Fabrication of island-type microelectrode via AFM lithography for a highly sensitive Pt-ion detection system

A sensor system for Pt-ion detection with a micron-sized electrode was fabricated via the combination of atomic force microscopy (AFM) lithography and a self-assembly method. For the adsorption of Pt ions, organosilane with imidazole functional groups was immobilized on the square frame of a mesa-patterned area, and gold nanoparticles (AuNPs) were deposited on the remaining area for use as a fixed electrode. This fabricated island-type electrode was characterized and applied as an effective Pt-ion detector. The existence of Pt ion adsorbed in detection zone was directly confirmed by lateral force microscopy (LFM) analysis, which demonstrates the dramatic height variations with respect to platinum concentrations. For further precise detection, conductance derived by the tunneling current between the AFM tip (mobile electrode) and the Au immobilized surface (fixed electrode) was measured. In the detection system, the change in the conductance is strongly dependent on the Pt ion concentration. Our results suggest that the island-type micro-electrode sensor system is useful to detect very small quantities of metal ions with short response time and high sensitivity when appropriate functional groups are introduced to the micron-sized detection area.