Single gold nanoparticle electrode for electrogenerated chemiluminescence and dark field scattering spectroelectrochemistry

Studying electrocatalytic metal nanoparticles (NPs) at the single particle level is highly desirable to unfold their structure-function correlation. In this report, we present the fabrication and spectroelectrochemistry characteristics of light-scattering single Au NP at the tip of an electrochemically etched sharp tungsten (W)electrode. Au NPs with a tunable particle size (≥60 nm) can be obtained at the W tips by adjusting the Au electrodeposition conditions. Catalyzed electrogenerated chemiluminescence (ECL) from Tris(2,2′-bipyridine) ruthenium (II) (Ru(bpy)32+)/Tri-n-propylamine (TPrA) system at single Au NP electrode shows an increase in its intensity with Au NP particle size in the range of 300 nm–500 nm. The potential application of these single Au NP electrodes in the studies of electrocatalytic reaction and spectroelectrochemistry at the nanometer scale is demonstrated using dark-field scattering (DFS) spectroelectrochemistry method. The decrease in DFS intensity upon oxidation of hydrazine at the single Au NP electrode is attributed to the formation of low-refraction-index N2 near the surface of the Au NP to decrease its light scattering cross-section. Single Au NP electrode presented in this work would help improve instrument capability of scanning electrochemical microscope (SECM) and near-field scanning optical microscope (NSOM) techniques for ultrasensitive electrochemical analysis. [Display omitted]