In this work, Cobalt (0-10) % doped MgO nanoparticles are prepared for magnetic and optical studies. X-ray diffraction studies show the particle size increases from 3.10 nm to 9.50 nm with increasing Cobalt concentration in MgO samples. The secondary phases are observed beyond 5% Cobalt in the host MgO which indicates the solubility limit of dopant in this material. SEM analysis further reconfirms the purity and spherical morphology of nanoparticles in all samples. Its result also reveals that the smallest particles have the largest oxygen vacancy concentration as compared to other samples. The dopant and size-induced effects are observed for electronic absorption spectra and bandgap of the samples.  UV-visible absorption spectra show a quantum confinement effect as the optical band gap decreases with the increase of the particle size. The optical band gap of the nanoparticles ranges from 4.68 eV to 3.15 eV which is very less in comparison with the bulk MgO band gap up to 7.2eV.  Vibrating sample magnetometer studies at room temperature clearly show the ferromagnetic behavior for pure MgO nanoparticles in contrast with the paramagnetic behavior for other samples.  It is suggested that the presence of the ferromagnetic behavior in pure MgO nanoparticles are due to the presence of oxygen vacancies.

Effects of Cu addition (0-5)% in ZnO are studied for structural and optical properties. The structural, photoluminescence properties and vibrational modes are strongly influenced with the Cu incorporation. Detailed investigations of the structural features of Cu doped ZnO nanostructures are reported. Our results show the systematic decrease in crystallite size (50.40 - 37.56 nm), lattice strain (1.82 - 1.49 micro), lattice stress (216.33 - 177.64 MPa) and energy density (196.78 - 132.69 KJ/m3) in the limit of small dopant concentration (0 < Cu ? 0.02). Decreasing trends are attributed to the smaller ionic size of Cu in comparison of Zn. Beyond Cu= 0.02 an increasing trend was noticed in crystallite size (41.67 - 70.67 nm), lattice strain (1.90 – 3.11 micro), lattice stress (226.32 – 369.35 MPa) and energy density (215.40 – 573.67KJ/m3. This increase in structural parameters is attributed to segregation of secondary phases for Cu content increase beyond 0.02. Two prominent regions in PL spectra were observed and the deconvoulution of these regions show a strong correlation with the structural changes observed within the limit of high and low dopant concentration. The FTIR spectra show shift of Zn-O vibrational mode toward higher frequency with increasing Cu concentration.