Andrographis paniculata extract mediated green synthesis of CdO nanoparticles and its electrochemical and antibacterial studies

CdO nanoparticles based on Andrographis paniculata plant extract were synthesizedby biological method and characterized by XRD, FESEM, HRTEM and FTIR. XRD exhibits face centred cubic structure with an average crystallite size of 22 nm and the lattice strain (W–H plot) is 0.0023. From the HRTEM, the particles are spherical. The vibrational stretching mode of Cd–O is 456 cm⁻¹. From the UV–Vis spectra, the optical energy bandgap is estimated as 2.33 eV. The photoluminescence emission peaks at 360, 430, 486, 528 and 616 nm are observed for the excitation at 220 nm. The electrochemical study by cyclic voltammetry reveals the quasi reversible reduction and irreversible oxidation versus Saturated Calomel Electrode (SCE). The potential is referred to the F_c/F_c ⁺ couple under the experimental conditions. The biosynthesized CdO nanoparticles are tested against gram positive (Rhodococcus rhodochrous and Staphylococcus aureus) and gram negative (Escherichia coli, Aeromonas hydrophila and Vibrio Cholera) bacterial strains. It is noted that the bioengineered CdO nanoparticles show a good antibacterial activity (zone of inhibition: E. coli-16 mm) bacteria.