Keggin polyoxometalates based hybrid compounds containing helix/nanocages for colorimetric biosensing

Two Keggin polyoxometalate (POMs) based hybrid compounds containing helix/nanocages as peroxidase-like mimics have been synthesized and structurally characterized. Single crystal X-ray diffraction analysis reveals that compound 1 exhibits a POM-pillared framework with open nanotube channels (ca. 5.6 × 5.8 A2), in which SiW12 polyanions are sandwiched between the adjacent Cu-fkz sheets with meso-helix. And an unprecedented twisted octahedral hexamer nanocage (ca. 10 × 10 A2) is observed in compound 2. Compared with the other POMs involved peroxidase-like mimics, both compounds 1 and 2 exhibit higher peroxidase-like catalytic activities, broader applications range, faster respond time and lower detection limit, which maybe attribute to the maximized synergistic effects of SiW12 clusters, fkz molecules, metal ions and the distinct structure. Based on the facts, compounds 1 and 2 as enzyme mimics might expand their application around physiological pH conditions, and can be used as one kind of effective probe to detect H2O2 in live organism.