Dual responsive magnetic Fe3O4-TiO2/graphene nanocomposite as an artificial nanozyme for the colorimetric detection and photodegradation of pesticide in an aqueous medium

The Fe3O4-TiO2/reduced graphene oxide (Fe3O4-TiO2/rGO) nanocomposite was successfully prepared by one step hydrothermal method and exhibit intrinsic peroxidase mimic activity and photocatalytic efficiency. The asprepared nanomaterials were characterized by several analytical tools including XRD, HRTEM, FESEM, XPS, VSM, FT-IR, AFM, TGA and zeta potential analysis. The average particle size of Fe3O4 and TiO2 NPs on the rGO nanosheets are found to be 9 +/- 0.2 nm. The synthesized nanocomposite showed dual responsive including highly sensitive calorimetric detection of harmful atrazine pesticide in an aqueous medium as well as photocatalytic degradation of atrazine pesticide. The Fe3O4-TiO2/rGO nanocomposite showed the efficient peroxidaselike catalytic activity throughout the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) as a peroxidase substrate to the blue-colored oxidized product (ox-TMB) in presence of H2O2. Based on this observation, the colorimetric detection technique is applied for the sensing of atrazine as model pesticides using TMB as a peroxidase substrate molecule and 2.98 mu g/L of the limit of detection (LOD) was obtained in the linear range of 2-20 mu g/L. Thus the proposed colorimetric sensing technique is simple and low cost for the real-time monitoring of the pesticides in an aqueous medium. Further, the Fe3O4-TiO2/rGO nanocomposite was also successfully utilized towards efficient photocatalytic degradation of atrazine molecule (100 %) under irradiation of natural sunlight. Moreover, Fe3O4-TiO2/rGO nanocomposite was successfully recycled for 10 times without a significant loss of its photocatalytic efficiency. This work delivers a new insight for the dual responsive of the Fe3O4-TiO2/rGO nano-composite as an artificial nanozyme for colorimetric sensing of the water pollutant and also removal of the water pollutant by simple photocatalytic degradation method under natural sunlight irradiation.