Padmanabhan Sibu C, Collins Timothy W, Pillai Suresh C, McCormack Declan E, Kelly John M, Holmes Justin D, Morris Michael A
Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, College Green, Dublin 2, Ireland.
School of Chemistry, Trinity College Dublin, College Green, Dublin 2, Ireland.
Sci Rep. 2020 Oct 27;10(1):18414. doi: 10.1038/s41598-020-75241-z.
Atomic and molecular level interactions in solutions dictate the structural and functional attributes of crystals. These features clearly dictate the properties of materials and their applicability in technologies. However, the microscopic phenomena of particle formation-nucleation and growth-in real systems are still not fully understood. Specifically, crystallisation occurring in closed systems are largely unproven. Combining coherent experimental data, we here demonstrate a fundamental nucleation-growth mechanism that occurs in a model zinc oxide system when particles are formed under continuous, rapid heating under closed reaction conditions. Defying all previous reports, we show that the nucleation commences only when the heating is terminated. A prenucleation clusters pathway is observed for nucleation, followed by crystallite assembly-growth. We show that the nucleation-growth processes result from temporal and dynamic activity of constituent ions and gaseous molecules in solution and by the irreversible expulsion of the dissolved gaseous molecules. We suggest that this nucleation process is generic to most closed systems that go through precipitation, and, therefore, important for the crystallisation of a variety of metal oxides, composites and minerals. We anticipate that the work may be a platform for future experimental and theoretical investigation promoting deeper understanding of the nucleation-growth phenomena of a variety of practical systems.
溶液中的原子和分子水平相互作用决定了晶体的结构和功能属性。这些特性清楚地决定了材料的性质及其在技术中的适用性。然而，实际系统中粒子形成（成核和生长）的微观现象仍未得到充分理解。具体而言，封闭系统中发生的结晶现象在很大程度上尚未得到证实。结合连贯的实验数据，我们在此展示了一种基本的成核 - 生长机制，该机制发生在模型氧化锌系统中，即在封闭反应条件下持续快速加热形成粒子时。与之前所有报告相悖的是，我们发现成核仅在加热终止时才开始。观察到成核过程通过预成核簇途径进行，随后是微晶组装 - 生长。我们表明，成核 - 生长过程是由溶液中组成离子和气态分子的时间和动态活性以及溶解气态分子的不可逆排出导致的。我们认为这种成核过程对于大多数经历沉淀的封闭系统来说是普遍存在的，因此对于各种金属氧化物、复合材料和矿物的结晶很重要。我们预计这项工作可能成为未来实验和理论研究的一个平台，以促进对各种实际系统中成核 - 生长现象的更深入理解。
