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Zn_0.97TM_0.03O (TM = Co, Fe) thin films were deposited onto glass substrates by the sol–gel method and the effects of transition metals substitution on structural and optical properties of ZnO films were investigated. The X-ray diffraction patterns revealed that the films have wurtzite structure. Optical transmittance of the films was recorded in the range of 200 -800 nm wave length and the band gap of the films was determined. The absorption edge of the films showed a small shift depending on the substitution elements. The optical constants of the films were calculated by using pointwise unconstrained minimization algorithm.

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The hydrothermal method due to advantages of low reaction temperatures and achieving fine particles in synthesized samples was used. Li₂SiO₃ has orthorhombic structure with Cmc21 space group and cell parameters a = 9.392, b = 5.397 and c = 4.660Å.  The structure, size and morphology of nano particles were investigated by XRD, FT-IR and SEM analysis methods. In addition, the cell parameters of lithium metasilicate nano particles were determined by CELREF software version3. Optical properties of synthesized silicates were investigated by UV-vis and Pl analysis methods.

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In this research, CdS nanoparticles and core/shell CdS/ZnS nanoparticles were prepared by using aqueous solution method and used 3-mercaptopropionic acid (MPA) as capping molecule. The effect of ZnS shell on optical and structural properties of CdS was investigated. X ray diffraction patterns of CdS nanoparticles at the room temperature and after heat treatment show zinc blende structure. X ray diffraction patterns of CdS/ZnS nanoparticles are wider because of overlapping diffraction patterns of ZnS and CdS. The size of CdS and CdS/ZnS nanoparticles was calculated by using Debay-Scherrer equation which is 2.7 nm and 1.7 nm at room temperature, respectively, and after heat treatment obtained 3.2 nm and 1.9 nm, respectively. FTIR studies were used to indicate coating of the MPA molecule on nanoparticles. In the TEM image of CdS/ZnS nanoparticles, it can be seen small nanoparticles and some agglomeration which is due to nonuniform distribution of particles on the grate sample holder in TEM measurement.

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The nanostructured nickel oxide thin films were prepared by dip coating sol – gel method. Three methods (drying with oven, IR and microwave) have used for drying the films. The effect of drying method on the optical, molecular, electrical, structural, and morphology properties of the films were studied by Uv-Visible spectrophotometry, Fourier Transform Infrared spectroscopy, Hall effect, X-ray diffraction, Atomic Force Microscopy, and Scanning Electron Microscopy. Optical constants of nickel oxide thin films were calculated by using Pointwise Unconstrained Minimization Approach. The optical band gap of the films dried by infrared, oven, and microwave methods obtained 3.62, 3.59, and 3.47eV, respectively. The X-ray diffraction patterns of samples show that the film dried by infrared is amorphous while by two other methods are crystalline.

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In this research, molybdenum oxide (α-MoO₃) thin films were coated on glass substrates using spray pyrolysis technique. 0.05 M ammonium heptamolybdate tetrahydrate was used as precursor and deionized water as solvent. The effects of carrier gas pressure, during the spraying of the solution, on the structural, optical, morphological and gas sensing properties of thin films were studied. X-ray diffraction (XRD) pattern analysis showed preferred growth at (020) peak direction and the formation of alpha phase of molybdenum oxide. The most intensive peaks were observed in the XRD pattern of the sample prepared under the carrier gas pressure of 2 bar, which indicates better crystallization of the sample. In addition, Raman spectrum of this sample confirmed the XRD results. UV-Vis spectroscopy results showed that the sample prepared under the carrier gas pressure of 1.8 bar has the highest optical absorption and the lowest band gap (~ 3.48 eV). Scanning electron microscope (SEM) images showed the layer structure of samples. Moreover, gas sensor devices based on the prepared samples at different carrier gas pressures, were fabricated and their sensing performances were investigated. Results showed that, the work temperature (i.e. the lowest temperature with the highest gas response at the specified ethanol vapor concentration of 200 ppm) was 200 ºC and belongs to the sample prepared under the carrier gas pressure of 1.8 bar. Also, studying the effect of ethanol vapor concentration extent for this sample showed the increasing of sensitivity percent from 1.42 to 15.62 % for 100 to 1000 ppm ethanol vapor, respectively.

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This study have been developed BiFeO₃/reduced graphene oxide (BFO/RGO) nanocomposites by introduction of RGO in the structure of BFO nanoparticles in a short term ultrasonic treatment. The X-ray diffraction pattern and Fourier-transform infrared spectroscopy analysis reveal that the BFO/RGO composites were successfully synthesized. UV-visible absorption show that the introduction of RGO can effectively reduce the recombination of photo-generated electron and hole pairs and the lower band gap energies were also identified for BFO/RGO composites as compared to 1.97 eV for BFO. The photocatalytic performance of BFO/RGO nanocomposites is stable and exhibit considerably higher photocatalytic ability over the pristine BFO for the degradation of methyl orange solution under visible light irradiation. The possible mechanism behind the superior photocatalytic performance of BFO/RGO nanocomposite has been critically discussed.

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In this work, the first ZnO/CuO nanocomposites were synthesized by chemical vapour deposition (CVD), thermal evaporation (PVD) and sputtering on silicon substrates (Si). Then, the structural, optical and electrical properties of the samples were investigated. Examination of the X-ray diffraction patterns confirmed the mixed-phase formation of hexagonal zinc oxide (ZnO) and monoclinic copper oxide (CuO) phases, resulting in the formation of ZnO/CuO composite in all methods. The plan view images obtained from FESEM analysis showed that the morphology of the samples prepared by the CVD method differs from other samples and is as nanowires with an average radius of about 400 nm. Examining the samples' optical properties showed that their bandgap is in the range of 2.05 eV-2.18 eV, which is larger than the bandgap of copper oxide (1.2 eV) and smaller than zinc oxide (3.3 eV). The composite synthesized by the CVD method has the lowest reflectance, and the sample prepared by the PVD method has the highest reflectance in the visible and near-infrared ranges. Examination of the room temperature photoluminescence (PL) spectrum of the sample prepared by PVD showed that these samples have emission peaks with significant intensities in the ultraviolet and visible ranges. The samples' electrical properties showed that the ZnO/CuO composite synthesized by sputtering and CVD had the lowest and highest electrical resistance, respectively. The samples' optical response study showed that the sputtering method's nanocomposites have the highest response. This study showed that, in general, the structural, optical and electrical properties and morphology of synthesized ZnO/CuO composites are significantly affected by their synthesis method.

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In this research, MASnICl₂ and FASnICl₂ thin layers were synthesized by the one-step spin coating method, and then their structural, optical and electrical properties were investigated. The study of these samples (structural properties) showed that the layers have a tetragonal structure (α- phase perovskite), and with the change of organic cation, the crystallinity and morphology of the layers significantly change. These changes also have influences in the optical and electrical properties of the samples. The perovskite layers have a high absorption coefficient (of the order of 10⁵ cm^-1) in the visible range. The bandgap for the FASnICl₂ layer was 1.48 eV and for the MASnICl₂ layer was 1.54 eV. A strong peak close to bandgap was observed in the room temperature PL of the layers, which was remarkably more intense for the FASnICl₂ sample. This study showed that the FASnICl₂ layers have better crystallinity, lower electrical resistance, higher optical sensitivity and acceptable optical response comparing the MASnICl₂ layers, and therefore, they can be suitable options for use as an adsorbent layer in perovskite solar cells.

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Preparation of two-dimensional nanostructures of WTe₂ and MoTe₂ by chemical solution synthesis methods is of great importance. In different synthesis methods, different precursors and concentrations are used. In this paper, we used the chemical reduction reaction method from solution for our analysis. Binary compounds of WO₃ - TeO₂ and MoO₃ - TeO₂ were prepared in two processes with reduction agents: (a) sodium borohydrate (NaBH₄) and (b) hydrazine in the presence of nitrogen gas. The structural and optical properties of the nanopowders were studied after chemical reduction. The results of X-ray diffraction (XRD) showed that in the WO₃ - TeO₂ binary compound, after chemical reduction with NaBH₄, the diffraction peaks of the TeO₂ and WO₃ binary compounds formed independently and after annealing in the presence of hydrazine, and the intensity of the peaks has been significantly increased. Field Emission Scanning Electron Microscopy (FE-SEM) images showed that the morphology of the nanoparticles was uniform in the form of spherical nanoparticles. In the combination of MoO₃ - TeO₂ with chemical reduction, other phases of Te₂O₅ and TeMo₅O₁₆ are formed in the shape of hemispheres, rods and polyhedrals, which indicates the formation of composite phases. The chemical bond structure and energy gap of samples were studied by FT-IR and UV-Vis spectroscopy.
 

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The effect of Ba ion substitution on structural, optical, and magnetic properties of Mn_0.3-xBa_xCu_0.2Zn_0.5Fe₂O₄ ferrites was investigated. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, UV-Vis spectroscopy, and vibrating sample magnetometer at room temperature. Structural results show that the structure of the samples with x up to 0.20 is completely indexed to a single-phase cubic structure (space group Fd m), while the impurity phase of BaO is observed in the samples with x = 0.25, 0.30. As the substitution content increases, the presence of non-magnetic Ba²⁺ ions in the octahedral site decreases the saturation magnetization of the samples. Comparison of the bandgap energy of the samples shows an increasing trend with Ba substitution for x up to 0.10 and then decreases, which can be interpreted in terms of changes in the electronic structure of the samples.
 

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Microstructural, optical, and photocatalytic properties of (x = 0, 0.05, 0.10, 0.15) LaMn_1-xZn_xO₃ nanoparticles have been investigated by X-ray diffraction, Raman and Fourier transform infrared spectroscopy, field emission scanning electron microscope, Energy-dispersive X-ray spectroscopy, and UV-Vis spectroscopy. Our study indicates that there is a structural phase transition from the rhombohedral (space group R3c) to the orthorhombic (space group Pbnm I) structure. Lanthanum manganese (LM) is one of the most promising and efficient photocatalysts for the degradation of organic pollutants. To determine the photocatalytic performance of LaMn_1-xZn_xO₃ nanoparticles, the effects of three operational parameters including irradiation time, pH, and the catalyst amount on the degradation of aqueous solution of methyl orange (MO) and methyl blue (MB) were investigated. The results showed that LaMn_0.9Zn_0.1O₃ has higher photocatalytic activity than the LM for degradation of MO and MB under sunlight. A possible mechanism for better photocatalytic performance of the samples was discussed. The LaMn_0.9Zn_0.1O₃ did not exhibit any significant loss after six cycles of the degradation of MO and MB under the same conditions.

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In this work, the structural, optical and photocatalytic properties of Cu_1-3xNi_xZn_2xFe₂O₄ ferrites prepared by citrate-nitrate method were investigated. The samples were characterized by X-ray diffraction (XRD) and UV-Vis spectrometer at room temperature. Examining the XRD patterns indicates the presence of a spinel structural phase transition from a tetragonal to cubic structure, which shows an increase in symmetry with the co-substitution of Ni and Zn in the copper ferrite. The bandgap values of the samples show a minimum value of 1.43 eV for x = 0.05. The highest catalytic activity of 95% in the degradation of methylene blue is obtained for the x = 0.05 sample due to its smaller energy gap.