Chemiluminescence initiated by nebulization of oxidant- and catalyst-free aqueous luminol solutions

Chemiluminescence (CL), i.e., the emission of light during chemical reactions without external optical excitation, is widely used in clinical medicine, bioassays, reporter gene assays, and bioimaging. Given the complexity of traditional CL systems, which typically contain catalysts and oxidants, one-component (i.e., luminophore-only) alternatives are urgently required. Herein, to demonstrate the feasibility of such simple systems, we realize CL by nebulizing oxidant- and catalyst-free aqueous luminol solutions and demonstrate that it originates from the oxidation of luminol by the center dot OH radicals spontaneously formed on the microdroplet surface. The higher intensity of this CL system compared to that observed for a reference bulk-phase CL system containing H2O2 as an oxidant and FeSO4 as a catalyst is ascribed to the high specific surface area and luminol adsorption capacity of the microdroplets, and excess hydroxide ions on their surface. Thus, this work demonstrates that microdroplets provide a favorable environment for CL reactions and paves the way for the establishment of one-component CL systems.