Surface Oxygen Vacancy-Rich Co3O4 Nanowires as an Effective Catalyst of Luminol–H2O2 Chemiluminescence for Sensitive Immunoassay

Oxygen vacancy is one intrinsic defect in metal oxide materials. Interestingly, we herein found that the surface oxygen vacancy can significantly enhance the catalytic activity of Co3O4 nanowires in the luminol-H2O2 chemiluminescence (CL) reaction. 0.1 ng/mL Co3O4 nanowires containing 51.3% surface oxygen vacancies possessed ca. 2.5-fold catalytic activity of free Co2+ (the best metal ionic catalyst for the luminol-H2O2 CL reaction). The superior catalytic efficiency is attributed to the enhanced adsorption of H2O2 by surface oxygen vacancies, which in turn accelerates the cleavage of O-O bonds and generates •OH radicals. More importantly, the surface oxygen vacancy-rich Co3O4 nanowires retained about 90% catalytic activity after modification with antibodies. The surface oxygen vacancy-rich Co3O4 nanowires were used to label the secondary antibody, and one sandwich-type CL immunoassay of carcinoembryonic antigen was established. The detection limit was 0.3 ng/mL with a linear range of 1-10 ng/mL. This proof-of-concept work proves that surface oxygen vacancy-rich Co3O4 nanowires are suitable for labeling biomolecules in CL bioanalysis and biosensing.