Modulation of dielectric and antibacterial properties of Zn_0.5Mn_0.5O nanoparticles by post growth annealing method

In this manuscript, we have investigated the dielectric and antibacterial potential of hydrothermally synthesized ZnMnO nanoparticles. The synthesized nanoparticles were annealed at various temperatures ranging from 450 to 650 °C with a step of 50 °C to modulate the structural, vibrational, dielectric, and antibacterial properties. XRD data confirmed the hexagonal structure of the synthesized samples and crystalline size was decreased to 4.8 nm at annealing temperature 600 °C. The lattice structure was further verified by Raman spectroscopy measurements, which strongly verified the XRD data due the presence of ZnMnO vibrational modes. The dielectric measurements revealed that the dielectric constant and los tangent were found to be increased with the increase annealing temperature and decreased with frequency, while a.c conductivity has an increasing trend with both parameters (temperature and frequency). The plot of real and complex parts of impedance against frequency demonstrated that both parameters decrease with the increased in frequency. But when we analyzed the behavior of the real part of impedance against the annealing temperature, a degradation in real part behavior is observed. The antibacterial activity of ZnMnO nanoparticles was determined by using the disc diffusion method against E. coli bacteria, which was grown on a Petri dish at room temperature for 24 h. This observation revealed that the samples annealed at 450 °C and 550 °C show remarkable antibacterial sensitivity as compared to other samples. It is concluded that crystalline size of 20 nm is found to be optimal value for good anti-baterial behavior.