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.
