Highly sensitive and specific colorimetric detection of phosphate by using Zr(Ⅳ) to synergistically suppress the peroxidase-mimicking activity of hydrophilic Fe3O4 nanocubes

Due to the role of phosphate (PO 4 3− ) as an indicator of eutrophication pollution, developing low-cost and high-performance approaches to detect it turns to be of great significance. Herein, we developed a highly sensitive and specific colorimetric sensor for PO 4 3− determination via utilizing Zr 4+ to synergistically inhibit the peroxidase-like activity of Fe 3 O 4 nanocubes. The decoration of hydrophilic 3,4-dihydroxyhydrocinnamic acid (DHCA) on Fe 3 O 4 endows it with enhanced ability to catalyze the 3,3′,5,5′-tetramethylbenzidine (TMB) chromogenic reaction. Because of electrostatic interaction, Zr 4+ is easy to be adsorbed onto the negatively charged Fe 3 O 4 -DHCA nanozyme. When PO 4 3− is added, it can interact with Zr 4+ and form a coating on Fe 3 O 4 -DHCA surface, significantly suppressing its peroxidase-mimicking activity. As a result, the TMB chromogenic reaction is seriously inhibited in the presence of PO 4 3− . Based on this strategy, PO 4 3− in the wide scope of 0.066–33.3 μM could be linearly determined, providing a detection limit down to 49.8 nM. Thanks to the strong and specific interaction between Zr 4+ and PO 4 3− , the colorimetric sensor could be employed to detect PO 4 3− with favorable selectivity. Reliable analysis of the target in practical water was also verified by our assay, indicating its great potential as a simple but efficient tool for environmental monitoring.