐的例子中，显示活性顺磁中心的数量在大约增加。当物质被紫外线 + 可见光照射时，为 22%。它在大约 20 分钟内达到饱和，而只有大约 20 分钟。在一周内观察到减少了 14%。