Self-assembled monolayers of aminosilanes chemically bonded onto silicon wafers for immobilization of purified humic acids

In this paper, we report on the covalent attachment of humic acids on silicon wafers. Monolayers of 11-amino-undecylsiloxane were prepared on silicon wafers by substitution of 11-bromo-undecylsiloxane with an azido group followed by a subsequent reduction. These substrates were coupled with humic acids via a diazotization procedure. Characterization of the functionalized surfaces was performed by different methods: ATR-FTIR, ellipsometry, AFM, TOF-SIMS and amino groups surface density was monitored by UV spectroscopy. These different methods confirmed the immobilization of humic acids on the substrates, consisting in a very useful tool for environmental applications, in particular, for determination of complexation constants between immobilized humic acid moiety and radionuclides. These miniaturized solid state system could be used as a sensitive detector for trace elements in fluid solutions or lixiviation studies in the framework of radionuclide dissemination and modelling studies from radioactive storage. (c) 2006 Elsevier B.V. All rights reserved.