Mimicking the silicon surface: reactivity of silyl radical cations toward nucleophiles
Rijksen, B.M.G. ; Lagen, B. van; Zuilhof, H. - \ 2011
Journal of the American Chemical Society 133 (2011)13. - ISSN 0002-7863 - p. 4998 - 5008.
hydrogen-terminated silicon - organic monolayers - alkyl monolayers - si(111) surfaces - porous silicon - si - functionalization - oligosilanes - attachment - 1-alkenes
Radical cations of selected low molecular-weight silicon model compounds were obtained by photoinduced electron transfer. These radical cations react readily with a variety of nucleophiles, regularly used in monolayer fabrication onto hydrogen-terminated silicon. From time-resolved kinetics, it was concluded that the reactions proceed via a bimolecular nucleophilic attack to the radical cation. A secondary kinetic isotope effect indicated that the central Si-H bond is not cleaved in the rate-determining step. Apart from substitution products, also hydrosilylation products were identified in the product mixtures. Observation of the substitution products, combined with the kinetic data, point to an bimolecular reaction mechanism involving Si-Si bond cleavage. The products of this nucleophilic substitution can initiate radical chain reactions leading to hydrosilylation products, which can independently also be initiated by dissociation of the radical cations. Application of these data to the attachment of organic monolayers onto hydrogen-terminated Si surfaces via hydrosilylation leads to the conclusion that the delocalized Si radical cation (a surface-localized hole) can initiate the hydrosilylation chain reaction at the Si surface. Comparison to monolayer experiments shows that this reaction only plays a significant role in the initiation, and not in the propagation steps of Si-C bond making monolayer formation
Light-enhanced microcontact printing of 1-alkynes onto hydrogen-terminated silicon
Maat, J. ter; Yang, M. ; Scheres, L.M.W. ; Kuypers, S. ; Zuilhof, H. - \ 2010
Chemical Communications 46 (2010)42. - ISSN 1359-7345 - p. 8005 - 8007.
self-assembled monolayers - scanning-electron-microscopy - organic monolayers - alkyl monolayers - visible-light - surfaces - 1-alkenes - alkanethiols - attachment - chemistry
method for the direct patterning of 1-alkynes onto hydrogen-terminated silicon is presented. It combines microcontact printing with illumination through the stamp, and results in the formation of an alkenyl monolayer. The formation of heterogeneous monolayers is demonstrated by subsequent backfilling
Self-Assembly of High-Quality Covalently Bound Organic Monolayers onto Silicon
Scheres, L.M.W. ; Arafat, A. ; Zuilhof, H. - \ 2007
Langmuir 23 (2007). - ISSN 0743-7463 - p. 8343 - 8346.
hydrogen-terminated silicon - acid mediated hydrosilylation - extremely mild attachment - alkyl monolayers - porous silicon - si(111) surface - visible-light - si - functionalization - 1-alkenes
A very mild method has been developed to obtain covalently attached alkyl monolayers from the attachment of 1-alkynes onto hydrogen-terminated silicon surfaces at room temperature in the dark. Apart from being the mildest method reported so far for the preparation of such monolayers, their quality, as indicated by water contact angles, XPS, and infrared spectroscopy, equals within experimental error that of the best reported alkyl monolayers on silicon.
Tailor-made functionalization of silicon nitride surfaces
Arafat, A. ; Schroën, C.G.P.H. ; Smet, L.C.P.M. de; Sudhölter, E.J.R. ; Zuilhof, H. - \ 2004
Journal of the American Chemical Society 126 (2004)28. - ISSN 0002-7863 - p. 8600 - 8601.
hydrogen-terminated silicon - alkyl monolayers - 1-alkenes
This communication presents the first functionalization of a hydrogen-terminated silicon-rich silicon nitride (Si3Nx) surface with a well-defined, covalently attached organic monolayer. Properties of the resulting monolayers are monitored by measurement of the static water contact angle, X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRRAS). Further functionalization was performed by reaction of Si3Nx with a trifluoroethanol ester alkene (CH2=CH-(CH2)8CO2CH2CF3) followed by basic hydrolysis to afford the corresponding carboxylic acid-terminated monolayer with hydrophilic properties. These results show that Si3Nx can be functionalized with a tailor-made organic monolayer, has highly tunable wetting properties, and displays significant potential for further functionalization.
Covalently Attached Saccharides on Silicon Surfaces
Smet, L.C.P.M. de; Stork, G.A. ; Hurenkamp, G.H.F. ; Qiao-Yu, S. ; Topal, H. ; Vronen, P.J.E. ; Sieval, A.B. ; Wright, A. ; Visser, G.M. ; Zuilhof, H. ; Sudhölter, E.J.R. - \ 2003
Journal of the American Chemical Society 125 (2003). - ISSN 0002-7863 - p. 13916 - 13917.
hydrogen-terminated silicon - alkyl monolayers - si(111) surface - dna - hybridization - chemistry - biosensor - 1-alkenes - acid
This paper presents the first functionalization of silicon surfaces with well-defined, covalently attached monolayers containing saccharides. Two methods were used to this aim: a thermal method (refluxing in mesitylene) and a recently developed, extremely mild photochemical method (irradiation with 447 nm at room temperature). The results were analyzed by FT-IR and angle-resolved X-ray photoelectron spectroscopy. The use of a two-dimensional detector in ARXPS allows for unparalleled, subnanometer resolution in the determination of the elemental composition of monolayers. Even for monolayers with a total thickness of only ~1.5 nm, a clear elemental depth profile can be obtained. Such analyses display for sialic acid-containing monolayers that the mild photochemical attachment does not destroy the (rather fragile) sialic acid moiety and that the sugar is present at the top of the monolayer and thus available for biological interactions.
Preparation of polystyrene brushes by reaction of terminal vinyl groups on silicon and silica surfaces
Maas, J.H. ; Cohen Stuart, M.A. ; Sieval, A.B. ; Zuilhof, H. ; Sudhölter, E.J.R. - \ 2003
Thin Solid Films 426 (2003). - ISSN 0040-6090 - p. 135 - 139.
alkyl monolayers - films - copolymers - 1-alkenes - forces
We have grafted end-functionalised polystyrene bonds via a covalent bond on hydrogen-terminated silicon and on silica surfaces. The reaction is carried out using a polymer melt. The grafting density of the brushes prepared in a polymer melt is much higher than those obtained by reaction in solution. The reaction of the vinyl-terminated polystyrene takes place at the surface under very mild conditions. The preparation of both brushes is a versatile `one pot¿ synthesis involving only the substrate and the vinyl-terminated polystyrene. The method also allows bimodal (mixed) brushes to be prepared from a suitable mixture of precursors