M. S. Li

Joint Experimental and Theoretical Analysis of Order−Disorder Effects in Cubic BaZrO3 Assembled Nanoparticles under Decaoctahedral Shape

Periodic first-principles calculations based on density functional theory at the B3LYP level has been carried out to investigate the photoluminescence (PL) emission of BaZrO(3) assembled nanoparticles at room temperature. The defect created in the nanocrystals and their resultant electronic features lead to a diversification of electronic recombination within the BaZrO(3) band gap. Its optical phenomena are discussed in the light of photoluminescence emission at the green-yellow region around 570 nm. The theoretical model for displaced atoms and/or angular changes leads to the breaking of the local symmetry, which is based on the refined structure provided by Rietveld methodology. For each situation a band structure, charge mapping, and density of states were built and analyzed. X-ray diffraction (XRD) patterns, UV-vis measurements, and field emission scanning electron microscopy (FE-SEM) images are essential for a full evaluation of the crystal structure and morphology.

Urea-based synthesis of zinc oxide nanostructures at low temperature

The preparation of nanometer-sized structures of zinc oxide (ZnO) from zinc acetate and urea as raw materials was performed using conventional water bath heating and a microwave hydrothermal (MH) method in an aqueous solution. The oxide formation is controlled by decomposition of the added urea in the sealed autoclave. The influence of urea and the synthesis method on the final product formation are discussed. Broadband photoluminescence (PL) behavior in visible-range spectra was observed with a maximum peak centered in the green region which was attributed to different defects and the structural changes involved with ZnO crystals which were produced during the nucleation process.

Correlation between structural and electronic order–disorder effects and optical properties in ZnO nanocrystals

The correlation between structural and electronic order–disorder effects in understanding the optical properties of flower-like ZnO nanocrystals synthesized by the microwave-assisted hydrothermal method at low temperatures and short times is discussed. Theoretical simulations were performed at the density functional theory level to gain a better understanding of the experimental data from X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), electron paramagnetic resonance (EPR), ultraviolet-visible diffuse reflectance (UV-vis) spectroscopy and photoluminescence (PL) measurement studies at different temperatures. The decrease in band gap values is due to the presence of intermediate states above the conduction band. These discrete levels are formed by structural and electronic disorder of tetrahedral [ZnO4] clusters which enhance the electron–hole pair.