Modification of the structural and optical properties of commercial ZnO powder by mechanical activation

Abstract

Mechanical activation was used as a method for modification of the structural and optical properties of commercial ZnO powder. For this purpose zinc oxide powder was mechanically treated by grinding in a high-energy vibro-mill in a continual regime in air up to 300 minutes. Starting and modified ZnO samples were characterized using XRD, BET and TEM measurements. Optical properties of these samples were investigated by Raman and photoluminescence (PL) spectroscopy. The color of commercial ZnO powder was white while mechanically activated ZnO powder was dark yellow, indicating the presence of nonstoichiometry. In the Raman spectra of non-activated sample Raman modes of bulk ZnO were observed, while the spectra of modified samples point out structural and stoichiometric changes. The PL spectra of modified samples excited by 325 and 442 nm lines of a He-Cd laser show great difference with respect to the spectra of the original sample. This study confirms that change in the defect structure of the ZnO crystal lattice introduced by mechanical activation affects the optical properties of this material

Modification of optical properties in ZnO particles by surface deposition and anchoring of NiO nanoparticles

“…The intensity decrease of the most intense second-order Raman mode with NiO addition is accompanied by a redshift (from ∼1154 cm −1 in ZnO down to ∼1140 cm −1 in ZN25) and broadening. The intensity ratio of this mode to the first-order E 1 (LO) mode, I 2LO /I LO , in ZnO and ZN samples can be used to estimate the electron-LO phonon coupling strength [27,28] . The I 2LO /I LO ratio is decreasing with NiO amount from ∼1.92 in ZnO down to ∼1.48 in ZN25 (Fig.…”

An evaluation of nanostructured zinc oxide as a fluorescent powder for fingerprint detection

“…Similar behaviour was observed for undoped zinc oxide powders indicating that the inclusion of lithium ions is not responsible for the spectroscopic changes upon mechanical grinding. A recent study [18] reported a similar decrease in the visible luminescence excited by UV light after grinding experiments and suggested that mechanical grinding induces changes in the defect structure of the zinc oxide crystal lattice. Our results are consistent with these findings but, in addition to the decrease in defect emission, we note the concomitant increase in the band gap emission intensity.…”

The Effects of Nonstoichiometry on Optical Properties of Oxide Nanopowders

“…The grinding time was 30 and 300 minutes and the powders are labeled as ZnO(30) and ZnO(300), respectively. Average crystallite size obtained from X-ray diffraction (XRD) results are: 190 nm for ZnO(0), 106 nm for ZnO(30), and 44 nm for ZnO(300) [2]. Anatase TiO 2 nanopowder was synthesized by laser-induced pyrolysis, using titanium isopropoxide as a liquid precursor.…”