Adsorption enhanced the oxidase-mimicking catalytic activity of octahedral-shape Mn3O4 nanoparticles as a novel colorimetric chemosensor for ultrasensitive and selective detection of arsenic.

Several researches have reported that Mn3O4 nanoparticles (NPs) could be used as adsorbent to remove arsenic from aqueous solution. However, we found that Mn3O4 NPs can not only adsorb arsenic, but also enhance the catalytic activity of Mn3O4 NPS, which enable us to establish a new method for the determination of arsenic. Herein, the adsorption of arsenic changes surface morphology of octahedral Mn3O4 NPs and further release Mn2+ to generate sufficient active sites, which enhances their oxidase-mimicking catalytic activity. Consequently, the solution changes to yellow and displays a characteristic absorption peak at 450 nm. This property enables us to construct a novel colorimetric chemosensor for arsenic detection. The limit of detection (LOD) of such colorimetric chemosensor for arsenic detection was determined as 1.32 μg⋅L-1, which is lower than the threshold recommended by WHO. The chemosensor allows arsenic to be determined visually at the concentrations as low as 10 μg⋅L-1, and displays excellent selectivity against other metal ions. Moreover, the chemosensor was successfully validated by analyzing several actual environmental and biological samples, indicating the excellent prospect of octahedral Mn3O4 NPs in the application of arsenic detection and removal.