| AVS 55th International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuA |
| Session: | Practical Surface Analysis |
| Presenter: | M.A. Bratescu, Nagoya University, Japan |
| Authors: | M.A. Bratescu, Nagoya University, Japan D.B. Allred, University of Washington N. Saito, Nagoya University, Japan M. Sarikaya, University of Washington O. Takai, Nagoya University, Japan |
| Correspondent: | Click to Email |
Ultraviolet attenuated total reflectance (UV–ATR) spectroscopy is a useful method to monitor electronic transitions of molecules at interfaces via the evanescent wave generated at a totally internally reflecting surface. Silane is a frequently used linker for functionalization and assembly on silica. Many efforts are still made to identify and to optimize the factors affecting the monolayer formation. Reaction conditions such as temperature and humidity, as well as silane and substrate chemistry influence the rate of reaction and the assembly process. We chose a silane based adsorption process to determine what insight this spectroscopic examination may yield. For this study we have used the molecule O-4-methyl-coumarinyl-N-[3-(thriethoxysilyl)propyl] carbamate (Gelest, Inc.), which has the formula C20H29NO7Si, and will be hereafter referred to as MCC-propylsilane. The coumarin group represents the observable chromophore in the UV spectral region, and the silane chemistry is desirable for the functionalization and possibly the assembly on silica.1 Experiments were performed using a custom-made apparatus,2 combining a fused quartz internal reflection element as the ATR sensor and a flow cell transparent to the light source. The measuring system was equipped with a chiller to control the interface temperature from -10°C to +60°C with 0.01°C resolution. The MCC-propylsilane concentrations were varied from 0.1 to 5.0 mM. The ATR-UV absorption spectrum of MCC-propylsilane shows two peaks at 270 and 325 nm attributed to pyrone and benzenoid groups, respectively, of the coumarin chromophore. From time-resolved spectra at different MCC-propylsilane concentrations and temperatures the adsorption-desorption isotherms were obtained. The thermodynamic properties are useful for a better understanding of the driving forces of this silane adsorption process.
1S.R. Wasserman, Y.T. Tao and G.M. Whitesides, Langmuir 5(1989)1074.
2M.A. Bratescu, D.B. Allred, N. Saito, M. Sarikaya and O. Takai, Appl. Surf. Sci.,254(2008)2960.