Covalent attachment of organic monolayers onto silicon and related surfaces (bionanotechnology)

Covalent attachment of organic monolayers onto silicon and related surfaces (bionanotechnology)

The following paragraphs display our recent results and objectives in a little bit more detail:
1) Covalent attachment of organic monolayers on silicon surfaces.

Our research generally focuses on the reactions displayed in the following scheme:


This yields densely packed monolayers that look somewhat like this:

Making reproducible monolayers is essential if these will be of interest for any application. The goals of our work over the last years therefore were a) to develop methods for the reproducible formation of monolayers, which b) would allow as wide a variation of functional groups attached to it as possible.
What’s been accomplished?
In our Langmuir 1998 paper we were the first to show that is was possible to do organic reactions on functionalized monolayers.  This has opened a big field in itself. Subsequently, in 1999 we published a somewhat boring but highly useful paper that delineates the best uncatalyzed thermal method for monolayer formation: refluxing in mesitylene.  Given its simplicity, it has started to find widespread application.  However, as a result of the high temperatures involved in this (b.p. of mesitylene = 165 ºC), we started to look for a method that was as reproducible, but could be used at room temperature.  After some ‘digging around’ we developed in 2003 the use of visible light photons to accomplish this (see our Angew. Chem. 2004 paper).  The potential of this method becomes clearest if one realizes that the reaction does not only take place at room temperature, but also that the photons do in fact not ‘touch’ the reactive alkenes or alkynes at all.  In other words: they are inert to everything, apart from the silicon surface, at which the reaction is initiated. This reaction proceeds via a chain mechanism (see our STM studies, JACS 2004, 14318), and both the scope and mechanism have been investigated in much detail (JACS 2005, 2514).Its potential becomes evident from the possibility to attach a highly labile sialic acid-derivate to the silicon surface (see our JACS 2003 paper).  Current projects extend both our methodological and mechanistic work in this area, and the introduction of a wide variety of functional groups.  The latter is specifically interesting for our recent work in the field of bionanotechnology that received a significant boost via grants to my group of Nanoimpuls, NanoNed and Wageningen University with a total value of >3 million Euro (2003 and 2004).

Current co-workers: dr. Ahmed Arafat, Barend van Lagen, Jurjen ter Maat, Michel Rosso, Aliaksei Pukin, Luc Scheres, Louis de Smet, dr. Bin Sun and Milena Vasic. Several vacancies are available for excellent candidates with interest in (bio-)nanotechnological projects.

Recent publications:

  • Solvent study: Alex B. Sieval, Vincent Vleeming, Han Zuilhof, Ernst J.R. Sudhölter Langmuir 1999, xx, yyy.
  • Covalently attached oligosaccharides on silicon surfaces. Louis C.P.M. de Smet, 8 others, H. Zuilhof, and E. J. R. Sudhölter J. Am. Chem. Soc. 2003, 13816. 
  • Qiao-Yu Sun, Louis C.P.M. de Smet, Barend van Lagen, Han Zuilhof, Ernst J. R. Sudhölter Angew. Chem. Int. Ed. 2004, 43, 1352.  Click here for pdf file.
  • A short review of this area was published in: High-Quality Alkyl Monolayers on Surfaces Alex B. Sieval, Ralf Linke, Han Zuilhof, Ernst J. R. Sudhölter Adv. Mat. 2000, 12, 1457.  Click here for pdf-file.
  • Covalently attached monolayers on crystalline hydrogen-terminated silicon: Extremely mild attachment by visible light. Qiao-Yu Sun, Louis C. P. M. de Smet, Barend van Lagen, Marcel Giesbers, Peter C. Thüne, Johan van Engelenburg, Frits A. de Wolf, Han Zuilhof, and Ernst J. R. Sudhölter, J. Am. Chem. Soc.; 2005; 127(8) 2514 – 2523.

Several post-graduate and post-doctoral positions are available for start in 2005 or 2006.  Please contact me for further information.