Femtoliter Batch Reactors for Nanofluidic Scattering Spectroscopy Analysis of Catalytic Reactions on Single Nanoparticles.

Macroscopic batch reactors are a core concept in chemical synthesis and catalysis due to their ability to ensure high conversion rates of the used reactants. At the nanoscale, such reactors hold promise due to their potential to enable chemistry in confinement under well-controlled mass transport conditions, and as enablers for the characterization of catalytic reactions on tiny active surface areas, such as single nanoparticles. However, their practical implementation and the readout of reaction products if used for the study of catalytic reactions is challenging due to their tiny volume and the requirement of being able to transiently open and close such nanoscopic batch reactors. Here, a liquid phase nanofluidic batch reactor with a volume of 4.8 femtoliters is introduced, which conveniently can be opened and closed using a bypassing N₂ gas stream. In combination with nanofluidic scattering spectroscopy (NSS) readout it enables the characterization of a catalytic reaction on a single nanoparticle inside the reactor, as demonstrated on the example of the catalytic reduction of fluorescein by sodium borohydride on a Au catalyst.