Anderson polyoxometalates with intrinsic oxidase-mimic activity for “turn on” fluorescence sensing of dopamine

Anderson-type polyoxometalate containing Fe 3+ and Mo 6+ , (NH 4 ) 3 [H 6 Fe(III)Mo 6 O 24 ] (FeMo 6 ), was found to work as an oxidase-mimicking nanoenzyme for the first time, exhibiting the ability of catalytic oxidation of o -phenylenediamine (OPD), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTs), and 3,3′,5,5′-tetramethylbenzidine (TMB), which features easy synthesis, low cost, simple operation, and low consumption. Attributed to the nature of FeMo 6 and Fenton-like effect, a novel sensor based on two consecutive “turn on” fluorescence was developed for detecting dopamine (DA) by employing the FeMo 6 -OPD system, and the linear range was from 1 to 100  μ M with the detection limit 0.0227  μ M (3σ/s). Moreover, to increase oxidase-mimic activity of FeMo 6 , reduced graphene oxide (rGO) loading FeMo 6 composites (FeMo 6 @rGO (n), n  = 5%, 10%, 15%) was fabricated, and results show that oxidase-like activities of FeMo 6 @rGO (n) are dependent on the mass ratio of FeMo 6 /rGO, and FeMo 6 @rGO (10%) exhibits the highest oxidase-mimic activity and the fastest respond time (4 min) among all reported oxidase mimic of DA to date. Anderson-type Mo-POMs FeMo 6 was found to work as an oxidase-mimicking nanoenzyme for the first time and was used to detect DA for two consecutive “turn on” fluorescence sensor modes