1. Structure of ZnO Nanorods using X-ray Diffraction Marci Howdyshell Albion College Mentors: Bridget Ingham and Michael Toney

2. Introduction What? – Zinc Oxide (ZnO) Why? –Future applications of ZnO such as chemical sensing and optoelectronics –The nanostructures enhance bulk characteristics –The crystal structures of nanorods affect different properties –We can look at orientations How? –X-ray diffraction!

3. The experiment Schematic diagram of experimental setup: CE is counter electrode; RE is reference electrode. -The electrochemistry is controlled as the x-ray beam reflects off the top of the quartz rod (working electrode) and onto the detector. 1/2 O 2 + H 2 O + 2e - --> 2OH - Zn 2+ + 2OH - --> ZnO + 2 H 2 O

4. Diffraction Pattern nλ = 2dsin(θ) (Q = 2π/d) ZnO (102)

5. Making some sense of it ZnO (102)

6. Making some sense of it: Intensity vs.  Plots Au (111) ZnO (101) ZnO (102) ZnO (002)

7. ZnO (102) Peak Width Less negative potential means greater width and therefore more variation of grains about the midpoint Width corresponds with how much the grain direction varies about the midpoint. Potential (mV vs. Ag/AgCl/KCl

8. Growth of ZnO Nanostructures Less negative potentials (-370 mV) More negative potentials (-970 mV) More negative: thicker Less negative: thinner

9. SEM Images -970 mV -370 mV -770 mV -670 mV 65°C, 5mM Zinc Nitrate,0.1M KCl

10. Future Analysis Complement with electron microscopy Time series; modeling XANES/EXAFS* B. Ingham, B. N. Illy, J. R. Mackay, S. P. White, S.C. Hendy, M. P. Ryan, Mat. Res. Soc. Symp. Proc. 1017 (2007) DD12.16 B. Ingham, B. N. Illy and M. P. Ryan, J. Phys. Chem. C (submitted)

11. Acknowledgements Bridget Ingham, Michael Toney (SSRL) Benoit Illy and Mary Ryan (Imperial College London) DOE, SULI Program Coordinators