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

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.