Development of a cysteine sensor based on the peroxidase-like activity of AgNPs@ FeO core-shell nanostructures.

In this study, a facile one step solvo-thermal procedure has been employed in generating magnetite-silver core-shell nanocomposites (AgNPs@ FeO) with superior peroxidase-like catalytic property than bare magnetic nanoparticles (FeO). The composites were characterized using different techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and surface-enhanced infrared absorption spectroscopy (SEIRA). In the presence of hydrogen peroxide, the synthesized composites were able to oxidize the colorless o-phenylenediamine (OPD) to a yellow colour 2, 3-diaminophenazine (DAP) with a better peroxidase-like activity than FeO alone. The obtained K value of AgNPs@ FeO with HO and OPD substrates are 28.0 mM and 2.91 mM respectively. These are substantially lower than previously reported values and indicate the strong binding affinity of the substrates towards AgNPs@ FeO nanocomposites. Based on the obstruction activity of cysteine on the peroxidase-like catalytic property of the nanocomposites, a sensor was developed for detection of cystein with a limit of detection as low as 87 nM and a wider range of linearity. The sensor also exhibited excellent selectivity against potentially interfering molecules.