Gold–Silver Bimetallic Alloy Nanoparticles in a Covalent Organic Framework for Real-Time Monitoring of Hydrogen Peroxide from Live Cells

An efficient and simple way has been described to prepare gold and silver bimetallic alloy nanoparticles (Au-AgNPs) in an organic framework with a metal-free core. The growth of alloy Au-AgNPs was monitored by UV–visible spectroscopy (UV–vis) and confirmed using various spectral, microscopy, and electrochemical techniques. The field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results revealed that the covalent organic framework (COF) had a uniform flake-like morphology, and the alloy-based Au-AgNPs had a flower-like structure. The results of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) indicated that Au-AgNPs are metallic in nature and highly crystalline. The surface of a glassy carbon electrode (GCE) was then modified with Au-AgNPs-COF, which was subsequently employed for enzyme-free electrochemical reduction of H2O2. The electrocatalytic cyclic voltammetry performance of the different modified electrodes was in the following order: COF (−14.82 μA) < AgNPs-COF (−26.95 μA) < AuNPs-COF (−31.78 μA) < Au-AgNPs-COF (−46.15 μA). The Au-AgNPs-COF/GCE displayed an excellent electrocatalytic activity toward reduction of H2O2, over a dynamic range of 2.0 nM–1.0 mM with a limit of detection (LOD) of 0.44 nM (S/N = 3). Furthermore, the present sensor showed appreciable selectivity, stability, and reproducibility against the reduction of H2O2. Practicality was demonstrated in fetal bovine serum (FBS), cat blood serum (CBS), and living cells (RAW 264.7).