Fossilization of bone studied in-operando by fluid-cell Raman spectroscopy

骨骼化石是重建地球脊椎动物生活史的重要地球化学档案。然而，骨骼的埋藏可以改变这些信息，甚至完全破坏它。在受控边界条件下进行骨埋藏的实验研究是必要的，特别是为了了解与早期石化相关的过程，因为这些过程似乎对骨骼的保存至关重要。在共聚焦高光谱拉曼光谱（RS）的帮助下，可以获得对骨分离的介观部分反应和运输过程的新见解。该技术可以在微米尺度和高温下使用特殊的流体电池（FC）对流体驱动反应过程中的移动反应界面进行实时成像，而无需中断反应，即在操作中进行。FC-RS可以提供丰富的信息，如相组成、结晶度、结晶尺寸、界面应变，同时还可以提供溶液中含水物质的浓度，甚至可以从中估计局部的pH值。此外，由于同位素移位，当使用同位素富集的前驱体材料时，FC-RS可以在operando中跟踪固体和水分子之间的氧和氢同位素交换。对牙本质和硅酸盐玻璃的初步实验结果显示，这种在操作中FC-RS研究的可行性的有趣证据。在这两种情况下，这些实验的结果都揭示了机制和整体反应动力学的不可预见的短期变化。他们还表明，当使用18-O和2-H作为示踪剂时，可以研究和量化诸如再平衡反应和分子水通过骨的潜在扩散等动态现象。第一次测量表明，在激光诱导光致发光/拉曼光谱的帮助下，甚至有可能跟踪Nd3+在operando骨骼中的微量扩散。因此，FC-RS为深入了解骨水反应提供了全新的可能性。该项目的主要目标是获得更深层次的机制理解(i)骨磷灰石的再结晶，（ii）骨矿化，（iii）胶原蛋白降解，以及最终（iv）作为pH值，溶液组成（含碳酸盐，磷酸盐和F）和温度的函数的可靠，定量，动力学信息，确定运输和反应过程。然而，最初的主要重点将放在模拟近地表条件的室温实验上。

Fossil bones represent an important geochemical archive for the reconstruction of the life history of vertebrates on Earth. However, the taphonomy of the bones can change this information or even destroy it completely. Experimental studies of bone taphonomy under controlled boundary conditions are necessary, in particular to understand the processes associated with early fossilization, as these appear to be critical to the preservation of bones. New insights into the mesoscopic partial reactions and transport processes of bone taphonomy can be gained with the help of confocal hyperspectral Raman spectroscopy (RS). This technique enables real-time imaging of moving reaction interfaces during fluid-driven reactions on the micrometre scale and at elevated temperatures using special fluid cells (FC) without the need to interrupt the reaction, i.e., in operando. FC-RS can provide a wealth of information, such as the phase composition, crystallinity, crystallite size, interfacial strain, and at the same time the concentrations of aqueous species in the solution, from which even the local pH value can be estimated. In addition, due to the isotope shift, the FC-RS enables the exchange of oxygen and hydrogen isotopes between solids and aqueous molecular species to be tracked in operando when isotopically enriched precursor materials are used. Intriguing evidence for the feasibility of such in-operando FC-RS studies emerges from the results of initial experiments on dentin and silicate glasses. The results of these experiments have in both cases revealed unforeseen, short-term changes in the mechanism and the overall reaction kinetics. They also show that dynamic phenomena such as re-equilibration reactions and potentially the diffusion of molecular water through bone can be studied and quantified when 18-O and 2-H are used as tracers. First measurements indicate that it will even be possible to follow the diffusion of traces of Nd3+ in bones in-operando with the help of laser-induced photoluminescence/Raman spectroscopy. The FC-RS therefore opens up completely new possibilities to get deeper insights into bone-water reactions. The main goals of the proposed project are to gain a deeper mechanistic understanding of (i) the recrystallization of bone apatite, (ii) bone mineralization, (iii) collagen degradation, and ultimately (iv) reliable, quantitative, kinetic information about the identified transport and reaction processes as a function of the pH value, the composition of the solution (containing carbonate, phosphate, and F) and the temperature. However, the main focus will initially be on room temperature experiments that simulate near-surface conditions.