Catalytic kinetics of single gold nanoparticles observed via optical microwell arrays.

Catalytic activities and kinetics are measured at the single-particle level for gold nanoparticles catalyzing a fluorogenic oxidation reaction. This measurement is accomplished by confining the reactions in optically addressable microwell arrays. Citrate-capped gold nanoparticles are isolated in sealed ∼70 fL microwells along with a substrate, and the accumulation of a fluorescent product over time is observed. Thousands of reactions are measured in parallel. Catalytic activities are calculated for each nanoparticle and the activity distribution is analyzed.