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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.’

The reaction kinetics of Prussian blue (PB)/NaNO2 initiated for the nitration of phenols by in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [phenol], [NaNO2], and [PB]. An increase in [KHSO4] accelerated the rate of nitration under otherwise similar conditions. The rate of nitration was faster in the solvent of higher dielectric constant (D). Observed results were in accordance with Amis and Kirkwood plots [log k′ vs. (1/D) and [(D − 1)/(2D + 1)]. These findings together with the linearity of plots, log k′ versus (vol% of acetonitrile (ACN)) and mole fraction of (nx) ACN, probably indicate the importance of both eloctrostatic and nonelctrostatic forces, solvent–solute interactions during nitration of phenols. Reaction rates accelerated with the introduction of electron-donating groups and retarded with electron-withdrawing groups, which are interpreted by Hammett's theory of linear free energy relationship. Hammett's reaction constant (ρ) is a fairly large negative (ρ < 0) value, indicating attack of an electrophile on the aromatic ring. Furthermore, an increase in temperature decreased the reaction constant (ρ) values. This trend was useful in obtaining isokinetic temperature (β) from Exner's plot of ρ versus 1/T. Observed β value (337.8 K) is above the experimental temperature range (303–323 K), indicating that the enthalpy factors are probably more important in controlling the reaction.

Pure and erbium (1.30, 1.79, 2.83 and 3.53 at. %) doped ZnO nanoparticles are synthesized by wet chemical co - precipitation method. The synthesized s amples are characterized by powder X - ray diffraction (XRD), energy - dispersive analysis of X - rays (EDAX), transmission electron microscopy (TEM), Raman spectroscopy, UV - visible diffusion reflectance spectroscopy (DRS) and LCR Impedance spectroscopy. The XRD measurements confirmed the hexagonal wurtzite structure of all samples and size of the particle is found to be decreased with Er content. TEM images show spherical shape with more agglomeration in Er doped ZnO nanoparticles. Raman spectra confirmed the he xagonal wurtzite structure of pure and Er doped ZnO nanoparticles with E 2 (high) mode at 438 cm - 1 and presence of other possible defects. UV - visible DRS shows decrease in the band gap with increasing Er 3+ in ZnO host. Dielectric constant, dielectric loss f actor and ac conductivity properties were decreased with Er

Pure and Dy(1.15, 2.24, 3.33 and 4.02 at.%)-doped ZnO nanoparticles were prepared by the chemical co-precipitation method. The as prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA-DTA), Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) studies. XRD studies confirm both undoped and Dy-doped ZnO nanoparticles reveal wurtzite structure with average grain size in the range of 24–16 nm and are in agreement with TEM analysis. EDS confirms the presence of Dy in Dy-doped ZnO nanoparticles. Raman studies, confirm the wurtzite structure of ZnO nanoparticles besides increase in defects with doping concentration. UV–Vis DRS measurements indicated a blue shift optical band gap with Dy-doping. PL spectrum demonstrated immense enhanced green emission which attributes to the increase in defects concentration. The emissions intensity could be tuned by varying the Dy concentration and excitation wavelength as well for the application of better optoelectronic devices.

The EPR and magnetic properties were investigated on vapour phase grown Zn 1− x Cr x Te ( 0.001 ⩽ x ⩽ 0.005 ) crystal samples at room temperature. The EPR spectra were observed for samples with x = 0.001 , 0.002 only. The simulations of the spectra confirm Cr 3+ charge state of the dopant ion at tetrahedral symmetry. The magnetic behaviour of the samples with x = 0.001 and 0.002 is neither that of Brillouin paramagnets nor Van Vleck systems while the samples with compositions x = 0.003 , 0.004 and 0.005 exhibited hysteresis behaviour.

Pure and Er (2, 3 and 4 at. %) doped ZnO nanoparticles have been synthesized by chemical co-precipitation method. EDS spectrum confirmed the presence of Zn, O and Er in the synthesized samples. The XRD measurements confirmed the hexagonal wurtzite structure of ZnO for all samples. The crystallite size of the samples decreases with increase in concentration and are compatible with the results that obtained from TEM analysis.EPR spectra exhibitedferromagnetic signals the substitution Er The possible ferromagnetic zinc interstials signal is appeared for 2 at. % of Er dopant. The room temperature ferromagnetic is observed only for 2 at. % of Er while all other samples exhibiting weak ferromagnetic nature.

Undoped ZnO and rare earth elements (Ce, Dy and Er with 2 at. %) doped nanoparticles were synthesized by wet chemical co-precipitation method at 90°C with Polyvinylpyrrolidone (PVP) as capping agent. The structural, morphological, compositional and photoluminescence studies were performed with X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS), FTIR spectroscopy and Photoluminescence (PL) respectively. XRD results revealed hexagonal wurtzite structure with average particle size around 18 nm - 14 nm and are compatible with TEM results. EDS confirm the incorporation of Ce, Dy and Er elements into the host ZnO matrix and is validated by FTIR analysis. PL studies showed a broad intensive emission peak at 558 nm in all the samples. The intensity for Er- doped ZnO found maximum with additional Er shoulder peaks at 516nm and 538 nm. No Ce, Dy emission centers were found in spectra.