There are coupling and decoupling among the layers of condensed matter, and the critical phenomenon is the key to understand the decoupling between the layers. Under unconventional conditions such as sub-supercritical, the structure of the reactants shows different changes, and some reactions that are difficult to occur under conventional conditions can occur smoothly, thus forming rich metastable phase, singular phase, and superconducting equivalence. This paper focuses on the variation and evolution of multi‑level condensed‑matter structures under subcritical and supercritical hydrothermal conditions. Firstly, the structure of water molecules is briefly introduced. Structural transformations of reactant molecules and compositional‑structural features of products are then discussed from three perspectives: homoelemental systems (carbon), hetero‑elemental systems (Si‑O garnet), and multi‑elemental systems (Ca‑Si‑O tobermorite). The structural correlations during hydrothermal crystallization‑transformation are elucidated, aiming to provide certain insights for hydrothermal synthetic chemistry. Furthermore, condensed‑matter structures of atomic‑ and molecular‑scale devices are summarized, including solid‑state atomic‑scale pn junctions, neuronal ionic junctions, and the surface atomic‑rotation catalytic model. Finally, it is predicted that subcritical and supercritical hydrothermal synthesis technologies will offer practical inspirations for fields such as tunable design of “neuron‑mimicking” semiconductor materials, “subconscious” biological image sensing, and the construction of atomic‑rotation catalytic models.
Contents
1 Introduction
2 The Structure of Water Molecules Under Subcritical/Supercritical Conditions
3 Changes and Evolution of Multi-level Condensed Matter Structures Under Subcritical and Supercritical Hydrothermal Conditions
3.1 Condensed‑Matter Structures of Homoelemental Species
3.2 Condensed‑Matter Structures of Two Distinct Elements
3.3 Condensed‑Matter Structures of Multi‑Elemental Systems
3.4 Fabrication of Porous, Hierarchical and Heterostructured Architectures
4 Condensed Matter Structures of Devices at the Atomic and Molecular Scale
4.1 Structure of Solid Atomic-scale p-n Junctions
4.2 Network Structure of Neuronal-Ion Junctions
4.3 Atomic Rotation Catalysis Model on Material Surfaces
5 Conclusion and Outlook
5.1 Tunable Design of “Neuron‑Mimicking” Semiconductor Materials
5.2 “Subconscious” Biological Image Sensing and Ionic p‑n Junctions
对于分级结构体系,微-纳复合结构、一维/二维纳米单元组装形成的三维多级结构,本质源于初级纳米晶的可控聚集与定向组装。亚/超临界水热环境显著提升了晶粒的扩散能力,促使纳米晶通过特定晶面择优贴合、晶格匹配重构,通过消除高能晶面降低体系自由能,自发沿低指数晶面定向拼接,最终构筑形貌规整、层级清晰的微纳分级组装结构。例如,亚临界水热合成TiO2花状微米球,钛源(TBOT、TiOSO4)前驱体水解生成无定形 TiO (OH)2;亚临界下溶解再沉淀,生成大量二维锐钛矿纳米片,高扩散条件下定向附着,自组装成三维花状微球[78]。
2015年,日本千叶大学Takeshi Murata课题组在V1-ATP酶的相关晶体结构与旋转机制研究中发现V1-ATP酶的旋转机制模型。2016年诺贝尔化学奖得主Ben L. Feringa教授团队受自然界生命体旋转马达启发,开创性地设计并合成了世界上首个能够单向旋转的人工分子马达。2025年,中山大学赵德鹏教授研究团队通过向联苯分子骨架引入点手性和螺旋手性,成功设计出一种化学能驱动的旋转分子马达。该分子马达能够围绕联苯碳碳单键实现将近100%单向360°的旋转。
利用原位扫描隧道显微镜(STM)和原子力显微镜,能够获取催化材料界面结构的详细信息,对单个吸附原子与吸附分子的动态行为进行定量研究。将这类表征方法的时间分辨率提升至毫秒量级后,电极表面的高动态过程便能被直接观测。2000年,德国基尔大学实验和应用物理研究所Olaf M. Magnussen教授课题组提出了一种新型原位STM方法,可在电化学环境中开展这类观测研究,实时记录电极表面原子尺度的运动[103]。俄亥俄大学Eric Masson教授课题组利用STM实现了金衬底表面稀土配合物的制备与旋转方向100%的精准控制。当STM针尖提供电能时,整个配合物作为一个独立单元发生旋转。值得注意的是,尽管金表面具有六重对称性,但配合物一侧的反离子可引导其发生精准的三重旋转[104]。
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