1. Brett Goldsmith, Alexander Kane, Vaikunth Khalap, John Coroneus, Gregory Weiss, Phil Collins Department of Physics and Astronomy University of California Irvine Electrical Measurement of Single Molecule Catalysis using Carbon Nanotubes

2. Outline Single Molecule Sensor Construction Measurement of Catalysis Reaction Rate Dynamics of the Bound State

3. Single Molecule Sensors EnsembleStochastic present absent binding analyte absent present absent binding analyte absent

4. Device Construction PMMA Source Drain Coroneus, et al. Chem. Phys. Chem. accepted Goldsmith, et al. Science 2007, 315, 77.

5. Device Characterization

6. The Catalysis Reaction EDC binds to the carboxyl group on the nanotube. EDC ++ attached EDCurea The bound EDC perturbs the current in the nanotube. A reaction with water releases the bound EDC as a mixed urea.

7. Functionalized CNTs in Buffer

8. Interaction With EDC Goldsmith et al. Nano Lett., 8 (1), 189 -194, 2008

9. Interaction With EDC Time BondedWaiting Time Turnover Time

10. Single Molecule Rate Constant Time BondedWaiting Time Turnover Time k -1 = 58.9 ± 18.3 s

11. Bound State Lifetime k -1 = 58.9 ± 18.3 s Bound State Lifetime: = 12.4 ± 2.1 s

12. Bound vs. Unbound

13. Dynamics of the Bound State

14. Energy of a Two Level System  E = k B T ln( / ) ~11% of these states are very different

15. Energy of a Two Level System 90% 10% at experimental pH = 4.5

16. Reaction Intermediate States

17. Summary Dr. Phil Collins Brett Goldsmith Alex Kane Bucky Khalap Steve Hunt Danny Wan Tatyana Sheps Dr. Gregory Weiss John Coroneus ACS-PRF Goldsmith, et al. Science 2007, 315, 77. Goldsmith et al. Nano Lett., 8 (1), 189 -194, 2008 Goldsmith et al. JMR, accepted Coroneus, et al. Chem. Phys. Lett., accepted

18. Other Samples… EDCPthalic Anhydride JMR…

19. Timescale of the Two Level System

20. Amplitude of the Two Level System The amplitude of the two groups of bound states also differs. These different bound state properties could be due to the ~10% protonated EDC in solution at our conditions.