Abstract
The aim of this work is the analysis of pH-dependent adhesion on micropatterned electrografted aryldiazonium salts on gold substrates. A PDMS stamp inked with 1-octadecanethiol (ODT) solution was used for microcontact printing. Electrografting of nitrophenyl (C6H5–NO2) occurred in the ODT-free regions. An additional electrochemical reduction step led to aminophenyl (C6H5–NH2) covered surfaces. The corresponding surface chemical states of the pattern were investigated by means of PM-IRRAS and XPS. The local surface structure was microscopically analyzed by means of FE-SEM and AFM as well as nano-FTIR spectroscopy. The ODT covered areas of the patterned substrates allowed for clear distinction between the pH-dependent forces of the nitrophenyl (C6H5–NO2)- and aminophenyl (C6H5–NH2)-terminated layers as measured by chemical force microscopy. COOH-functionalized AFM tips in aqueous electrolytes ranging from pH 5–10 were employed. It could be shown that the aminophenyl (C6H5–NH2) terminated surface led to higher adhesion forces in comparison to the nitrophenyl (C6H5–NO2) group.
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