| AVS 54th International Symposium | |
| Surface Science | Wednesday Sessions |
| Session SS1-WeM |
| Session: | Oxide Surface Reactivity |
| Presenter: | J. Schnadt, Lund University, Sweden |
| Authors: | E. Ataman, Lund University, Sweden C. Isvoranu, Lund University, Sweden J.N. Andersen, Lund University, Sweden J. Schnadt, Lund University, Sweden |
| Correspondent: | Click to Email |
The bonding of organic molecules to transition metal oxide surfaces such as TiO2 is a concern central to the construction and optimization of molecule-based devices. Organic–inorganic interfaces are presently receiving increasing attention due to both fundamental and application interests. Interest also derives from the role of TiO2 as a support for metal catalyst particles such as Au nanoclusters, which act as an excellent catalyst for, e.g., the low temperature CO oxidation reaction. The cluster size of the Au particles has to remain within an optimum range for the catalyst to preserve its activity. However, the Au clusters are prone to coalescence as a function of temperature and gas exposure. In order to retain the catalytic activity it is important to hinder this growth process. The idea developed here is to use L-cysteine as a spacer between the clusters, since it strongly binds to the TiO2 surface via its carboxylic group. It is well-known that the thiol group of cysteine interacts with gold, which then might establish the missing link between the gold clusters and the spacer molecules. We have investigated the adsorption of L-cysteine as well as the co-adsorption of L-cysteine and gold on rutile TiO2(110) by means of x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and scanning tunneling microscopy (STM). The spectroscopy results clearly show that the notion of a molecule-TiO2 substrate bond via the carboxylic group of the molecule is correct. This finding receives further support from the STM measurements. The basic geometry characterized by the oxide-carboxylate bond is retained even for the co-deposition case; however, the S 2p spectra indicate an additional interaction between the gold clusters and molecules. An interesting additional feature of the spectroscopy experiments was the observation of very rapid beam damage, which we attribute to a facile change in the protonation status of the amino and thiol functional groups.