Matrix redox interference-free nanozyme-amplified detection of Hg2+ using thiol-modified phosphatase-mimetic nanoceria

Given heavy metals pose huge threats to ecological system and human health, it is significant to monitor them. With the favorable feature of catalytic signal amplification , redox-type nanozymes have been widely used to detect heavy metals. However, the presence of redox substances in samples can interfere with these catalytic reactions , impacting the accuracy and repeatability of detection. To avoid the situation, here we designed a non-redox nanozyme (3-mercaptopropionic acid modified nanoceria, MPA-CeO 2 ) and developed a novel approach free from matrix redox interference to detect Hg 2+ . The well-dispersed MPA-CeO 2 showed high and stable phosphatase-mimetic activity to catalyze the hydrolysis of colorless p -nitrophenyl phosphate ( p -NPP) to yellow p -nitrophenol ( p -NP). The addition of Hg 2+ could bind specifically onto the MPA-CeO 2 particles through S–Hg bond and cause the latter to aggregate, thereby suppressing the ability of MPA-CeO 2 with shielded active surfaces to hydrolyze p -NPP. According to the simple principle, highly sensitive and specific colorimetric measurement of Hg 2+ was achieved, and excellent reliability and practicability were demonstrated by real sample analysis. To our best knowledge, this study is the first one of detecting Hg 2+ using phosphatase-mimicking nanozymes, and it will inspire the exploration of new analytical methods via designing non-redox nanozymes for various targets.