Adam Washburn and Dr. Adam Woolley, Chemistry and Biochemistry

Project Background

The construction of nanometer-scale electronic devices is an emerging and promising interdisciplinary field. Nanoelectronic devices may reduce size limits in integrated circuits and also function as miniature chemical detectors.1 Nanowire connections are essential components of nanoelectronic devices. A recently developed method for creating nanowires is to deposit metal onto a DNA template. Because DNA can be manipulated into specific shapes and surface patterns, DNA templates are particularly appealing for nanowire formation.2

Copper is an ideal metal for DNA-templated nanowires because of its low cost and frequent use in modern integrated circuits. However, DNA-templated copper nanowire fabrication techniques often result in uneven or nonspecific copper deposition along DNA. Prior to this research project, Dr. Woolley’s lab had some success in forming DNA-templated copper nanowires3, but the conductivity properties of the wires were not evaluated. In this project, I worked with Dr. Woolley in developing an electroless plating method for creating uniform copper nanowires that we could test for conductivity. Our method of nanowire synthesis was an analogous method to previously reported methods for depositing gold4 and silver5 onto silver-seeded DNA.

Results of Project

Near the beginning of 2006, we discovered a simple method for reproducibly creating copper nanowires on DNA templates. After characterizing the wires with atomic force and scanning electron microscopy (see Figure 1 for a scanning electron microscope image of a copper nanowire), it seemed that the wires should be conductive. As a result, we began designing methods to test the conductivity of the copper nanowires.

Unexpectedly, the simple matter of measuring conductivity turned out to be the most challenging and demanding requirement of the research project. Through a collective effort by Dr. Woolley, graduate student Hector Becerril, and myself, we developed and tested nine different methods for measuring the conductivity of the nanowires. This experimental process involved searching the literature, modifying literature procedures, and inventing new methods for placing gold electrodes into contact with DNA-templated nanowires. Throughout this process, I learned about clean-room techniques, surface modifications, and electroless plating processes. Sometimes methods for placing electrodes would destroy the nanowires, and sometimes the electrodes would not have sufficient electrical contact with the nanowires. In the end, we were able to obtain limited data about the conductivity of the nanowires. However, we continue to persevere in finding better methods for obtaining conductivity data.

Although we still have not found an ideal method for measuring the conductivity of copper nanowires, this research project has given me a clear perspective on how to innovate and collaborate with fellow researchers in a creative process. I have also learned how to present my research findings to audiences in small and large group settings. At the Spring Research Conference sponsored by the College of Physical and Mathematical Sciences, I was able to present our research results in the Materials Division of the conference. Later, I was presented with an award for the best presentation out of the Materials Division. Also, I was able to put some of our results in a poster for the Spring 2006 National Meeting of the American Chemical Society. Later, in the Fall 2006 National Meeting, I was able to go to San Francisco and present our results in poster format.

Overall, the experience of working with an ORCA has prepared me for future work as a graduate student. I am currently applying for several competitive graduate research fellowships, as well as seeking admittance to several competitive graduate schools. Because of my undergraduate research experience, I believe I have significant opportunities that would not be available otherwise.

References

1. Davis, J. J.; Morgan, D. A.; Wrathmell, C. L.; Axford, D. N.; Zhao, J.; Wang, N. J. Mater. Chem. 2005, 15, 2160–2174.
2. Becerril, H. A.; Stoltenberg, R. M.; Wheeler, D. R.; Davis, R. C.; Harb, J. N.; Woolley, A. T. J. Am. Chem. Soc. 2005, 127, 2828–2829.
3. Monson, C. F. and Woolley, A. T. Nano Lett. 2003, 3, 359-363.
4. Keren, K.; Berman, R. S.; Braun, E. Nano Lett. 2004, 4, 323–326.
5. Park, S. H.; Barish, R.; Li, H. Y.; Reif, J. H.; Finkelstein, G.; Yan, H.; LaBean, T. H. Nano Lett. 2005, 5, 693–696.