| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Thin Films | Monday Sessions |
| Session TF-MoM |
| Session: | Nanostructured Surfaces and Thin Films: Synthesis and Characterization I |
| Presenter: | Gregory Cabailh, Sorbonne Université, France |
| Authors: | G. Cabailh, Sorbonne Université, France E. Meriggio, Sorbonne Université, France R. Lazzari, CNRS, France C. Méthivier, Sorbonne Universitévier, France V. Humblot, Sorbonne Université, France X. Carrier, Sorbonne Université, France |
| Correspondent: | Click to Email |
1. Objectives :
Chiral molecules play a vital role in the biochemistry of living organisms, justifying the essential challenge of controlling enantioselectivity in several fields such as the pharmaceutical and agrochemical industry. Heterogeneous asymmetric catalysis for the synthesis of enantiopure chiral compounds is a tool of choice for its many economic and ecological benefits. Several techniques have been developed, including the modification of a metal surface by an organic chiral inducer. Nevertheless, the number of systems developed successfully remains limited. Unlike monocrystalline metal surfaces, very little is known on the role of the oxide support in catalysts based on supported metallic nanoparticles. The control of the role of the oxide support and the chiral inducer is based on the knowledge of the interactions at the molecular level between the three parties involved in the reaction: the oxide, the metal nanoparticles and the chiral inducer, represented in this work by TiO2 single crystals, nickel nanoparticles (NPs) and tartaric acid (TA). A model approach is used here, where TA molecules and NPs are deposited by evaporation in an ultra-vacuum environment and then characterized by surface analysis techniques.
2. Results :
The chemical state of TA is characterized by X-ray Photoemission Spectroscopy (XPS) and High Resolution Electron Energy Loss Spectroscopy (HREELS). TA is first deposited on single crystals of Cu (110) and Au (111), on which the chemical nature of TA is well known, in order to obtain reference XPS spectra. By analyzing the C 1s and O 1s spectra, the presence of monotartrate adsorbed species (COO- / COOH) is demonstrated on copper, while the molecules are in the bi-acid form (COOH / COOH) on gold. The comparison of these results with the data recorded on rutile TiO2(110) (in particular the energy differences between the C1s peaks) and complementary HREELS measurements allow to conclude that TA is absorbed as monotartrate on TiO2 in analogy with other carboxylic acids. In addition, the organization and the nucleation point on the surface can be observed by scanning tunneling microscopy (STM). TA is finally deposited on the Ni / TiO2system at different coverage rates and studied by XPS and STM to characterize the interaction between the three parties of the system.