Colloidal Atomic Layer Deposition (c-ALD): quest for atomic precision in nanomaterial synthesis

纳米材料是由几千个原子组成的小颗粒，直径只有几十亿分之一米，为变革性的科学和技术应用提供了许多机会。然而，在纳米尺寸晶体的制造过程中缺乏原子精度，限制了利用这一广泛而多样的材料的所有能力。例如，真实的纳米颗粒的集合总是不均匀的，并且包括在组内具有一些尺寸变化的颗粒。Talapin博士正在研究如何消除这种尺寸变化，并在纳米材料的合成中实现原子精度。许多实际应用，从平板电视到光电探测器和太阳能电池，都将受益于高度均匀、近乎原子级精确的纳米材料。Talapin博士正在开发一种称为胶体原子层沉积（c-ALD）的技术，以控制基于溶液的纳米材料合成，使用两个互补的自限制表面反应序列。这一概念的灵感来自于气相原子层沉积（ALD）的成功，ALD广泛应用于微电子和其他领域。Talapin博士的研究具有更广泛的社会影响，因为它与新技术相关材料的开发直接相关，并有可能解决限制这一广泛类别材料开发速度的根本问题。Talapin博士通过帮助本科生和高中生获得研究经验来指导他们。他的外展计划的一个重要方面是通过科学俱乐部和科学之夜为芝加哥南区当地代表性不足的非洲裔美国人和西班牙裔K-12人口提供丰富的教育。该项目还支持在芝加哥大学Talapin实验室网站上开发和分发可供公众访问的纳米科学教育资源。芝加哥大学的Talapin博士得到了超分子和纳米化学（MSN）计划的支持，以开发具有精确尺寸分散的纳米级材料的胶体原子层沉积（c-ALD）。该项目旨在通过逐层生长功能性纳米材料来消除不均匀的系综加宽，从原子定义的不同技术重要材料的簇开始。纳米材料的多分散性源于与向纳米级物体添加或从纳米级物体移除单个原子相关的自由能的弱尺寸依赖性。在这种情况下，粒度分布只能由动力学因素控制。理论建模和大量的实验研究表明，仅仅通过动力学控制反应产物很难显著提高均匀性。Talapin博士正在研究一种范式转换方法，用于纳米材料的胶体合成，其尺寸分布最小，理想情况下没有。我们的目标是建立方法来控制纳米材料的合成，使用一系列的两个互补的自限性表面反应。这一概念的灵感来自于广泛应用于微电子和其他领域的气相原子层沉积（ALD）的成功。初步研究表明，ALD概念可以在溶液中实现，并且当应用于胶体纳米材料时，能够以接近原子精度逐层生长晶格。在系综水平上消除多分散性可以说是纳米材料合成中最重要的挑战之一。人们可以在纳米材料的尺寸分布和聚合物的多分散指数（PDI）之间进行类比。先进的活性聚合技术的发现，几乎消除了链的多分散性，一直是大分子化学中最重要的近期发展之一。Talapin博士将具有更广泛社会影响的活动纳入他的研究计划。 他积极培训本科生和高中生在他的实验室，给他们研究经验的机会。他还开发了适用于K-12学生的课程模块和纳米科学教育资源，这些资源可在芝加哥大学的Talapin实验室网站上向公众开放。这些动手实验室和实验也被用于芝加哥南区当地代表性不足的非洲裔美国人和西班牙裔K-12人口的外展和教育富集活动。

Nanomaterials, small particles consisting of only several thousand atoms and of only a few billionths of a meter in diameter, offer many opportunities for transformative science and technological applications. However, the lack of atomic precision during fabrication of nanometer-sized crystals restricts the ability to harness all the power of this broad and diverse class of materials. For example, a collection of real nanoparticles is always non-uniform and comprises particles with some variation in size within the group. Dr. Talapin is investigating how to eliminate this size variation and enable atomic precision in synthesis of nanoscale materials. Many practical applications, from flat-panel televisions to photodetectors and solar cells, will benefit from highly uniform, nearly atomically precise nanomaterials. Dr. Talapin is developing a technique called colloidal atomic layer deposition (c-ALD) to control the solution-based synthesis of nanomaterials using a sequence of two complementary self-limiting surface reactions. This concept is inspired by the success of gas-phase atomic layer deposition (ALD), which is widely used in microelectronics and other fields. Dr. Talapin's research has broader societal impact since it is directly relevant to the development of new technologically-relevant materials and has the potential to solve a fundamental problem that limits the pace of development for this broad class of materials. Dr. Talapin mentors undergraduate and high school students by helping them gain research experience. An important aspect of his outreach program focuses on education enrichment via science clubs and science nights for the local underrepresented African-American and Hispanic K-12 populations on Chicago's South Side. This project also supports the development and distribution of nanoscience educational resources accessible to the general public on the Talapin Lab website at the University of Chicago. Dr. Talapin of the University of Chicago is supported by the Supramolecular and Nanochemistry (MSN) Program to develop colloidal atomic layer deposition (c-ALD) of nanoscaled materials with precise size dispersion. The project aims to eliminate inhomogeneous ensemble broadening by growing functional nanomaterials in a layer-by-layer fashion, starting from atomically defined clusters of different technologically important materials. The polydispersity of nanomaterials originates from a weak size dependence of the free energy related to the addition or removal of individual atoms to/from a nanoscale object. In this case, size distribution can only be controlled by kinetic factors. Both theoretical modeling and numerous experimental studies show that it would be difficult to improve homogeneity significantly by only kinetically controlling reaction products. Dr. Talapin is working on a paradigm-shifting approach for colloidal synthesis of nanomaterials with minimal, ideally no, size distribution. The goal is to establish means to thermodynamically control nanomaterials synthesis using a sequence of two complementary self-limiting surface reactions. This concept is inspired by the success of gas-phase atomic layer deposition (ALD) widely used in microelectronics and other fields. Preliminary studies show that the ALD concept can be implemented in solution and, when applied to colloidal nanomaterials, enables layer-by-layer growth of crystalline lattices with close to atomic precision. Eliminating polydispersity at the ensemble level is arguably one of the most important challenges in nanomaterial synthesis. One can draw an analogy between size distribution of nanomaterials and the polydispersity index (PDI) of polymers. The discovery of advanced living polymerization techniques, which nearly eliminate chain polydispersity, has been among the most important recent developments in macromolecular chemistry. Dr. Talapin incorporates activities with broader societal impact into his research program. He actively trains undergraduate and high school students in his lab by giving them research experience opportunities. He also develops course modules and nanoscience educational resources applicable to K-12 students which are accessible to the general public on the Talapin Lab website at the University of Chicago. These hands-on labs and experiments are also used in outreach and education enrichment events for the local underrepresented African-American and Hispanic K-12 populations in on Chicago's South Side.