Comparison of ZnO Nanoparticles Synthesized by Microwave-assisted and Precipitation Method*

In this work, Zinc Oxide (ZnO) Nanoparticles were synthesized using precipitation and microwave methods with different pH values (8, 9, and 10). Structural properties were studied by means of Transmission Electron Microscopy (TEM), X-ray Diffraction Spectroscopy (XRD), Impedance Spectroscopy, and Optical Spectroscopy. TEM images revealed that the morphology of nanoparticles increased from 8 nm to 16 nm synthesized by precipitation method while the diameter increased from 9 nm to 15 nm in microwave assisted method. The XRD confirmed the wurtzite structure in all samples with no secondary phases. Optical properties were studied by means of Photoluminescence (PL) and absorption measurement. Band gap of nanoparticles were also calculated and found to decrease from 3.25 eV to 3.18 eV in ZnO particles prepared by the precipitation method, whereas bandgap decreases from 3.21 eV to 3.19 eV in the microwave method. Electrical transport properties of nanoparticles were analyzed by impedance spectroscopy using Cole-Cole plot technique. From Impedance spectra, we observe that resistance and capacitance of nanoparticles depend on the size of nanoparticles synthesized by both precipitation and microwave method.