Professor Lukas Novotny of University of Rochester is supported by the Analytical and Surface Chemistry program for near-field Raman spectroscopy of carbon nanotubes. The idea is to bring a near field tip close to the surface of a carbon nanotube and then to irradiate the tip with a laser. Enhanced Raman signals yield the vibrational spectrum of that locality on the nanotube with 10 nanometer resolution. Translating the tip along the sample allows the PI to map the local vibrational character along the tube's length and to study the tube ends and on-tube junctions. The PI is also studying the mechanism of the Raman enhancement. Previously, carbon nanotubes have been difficult to study spectroscopically because a macroscopic sample is heterogeneous, encompassing many lengths. By studying one tube at a time, the PI and his group are able to get the isolated spectra that reveal features such as defects and dopants if the tube is loaded with another element such as boron. The PI collaborates with Todd Krauss, also of U. Rochester, to fabricate the samples.
Understanding the role of dopants in the uptake of hydrogen by carbon nanotubes is relevant to fuel cell technologies. Further, the valuable feedback on the physical properties of carbon nanotubes will lead to new device concepts, and provide input for improved synthesis. While the work is particularly well suited to nanotubes, the development of the method will also benefit efforts to chemically image other small structures such as those that might be found inside a living cell. Chemical imaging of samples is an important goal for understanding the relationship of structure and function in biological and material systems.
