Why is tubular shape desirable?

1. 1.98Å 8.7Å 1.94Å Anatase Unit Cell Delaminated Anatase Titania nanotubes reveal some secrets and magic Yue Wu, University of North Carolina-Chapel Hill, DMR 0513915 Why is tubular shape desirable? Large surface area, unique surface structure, and accessibility by guest molecules are just few of the key ingredients of valuable functional materials used in solar cells, hydrogen production, and catalysis. For one of the most widely used photocatalytic materials, titania TiO2, the best way to achieve all these properties is by going tubular. How? The secret of achieving this tubular form is delamination. We demonstrated that the structure of anatase TiO2 crystal has the characteristics of layered structures and can be delaminated into monolayer-thick sheets and rolled into tubular form. Such nanotubes of delaminated anatase possess the largest surface area achievable in any titania. The surface is stable and accessible and it possesses the structure of anatase (001) surface, one of the most active surfaces for photocatalytic reactions. Delamination through Na+ intercalation Rolling into tubular form X-ray Diffraction Experimental Simulation The unit cell of anatase TiO2 reveals its layered characteristics and can be separated or delaminated into layers separated by 8.7 Å via Na+ intercalation. Such sheets roll into multilayered titania nanotubes. This structural model produces an excellent match for the observed x-ray diffraction pattern for the first time.

2. VX EMPA EMPA VX Frequency (ppm) Titania Nanotubes Reveal Some Secrets and Magic Yue Wu, University of North Carolina-Chapel Hill, DMR 0513915 • The superior decontamination ability of titania nanotubes for chemical warfare agents led to joint filing of patent application between our school and U.S. Army Edgewood Chemical Biological Center. • This material has led to collaboration with industry for product development. • Undergraduate students, including female students and other minority students, have been trained to make titania nanotubes. • High school students were involved in summer research on using titania nanotubes for constructing solar cells and hydrogen production. • It is clear that this project has led to deep understanding of nanostructures, important applications, and a broad outreach in education including graduate students, undergraduate students, and high school students. Chemical Warfare Agent: VX Decontamination Scheme VX is the most potent chemical warfare agent and is very hard to decontaminate and remove. The decontamination scheme of VX to EMPA proceeds extremely slowly. Al2O3 nanocrystals Titania nanotubes 31P NMR When absorbed by titania nanotubes (illustration in the middle), VX almost immediately turned into nontoxic EMPA and other products (left), as revealed by 31P NMR, whereas it survives in the currently fielded product of Al2O3 nanocrystals for many days (right).