Nano-FTIR and chemical force analysis of electrografted aryldiazonium salts on ODT-microcontact printed Au-surfaces

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 electro-chemical 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 nitro-phenyl (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.