Facile synthesis of Au@Ag–hemin decorated reduced graphene oxide sheets: a novel peroxidase mimetic for ultrasensitive colorimetric detection of hydrogen peroxide and glucose

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Herein we report the facile synthesis of a quaternary nanocomposite material (hemin–silver coated gold–graphene oxide) and evaluate its efficacy as a novel peroxidase mimetic. A strong synergistic coupling between the various components involved results in an excellent catalytic performance of this nanocomposite. A comparison of the different morphologies of the silver coated gold particles strongly indicates a greater sensitivity of the nanostar morphology over the nanoparticle morphology owing to its high surface-to-volume ratio. Furthermore, the immobilization of hemin and silver coated gold nanostars on a graphene oxide sheet framework imposes a nanoscale confinement, effectively augmenting the overall catalytic performance of the composite. The nanocomposite followed typical Michaelis–Menten theory and electrochemical analysis suggested facilitation of accelerated electron transfer between TMB and H2O2. A KM value of 2.75 mM−1 suggested a high affinity of the nanocomposite towards TMB. Furthermore, a 2.8 times increase in the maximum reaction rate compared to HRP established the high catalytic activity of the nanocomposite. The nanocomposite demonstrates a nanomolar range sensitivity towards hydrogen peroxide and glucose (limit of detection = 1.26 nM and 425 nM). The nanocomposites have also been employed to develop a paper-based point-of-care diagnostic device. The device has been utilized for detection of glucose in human blood serum samples with satisfactory results.