Hollow Double-Shell CuCo2O4@Cu2O Heterostructures as a Highly Efficient Coreaction Accelerator for Amplifying NIR Electrochemiluminescence of Gold Nanoclusters in Immunoassay

The evolution of electrochemiluminescence (ECL) emission amplified by coreaction accelerator in near-infrared (NIR) area has been overwhelmingly anticipated for ultrasensitive detection of disease biomarkers. Herein, the hollow double-shell CuCo₂O₄@Cu₂O (HDS-CuCo₂O₄@Cu₂O) heterostructures were conveniently prepared and utilized as an attractive coreaction accelerator to improve the NIR ECL performance of gold nanoclusters (AuNCs) for the first time. Benefiting from perfect-matched lattice spacing, unique Cu₂O nanoparticles (NPs) were formed in situ on the layered-hollow CuCo₂O₄ nanospheres (NSs) to obtain HDS-CuCo₂O₄@Cu₂O heterostructures. The formed heterojunctions supplied shorter charge transfer distance and better interfacial charge transfer efficiency as well as more effective separation performance. Consequently, HDS-CuCo₂O₄@Cu₂O heterostructures as an admirable electroactive substrate could significantly promote the formation of sufficient coreactant intermediate radicals to react with AuNCs cationic radicals, realizing about 3-folds stronger NIR ECL response than that of individual AuNCs. In addition, the AuNCs templated by l-methionine (l-Met) exhibited NIR ECL emission around 830 nm, which could decrease the photochemical damage to even realize a nondestructive detection with improved susceptibility and circumambient adaptability. Subsequently, a well site-oriented fixation strategy utilizing HWRGWVC heptapeptide as the specific antibody immobilizer was introduced to further preserve the bioactivity of antibody on the HDS-CuCo₂O₄@Cu₂O and AuNCs surface along with enhancing the incubation performance markedly. In view of the progressive sensing mechanism, a NIR immunosensor was obtained for the ultrasensitive analysis of CYFRA21-1, which achieved a broad linear ranging from 2 fg/mL to 50 ng/mL and a low limit of detection (LOD) of 0.67 fg/mL (S/N = 3).