title: Formation of smooth, conformal molecular layers on ZnO surfaces via photochemical grafting.
abstract: We have investigated the photochemical grafting of organic alkenes to atomically flat ZnO(10 ̅10) single crystals and ZnO nanorods as a way to produce functional molecule-semiconductor interfaces. Atomic force microscopy shows that photochemical grafting produces highly conformal, smooth molecular layers with no detectable changes in the underlying structure of the ZnO terraces or steps. X-ray photoelectron spectroscopy measurements show that grafting of a methyl ester-terminated alkene terminates near one monolayer, while alkenes bearing a trifluoroacetamide-protected amine form very smooth multilayers. Even with multilayers, it is possible to deprotect the amines and to link a second molecule to the surface with excellent efficiency and without significant loss of molecules from the surface. This demonstrates that the use of photochemical grafting, even in the case of multilayer formation, enables multistep chemical processes to be conducted on the ZnO surface. Photoresponse measurements demonstrate that functionalization of the surface does not affect the ability to induce field effects in the underlying ZnO, thereby suggesting that this approach to functionalization may be useful for applications in sensing and in hybrid organic-inorganic transistors and related devices.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, Wisconsin 53706, USA.
authors.forename: Rose E
authors.initials: RE
authors.lastname: Ruther
authors.forename: Ryan
authors.initials: R
authors.lastname: Franking
authors.forename: Alex M
authors.initials: AM
authors.lastname: Huhn
authors.forename: Jaritza
authors.initials: J
authors.lastname: Gomez-Zayas
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hamers
mesh_terms: D000475:Alkenes / Q000737:chemistry; D015394:Molecular Structure; D043942:Nanotubes / Q000737:chemistry; D010316:Particle Size; D010777:Photochemistry; D013499:Surface Properties; D015034:Zinc Oxide / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D000475:Alkenes; D015034:Zinc Oxide