Mono V-substituted phosphomolybdic acid with intrinsic oxidase-like activity and near-instantaneous response

Compared with peroxidase, oxidase does not rely on H ₂ O ₂ as a substrate, and usually has high selectivity towards substrates, catalyzing specific oxidation reactions. Fortunately, in the work, mono V-substituted phosphomolybdic acid H ₅ [PMo ₁₁ VO ₄₀ ] (PMo ₁₁ V ₁ ) was found for the first time to possess oxidase-like activity and exhibits near-instantaneous response time (5s, the fastest respond among all reported nanozyme to date), where the coexistence of Mo ⁶⁺ /Mo ⁵⁺ and V ⁵⁺ /V ⁴⁺ after the reaction implies that the transformation between elemental oxidation states dominates the reaction mechanism, rather than a unidirectional decrease. More specifically, high valent Mo and multi-valent V can catalyze the oxygen in water to generate O ₂ ^{· −} , · OH, and H ₂ O ₂ , a cascade catalytic reaction, further catalyze H ₂ O ₂ into · OH. With the reducibility of tannic acid (TA), a convenient, sensitive and effective colorimetric platform for TA detection was successful established, which shows good respond toward TA with a linear relationship in the range of 0-100 µM and a low detection limit of 0.34 µM. Also the application of the PMo ₁₁ V ₁ sensor for TA detection in real tea was demonstrated and satisfactory results was obtained.