Images were obtained with a Molecular Imaging PicoPlus 2500 AFM (Agilent Technologies). Silicon cantilevers (Model Pointprobe, Nanoworld) with a resonance frequency of around 240 kHz and nominal force constant of 42 N m−1 were used. All AFM images were recorded in air and in tapping mode, with scan speeds of about 0.5 Hz and data collection at 256 × 256 pixels. At least two mica specimens were prepared for each solution, and at least 6 distinct areas of each specimen were investigated using the sample probe tip. The solutions were prepared in the absence and presence of 2.0 × 10−4 M [Ru(bpy)3]2+ complex and 2.0 × 10−3 M C2O42− plus cacodylate buffer at pH 7.0 plus the suitable [AuNP].
100 μL of solutions was dropped onto a mica surface and adsorbed for 30 min in a humidified chamber. Following incubation, samples were washed with ultra-pure water and subsequently air dried for AFM imaging. In order to prevent the formation of salt crystals on the mica surface, the rinse was performed without cacodylate buffer.
100 μL of solutions was dropped onto a mica surface and adsorbed for 30 min in a humidified chamber. Following incubation, samples were washed with ultra-pure water and subsequently air dried for AFM imaging. In order to prevent the formation of salt crystals on the mica surface, the rinse was performed without cacodylate buffer.