Nonclassical mechanisms to modify and control organic crystal nucleation and growth

非技术概述溶液生长单晶用作半导体、光电和光伏器件以及高能辐射探测器。这些研究由材料研究部的固态和材料化学计划支持，填补了理解有机材料结晶的空白，这些材料具有有前途的光学和电子特性，可用作半导体，太阳能电池和场效应晶体管。此外，这项研究可以提供有关结晶过程的有价值的信息，这对无数的工业，自然和生理过程至关重要。休斯顿大学的研究人员通过设计强大的控制策略来控制结晶，这一控制策略依赖于对基本热力学和动力学机制的理解，特别是外来化合物的作用。在工业中，与溶液或晶体-溶液界面相互作用的可溶性外来化合物被用于促进或抑制结晶。自然界通过应用控制形成的晶体数量及其生长速率的成分，实现了所产生的晶体结构的形状，图案，成分和功能的显着多样性。从该项目中获得的见解推进了有机结晶科学的发展，特别是外来化合物对固态有机材料合成的影响。研究人员还涉及高中，本科和研究生的不同群体进行这项研究，这为他们提供了先进的科学和工程概念和方法的培训。这反过来又有助于缩小休斯顿受过教育的劳动力的需求和可用性之间的差距，这是美国大城市中差距最大的。PI和这个团队设计了新的策略来控制有机溶剂中晶体的成核和生长，这些有机溶剂使用外来化合物来调节非经典结晶行为以及成核和生长前体。公认的改性剂活性模型假定晶体成核和生长沿着经典途径进行。最近的实验积累了与经典理论的重大差异。突出显示的非经典特征涉及有序或无序的介观结晶前体，其在溶液中独立于结晶组装，并且可以促进成核并提供快速的晶体生长模式。添加剂如何影响结晶前体的性质以增强或抑制晶体成核和生长尚未被研究。研究人员带来了分子热力学和结晶动力学，晶体设计和先进表征以及分子模拟方面的互补专业知识，以实现三个具体目标：1。通过操纵非经典成核模式中的前体来控制晶体成核的设计策略。2.通过利用改性剂与晶体生长前体和晶体表面上的台阶束的相互作用，阐明从生长介质中去除改性剂后持续存在的分子和介观结晶机制。3.表征由步骤结构和动力学介导的修饰剂对之间的相互作用，导致修饰剂之间的拮抗，相加或协同协同作用;这些相互作用已被经典抑制模型所忽略。为了涵盖成核和结晶行为的多样性，研究人员采用了具有良好光学和电子性能的有机晶体，用于半导体、太阳能电池和场效应晶体管。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYSolution-grown single crystals serve as semiconductor, optoelectronic, and photovoltaic devices and detectors for high-energy radiation. These studies, supported by the Solid State and Materials Chemistry Program in the Division of Materials Research, fill a gap in understanding crystallization of organic materials that carry promising optical and electronic properties for use as semiconductors, solar cells, and field-effect transistors. Additionally, the research can provide valuable information about crystallization processes, which are essential for a myriad of industrial, natural, and physiological processes. Researchers at the University of Houston take on the grand fundamental science challenge to control crystallization by designing robust control strategies that rest on understanding the fundamental thermodynamic and kinetic mechanisms, and in particular the role of foreign compounds. In industry, soluble foreign compounds that interact with the solution or the crystal-solution interface are deployed to promote or inhibit crystallization. Nature achieves remarkable diversity of shapes, patterns, compositions, and functions of the arising crystalline structures by applying ingredients that control the number of formed crystals and their rates of growth. Insights gained from this project advance the science of organic crystallization in general, and the influence of foreign compounds on the synthesis of solid state organic materials in particular. The researchers also involve a diverse cohort of high school, undergraduate, and graduate students in carrying out this research, which provides them with training in advanced science and engineering concepts and methods. This in turn contributes to narrowing the gap between the demand and availability of educated workforce in Houston, which is among the widest in large U.S. cities.TECHNICAL SUMMARYAs part of this project, which is supported by the Solid State and Materials Chemistry Program in the Division of Materials Research, the PI and this team design novel strategies to control the nucleation and growth of crystals from organic solvents that employ foreign compounds to regulate nonclassical crystallization behaviors and the nucleation and growth precursors. The accepted models of modifier activity presume that crystal nucleation and growth advance along classical pathways. Recent experiments have accumulated significant discrepancies with the classical theories. The highlighted nonclassical features involve mesoscopic crystallization precursors, ordered or disordered, which assemble in the solution independently of crystallization and may both facilitate nucleation and feed a fast mode of crystal growth. How additives impact the properties of the crystallization precursors to enhance or suppress crystal nucleation and growth has not been examined. The researchers bring complementary expertise in molecular thermodynamics and kinetics of crystallization, crystal design and advanced characterization, and molecular simulations to pursue three specific aims: 1. Design strategies to control crystal nucleation by manipulating precursors involved in nonclassical nucleation modes. 2. Elucidate molecular and mesoscopic crystallization mechanisms that persist after removal of the modifier from the growth medium by exploiting the interactions of modifiers with crystal growth precursors and with step bunches on the crystal surface. 3. Characterize interactions between pairs of modifiers mediated by the step structures and dynamics that lead to antagonistic, additive, or synergistic cooperativities between modifiers; these interactions have been disregarded by classical inhibition models. To cover a diverse array of nucleation and crystallization behaviors, the researchers employ organic crystals that carry promising optical and electronic properties for use as semiconductors, solar cells, and field-effect transistors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.