| AVS 65th International Symposium & Exhibition | |
| Surface Science Division | Wednesday Sessions |
| Session SS+AS+EM-WeA |
| Session: | Semiconducting Surfaces |
| Presenter: | Chuan He, University of Delaware |
| Authors: | C.H. He, University of Delaware A.V. Teplyakov, University of Delaware B. Abraham, University of Delaware M. Konh, University of Delaware Z. Li, University of Delaware L. Gundlach, University of Delaware S. Bai, University of Delaware E. Galoppini, Rutgers, the State University of New Jersey H. Fan, Rutgers, the State University of New Jersey R. Harmer, Rutgers, the State University of New Jersey |
| Correspondent: | Click to Email |
The dye sensitization on metal oxide (ZnO, TiO2, Fe2O3, CuO) surfaces has attracted plenteous attention due to their numerous applications in solar energy conversion, photo-catalysis, sensing, etc. Substantial research efforts focused on designing different dyes and surface nanostructuring. However, the actual chemical attachment schemes still heavily rely on the use of sensitizer molecules functionalized with carboxylic (COOH) or phosphonic (P(O)(OH)2) anchor groups. Despite consequential progress in chemical modification schemes, the very nature of these functional groups may cause very pronounced surface morphology change of the nanomaterials designed because of etching process in liquid phase. In addition, these acidic groups often lead to the formation of multiple binding configurations (such as monodentate or bidentate miixtures) on the surface. To address both issues, we developed a two-step preparation procedure to achieve the morphology preservation of metal oxide surfaces and well-defined covalent binding of the intersurface functionality. The first step requires exposing clean metal oxide nanostructures to a gas-phase prop-2-ynoic acid (propiolic acid) in medium or high vacuum, which results in the formation of a robust and stable surface-bound carboxylate with ethynyl groups available for further modification. For the second step, we applied copper catalyzed click reaction on this preserved surface to covalently bind dye molecules functionalized with azido groups to these pre-functionalized surfaces. For example, a suitable organic dye (9-(4-azidophenyl)-2,5-di-tert-butylperylene (DTBPe-Ph-N3)) was used to investigate a distinct signature of covalently-bound dye molecules on ZnO nanorods surface. In this study, we have confirmed the morphology preservation and selective covalent attachment of the carboxylic acid onto the metal oxide surface by the combination of measurements including scanning electron microscopy (SEM), infrared, X-ray absorption photoelectron spectroscopy (XPS), solid-state 13C NMR, transient absorption spectroscopy (TA) and density functional theory (DFT) calculations.