NSF Materials World Network: Heterogeneous Nucleation on Nanoporous Substrates

拟议的研究工作将支持伦敦帝国理工学院（IC）的Chayen小组（专门研究蛋白质结晶）和巴尔的摩约翰霍普金斯大学（JHU）的Erlebacher小组（专门研究纳米多孔金属的合成和表面改性）之间的国际合作。通过结合这些专门化，将有效地进行纳米孔基质上非均相晶体成核的基础研究。合作的结构是大量交换学生和初级人员；最终，JHU团队将在固相结晶方面发展内部技能，IC团队将学习制造纳米多孔金属和纳米多孔金属复合材料的材料合成技术，从而在结晶方面取得普遍进展。从根本上说，我们提出的研究考虑了一种新的方法来思考大分子物种的非均相成核。在传统的非均相成核理论中，成核速率由溶剂、底物和原子核之间的相对界面能控制。在这里，我们将定制衬底，使其不只是暴露一个均匀的表面到溶液中，而是暴露一个统计上相关的三维定向成核位点分布。修正成核理论以探索这一思想是所提出工作的重要组成部分，也是普遍应用该技术所必需的。纳米孔金是一种随机的、均匀的介孔材料，其平均孔径可以在3-50纳米之间变化。它的表面也很容易被化学修饰，所有这些特征加在一起使它成为这种研究的完美选择。本研究结果将对非均相成核的基本原理产生新的认识，对蛋白质和胶体结晶具有普遍的适用性。此外，国际合作将有助于建立成核理论和实验的国际网络，架起薄膜冶金和固相结晶学科的桥梁。

The proposed research effort will support an international collaboration between the Chayen group at Imperial College, London (IC), specializing in protein crystallization and the Erlebacher group at Johns Hopkins University, Baltimore (JHU), which specializes in the synthesis and surface modification of nanoporous metals. By marrying these specializations, a fundamental study of heterogeneous crystal nucleation on nanoporous substrates will be efficiently pursued. The collaboration is structured with significant exchange of students and junior personnel; ultimately, the JHU team will develop in-house skills in solution-phase crystallization, and the IC group will learn materials synthesis techniques for fabricating nanoporous metals and nanoporous metal composites, leading to advances in crystallization generally. Fundamentally, our proposed research considers a new approach to thinking about the heterogeneous nucleation of macromolecular species. In traditional heterogeneous nucleation theory, nucleation rates are controlled by the relative interfacial energies between the solvent, substrate, and nucleus. Here, we will tailor the substrate to expose not just one uniform surface to the solution, but instead to expose a statistically relevant distribution of three-dimensionally oriented nucleation sites. Modifications of nucleation theory to explore this idea is an important part of the proposed work and is required for applying the technique generally.A detailed study of the nucleation rate of macromolecules over porous substrates will be performed using a new substrate material / nanoporous gold Nanoporous gold is a random, uniform, mesoporous material whose mean pore size can be varied from 3-50 nm using simple chemistry. Its surface is also easily chemically modified, and all these features together make it uniquely perfect for this kind of study.The results of this research will yield new understanding of the fundamentals of heterogeneous nucleation, with general applicability to protein and colloidal crystallization. Furthermore, the international collaboration will help to build international networks in nucleation theory and experiment, bridging the disciplines of thin film metallurgy and solution phase crystallization.