Search

The dysprosium (Dy) (1.12, 2.24, 3.33 and 4.02 at.%) modified zinc oxide (ZnO) nanoparticles were synthesized by simple chemical co-precipitation method. The prepared nanoparticles were analyzed by EDAX, TEM, FTIR, EPR, VSM and dielectric studies. The energy dispersive analysis of X-rays confirms the presence of Dy, Zn and O in the prepared samples. The transmission electron micrographs of the prepared samples show that the particles are spherical in nature with average size 22–18 nm. The shifting of Zn–O peak towards lower frequency side in the FTIR spectra of the prepared samples confirms the substitution of Dy ion in the ZnO lattice. EPR investigations exhibit paramagnetic signals at g- 1.956, 2.04 and 2.323. The magnetic properties of the synthesized Dy doped ZnO NPs reveal weak ferromagnetic behavior. The studies on electrical properties of the prepared samples provided new and interesting information on the contribution of grains, grain boundaries and interfacial polarization on dielectric parameters and electrical conductivity.

Ce-doped ZnO nanoparticles (NPs) with different Ce doping concentrations (0, 0.96, 1.96, 2.52 and 3.12 at.% of Ce) were prepared by the chemical co-precipitation method. Energy-dispersive analysis of X-rays confirms the presence of Ce in Ce-doped ZnO nanoparticles. Raman spectra revealed the hexagonal wurtzite structure of pure and Ce-doped ZnO nanoparticles and presence of various defects. The photoluminescence spectra exhibited enhanced violet and blue emission peak intensities for 0.96 at.% of Ce, while broad band green emissions decreased with Ce content. Electron paramagnetic resonance (EPR) studies revealed the presence of oxygen vacancies (V O), zinc vacancies (V Zn) and Ce3+ ions in the prepared ZnO nanoparticles. VSM studies showed room temperature ferromagnetism (RTFM) in the Ce-doped ZnO NPs. The substituted Ce3+ions found to induce RTFM along with V O, V Zn in correlation with the results obtained from the EPR, PL and Raman studies. The variation of dielectric constants (e r), dielectric loss (e″) and ac conductivity (σ ac) as a function of frequency and Ce concentration is studied using ‘Maxwell–Wagner Model.’

Transesterification of β-ketoesters with different alcohols has been studied under conventional and unconventional conditions using the simple desktop chemical cesium carbonate as catalyst. These methods enabled transesterification of β-ketoesters in good yields with dramatic rate acceleration and reduced reaction times. The procedures which used unconventional methods, for example sonication and microwave irradiation, are highly promising compared with conventional procedures.