Target-triggered oxygen vacancy increase of Co 3 O 4 nanoparticles with promoted peroxidase-like activity for specific turn-on colorimetric sensing of uranyl ions

As the most stable form of uranium in water and soil, uranyl ions (UO 2 2+ ) possess strong biological toxicity and radioactivity, causing a great threat to human health. Therefore, it is of significance to develop reliable methods for monitoring uranyl ions in the environment. Here we propose a “light-up” colorimetric strategy based on target-accelerated peroxidase-mimicking activity of Co 3 O 4 for the specific detection of uranyl ions. Original Co 3 O 4 nanoparticles exhibit a certain peroxidase-like activity in catalyzing colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB with the participation of H 2 O 2. When UO 2 2+ is introduced, it interacts with the nanozyme rapidly and specifically and promotes the latter’s catalytic ability via increasing active oxygen vacancies on Co 3 O 4 surface. According to such a phenomenon and mechanism, selective determination of UO 2 2+ with favorable performance is achieved, with a linear measurement range of 0.2–10 μM and a detection limit of 0.08 μM. Reliability and practicability of the proposed method are demonstrated by analyzing the pollutant in several environmental water matrices. Our work not only offers a novel, efficient yet convenient approach for measuring UO 2 2+, but may also inspire the exploration of new nanozyme-based sensing principles and strategies for other analytical applications.