Green synthesized ZnO@CuO nanocomposites using Achyranthes aspera leaves extract for dielectric applications

Abstract

ZnO@CuO Nanocomposites (NCPs) were synthesized using Achyranthes aspera plant’s leaves extract with varying weight percents of 25, 50 and 75 of ZnO. The leaves extract was prepared using laboratory distilled water with the help of magnetic stirrer at a temperature of 60ᵒC. An appropriate amount of zinc nitrate and copper nitrate were then mixed in the extract. ZnO@CuO NCPs were obtained after calcination of paste at a temperature of 400ᵒC. The annealed samples were characterized using various characterization techniques such as x-ray diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and UV–vis spectrophotometry. FESEM images showed spherical morphology for CuO and ZnO@CuO NCPs, whereas, ZnO exhibited nanocapsules like morphology. The XRD patterns and FTIR spectra of green synthesized CuO and ZnO confirmed the formation of single-phase crystalline structure with monoclinic and hexagonal lattices. The XRD patterns of ZnO@CuO NCPs exhibited both phases corresponding to CuO and ZnO. FTIR spectra indicated all characteristic absorption bands of CuO and ZnO nanoparticles, which along with XRD Patterns confirmed the formation of ZnO@CuO NCPs. The optical band gap energy was calculated through Tauc’s relation using UV-Vis absorbance data and was found in the range of 1.54–3.05 eV. Optical band gap for nanocomposites is slightly less than that of pure ZnO and CuO nanoparticles. Dielectric studies established that the nanocomposites ZnO@CuO (25 and 50 wt% of ZnO) possess higher dielectric constant (K), dielectric loss and AC conductivity. ZnO@CuO (50 wt%) exhibits maximum dielectric constant of 14.49 × 103 with moderate dielectric loss. Hence, ZnO@CuO (50 wt%) could be a potential candidate for high K value device applications like capacitors and supercapacitors.