Surface Oxygen Vacancy-Rich Co<sub>3</sub>O<sub>4</sub> Nanowires as an Effective Catalyst of Luminol–H<sub>2</sub>O<sub>2</sub> Chemiluminescence for Sensitive Immunoassay
Jing Lei, Ling Zhang, Mei Li, Wei Liu, Yan Jin, Baoxin Li
Abstract
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 Co 3 O 4 nanowires in the luminol–H 2 O 2 chemiluminescence (CL) reaction. 0.1 ng/mL Co 3 O 4 nanowires containing 51.3% surface oxygen vacancies possessed ca. 2.5-fold catalytic activity of free Co 2+ (the best metal ionic catalyst for the luminol–H 2 O 2 CL reaction). The superior catalytic efficiency is attributed to the enhanced adsorption of H 2 O 2 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 Co 3 O 4 nanowires retained about 90% catalytic activity after modification with antibodies. The surface oxygen vacancy-rich Co 3 O 4 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 Co 3 O 4 nanowires are suitable for labeling biomolecules in CL bioanalysis and biosensing.