Quantification of grafted poly(ethylene glycol)​-​silanes on silicon by time-​of-​flight secondary ion mass spectrometry

Fadhil S. Kamounah, K. Norrman , A Papra, N. Gadegaard, N.B. Larsen

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Abstract

Silicon grafted monodisperse poly(ethylene glycol) (PEG) silanes with various PEG chain lengths and mixtures of these were systematically analyzed with static time-of-flight secondary ion mass spectrometry (TOF-SIMS). The mass spectra show differences in the various relative signal intensities, an observation that was used to elucidate important aspects of the grafting process. The relationship between PEG-silane fragment ion abundances and Si+ ion abundances were used to (i) qualitatively describe layer thicknesses of grafted mixtures of PEG-silanes on silicon, (ii) construct a calibration curve from which PEG chain length (or molecular mass) can be determined and (iii) quantitatively determine surface mixture compositions of grafted monodisperse PEG-silanes of different chain lengths (3, 7 and 11 PEG units). The results suggest that discrimination does take place in the adsorption process. The PEG-silane with the shorter PEG chain is discriminated for mixtures containing PEG3-silane, whereas the PEG-silane with the longer PEG chain is discriminated in PEG7/PEG11-silane mixtures. The origin of this difference in adsorption behavior is not well understood. Aspects of the grafting process and the TOF-SIMS analyses are discussed
OriginalsprogEngelsk
TidsskriftJournal of Mass Spectrometry
Vol/bind37
Udgave nummer7
Sider (fra-til)699-708
Antal sider10
ISSN1076-5174
DOI
StatusUdgivet - 2002
Udgivet eksterntJa

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