Enhanced electrochemiluminescence of luminol based on Cu₂O-Au heterostructure enabled multiple-amplification strategy

Herein, a credible construction strategy to improve electrochemiluminescence (ECL) of luminol was developed based on Cu₂O-Au heterostructures. Summarily, gold nanoparticles (AuNPs) were anchored on surface of Cu₂O nanocube (Cu₂O@AuNPs) by spontaneous reduction reaction. Then, luminol molecules were concentrated on Cu₂O@AuNPs using L-Cysteine (Cys) as covalent linkage to build the composite emitter (Cu₂O@AuNPs-Cys-luminol). The enhancement mechanism was realized by following aspects: (I) Cu₂O@AuNPs worked as electrocatalyst for glucose to generate coreactant of H₂O₂ in situ, avoiding the instability of direct addition of H₂O₂. (II) luminol molecules were firmly attached on Cu₂O@AuNPs to achieve centralized and strong luminescence at low consumption. (III) Cys acted as an intramolecular coreactant and directly linked to luminol to increase luminous efficiency. To validate the effectiveness, a sandwiched immunoassay was built using concanavalinA (ConA) as analyte. Electroreduced graphene film as substrate provided phenoxy-derivatized dextran (DexP) with abundant binding sites and improved conductivity. To improve the specificity, DexP was used to identify ConA via the specific carbohydrate-ConA interaction. Then, Cu₂O@AuNPs-Cys-luminol was modified on electrode as ECL signal indicator. The ECL immunosensor achieved determination of ConA with low detection limit of 2.9 × 10^-5 ng/mL and excellent stability of continuous potential scan for 8 cycles. Experimental results demonstrated that the proposed construction strategy made considerable progress in ECL efficiency and stability of luminol. The creational pattern of construction strategy achieves high detection capabilities to ConA and expands the applicability of luminol in ECL system. It is expected to have more potential application value in immunoassay with universality.