Materials World Network : Heterogeneous Nucleation on Nanoporous Substrates

材料世界网络：纳米多孔基底上的异质成核

• 批准号: 0804187
• 负责人: Jonah Erlebacher
• 金额: $ 31.8万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0804187&HistoricalAwards=false
• 关键词: Materials; World; Network; Heterogeneous; Nucleation

This a joint research and education project between investigators at Johns Hopkins University in the US and Naomi Chayen at Imperial College in the United Kingdom, with a goal to study the heterogeneous nucleation of crystals of macromolecular species with diameters in the 1-10 nm range. Typical species with this mesoscale include proteins and macromolecules, and are distinguished from colloidal spheres (at larger scales) and molecules (at smaller scales) by a large degree of internal configurational entropy; for this reason, they are difficult to crystallize. The work here builds on an experimental observation made by Chayen that the nucleation rate of macromolecules on nanoporous substrates is greatly enhanced. The working hypothesis is that the nucleation rate enhancement is specifically linked to the idea that the entropy of crystallization of macromolecules is minimized on porous substrates when a highly random porosity with void size of order the macromolecule width is used. This idea competes with a published notion that the substrate curvature enhances crystallization, which we don?t think is relevant for macromolecules on porous substrates. A detailed study of the nucleation rate of macromolecules over porous substrates as it varies with supersaturation, temperature, surface chemistry, and pore size, is being performed using a new substrate material ? nanoporous gold made by dealloying of silver/gold alloys. Nanoporous gold is a random, uniform, mesoporous material whose mean pore size can be varied from 3-50 nm using only simple chemistry. Its surface is also easily chemically modified, and all these features together make it uniquely perfect for this kind of study. Nanoporous gold is also useful here because gold nanoparticles with equivalent curvatures can be made, and we can compare and contrast crystallization in solutions containing gold colloid to crystallization on porous substrates. The research effort supports an international collaboration between the Chayen group at Imperial College, London, specializing in protein crystallization and the Erlebacher group at Johns Hopkins University, Baltimore, 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. 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 networks in nucleation theory and experiment, bridging the disciplines of thin film metallurgy and solution phase crystallization, and involving undergraduates and graduate students all stages.

这是美国约翰霍普金斯大学和英国帝国理工学院的Naomi Chayen研究人员之间的联合研究和教育项目，目标是研究直径在1-10 nm范围内的大分子物质晶体的异质成核。 具有这种介观尺度的典型物种包括蛋白质和大分子，并且通过较大程度的内部构型熵与胶体球（在较大尺度下）和分子（在较小尺度下）区分;因此，它们难以结晶。 这里的工作建立在Chayen的实验观察基础上，Chayen发现纳米多孔基底上大分子的成核速率大大提高。 工作的假设是，成核速率的增强是特别联系到的想法，即大分子的结晶熵最小化的多孔基板时，使用的顺序的大分子宽度的空隙尺寸的高度随机的孔隙率。 这一想法与已发表的一种观点相竞争，即衬底曲率增强了结晶，而我们不？t认为与多孔基质上的大分子无关。 一个详细的研究的成核率的大分子在多孔基板，因为它与过饱和度，温度，表面化学，和孔径的变化，正在使用一种新的基板材料？通过银/金合金的去合金化制成的纳米多孔金。 纳米多孔金是一种随机、均匀的中孔材料，其平均孔径可以仅使用简单的化学方法从3-50 nm变化。 它的表面也很容易进行化学改性，所有这些特征使它非常适合这种研究。 纳米多孔金在这里也是有用的，因为可以制造具有相等曲率的金纳米颗粒，并且我们可以比较和对比含有金胶体的溶液中的结晶与多孔基底上的结晶。这项研究工作支持了伦敦帝国理工学院的Chayen小组和巴尔的摩约翰霍普金斯大学的Erlebacher小组之间的国际合作，该小组专门从事蛋白质结晶和纳米多孔金属的合成和表面改性。 通过结合这些专业，将有效地进行纳米多孔基底上非均质晶体成核的基础研究。 合作的结构与学生和初级人员的重要交流。 这项研究的结果将产生新的理解的基础上的非均质成核，一般适用于蛋白质和胶体结晶。 此外，国际合作将有助于建立成核理论和实验网络，桥接薄膜冶金和溶液相结晶学科，并涉及本科生和研究生的所有阶段。