Dongyun Guo, Yang Ju, Chengju Fu, Zhixiong Huang and Lianmeng Zhang
Zinc oxide (ZnO) is an n-type semiconductor with a wide direct band gap of 3.37 eV and a large exciton binding energy (60 meV). ZnO thin films have been widely applied in high technology such as optoelectronic devices, solar cells, piezoelectric transducers and gas sensors [ 1 – 7 ]. Many techniques have been utilized to prepare ZnO thin films, such as metal organic chemical vapor deposition, pulsed laser deposition, sputtering, hydrothermal, sol-gelmethod, etc. [ 8 – 18 ]. Due to the low cost and simple equipment, sol-gelmethod has been
Aluminosilicate materials were obtained by sol-gel method, using different Al2O3 and SiO2 precursors in order to prepare sols based on water and organic solvents. As SiO2 precursors, Aerosil 200TM and tetraethoxysilane TEOS: Si(OC2H5)4 were applied, while DisperalTM and aluminium secondary butoxide ATSB: Al(OC4H9)3 were used for Al2O3 ones. Bulk samples were obtained by heating gels at 500 °C, 850 °C and at 1150 °C in air, while thin films were synthesized on carbon, steel and alundum (representing porous ceramics) substrates by the dip coating method. Thin films were annealed in air (steel and alundum) and in argon (carbon) at different temperatures, depending on the substrate type. The samples were synthesized as gels and coatings of the composition corresponding the that of 3Al2O3·2SiO2 mullite because of the specific valuable properties of this material. The structure of the annealed bulk samples and coatings was studied by FT-IR spectroscopy and XRD method (in standard and GID configurations). Additionally, the electron microscopy (SEM) together with EDS microanalysis were applied to describe the morphology and the chemical composition of thin films. The analysis of FT-IR spectra and X-ray diffraction patterns of bulk samples revealed the presence of γ-Al2O3 and δ-Al2O3 phases, together with the small amount of SiO2 in the particulate samples. This observation was confirmed by the bands due to vibrations of Al–O bonds occurring in γ-Al2O3 and δ-Al2O3 structures, in the range of 400 to 900 cm−1. The same phases (γ-Al2O3 and δ-Al2O) were observed in the deposited coatings, but the presence of particulate ones strongly depended on the type of Al2O3 and SiO2 precursor and on the heat treatment temperature. All thin films contained considerable amounts of amorphous phase.
S. Menassel, M.-F. Mosbah, Y. Boudjadja, S.P. Altintas, A. Varilci and C. Terzioglu
results. This curvature, which occurs in most of the cited works, is evident in the results presented in Fig. 4 . Nearly the same values of U 0 were also obtained by Sharma et al. [ 45 ] in the measurements up to 14 T on Bi-2212 polycrystalline samples, prepared by sol-gelmethod and annealed between 760 °C and 840 °C, where they showed an influence of annealing temperature on U 0 . With lead containing (Bi, Pb)2212 samples doped by a rare earth on Sr site the obtained values are much higher, 0.075 eV to 0.308 eV with an applied field of 0.28 T for Gd doping [ 40
Nina K. Ivanova, Angelina M. Stoyanova, Albena D. Bachvarova-Nedelcheva and Reni S. Iordanova
Pure and nitrogen-doped titanium dioxide (N-doped TiO2) photocatalysts were prepared by non-aqueous sol-gel method by means of the reaction between titanium (IV) chloride (TiCl4) and C6H5CH2 OH (benzyl alcohol), used as precursors and urea serving as a nitrogen source. The phase formation and short-range order of the resulting particles were characterized by X-ray powder diffraction (XRD) and infrared (IR) spectroscopy. The crystallite size of as-prepared composite powders was in the range 12-35 nm. The aim of this work was to investigate the efficiency of N-doped TiO2 as a photocatalyst in degradation of model organic pollutants - dyes Reactive Black 5 (RB5) and Malachite Green (MG), under ultraviolet (UV) and visible (Vis) irradiation. 0ur results indicated that synthesized N-TiO2 nanocomposites slightly improved the photocatalytic activity under UV irradiation, compared to the pure titanium dioxide (TiO2), and had no effect under Vis light illumination.
Abdelali Merah, Abdenabi Abidi, Hana Merad, Noureddine Gherraf, Mostepha Iezid and Abdelghani Djahoudi
Interest in nanomaterials, especially metal oxides, in the fight against resistant and constantly changing bacterial strains, is more and more expressed. Their very high reactivity, resulting from their large surface area, promoted them to the rank of potential successors of antibiotics.
Our work consisted of the synthesis of zinc oxide (ZnO) and copper oxide (CuO) in the nanoparticle state and the study of their bactericidal effect on various Gram-negative and Gram-positive bacterial strains.
The nanoparticles of metal oxides have been synthesized by sol-gel method. Qualitative analysis and characterization by UV / Visible and infrared spectrophotometry and X-ray diffraction confirmed that the synthetic products are crystalline. The application of the Scherrer equation allows to determine the size of the two metal oxides, namely: 76.94 nm for ZnO and 24.86 nm for CuO.
The bactericidal effect of ZnO and CuO nanoparticles was tested on Gram-positive bacteria (Staphylococcus aureus, Staphylococcus hominis, Staphylococcus haemolyticus, Enterococcus facials) and Gram-negative bacteria (Escherichia coli, Schigella, Klepsiella pneumoniae and Pseudomonas aeruginosa). The results indicate that the tested metal oxides nanoparticles have an effect that varies depending on bacterial species. Indeed, Gram-positive bacteria show greater sensitivity to ZnO nanoparticles whereas Gram-negative bacteria are more sensitive to CuO nanoparticles.
on the fabrication and crystallization of this compound [ 29 ]. In this manufacturing process, the CeYIG can be produced in the temperature range between 800 °C to 1400 °C [ 30 , 31 ]. In literature, getting YIG phases via different methods have been reported [ 33 , 34 ]. For example, by using the solgel method, Xu et al. [ 19 ] obtained a single phase of garnet structure at 850 °C, while Kum et al. [ 31 ] got a single phase garnet cubic structure only above 1200 °C [ 19 , 31 ]. However, in another study using the proteic sol-gelmethod, the pure YIG phase could
K2FeZrP3O12 was prepared by sol-gel method and used as a mild and efficient solid acid catalyst for Friedel-Crafts benzylation of various arenes with benzyl bromide under solvent-free conditions. The method is green and has high yields.
Gnana Praveena Nethala, Ravindar Tadi, Aroli Venkateswara Anupama, Satish Laxman Shinde and V. Veeraiah
Mg substituted cobalt ferrite spinel powder samples with the general formula MgxCO1-xFe2O4(x = 0 to 0.25) were synthesized chemically through sol-gel method and annealed at 1100 °C for 2 h. They were initially screened for the structural and morphological properties by X-ray diffraction and field emission scanning electron microscopy, respectively. Vibrational properties of the samples were studied by Raman and infrared spectroscopies. X-ray diffraction confirmed the formation of single pure or near-pure phase with cubic spinel structure for all the samples with expected occupancy values. The field emission scanning electron microscopy revealed a decrease in the particle size with an increase in Mg concentration. Both structural and magnetic properties of the samples were characterized using Mössbauer spectroscopy while the magnetic properties were studied using vibrating sample magnetometry. The changes in magnetic moment of ions, their coupling with neighboring ions and cation exchange interactions were confirmed from the Mössbauer spectroscopy analysis. Saturation magnetization and coercivity values can be explained based on the Slater-Pauling curve. The magnetometry results showed a decrease in saturation magnetization of the samples with increase in Mg concentration
Nanocomposite silica thin films made using the sol-gel method were studied. The nano-silica films were prepared using a mixture of tetraethyl orthosilicate (TEOS), deionized water, ethanol, and ammonia solution. To control the growth of the particles inside the film, the nanocomposite silica film was prepared using a mixture of the nano-silica sol and the silica sol. The change in the particle size with the heat treatment temperature ranging from 450 °C to 1100 °C was investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), NKD (refractive index-N, extinction coefficient-K, and thickness-D) and ultraviolet-visible (UV-Vis) spectrophotometry were used for characterization purposes. The XRD studies showed that the nano-silica thin films were amorphous at all annealing temperatures except for 1100 °C. The_-cristobalite crystal structure formed at the annealing temperature of 1100 °C. Optical parameters, such as refractive indices and extinction coefficients, were obtained using the NKD analyzer with respect to the annealing temperature of the films. The activation energy and enthalpy of the nanocomposite silica film were evaluated as 22.3 kJ/mol and 14.7 kJ/mol, respectively. The cut-off wavelength values were calculated by means of extrapolation of the absorbance spectra estimated using the UV-Vis spectroscopy measurements. A red shift in the absorption threshold of the nanocomposite silica films indicated that the size of the silica nanoparticles increased with an increase of the annealing temperatures from 450 °C to 900 °C, and this confirms the quantum confinement effect in the nanoparticles.