In this work, pure and Alumina doped cobalt ferrite nanoparticles CoFe 2−x Al x O 4 (for x = 0.44) have been synthesized by the sol gel method. The influence of alumina doping on the morphological and mechanical properties of CoFe 2 O 4 nano-particles were investigated by means of X-ray powder diffraction (XRD) and rietveld analysis. XRD analysis confirmed that the single phase formation of pure nano particles with the expected cubic inverse spinel structure with Fd3m space group and without any impurity phase. Alumina doping were led to a decrease in the crystallite size, lattice parameter, elastic constants and magnitude of moduli. It is explained on the basis of the replacement of Fe ions with half-filled d-shell (3d 5 ) and larger radius by Al 3+ ions with a completely filled shell (2p 6 ) and smaller radius.

Synthesis and complex theoretical and experimental studies of Co/TiO 2 anatase have been reported. The preparation of Co/TiO 2 was carried out by sol-gel method. Distribution of cations among the two tetrahedral and octahedral sites was estimated by analyzing the powder X-ray diffraction patterns by employing Rietveld refinement technique, and the results revealed the existence of tetragonal structure. Band structure and density of states calculations were performed using the first-principles methods. The structural and electronic properties of Co/TiO 2 were calculated in the general gradient approximation (GGA). An additional comparison with pure TiO 2 anatase allowed us to clarify cobalt doping effect on the electronic structure and the band gap. The band gap of Co/TiO 2 was decreased by broadening the valence band as a result of the overlap among Co 3d, Ti 3d, and O 2p states, which made it respond better to visible and solar light.

In this study, we present a systematic study of linear and nonlinear optical properties of Para Red with the aim of Z-scan technique and quantum mechanical calculations. The Z-scan experiments were performed using a 532 nm Nd: YAG (SHG) CW laser beam. Para Red exhibited a strong nonlinear refractive index, nonlinear absorption coefficient and third-order nonlinear susceptibility 3.487 × 10−6 cm2/W, 2.341 × 10−1cm/W and 2.157 × 10−4 esu, respectively. Also, quantum chemical analysis was used for the calculation of the dipole moment μ, dipole polarizability α, anisotropy of polarizability Δα and molecular hyperpolarizabilities (β,γ). The results revealed that Para Red has large first and second hyperpolarizabilities. However, from the obtained results, it was found that Para Red can be a promising material for applications in the development of non-linear optical materials.

ABSTRACT. In this work, we have characterized the linear and nonlinear optical properties of N,N′-bis(salicylidene)-p-phenylenediamine (BSP) in both macroscopic and microscopic modes by using Z-scan technique and quantum chemical calculations. The microscopic nonlinear optical properties of BSP were investigated by density functional theory with the basis set of 6-311G++dp. Electronic properties such as frontier molecular energies, band-gap energy, electron affinity, hardness, softness, and ionization potential were evaluated. The calculation of microscopic quantities included first-order hyperpolarizability and natural bond orbitals showed the electron delocalization, which confirmed the nonlinear optical properties in this compound. The results of the absorption spectrum of BSP in DMSO, DMF, CH3Cl solvents were shown that the dissolved sample in DMSO had better nonlinear properties than others. Then the macroscopic nonlinear properties of the sample were determined by the Z-scan technique. The values of the nonlinear refractive index (n2), nonlinear absorption coefficient (β), and third-order nonsusceptibility of the sample in DMSO were, 0.09250×10-10 cm2/W, -0.174×10–6 cm/W and 4.101× 10-5 esu, respectively. The two-photon absorption in this molecule has been enhanced by the donor–bridge–donor (D–π–D) architecture. The theoretical and experimental results concluded that BSP seems to be promising candidates for future photonic and optoelectronic devices.                 KEY WORDS: Azo dye, Nonlinear optic, Hyperpolarizability, One photon absorption, Two photon absorption, Schiff bases   Bull. Chem. Soc. Ethiop. 2022, 36(2), 465-477.                                                               DOI: https://dx.doi.org/10.4314/bcse.v36i2.18                                                      

In the present work, the Co/TiO 2 nanocomposite was prepared by sol-gel method. The structural and optical properties of nanocomposite were studied using, X-ray diffraction (XRD) and diffuse reflectance UV-VIS spectrometry. The XRD spectra revealed its tetrahedral anatase structure. The grain size and optical properties of composite are also reported. Syntesied Co/TiO 2 photocatalyst showed excellent activity for the photodegradation of Methyl orange whether under visible and ultraviolet light irradiation.