生物利用無機礦物作為身體結構之組成，並藉由對礦物生成機制的調控，得以使同樣的化學組成成分變化出多樣的型態和材料性質，滿足生存所需功能並達到演化優勢。在過去20年間，研究已發現大多數生物礦化並非單純從溶液中析出晶體，而是藉由先形成如非晶碳酸鈣 (Amorphous Calcium Carbonate, ACC) 等非晶態固體作為前驅物，再進行後續的晶體生長。透過控制非晶態前驅物的形成與成長環境，生物能夠將前驅物轉變為不同晶型和微結構的生物礦物。
在過去研究中，已知ACC可以透過粒子附著方式，作為生物礦化的前驅物。然而，對於生物是通過何種方式調控ACC結晶晶型還有很多未知的部分。因此，本研究將透過使用不同晶型的生長基板和控制溶液環境中的添加劑，探討ACC在基板和添加劑的影響下，會如何產生不同之晶型選擇。
本研究中利用CaCl2溶液和Na2CO3溶液在不同的結晶基板上混合，並使用MgCl2作為添加劑，以觀察Mg2+以及基板之晶格排列對於ACC晶型選擇的影響與兩者間的關係。結果顯示沒有添加劑的環境，ACC會轉變為與基板相同晶型之結晶，逐步提升Mg2+濃度，晶型選擇則會由基板主導轉為溶液環境主導。此外，由於Mg2+的添加涉及混合溶液pH值的差異，而我們發現此因素顯著影響結晶結果，因此我們也針對不同pH值下生成的ACC結晶過程差異進行探討。發現不同pH值環境會生成大小各異的ACC，大尺寸的ACC會經歷溶解、再結晶，並在此過程中受Mg2+影響劇烈。而小尺寸ACC更傾向做固-固轉變，結晶受基板影響更大。
本研究探討了生長基板之晶格排列與溶液環境如何影響ACC前驅物之晶型選擇，以及ACC結晶機制與前驅物尺寸之關聯性，對於理解生物礦化機制及設計仿生晶體材料具有重要參考價值。

Over the past two decades, research in biomineralization has discovered new crystallization pathways via amorphous precursors, such as the transient form of amorphous calcium carbonate (ACC). Organisms control the phase transformation of ACC into crystalline calcium carbonate biominerals to produce biological materials with distinct morphologies and fulfill functions to gain evolutionary advantages. The crystallization of ACC involves classical and nonclassical pathways, and previous reports have shown that both the solution chemistry and the substrate crystallinity can affect the crystallization process, respectively. However, research combining the two factors has been limited. Therefore, this study aims to investigate the how different crystalline substrates and Mg concentrations affect polymorph selection of ACC.
In this study, ACC nanoparticles were synthesized by mixing CaCl2 and Na2CO3 solutions on crystalline CaCO3 substrates to allow overgrowth, with MgCl2 introduced as an additive. We used Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) to examine the crystallization results on the substrates. By comparing different setups, we are able to show the competing effects between the substrate-dominated epitaxial growth and the solution-dominated Mg inhibition. Additionally, we discovered that solution pH also changes the dominating crystallization pathway by influencing the ACC particle size.
This research focuses the competition between growth substrate arrangement and the solution environment in dictating the polymorph selection of ACC precursors. Furthermore, it reveals how precursors of different sizes yield distinct crystallization outcomes through differing crystallization mechanisms. These findings offer valuable insights into understanding biomineralization mechanisms and designing biomimetic materials.

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