Tuning Carbon Nanotube Band Gaps by Guanine Functionalization

William Marsh Rice University, Houston TX

Investigators

Abstract

Professor Robert B. Weisman of William Marsh Rice University is supported by the Macromolecular, Supramolecular and Nanochemistry Program of the Division of Chemistry to investigate and control the properties of single-wall carbon nanotubes linked to DNA. These nanotubes are a prominent family of artificial nanomaterials whose unusual properties and potential uses can lead to new scientific discoveries and useful real-world applications in the areas of health care, energy, and infrastructure safety. This project is based on the discovery by Weisman and co-workers of a reaction that bonds DNA to nanotubes to form stable hybrid structures that have controllable optical and electronic properties. The investigators will use experiments and computations to further explore the nature of these nanotube-DNA hybrids and to examine their potential for use in biomedical sensing and quantum information processing. Apart from these research goals, the project will advance science education at several levels. Graduate students working on the project will gain essential hands-on training and will develop skills in oral and written technical communication. Undergraduate students participating in the studies will get valuable research experience. The Weisman lab will also host high school teachers during the summers in an ongoing program that expands their knowledge and leads to enriched science curricula affecting hundreds of high school students. This project will deepen our understanding of the unique covalent reaction between guanine nucleobases and carbon nanotubes induced by singlet O2. This reaction perturbs the nanotube electronic structure by introducing a dense array of shallow excitonic traps whose spacing and depth can be controlled by the choice of ssDNA oligo structure. It thus has the potential to produce nanotube hybrids with engineered band gaps. Experiments supported by molecular dynamics and quantum chemical computations will investigate 1) how interactions between sensitizer and nanotube affect the covalent reaction; 2) the chemical bonding between DNA and nanotube; 3) the source of spectral broadening in the hybrids; 4) the parameters controlling functionalization extent. The results will clarify the detailed structures of the hybrids and the mechanism of the functionalization reaction. Optimal conditions for efficient formation of the desired products will also be identified. Customized DNA-functionalized nanotube samples will be prepared for targeted collaborative projects to further probe their properties and explore possible applications in quantum optics and biomedical sensing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.