| AVS 55th International Symposium & Exhibition | |
| Biological, Organic, and Soft Materials Focus Topic | Friday Sessions |
| Session BO+SS+AS-FrM |
| Session: | Self Assembled Ultrathin Organic Interfaces |
| Presenter: | A.M. Track, University of Graz, Austria |
| Authors: | A.M. Track, University of Graz, Austria A. Lex, Graz University of Technology, Austria T. Höfler, Graz University of Technology, Austria T. Griesser, Graz University of Technology, Austria P. Pacher, Graz University of Technology, Austria H.-G. Flesch, Graz University of Technology, Austria G. Hlawacek, University of Leoben, Austria R. Schenach, Graz University of Technology, Austria G. Trimmel, Graz University of Technology, Austria W. Kern, University of Leoben, Austria G. Koller, University of Graz, Austria M.G. Ramsey, University of Graz, Austria |
| Correspondent: | Click to Email |
Self-assembled monolayers (SAMs) can provide a simple, flexible, highly ordered and convenient system to tailor and functionalize surface and interface properties of metals, metal oxides and semiconductors. For instance a simple way to change the chemical reactivity of the substrates is to use organic photosensitive SAMs which will also allow patterning with UV illumination. We focus on the characterization of the reactions occurring in SAMs and thin interfacial layers using X-ray photoemission spectroscopy (XPS). To increase the contrast between the non-illuminated and illuminated SAMs (or thin films) we perform a selective post modification of the patterned films with organic reagents containing heteroatoms. The chemical differences of the structured film have been followed with spatially resolved XPS. Further chemical and structural information has been obtained with reflection absorption infrared spectroscopy (RAIRS), friction force microscopy (FFM), contact angle measurements and X-ray reflectivity (XRR). Two different types of photo-reactive functional groups have been investigated: a benzyl thiocaynate and a phenylester. First we present thin films of silanes on SiOx, which bear the photoreactive benzyl thiocyanate (-SCN) unit. This photoisomerizes to the corresponding isothiocyanate (-NCS). The photoisomerization can be detected by a significant shift of the S2s core level. Additionally, we can prove the change of chemical reactivity due to the illumination via a post modification with fluorinated amines introduced in gas phase. Here more fluorine could be detected with the spatially resolved XPS on the illuminated areas of the sample.1 In the second example the SiOx substrates are modified with photosensitive silanes of different chain length containing the phenylester group. The phenylester can undergo the Photo-Fries rearrangement upon UV illumination forming a hydroxyphenyl keton. The different chemical reactivity of these two groups is again shown with a selective post modification with, e.g., fluorinated acid chlorides. The corresponding reaction has again been followed by the appearance of the F1s signal only on the illuminated areas of the samples. Finally, results of investigations extended to patterned photo-reactive thiol-SAMs on Au(111) will be discussed.
1 A. Lex et. al., Chem. Mater. 2008, 20, 2009-2015.