Versatile fabrication and characterization of Cu-doped ZrO2 nanoparticles: enhanced photocatalytic and photoluminescence properties

Abstract

Pristine ZrO2 and molar ratios of Cu-doped ZrO2 nanoparticles were synthesized by chemical precipitation. The XRD pattern of pristine ZrO2 and Cu-doped ZrO2 nanoparticles shows the formation of t-tetragonal phase and shifting of tetragonal phase to monoclinic phase. The average crystallite sizes of the pristine ZrO2 and Cu-doped ZrO2 nanoparticles were calculated as 2.9, 4.65, 4.76, 5.02, and 4.96 nm, respectively. The Cu (0.06 M)-doped ZrO2 nanoparticles are present as spherical morphology and high agglomeration was confirmed by FE-SEM and TEM analyses. The XPS spectra affirmed the presence of Cu2+, Zr4+, and oxygen ions in the Cu (0.06 M)-doped ZrO2 nanoparticles. The Cu-doped ZrO2 nanoparticles exhibit two energy gaps at 5.30 and 3.05 eV, 5.21 and 2.22 eV, 4.65 and 2.11 eV, and 4.44 and 2.65 eV. The surface defects and oxygen vacancies were analyzed by PL and ESR spectroscopy. The ESR spectra are clearly asymmetric in shape and contain a peak signal related to the presence of the copper species (Cu2+) in the distorted tetragonal coordination of ZrO2. The photocatalytic activities of Cu (0.06 M)-doped ZrO2 nanoparticles were successfully sought on degradation of the two azo dyes: methyl violet and methyl blue under sunlight irradiation. Cu (0.06 M)-doped ZrO2 showed complete degradation at 70 min. The reusability of Cu (0.06 M)-doped ZrO2 nanoparticles shows maximum degradation efficiency for six successive runs.