Enhanced luminol chemiluminescence with oxidase-like activity of NiOOH/Ni(OH) nanoflakes for the sensitive detection of Mn.

Nickel hydroxide nanoflakes incorporating amorphous nickel oxyhydroxide (NiOOH/Ni(OH) NFs) were synthesized through a chemical oxidation approach. NiOOH/Ni(OH) NFs maintains the two-dimensional structure of Ni(OH) nanoflakes with an enlarged specific surface area. Furthermore, the amorphous NiOOH possesses abundant high-valence nickel active sites, endowing the material with remarkable oxidase-like activity. This catalytic property enabled the generation of reactive oxygen species (ROS) from dissolved oxygen, enhancing the luminol chemiluminescence (CL) intensity by over 2,000-fold without requiring external oxidants. Mn significantly quenched the CL signal by scavenging ROS, enabling a linear detection range of 1 - 30 μmol·L and a detection limit of 0.60 μmol·L, which is threefold lower than the World Health Organization (WHO) permissible limit (1.80 μmol·L) for drinking water. The sensor was successfully applied to tap and lake water samples, demonstrating simplicity, rapid response, and high selectivity, making it a promising method for environmental monitoring.