Imaging the Dynamics of Freezing and Melting with Colloids

用胶体成像冻结和熔化的动力学

• 批准号: 0907195
• 负责人: Anthony Dinsmore
• 金额: $ 40万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-12-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0907195&HistoricalAwards=false
• 关键词: Imaging; Dynamics; Freezing; Melting; Colloids

****NON-TECHNICAL ABSTRACT****The freezing and melting of crystals are fascinating and technologically important phenomena, yet are very difficult to study in the laboratory. Experiments that follow the motions of individual atoms as they form crystals can provide powerful insight, but major technical challenges prevent many of the needed measurements. This project will use microscopic spherical particles suspended in solution (colloidal particles) as ?model atoms,? with which to study crystallization and melting. These particles follow the same physical principles that govern atoms or molecules, but are much larger and slower than atoms and hence directly visible in optical microscopes. The experiments will offer new insight into the role of transient structures, which are not stable but which can nonetheless control the rate at which crystals grow or melt, or even arrest crystal growth. The research may lead to more efficient crystallization of proteins (a major step in determining their structure and function), and controlled crystallization of atoms in nanoparticles (potentially leading to novel materials). The project will provide training for graduate and undergraduate students and includes outreach to high-school students to expose them to the excitement and career opportunities in cutting-edge science. The project will also support a new series of visits and seminars by physicists working in industrial research, with the goals of creating opportunities for collaborative research and of exposing students to a range of career options.****TECHNICAL ABSTRACT****The phenomena of freezing and melting are familiar in everyday life and have been studied intensively for many years, but many important questions remain unanswered. Recent experiments have shown that micron-sized particles or droplets can be used as powerful experimental models, providing direct insight into these phenomena with single-particle resolution. This individual-investigator award supports experiments with colloidal spheres and liquid droplets whose interaction potentials can be tuned to induce crystallization, gelation, or melting. The particle motions will be quantitatively tracked in two or three dimensions using optical microscopy. Of particular interest is the role of thermodynamically metastable states, which have a major effect on the free-energy barriers, the rates, and on the final state in cases where the system is trapped out of equilibrium. The results should be helpful in applications such as crystallization of globular proteins or synthesis of inorganic nanocrystals. Graduate and undergraduate students will play key roles in the project and receive training in laboratory research. An outreach program will expose high-school students to the excitement and career potential of cutting-edge science. Reflecting the investigator?s combined interests in industrial applications of soft matter and in training graduate students, the project will also support a series of visits and seminars by physicists currently working in industry.

* 非技术摘要 * 晶体的冻结和熔化是迷人的和技术上重要的现象，但在实验室中研究非常困难。 跟踪单个原子形成晶体时的运动的实验可以提供强大的洞察力，但主要的技术挑战阻止了许多必要的测量。 这个项目将使用悬浮在溶液中的微观球形颗粒（胶体颗粒）作为？原子模型？用来研究结晶和熔化。 这些粒子遵循与原子或分子相同的物理原理，但比原子大得多，速度也慢得多，因此在光学显微镜下直接可见。 这些实验将为瞬态结构的作用提供新的见解，瞬态结构并不稳定，但仍然可以控制晶体生长或熔化的速度，甚至可以阻止晶体生长。 这项研究可能会导致蛋白质更有效的结晶（确定其结构和功能的重要一步），以及纳米颗粒中原子的受控结晶（可能导致新材料）。 该项目将为研究生和本科生提供培训，并包括对高中生的宣传，使他们接触到尖端科学的兴奋和职业机会。 该项目还将支持在工业研究领域工作的物理学家进行一系列新的访问和研讨会，目的是为合作研究创造机会，并使学生接触到一系列职业选择。冻结和融化现象在日常生活中是常见的，多年来一直被深入研究，但许多重要的问题仍然没有答案。 最近的实验表明，微米大小的颗粒或液滴可以用作强大的实验模型，提供直接洞察这些现象与单粒子分辨率。这个个人研究者奖支持胶体球和液滴的实验，其相互作用势可以调整，以诱导结晶，凝胶化或熔化。 粒子运动将使用光学显微镜在二维或三维中定量跟踪。特别令人感兴趣的是介稳态的作用，它对自由能势垒、速率和系统被困在平衡之外的最终状态有重大影响。 研究结果对球形蛋白质的结晶、无机纳米晶的合成等应用有一定的指导意义。 研究生和本科生将在项目中发挥关键作用，并接受实验室研究培训。 一个推广计划将使高中生接触到尖端科学的兴奋和职业潜力。 反映调查员？该项目还将支持目前在工业界工作的物理学家的一系列访问和研讨会。