Green synthesis of silver and palladium nanoparticles using Lithodora hispidula (Sm.) Griseb. (Boraginaceae) and application to the electrocatalytic reduction of hydrogen peroxide

Biosynthesis of silver and palladium nanoparticles was carried out by using Lithodora hispidula (Sm.) Griseb. Leaf extract as a reducing agent. The silver and palladium nanoparticles (NPs) were characterized by UV-Visible spectroscopy, inductively coupled Plasma-Mass Spectrometer, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis. UV-Vis spectra of biosynthesized silver nanoparticles showed an absorption band at 425 nm. The formation of palladium nanoparticles was confirmed by the disappeared absorption band at 410 nm. Scanning electron microscopy analysis showed that Ag, AgPd spherical and Pd nanoparticle morphology were rod in shape. The electrochemical behaviour of Ag, Pd and AgPd alloy nanoparticles were investigated by cyclic voltammetry. Modified glassy carbon electrodes were constructed by using Ag, Pd and AgPd nanoparticles and used in electrocatalytic reduction of hydrogen peroxide in phosphate buffer medium (pH = 6.5), in potential range of 0.0 and -0.8 V vs. Ag/AgCl at 100 mV/s scan rate. The AgPdNPs-GCE based sensor could detect the H2O2 in the linear range of 0.02-5.0 mM with a detection limit of 0.52 μM. The AgPdNPs-GCE showed a good repeatability and stability for detection of H2O2. Furthermore, it exhibited no interference with some biological species such as glucose, ascorbic acid and uric acid.