| AVS 54th International Symposium | |
| Surface Science | Wednesday Sessions |
| Session SS2+EM+TF-WeM |
| Session: | SAMs and Organic Films I |
| Presenter: | M. Dubey, Princeton University |
| Authors: | M. Dubey, Princeton University J. Schwartz, Princeton University S.L. Bernasek, Princeton University |
| Correspondent: | Click to Email |
Detection of gaseous nitric oxide (NO) in biological systems has attracted significant attention since the identification of NO as the endothelial-derived relaxing factor (EDRF).1 NO also acts as a signal molecule in the nervous system, and is associated with the presence of infection and Alzheimer’s and other diseases. Apart from biological systems, NO is a main product released on the pyrolysis of nitro-organic explosives. For these reasons, much work has been done in the field of NO detection, and the need for a sensitive detector is evident. In this study, we report a direct and a highly sensitive technique to detect gaseous NO using X-ray Photoelectron Spectroscopy (XPS). The binding of NO by heme proteins is well understood,2 and we have utilized it for detection. We have developed a reliable method to grow Self-Assembled Monolayers (SAMs) of alkylphosphonic acids on oxide surfaces.3 This platform is used to covalently attach a uniform layer of an iron heme-like molecule, which was synthesized separately. Differential charging in XPS has been used to ascertain the uniformity of the organic film.4 The N1s signal from the heme ligand was measured by XPS before and after exposure to NO. Before NO binds to the iron, a single nitrogen peak is present, attributed to the nitrogens of the porphyrin ring. After reaction with NO, a new, distinct peak was observed in the high resolution N1s spectrum. This peak is at a higher binding energy (approx 5.5 eV), and is attributed to the NO bound to the iron. An estimate of the bound NO was calculated using XPS and QCM to be about 40 picomoles.
1 R. M. J. Palmer, A.G. Ferrige, S. Moncada, Nature, 1987, 327, 524.
2 K. R. Rodgers, Curr Opin Chem Biol, 1999, 3, 158.
3 E. L. Hanson, J. Schwartz, B. Nickel, M. Koch, M. F. Danisman, J. Am. Chem. Soc., 2003, 125, 16074.
4 M. Dubey, I. Gouzman, S. L. Bernasek, J. Schwartz, Langmuir, 2006, 10, 4649.