Northwestern University, Department of Materials Science and Engineering, 2220 Campus Drive, Evanston, Illinois 60208, USA.
Nature. 2011 Jan 13;469(7329):194-7. doi: 10.1038/nature09686.
Biological organisms possess an unparalleled ability to control the structure and properties of mineralized tissues. They are able, for example, to guide the formation of smoothly curving single crystals or tough, lightweight, self-repairing skeletal elements. In many biominerals, an organic matrix interacts with the mineral as it forms, controls its morphology and polymorph, and is occluded during mineralization. The remarkable functional properties of the resulting composites-such as outstanding fracture toughness and wear resistance-can be attributed to buried organic-inorganic interfaces at multiple hierarchical levels. Analysing and controlling such interfaces at the nanometre length scale is critical also in emerging organic electronic and photovoltaic hybrid materials. However, elucidating the structural and chemical complexity of buried organic-inorganic interfaces presents a challenge to state-of-the-art imaging techniques. Here we show that pulsed-laser atom-probe tomography reveals three-dimensional chemical maps of organic fibres with a diameter of 5-10 nm in the surrounding nano-crystalline magnetite (Fe(3)O(4)) mineral in the tooth of a marine mollusc, the chiton Chaetopleura apiculata. Remarkably, most fibres co-localize with either sodium or magnesium. Furthermore, clustering of these cations in the fibre indicates a structural level of hierarchy previously undetected. Our results demonstrate that in the chiton tooth, individual organic fibres have different chemical compositions, and therefore probably different functional roles in controlling fibre formation and matrix-mineral interactions. Atom-probe tomography is able to detect this chemical/structural heterogeneity by virtue of its high three-dimensional spatial resolution and sensitivity across the periodic table. We anticipate that the quantitative analysis and visualization of nanometre-scale interfaces by laser-pulsed atom-probe tomography will contribute greatly to our understanding not only of biominerals (such as bone, dentine and enamel), but also of synthetic organic-inorganic composites.
生物有机体具有无与伦比的控制矿化组织结构和性质的能力。例如，它们能够引导单晶的平滑弯曲形成，或者形成坚韧、轻巧、可自我修复的骨骼元素。在许多生物矿化中，有机基质在矿物形成过程中与其相互作用，控制其形态和多型性，并在矿化过程中被包裹。由此产生的复合材料的卓越功能特性，如出色的断裂韧性和耐磨性，可以归因于在多个层次上存在有机-无机埋置界面。在新兴的有机电子和光伏混合材料中，分析和控制这种纳米级的埋置有机-无机界面也至关重要。然而，阐明埋置有机-无机界面的结构和化学复杂性对最先进的成像技术提出了挑战。在这里，我们展示了脉冲激光原子探针断层成像技术能够揭示海洋软体动物 chiton Chaetopleura apiculata 牙齿中纳米晶磁铁矿（Fe3O4）周围直径为 5-10nm 的有机纤维的三维化学图谱。值得注意的是，大多数纤维与钠或镁共定位。此外，这些阳离子在纤维中的聚集表明存在以前未检测到的结构层次的分级。我们的结果表明，在 chiton 牙齿中，单个有机纤维具有不同的化学成分，因此在控制纤维形成和基质-矿物相互作用方面可能具有不同的功能作用。原子探针断层成像技术能够通过其在整个元素周期表上的高三维空间分辨率和灵敏度来检测这种化学/结构异质性。我们预计，通过激光脉冲原子探针断层成像技术对纳米级界面的定量分析和可视化将极大地促进我们对生物矿化（如骨骼、牙本质和牙釉质）以及合成有机-无机复合材料的理解。
