Gold Nanocatalysts Towards Digital Sensing Probes with Electrochemiluminescence Based Micro Electrodes Array

Abstract The authors have found that gold nanoparticles (AuNP) function as nanocatalysts for the generation of reactive oxygen species such as hydrogen peroxide from dissolved oxygen in coexistence with tris(hydroxymethyl)aminomethane (Tris) or N ‐[tris(hydroxymethyl) methyl]glycine (Tricine) chemicals, and that these can be evaluated by luminol electrochemi‐luminescence (ECL). In the present study, we investigated the effects of reaction time, particle concentration, and temperature on the catalytic properties of gold nanoparticles. Unlike biocatalysts such as enzymes, the gold nanoparticles showed an Arrhenius plot‐like increase in activity with temperature without inactivation. In addition, the catalytic activity of the gold nanoparticles varied with the size and shape of the nanoparticles for spherical gold nanoparticles of different sizes (5, 15, 30, 50 and 400 nm) and the activity per nanoparticle increased with the size and surface area. When compared activity per surface area, 15 nm nanoparticles showed higher activity. We prepared gold nanoparticles with nanoflower (AuNF) structure of approx.200 nm in size which showed higher activity per particle than 400 nm spherical particles. The increase in surface area and the difference in surface condition may have influenced these results. We also prepared microelectrode arrays capable of holding small amounts of nl‐pL test reagents. They showed the possibility of imaging ECL of the activity of gold nanoparticles at the level of tens of nanoparticles which could lead to nanocatalysts as probes for digital analysis.