Synthesis of a Photosensitive Thiocyanate-Functionalized Trialkoxysilane and Its Application in Patterned Surface Modifications Alexandra Lex, † Peter Pacher, ‡ Oliver Werzer, ‡ Anna Track, ‡,§ Quan Shen, | Robert Schennach, ‡ Georg Koller, § Gregor Hlawacek, | Egbert Zojer, ‡ Roland Resel, ‡ Michael Ramsey, § Christian Teichert, | Wolfgang Kern, †,⊥ and Gregor Trimmel* ,† Institute for Chemistry and Technology of Organic Materials, Graz UniVersity of Technology, Stremayrgasse 16, 8010 Graz, Austria, Institute of Solid State Physics, Graz UniVersity of Technology, Petersgasse 16, 8010 Graz, Austria, Institute of Physics, UniVersity of Graz, UniVersitätsplatz 5, 8010 Graz, Austria, Institute of Physics, MontanuniVersität Leoben, Franz Josef Strasse 18, 8700 Leoben, Austria, and Institute of Chemistry of Polymeric Materials, MontanuniVersität Leoben, Franz Josef Strasse 18, 8700 Leoben, Austria ReceiVed September 26, 2007. ReVised Manuscript ReceiVed December 10, 2007 A bifunctional molecule, trimethoxy[4-(thiocyanatomethyl)phenyl]silane (Si-SCN), bearing both a photoreactive unit, the benzyl thiocyanate group, and an anchoring unit, the trimethoxysilyl group, was synthesized. Upon irradiation with UV light of 254 nm under inert atmosphere, the benzyl thiocyanate group undergoes an isomerization reaction to the benzyl isothiocyanate. Kinetic investigations of liquid films of Si-SCN by Fourier transform infrared (FTIR) spectroscopy show that the thiocyanate is almost quantitatively consumed during illumination, but only 25–30% of isothiocyanate is formed. From the subsequent reaction with propylamine from the vapor phase, the isothiocyanate groups react to the corresponding thiourea compound. Thin layers of Si-SCN were applied to modify oxidized silicon surfaces. X-ray reflectivity measurements revealed a layer thickness of 6 nm. The above-described photochemistry also proceeds in these very thin layers as determined by FTIR spectroscopy and X-ray photoelectron spectroscopy. Photopatterned surfaces were produced using a contact mask during illumination followed by postmodification with propylamine. The structures of the used photomask were clearly reproduced on the surface as revealed by friction force microscopy. Because of the versatility of this photochemistry, the new photosensitive silane Si-SCN is a promising molecule for applications in modern immobilization techniques and for the (structured) modification of inorganic surfaces. Introduction Thin layers of bifunctional organosilanes, containing a chloro- or alkoxysilane moiety as anchoring group to surfaces and a second functionality, are of great interest for numerous applications and play an increasingly important role in nanotechnology, biotechnology, and molecular electronics. 1–6 The range of organic functionalities spans from apolar to polar groups, from anionic to cationic groups, and includes, for example, also fluorescent dyes and electroactive moieties. While chlorosilyl and alkoxysilyl units bind to surface hydroxy groups of glass and inorganic oxides, the second functionality, if desired, separated by an alkyl or aryl spacer from the anchoring group, determines the final properties of the surface. Because of the plenitude of available and described silanes, the polarity and chemical reactivity of the surface can be tailored over a wide range. These functional organosilanes are widely used in immobilization techniques, e.g., for the attachment of catalysts, (bio)molecules, nano- particles, and analytes onto oxidic surfaces. For many applications, such as biochips and nanotechnology, two- dimensional patterning of surface properties and site-selective immobilization is required. An elegant route for obtaining such features is the use of photolithographic techniques. Different patterning concepts using UV light have already been described. In most cases, they result in surface structures of hydrophobic and hydrophilic areas that can then be used for selective immobilization. An example for a patterning process is the light-induced oxidation of alkyl chains and phenyl alkyl chains resulting in aldehyde- and carboxylic- acid-terminated layers (e.g., see refs 7–10). Alternatively, To whom correspondence should be addressed. Telephone: ++43316- 8734958. Fax: ++43316-8738951. E-mail: gregor.trimmel@tugraz.at. † Institute for Chemistry and Technology of Organic Materials, Graz University of Technology. ‡ Institute of Solid State Physics, Graz University of Technology. § University of Graz. | Institute of Physics, Montanuniversität Leoben. ⊥ Institute of Chemistry of Polymeric Materials, Montanuniversität Leoben. (1) Onclin, S.; Ravoo, B. J.; Reinhoudt, D. N. Angew. Chem., Int. Ed. 2005, 44, 6282 and references therein. (2) Ulman, A. Chem. ReV. 1996, 96, 1533. (3) Descalzo, A. B.; Martínez-Mánez, R.; Sancenón, F.; Hoffmann, K.; Rurack, K. Angew. Chem., Int. Ed. 2006, 45, 5924. (4) Schreiber, F. Prog. Surf. Sci. 2000, 65, 151. (5) Senaratne, W.; Andruzzi, L.; Ober, C. K. Biomacromolecules 2005, 6, 2427. (6) Aswal, D. K.; Lenfant, S.; Guerin, D.; Yakhmi, J. V.; Villaume, D. Anal. Chim. Acta 2006, 568, 84. (7) Hong, L.; Sugimura, H.; Furukawa, T.; Takai, O. Langmuir 2003, 19, 1966. (8) Friedli, A. C.; Roberts, R. D.; Dulcey, C. S.; Hsu, A. R.; McElvany, S. W.; Calvert, J. M. Langmuir 2004, 20, 4295. 2009 Chem. Mater. 2008, 20, 2009–2015 10.1021/cm702758n CCC: $40.75  2008 American Chemical Society Published on Web 02/19/2008