Electrochemistry and electrochemiluminescence of benzopyrene and its nanoparticles

We systematically investigated the photophysical, electrochemical and electrochemiluminescence (ECL) behaviour of benzopyrene (BP), a representative polycyclic aromatic hydrocarbon composed of five fused benzene rings, as well as its organic nanoparticles (NPs). Cyclic voltammetry (CV) revealed that BP exhibited a reversible oxidation half-wave potential at +1.13 V and a reversible reduction half-wave potential at −1.94 V (vs. SCE), indicating its stable redox activity. Notably, BP demonstrated strong ECL emission during the reduction-oxidation process, producing a red-shifted spectrum with a broad tailing band spanning 500–750 nm, compared with its photoluminescence (PL) spectrum. To enhance its aqueous dispersibility and functionality, we developed well-dispersed and spherical BP NPs (2–8 nm in diameter) using a reprecipitation method. Key preparation parameters, including optimal good solvent selection, BP concentration in THF, THF/water volume ratio and dropwise addition time, were carefully optimized to ensure monodisperse BP NPs formation. Compared to molecular BP, the BP NPs exhibited a distinct red shift in absorption and a broad PL emission peak at 525 nm, likely due to nanoparticle-induced electronic interactions. Remarkably, the BP NPs displayed strong ECL emission in the presence of tri-n-propylamine (TPA) as a co-reactant, which was effectively quenched upon the addition of dopamine. The ECL intensity exhibited a linear response to dopamine concentration (0.10–10 μM), with a detection limit of 0.09 μM, highlighting their potential as efficient ECL probes for analytical applications. These findings not only advance the understanding of polycyclic aromatic hydrocarbon-based nanomaterials but also open new avenues for designing ECL-active nanostructures for biosensing and environmental monitoring.