Ionic liquid coated iron nanoparticles are promising peroxidase mimics for optical determination of H 2 O 2 .

Ionic liquid coated nanoparticles (IL-NPs) consisting of zero-valent iron are shown to display intrinsic peroxidase-like activity with enhanced potential to catalyze the oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This results in the formation of a blue green colored product that can be detected with bare eyes and quantified by photometry at 652 nm. The IL-NPs were further doped with bismuth to enhance its catalytic properties. The Bi-doped IL-NPs were characterized by FTIR, X-ray diffraction and scanning electron microscopy. A colorimetric assay was worked out for hydrogen peroxide that is simple, sensitive and selective. Response is linear in the 30-300 μM H2 O2 concentration range, and the detection limit is 0.15 μM. Graphical abstract Schematic of ionic liquid coated iron nanoparticles that display intrinsic peroxidase-like activity. They are capable of oxidizing the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This catalytic oxidation generated blue-green color can be measured by colorimetry. Response is linear in the range of 30-300 μM H2 O2 concentration, and the detection limit is 0.15 μM.