Scanning optical microscopy with an electrogenerated chemiluminescent light source at a nanometer tip

Electrogenerated chemiluminescence at electrodes with effective diameters down to 155 nm was used as a stable light source for near-field scanning optical microscopy imaging of an interdigitated array and a submicrometer size test substrate. Light was generated in a thin (∼500 μm) layer of an aqueous solution of 15 mM Ru(bpy)₃²⁺ and 100 mM tri-n-propylamine in a pH 7.5 buffer, The resolution obtained was compared to that found with a micrometer size electrode. The shear force from the tip attached to a quartz tuning fork was used to monitor and control the tip-to-substrate separation within the near field regime.