School of Materials Science and Engineering UNSW Sydney, E10 Gate 2 Avenue, UNSW Sydney, Kensington NSW 2052, Australia.
Mark Wainwright Analytical Centre UNSW Sydney, Chemical Sciences Building, High Street, UNSW Sydney, Kensington NSW 2052, Australia.
J Colloid Interface Sci. 2021 Dec 15;604:327-339. doi: 10.1016/j.jcis.2021.06.171. Epub 2021 Jul 2.
The air-solution interface of supersaturated calcium hydrogen carbonate (Ca(HCO)) represents the highest saturation state due to evaporation/CO-degassing, where calcite crystals are expected to nucleate and grow along the interface. Hence, it should be possible to form a free-standing mineral-only calcium carbonate (CaCO) microfilm at the air-solution interface of Ca(HCO). The air-solution interface of phosphate buffered saline (PBS) could represent a phase boundary to introduce a hybrid microstructure of CaCO and carbonate-rich dicalcium hydroxide phosphate (carbonate-rich hydroxylapatite).
Supersaturated Ca(HCO) was prepared at high pressure and heated to form CaCO microfilms, which were converted to bone-like microfilms at the air-solution interface of PBS by dissolution-recrystallisation. The microfilms were characterised by scanning electron microscopy, 3D confocal microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, laser Raman microspectroscopy, and X-ray photoelectron spectroscopy. An in situ X-ray diffraction (XRD) system that simulates the aforementioned interfacial techniques was developed to elucidate the microfilms formation mechanisms.
The CaCO and bone-like microfilms were free-standing, contiguous, and crystalline. The bone-like microfilms exhibited a hybrid structure consisting of a surface layer of remnant calcite and a carbonate-rich hydroxylapatite core of plates. The present work shows that the air-solution interface can be used to introduce hybrid microstructures to mineral microfilms.
过饱和的碳酸氢钙（Ca(HCO))的气-液界面由于蒸发/CO 脱气而达到最高饱和度，碳酸钙晶体预计沿着界面成核和生长。因此，应该有可能在 Ca(HCO)的气-液界面形成独立的纯矿物碳酸钙（CaCO）薄膜。磷酸盐缓冲盐水（PBS）的气-液界面可以作为引入 CaCO 和富碳酸盐二水合羟磷灰石（富碳酸盐羟基磷灰石）混合微观结构的相界。
在高压下制备过饱和 Ca(HCO)，并加热形成 CaCO 薄膜，然后通过溶解-再结晶将其转化为 PBS 气-液界面处类似骨的薄膜。通过扫描电子显微镜、3D 共焦显微镜、原子力显微镜、傅里叶变换红外光谱、激光拉曼微光谱和 X 射线光电子能谱对薄膜进行了表征。开发了一种原位 X 射线衍射（XRD）系统，模拟上述界面技术，以阐明薄膜形成机制。
CaCO 和类似骨的薄膜是独立的、连续的和结晶的。类似骨的薄膜呈现出混合结构，表面层为残余方解石，核心为板状富碳酸盐羟基磷灰石。本工作表明，气-液界面可用于向矿物薄膜引入混合微观结构。
