Most known chemiluminescence (CL) reactions exhibit flash-type light emission. Great efforts have been devoted to the development of CL systems that emit light with high intensity and long-lasting time. However, a long-lasting CL system that can last for hundreds of hours is yet-to-be-demonstrated. Here we show firefly-mimicking intensive and long-lasting CL hydrogels consisting of chitosan, CL reagent N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and catalyst Co2+. The light emission is even visible to naked eyes and lasts for over 150 h when the hydrogels are mixed with H2O2. This is attributed to slow-diffusion-controlled heterogeneous catalysis. Co2+ located at the skeleton of the hydrogels as an active site catalyzes the decomposition of slowly diffusing H2O2, followed by the reaction with ABEI to generate intensive and long-lasting CL. This mimics firefly bioluminescence system in terms of intensity, duration time and catalytic characteristic, which is of potential applications in cold light sources, bioassays, biosensors and biological imaging.

Graphene- or graphene oxide (GO)-supported metallic nanoparticles and single metal atom as potentially effective catalysts for chemical reactions have recently received extensive research interests. However, metal utilization in nanoparticle catalysts is limited and metal atoms readily drift on the graphene surface and consequently form aggregated large particles, making practical applications limited. Here, we report metal ions directly immobilized on GO as a novel GO-supported single-ion catalyst for chemiluminecence (CL) reactions. It is found that GO-supported cobalt ions with good stability could catalyze strongly luminol-HO and lucigenin-HO CL reactions, accompanied by dramatically enhanced CL emission. Theoretical studies reveal that the coupling between Co and GO induces effective polarization charges, improving chemical activity of the reaction site, which promotes the generation of intermediate radicals and accelerates the CL reactions. This work may be generalized to other GO-supported metal ions as catalysts for a wide range of chemical reactions. The developed GO-supported cobalt single-ion nanocomposites as nanointerfaces may find future applications in CL bioassays.

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