Different from crystalline cobalt oxides (Co(3)O(4) and CoO) and most reported nanozymes, amorphous CoO(x) was found to exhibit better oxidase-like catalytic performance than the peroxidase one. Mechanistic investigations revealed that the introduction of H(2)O(2) could decompose CoO(x) into inactive Co(2+) under acidic conditions, leading to the loss of catalytic activity. With the unusual phenomenon, a proof-of-concept "turn-off" cascade system was fabricated to detect glucose color...
