利用密度泛函理論討論置換二價金屬離子對氫氧基磷灰石表面性質的影響

The influence of substituting divalent metal ions on the surface properties of Hydroxyapatite by Density Functional Theory Calculation

楊祖翔(TSU-HSIANG YANG)

指導教授 ： 林子仁

中原大學/工學院/化學工程學系/碩士(2022年)

https://doi.org/10.6840/cycu202201426

摘要

隨著經濟發展造成地球生態的破壞，環保意識提高，促使越來越多人投入到環境修復以及環保材料的研究中。氫氧基基磷灰石（Hydroxyapatite,HAP）原是一種生醫材料，但由於其良好的熱穩定性、酸鹼可調節性及離子吸附和離子交換性能，為很有前景的環境修復材料之一，它可以通過離子吸附和交換去除環境中的有毒金屬，而HAP離子摻雜機理以及參雜後性能的理解變得相對重要，這也是此研究的方向。由於實體實驗環境與材料有時難以製備及控制，我們採用量子化學計算模擬進行實驗，利用密度泛函理論來計算HAP金屬離子摻雜後之表面性質。將HAP (001)、(010)兩表面模型中摻雜鋅、鎘、汞、鉛和錫五種二價金屬離子置換原本的鈣離子而後計算表面交換能量以及表面能量進行比對，並利用福井函數(Fukui function)觀察表面離子在離子置換後對反應性之影響。
可以發現在真空與水溶液環境下各離子在HAP (001)與HAP (010)表面交換能量為錫>鉛>汞>鎘>鋅。而離子交換的難易程度似乎與離子半徑呈現正相關。而在表面能量的計算上，我們利用各表面模型進行拉伸以及壓縮邊長至3%，接著利用能量和表面積的關係擬合二次曲線並計算表面能量。在沒有參雜的表面，HAP (001)的表面能都比HAP (010)高不論是在真空和水溶液環境下。在水溶液環境下HAP (010)表面離子分布較為鬆散使水分子能夠進入嵌入表面與磷酸跟做更多接觸導致大幅增加其固體/液體表面能。HAP真空模型及單層水分子模型鋅、鎘、汞、鉛、錫離子的摻雜都能夠明顯增加(010)表面之表面能量，但對於(001)表面則無太大影響。值得注意的是，在水溶液環境且有參雜的條件下，(010)表面能量變得比(001)還要高。

關鍵字

氫氧機磷灰石 ； 表面交換能量 ； 表面能量 ； 福井函數

並列摘要

Because the destruction of the earth's ecology caused by economic development, the awareness of environmental protection has increased. Lots of people start to invest the research in environmental restoration and environmental protection materials. Hydroxyapatite (HAP) is often considered as a biomedical material. Due to its good thermal stability, acid-base adjustability, and ion adsorption and ion exchange properties, it is a promising environmental bioremediation material. HAP is able to remove toxic metals in the environment through ion adsorption and exchange. The understanding of the surface property of HAP after ion exchange becomes important. Because it is hard to control experimental environment and materials in aqueous environment, we used density functional theory (DFT) calculations to study the surface properties of HAP before and after ion exchange.
We created vacuum and water-monolayer surface models for HAP (001) and (010). All surface models were exchanging surface calcium ions with five divalent metal ions, Zinc, Cadmium, Mercury, Lead and Tin. Then, the ion exchange energy and surface energy were calculated and compared. At vacuum state, the ion exchange is in the following order Tinc>Lead>Cadmium>Mercury>Zinc, which is highly related to the ionic radius.
Regarding to the surface energy, we stretched and compressed the surface from 1% to 3%. The energy-area curve was fit by quadratic curve and then the surface energies were evaluated. In vacuum and aqueous environment, the pristine HAP (001) surface energy was higher than the pristine HAP (010) surface. Because of the ions on the HAP (010) surface does not close packed, the water molecules are go into the void space at the surface and strongly interact with the phosphate ions. Therefore, the decrease from the solid/vacuum to solid/liquid interface energy of HAP (010) surface was less than that of HAP (001) surface. The dopant increased the interface energy of HAP (010) surface, but did not show significant effect on HAP (001) surface no matter in vacuum or aqueous environment, Interestingly, the surface energy of doped HAP (010) surface is higher than doped HAP (001) surface in aqueous environment.

並列關鍵字

Hydroxyapatite ； surface exchange energy ； surface energy ； Fukui function

參考文獻

參考文獻

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