SusChEM: Organic Linkages to Control and Enhance Titanium Dioxide Nanocatalysts

二氧化钛(二氧化钛)是一种廉价的晶体材料，长期以来一直被用作白色，应用范围从油漆到粉状甜甜圈。当二氧化钛颗粒尺寸约为0.00000005英寸时，二氧化钛表现出增强的催化活性，这是一种化学现象，即二氧化钛通过提供替代的反应途径来提高化学过程的效率和选择性。近年来，二氧化钛纳米催化剂的低成本和无毒特性使其在第三世界国家用于太阳能净水、卷筒印刷制造的柔性太阳能电池和自清洁建筑材料的商业化。虽然化学家们早就知道这些纳米晶体的反应性在很大程度上取决于它们的形状和结构，但对这些依赖关系几乎没有基本的了解，因此没有合理的方法来改善它们的性能。在这项研究项目中，康奈尔大学的Melissa Hines教授和她的研究生们正在使用原子尺度显微镜来研究各种小分子在与二氧化钛表面相互作用过程中的结构和反应活性。利用从这些实验中获得的见解，她和她的学生正在开发新的方法来改善这些晶体的性能，包括生长表面支持的纳米级网络。从这些实验中获得的基本理解将有助于未来的应用，例如性能更好的新型电池或太阳能电池。为了与在校学生分享他们对科学的热情，她和她的团队正在为中学生开发动手科学课程，访问学校进行这些实验，并将这些课程贡献给一个面向全国教师的在线科学实验库。在这个由化学系高分子、超分子和纳米化学(MSN)计划资助的项目中，康奈尔大学的Melissa A.Hines教授和她的学生使用基于溶液的化学反应和表面科学技术来产生开发可持续、无毒、富含地球的纳米催化剂、光催化剂、光伏设备和储能材料所需的基本知识。这项研究使用溶液沉积的、自组装的分子样品单分子层来研究七种最常用的金属氧化物表面有机键的原子级结构。这些单分子膜沉积在控制良好的金红石(110)单晶和外延锐钛矿(001)薄膜的表面，并结合实验和计算技术进行研究，包括扫描隧道显微镜、红外和X射线光电子能谱以及第一性原理模型。这项研究为合理开发金属氧化物纳米催化剂和薄膜上的高强度和/或高导电性有机涂层提供了必要的理解，同时也开发了分子-二氧化钛连接的电子表征所需的高质量自组装单分子膜。有机连接化学正在探索用于一类新的表面支撑的、高度多孔的导电纳米网络。除了这项研究，海因斯和她的团队正在开发新的动手科学实验，这些实验符合下一代科学标准，适合中学课堂。该小组在K-12课堂上和通过教师发展计划对这些活动进行实地测试。完成的实验可以通过在线借阅图书馆向全国任何教师开放。

Titanium dioxide (TiO2) is an inexpensive crystalline material that has long been used as white coloring in applications ranging from paint to powdered doughnuts. When the titanium dioxide particle size is on the order of 0.00000005 inches, TiO2 exhibits enhanced catalytic activity, a chemical phenomenon in which the TiO2 increases the efficiency and selectivity of chemical processes by providing alternative reaction pathways. In recent years, the low cost and non-toxic properties of titanium dioxide nanocatalysts have led to their commercialization for solar water purification in third-world countries, for flexible solar cells fabricated by roll-to-roll printing, and for self-cleaning building materials. While chemists have long known that the reactivity of these nanocrystals depends critically on their shape and structure, there is little fundamental understanding of these dependencies and thus no rational means for improving their performance. In this research project, Prof. Melissa Hines and her graduate students at Cornell University are using atomic-scale microscopy to study the structure and reactivity of a variety of small molecules during their interaction with titanium dioxide surfaces. Using insights gained from these experiments, she and her students are developing new methods to improve the performance of these crystals, including the growth of surface-supported, nanoscale networks. The fundamental understanding gained from these experiments will help future applications, such as new types of batteries or solar cells with improved performance. To share their enthusiasm about science with school children, she and her group are developing hands-on science lessons for middle school students, visiting schools to perform these experiments, and contributing these lessons to an online lending library of science experiments for teachers nationwide.In this project, funded by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Chemistry Division, Prof. Melissa A. Hines of Cornell University and her students are using solution-based chemical reactions and surface science techniques to produce the fundamental understanding necessary for the development of sustainable, non-toxic, earth-abundant nanocatalysts, photocatalysts, photovoltaic devices, and energy-storage materials. The research uses solution-deposited, self-assembled monolayers of molecular exemplars to study the atomic-scale structure of seven of the most commonly used organic linkages to metal oxide surfaces. These monolayers are deposited on the surfaces of well-controlled rutile (110) single crystals and epitaxial anatase (001) films and studied with a combination of experimental and computational techniques, including scanning tunneling microscopy, infrared and x-ray photoemission spectroscopies, and first-principles modeling. This research is producing the understanding necessary for the rational development of high strength and/or high conductivity organic coatings on metal oxide nanocatalysts and thin films, while also developing the high quality self-assembled monolayers necessary for electronic characterization of molecule-titanium dioxide linkages. The organic linkage chemistries are being explored for use in a new class of surface-supported, highly porous, conducting nanoscale networks. Coupled with this research, Hines and her group are developing new hands-on science experiments that are aligned with the Next Generation Science Standards and suitable for the middle school classroom. The group field tests these activities in K-12 classrooms and through teacher development programs. The finished experiments are made available to any teacher in the nation through an online lending library.