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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Surface structure, hydration, and cationic sites of nanohydroxyapatite: UHR-TEM, IR, and microgravimetric studies
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Surface structure, hydration, and cationic sites of nanohydroxyapatite: UHR-TEM, IR, and microgravimetric studies

机译：纳米羟基磷灰石的表面结构，水合和阳离子位点：UHR-TEM，IR和微重力研究

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摘要

A multi-technique study devoted to investigate the surface features of nanosized hydroxyapatite (HA) was carried out. UHR-TEM observation provided evidence that HA nanoparticles are constituted by a crystalline core, elongated in the direction of the crystallographic c-axis, coated by an amorphous layer 1-2 nm thick. By means of IR spectroscopy and microgravimetry, the amount of water and hydroxy groups on the surface was evaluated. For the as-prepared material, it was found that the first hydration layer is mainly constituted by H2O molecules interacting through a coordinative bond with Ca2+ in a 1:1 ratio, while hydroxy groups account only for ca. 20% of surface hydration species. Outgassing at increasing temperatures up to 300 degrees C resulted in a complete surface dehydration, accompanied by a decrease of the capability to readsorb water. Possible changes of the local structure of surface Ca2+ ions were probed by IR spectra of adsorbed CO. The combination of these data with rehydration tests suggested that a significant part of surface Ca2+ ions, once dehydrated, can undergo a relaxation inward the surface, progressively more irreversible as the outgassing temperature increases.
机译：进行了一项旨在研究纳米羟基磷灰石（HA）表面特征的多技术研究。 UHR-TEM观察提供的证据表明，HA纳米粒子由结晶核构成，该结晶核在晶体学c轴方向上伸长，并被1-2 nm厚的非晶层覆盖。通过红外光谱和微重力法，评估表面上的水和羟基的量。对于所制备的材料，发现第一水合层主要由H 2 O分子构成，该H 2 O分子通过与Ca 2+的配位键以1：1的比例相互作用，而羟基仅占ca。表面水合物种的20％。在高达300摄氏度的升高温度下的脱气导致表面完全脱水，同时降低了重新吸收水的能力。通过吸附的CO的红外光谱探测了表面Ca2 +离子局部结构的可能变化。这些数据与再水化试验的结合表明，表面Ca2 +离子的很大一部分一旦脱水，便会向内向内松弛，并逐渐释放。随着脱气温度的升高不可逆转。

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