Fe₃O₄ Magnetic Nanoparticles as Peroxidase Mimetics Used in Colorimetric Determination of 2,4-Dinitrotoluene

Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) were prepared by co-precipitation method, which possessed intrinsic peroxidase-like activity. It was found that the as-prepared Fe₃O₄ MNPs could not only catalyze the oxidation of peroxidase substrate, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate acid) (ABTS) by H₂O₂ to produce the colored product with maximum absorbance at 417 nm, but also catalyze the oxidation of 2,4-dinitrotoluene (DNT) by H₂O₂ and thus consume H₂O₂ in the reaction system. On the basis of the reaction mechanism described above, a novel colorimetric reaction system of Fe₃O₄ MNPs-ABTS-H₂O₂-DNT was established for the determination of trace amount of DNT. Some key influencing factors of the proposed Fe₃O₄ MNPs-ABTS-H₂O₂-DNT system were systematically discussed and optimized. Under the optimal conditions, the absorbance of the system at 417 nm displayed a good linear relationship with DNT concentration in the range from 5.0 × 10^-7 M to 2.0 × 10^-5 M with a detection limit of 1.5 × 10^-7 M (S/N = 3).