Cinnamon extract's phytochemicals stabilized Ag nanoclusters as nanozymes “peroxidase and xanthine oxidase mimetic” for simultaneous colorimetric sensing of H₂O₂ and xanthine

Green and cost-effective technique for the preparation of silver nanoparticles stabilized with cinnamon's phytochemicals (CIN-AgNPs) as H₂O₂ and xanthine nonozyme is described in the present study. Cinnamon's phytochemicals played the role of effective reducing agents as well as stabilizers of the silver. Nanoparticles were obtained in an optimum time of 90 min at room temperature. The optimum pH was found to be the normal pH of the plant extract (pH = 4.5). High Resolution Transmission Electron Microscopy (HRTEM) showed that most of the particles were regular spherical shaped with particle sizes ranging from 10.0 to 70.0 nm. The patterns were indexed as (111), (200), (220) and (311) reflections of the FCC silver crystal based on their d-spacing of 2.47, 2.13, 1.49 and 1.27 Å respectively. CIN-AgNPs test showed the peroxidase enzyme like activity in the absence of 3,3′,5,5′-tetramethylbenzidine (TMB), while the xanthine oxidase enzyme like activity is shown only when the CIN-AgNPs are combined with TMB. This combination was suitable for the detection of xanthine in the range of 1.0–28 µM with a detection limit of 0.48 µM and a limit of quantitation of 1.45 µM. While CIN-AgNPs test was suitable for the detection of H₂O₂ without the need of TMB with a linear range from 4.7 nM to 25 µM with a limit of detection of 0.62 nM and limit of quantitation of 1.88 nM.