Counter Anion-Directed Growth of Iron Oxide Nanorodsin a Polyol Medium with Efficient Peroxidase-Mimicking Activity forDegradation of Dyes in Contaminated Water

摘要

Development of nanozymes, which are nanomaterials with intrinsic enzymatic properties, has emerged as an appealing alternative to the natural enzymes with tremendous application potential from the chemical industry to biomedicine. The self-assembled growth of micrometer-sized oxide materials with controlled nonspherical shapes can be an important tool for enhancing activity as artificial enzymes, as the formation of these superstructures often results in high surface area with favorable impact on catalytic activity. Herein, the growth of rod-shaped Fe3O4 microstructures via a one-pot microwave-based method and using a water–poly(ethylene glycol) mixture as a solvent is reported, without the involvement of external shape-directing agents. The precursor metal salt played a key role in the size, shape, and phase selective evolution of iron oxide microanomaterials. Whereas self-assembled microrod superstructures were obtained using Fe(NO3)3 as the metal salt precursor, use of FeCl3 or Fe-acetate as precursors afforded hollow Fe2O3 microparticles and Fe3O4 nanoparticles, respectively. A graphitic layer was deposited on the Fe3O4 surface, imparting a negative surface charge as a result of a high-temperature treatment of poly(ethylene glycol). The rod-shaped Fe3O4 microcrystals show efficient peroxidase-mimickingactivity toward 3,3,5,5′-tetramethylbenzidine and pyrogallolas peroxidase substrates with a Michaelis–Menten rate constant(Km) value of 0.05 and 0.52 mM, respectively.The proficient enzyme mimicking behavior of these magnetic superstructureswas further explored for the degradation of organic dyes that includesrhodamine B, methylene blue, and methyl orange with a rate constant(k) of 0.038, 0.011, and 0.007 min^–1 respectively, using H2O2. This fast and simplemethod could help to develop a new pathway for differently shapedoxide nanoparticles in a sustainable and economical manner that canbe harnessed as nanozymes for industrial as well as biological applications.