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Nickel acetylacetonate of 0.2 M aqueous solution is used to synthesize (NiO) thin films by pulsed spray pyrolysis method onto glass substrates. Structural and morphological properties of the deposited films were examined using (XRD) and (FESEM) techniques. The results revealed that at low substrate temperatures and short spray time, the obtained films were amorphous, whereas the films deposited at higher temperatures and long spray time has a cubic phase. Cross-sectional FESEM is used to properly estimate films thicknesses. The energy band gap is calculated to be 3.52–3.89 eV using optical spectrum measurements. Electrochromic properties of NiO films deposited on FTO working electrode substrates are measured in a three-electrode cell containing KOH with Ag/AgCl reference electrode at a scan rate of 20 mV/s. The charge density increases with the thickness, and it is 98.0 mC/cm2 at the thickness of 360 nm after 30-min deposition time at 400 °C and for most of the samples the film stability increases after cycling. Graphical abstract

Glasses belonging to the xWO3-(30-x) Bi2O3–15Li2O–15CaO–40B2O3 (0 ≤ x ≤ 10) have been obtained by melt-quenching technique. With increasing the concentration of WO3, an increase in the measured glass transition temperature $${T}_{\mathrm{g}}$$ T g and crystallization temperature $${T}_{\mathrm{c}}$$ T c are observed, while the values of the thermal expansion coefficient decrease. Due to the unpaired pentavalent ions, the electron spin resonance spectra of glasses doped with $${\mathrm{WO}}_{3}$$ WO 3 them show unique signals. The results of Raman spectra show that the glass network is mainly constituted by [$${\mathrm{BiO}}_{6}$$ BiO 6 ], [$${\mathrm{BO}}_{3}$$ BO 3 ], [$${\mathrm{BO}}_{4}$$ BO 4 ], and [$${\mathrm{WO}}_{4}$$ WO 4 ] basic structural units. The activation energies for all studied samples were observed to range from 0.02 to 0.08 eV, and the dielectric constant and the conductivities of the investigated glasses increased with increasing temperature. The electrical behavior of the prepared samples revealed their semiconducting character. The prepared samples are being investigated as potential semiconductor material candidates for use in electronic devices.

Coating with hydroxyapatite (HAP) presents a mainstream strategy for rendering bioinert titanium implants bioactive. However, the low porosity of pure HAP coatings does not allow for the infiltration of the surface of the metallic implant with the host cells. Polymeric scaffolds do enable this osseointegration effect, but their bonding onto titanium presents a challenge because of the disparity in hydrophilicity. Here, we demonstrate the inability of a composite scaffold composed of carbonated HAP (CHAP) nanoparticles interspersed within electrospun e-polycaprolactone (PCL) nanofibers to bind onto titanium. To solve this challenge, an intermediate layer of graphene nanosheets was deposited in a pulsed laser deposition process, which facilitated the bonding of the scaffold. The duration of the deposition of graphene (0, 5, 10, 15, and 20 min) and the thickness of its mesolayer affected numerous physical and chemical properties of the material, including the surface atomic proportion of carbon bonds, the orientation and interlinking of the polymeric nanofibers, and the surface roughness, which increased in direct proportion with the thickness of the graphene mesolayer. Because the polymeric scaffold did not adhere onto the surface of pure titanium, no cells were detected growing on it in vitro. In contrast, human fibroblasts adhered, spread, and proliferated well on all the substrates sputtered with both graphene and the composite scaffold. The orientations of cytoskeletal filopodia and lamellipodia were largely determined by the topographic orientation of the nanofibers and the geometry of the surface pores, attesting to the important effects that the presence of a scaffold has on the cellular behavior. The protection of titanium from corrosion in the simulated body fluid (SBF) was enhanced by coating with graphene and the composite scaffold, with the most superior resistance to the attack of the corrosive ions being exhibited by the substrate subjected to the shortest duration of the graphene deposition because of the highest atomic ratio of C-C to C-O bonds detected in it. Overall, some properties of titanium, such as roughness and wettability, were improved monotonously with an increase in the thickness of the graphene mesolayer, while others, such as cell viability and resistance to corrosion, required optimization, given that they were diminished at higher graphene mesolayer thicknesses. Nevertheless, every physical and chemical property of titanium analyzed was significantly improved by coating with graphene and the composite scaffold. This type of multilayer design evidently holds a great promise in the design of biomaterials for implants in orthopedics and tissue engineering.

In the current work, we have developed a new composite catalyst for methanol oxidation based on Ni and/or NiO incorporated in activated carbon (AC) derived from agricultural wastes (Rice straw). The new electrocatalysts based on nickel-activated carbon (Ni/AC) and nickel oxide-activated carbon (NiO/AC) composites were prepared by electroless plating technique. Physico-chemical characteristics of the composites such as structure, composition and morphology were studied by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and particle size analyzer. The electrochemical activity of the prepared composites towards methanol electrooxidation reaction (MOR) has been evaluated under alkaline conditions by cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. Among the examined electrodes, the electrochemical performance of NiO/AC preceded either Ni/AC or Ni free AC and showed better stability. The dispersion of different forms of Ni in activated carbon in case of NiO/AC electrode is predicted to give rise to the increase in electrocatalytic activity in the potential range under study and makes it more resistant to poisoning by the byproduct of methanol oxidation. The effect of changing methanol concentrations and scan rates on the electrochemical characteristics of the modified electrode was studied and it was found that the diffusion process is controlled by methanol rather than OH− ions.

Using eco-friendly organic compounds to control metallic corrosion in various corrosive media has extended to the use of polymers to inhibit metallic corrosion. In this paper, poly(1,5-diaminonaphthalene) (1,5-DAN) coatings were electrodeposited on the surface of a copper electrode using a potentiostatic technique under different conditions. The protection efficiency of the formed polymer in 0.6 M NaCl as an aggressive medium was investigated by open-circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy. All of the anterior studies proved that the poly(1,5-DAN) formed at 0.7 V acts as an excellent coating for the copper (Cu) surface in 0.6 M NaCl and shows a high protective efficiency of approximately 99.9%. The surface morphology of the formed polymer was characterized by UV–visible absorption spectroscopy, FT-IR spectroscopy and scanning electron microscopy. All the analyses confirmed that poly(1,5-DAN) efficiently protects the Cu substrate.

Heavy metal glass samples of the system x(2Bi2O3.MnO).(10-x)B2O3 with different compositions were prepared via the conventional method. Differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were utilized to study the thermal behaviour and structure of the glasses. Their physical, optical and electrical properties were studied to characterize the materials. The higher strength of the B O bond than the Bi O bond leads to an increase in the thermal stability of the prepared glass. Both the density and molar volume were increased with an increase in the x value, i.e., the Bi2O3 content. Phase separation is the main feature of the glass structure observed using SEM. Some traces from Bi2O3 and/or MnB4O7 were detected in samples B6 (x = 6) and B3 (x = 3) by XRD. The optical band gap (Eopt) lies between 2 and 3 eV; it increases with a decrease in Bi2O3 content. All glasses exhibited good transmission in the infrared (IR) region, reaching ~45% at ~1750 nm. The activation energies of these prepared compositions were estimated, and their conductivities were found to increase with increasing temperature, revealing their semiconducting character.

Photophysical properties of some 1-naphthol and 2-naphthol sulfonate derivatives and their efficiency as singlet oxygen photosensitizers in aqueous media are reported. The fluorescence emission is mainly from the deprotonated form (conjugate base) and their maxima cover the range of 433–529 nm. The fluorescence decay of these derivatives was found to be fitted with bi-exponential function with χ2 of about 1.0 ± 0.1 in all cases. Rate constants for oxygen quenching of the excited singlet states of these compounds in H2O are found to be (1.2 ± 0.2) × 1010 M−1 s−1 for the neutral form and much lower for the quenching of their conjugate bases. p K a values were found to be in the range 7.4–9.5 while p K a * are close to zero and about 3.3 for 2-naphthol and 2-naphthol-6-sulfonate using Forster equation and in the range of 1.4–3.0 using the fluorescence titration method obtained from the relative integrated fluorescence intensity. Singlet oxygen quantum yields photosensitized by these photoacids were reported in D2O and found to be in the range 0.13–0.35 for the sulfonated derivatives.

In this study we report on the photophysical properties of some imidazo[1,2-a]pyridine and 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine derivatives and their efficiency as singlet oxygen photosensitizers in aqueous media. In aqueous solution, the wavelengths of maximum absorption are in the range of 269–307 nm, while the wavelengths of maximum emission cover the range of 357–462 nm. It has been found that the fluorescence decay of these derivatives were fitted very well with mono-exponential function for one of the compounds and with bi- exponential function for the other compounds with χ2 of about 1.0±0.1 in all cases and show solvent isotope effect. It has also been found that excited singlet state relaxation is dominated by non-radiative relaxation pathways. Rate constants for oxygen quenching of the excited singlet states of these compounds are close to the diffusion rate constant in H2O and D2O. Singlet oxygen quantum yields photosensitized by imidazo[1,2-a]pyridine and 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine derivatives were reported in D2O and found to be in the range 0.01-0.1 relative to phenalenone as a standard. The rate constants, kqΔ, for quenching of singlet oxygen by ground state sensitizers in D2O are also reported and found to be in the range (0.82–6.74)×109 M−1 s−1.

The electrochemical behavior of a series of the metal complexes [Fe(III), Ni(II), Ru(III),Pd(II) and Hf(IV)]derived from the Schiff base ligand(E)-5-((phenyl(-pyridin-2-yl) methylene) amino) pyrimidine-2,4(1H, 3H)‑dione(H2L) which was previously prepared from condensation of 5-aminouracil and 2-benzoylpyridine was studied by using cyclic voltammetric technique. The Schiff base ligand H2L and its metal complexes exhibited quasi- reversible oxidation- reduction with three electron transfer and it was suggested that their reactions on the platinum surface electrode are not purely diffusion controlled but also under adsorption control. The redox reactive sites of the H2L and its complexes were located via the geometry optimization and frequency calculations using density functional theory (DFT) at the B3LYP/LanL2DZ level of theory. In addition, the Schiff base ligand and its metal complexes exhibit fluorescent properties. The antimicrobial activity of the Schiff base ligand H2L and its metal complexes was tested against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus(, Gram-negative bacteria (E. coli and Pseudomonas aeruginosa) and fungal strain (Aspergillus niger) by using agar well-diffusion method. The microbial testes of the ligand (H2L) and its metal complexes exhibited good inhibition efficiency to prevent growth of bacteria.

In this study, nanoscale crednerite (CuMnO2) was prepared in the system xCuO–(70–x)MnO–30SiO2 , where x has values 10, 15, 20, 25 and 30, via melting quenching glass-ceramic technique. The electrocatalytic activity of the oxygen evolution reaction (OER) on CuMnO2 deposits has been studied in 1.0 M KOH (25 ℃) by means of cyclic voltammetry, linear sweep voltammetry, chronoamperometric and electrochemical impedance techniques. The study has shown that the catalytic activity had increased with the increase of Cu content in the electrode composition, where the optimum improvement in the apparent electrode catalytic activity was obtained at the M30 electrode (with x = 30). At E = 0.6 V versus Ag/AgCl, the apparent oxygen evolution current density observed at the M30 electrode is 4 times greater than that observed with M10 (x = 10). The order of the OER with respect to OH – concentration measured at low and high potentials is ∼ 1.0 and the roughness of the electrodes was decreased with the increase of the Cu content.

Preparation of LiTi2(PO4)3 (NASICON-type) glass ceramic from LiF.(2-x)TiO2.xB2O3.1.5P2O5 system were achieved via melt-quenching technique. The effect of gradual replacement of Ti4+ ions with B3+ ions was investigated. The prepared samples were characterized using differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy and high-resolution transmission electron microscope. The results revealed crystallization of LiTi2(PO4)3 as the major phase with traces of Li2TiF6 phase in the quenched samples. The quantities of these phases decreased with increasing B3+ ions until x = 1; beyond this value, B2O3 and β-Li4B2O5 were the dominant phases. After heat treatment at 800 °C/2 h, pure LiTi2(PO4)3 was detected till x = 1 then BPO4 appeared and increased with increasing B3+ ions. At x = 2, pure BPO4 was achieved. TEM revealed nanocrystalline size for the formed phase. In deduction, the substitution of Ti4+ ions by B3+ ions in the glass matrix improved the dc-conductivity at room temperature from 1.29 × 10−10 Ω−1 cm−1 in boron-free sample to 3.41 × 10−3 Ω−1 cm−1 for x = 2 sample due to the precipitation of β-Li4B2O5 in addition to B2O3. However, after heat treatment free boron sample (B0) showed the highest dc-conductivity at room temperature ∼1.23 × 10−4 Ω−1 cm−1 and lowest activation energy 0.032 eV. Therefore, the high conductivity, low activation energy and high diffusion coefficient (1.8 × 10−7 cm2/s) suggesting the use of the prepared materials in Li-ion battery applications.

Nickel-copper-phosphorous layers were electro-less deposited on the surface of anodized aluminum and aluminum alloys. The electrochemical behavior of the improved surface was investigated in 0.5 M Na2SO4. The corrosion resistance of the modified alloy's surface is ten folds that measured on the anodized materials. The surface morphology was examined by scanning electron microscopy, SCE, and the deposit composition was subjected to x-ray energy dispersive analysis, EDAX. The experimental impedance data were fitted to theoretical data according to a proposed equivalent circuit model. The results show that the Ni–Cu–P layer was deposited homogeneously on the anodized Al surface but on the anodized-alloy surface the layer had a defective nature.

This work pointed out the preparation of glass-ceramic based on fluoramphibole using different alkalis. Phases were crystallized using heat-treatment at 850 °C/2.5 h and were identified using XRD. Fluorophlogopite, fluorrichterite, enstatite and cristobalite were found in the heat-treated glasses. Crystallization of fluorophlogopite or fluorrichterite was detected in samples containing high K and Na, respectively, accompanied with crystallization of enstatite in the last sample. Cristobalite was crystallized only in equal alkali-containing glass beside enstatite and richterite. Nanoparticles of silver have grown within a silicate glass via modification of ion exchange process. The metal particle diameters were detected using XRD and TEM. The particles size ranges from 4 to 10 nm. The amount of silver ions exchanged was varied according to type and amount of alkali on fluoramphibole compositions. The composites show low values of dielectric permittivity (10–30) due to the formation of interconnected metal nanoparticle chains. The resistivity of the specimen dropped from 10 8 to 10 10 Ω cm 2 to 10 4 to 10 8 Ω cm 2 after ion exchange process which shows metallic and semiconducting behavior according to the reduction temperature.

The electrochemical behavior of Cu–Ni alloys with different Ni contents (5–65 mass%) in acidic sulfate solutions was investigated. The effects of working conditions e.g. concentration of sulfate ions, immersion time and temperature were studied and discussed. In this respect, open-circuit potential measurements, polarization techniques and electrochemical impedance spectroscopy (EIS) were used. Potentiodynamic measurements revealed that the increase in the Ni content improves the stability of the Cu–Ni alloys. The polarization measurements were confirmed by EIS experiments. The stability of the alloys with higher Ni contents is due to the increased amount of Ni in the surface film. The corrosion process of the cupronickels in the acidic sulfate solution was found to be diffusion controlled. The experimental impedance data were fitted to theoretical data according to an equivalent circuit model representing the electrode/electrolyte interface.

Porous titania, TiO 2 , films on Ti substrates were prepared electrochemically. The adsorption of biologically compatible ions, like calcium and phosphate ions, on the formed TiO 2 films was investigated by electrochemical impedance spectroscopy, EIS, and electron diffraction X-ray, EDX, techniques. The morphology of the formed oxide films and the adsorbed layers on their surfaces was investigated by the scanning electron microscopy, SEM. The experimental impedance data were fitted to theoretical data according to proposed equivalent circuit models. The impedance data fitting enabled the explanation of the structure of the oxide film and the adsorption phenomena occurred on its surface. The film characteristics under different conditions were discussed and the adsorption of Ca 2+ and PO 4 3− was explained. The results have shown that the oxide films formed potentiostatically on Ti in H 2 O 2 containing H 2 SO 4 are capable to adsorb biologically compatible ions. The adsorbed layer thickness was found to increase with the increase of concentration of calcium ions present in the ambient electrolyte. The biocompatibility of these materials depends essentially on the apatite-forming ability of TiO 2 due to calcium ion incorporation in the adsorbed films. The formed oxide films with the relatively thick apatite-like adsorbed layer are good implants for bone surgeries and dental applications.

The electrochemical behavior of Cu–Ni alloys in acidic chloride medium was investigated. Commercial Cu–Ni alloys were investigated using potentiodynamic techniques, complemented by electrochemical impedance spectroscopy. The influence of alloy composition, chloride ion concentration and immersion time on the electrochemical response of the alloys was analyzed. Results of present investigations with pure metals (Cu and Ni) are also considered in this paper for the sake of comparison. Potentiodynamic measurements reveal that the increase in nickel content decreases the corrosion rate of the alloy and when the nickel content exceeds 30%, an increase in the corrosion rate was recorded. Also, the corrosion current density increases with increasing the concentration of chloride ions up to 0.6 M. The experimental impedance data were fitted to an equivalent circuit model representing the electrode/electrolyte interface. The relevance of the proposed model to the corrosion/passivation phenomena occurring at the electrode/solution interface was discussed.

The corrosion inhibition of Cu–Ni alloys was investigated in aqueous chloride solutions using amino acids as environmentally safe materials. The corrosion rate was calculated in absence and presence of the corrosion inhibitor using polarization and impedance techniques. The inhibition efficiency of the different amino acids was also calculated. The experimental results have shown that a simple amino acid like glycine can be used as efficient corrosion inhibitor for the Cu–Ni alloys in neutral chloride solutions. An inhibition efficiency of about 85% could be achieved at very low concentrations of the amino acid (0.1 mM). For low Ni content alloy (Cu–5Ni), 2.0 mM cysteine shows a remarkable high (∼96%) corrosion inhibition efficiency. The experimental impedance data were fitted to theoretical data according to a proposed equivalent circuit model for the electrode/electrolyte interface, and the mechanism of the corrosion inhibition process was suggested. Different adsorption isotherms were tested and the corrosion inhibition process was found to depend on the adsorption of the amino acid molecules and/or the deposition of corrosion products on the alloy surface. The adsorption free energy of cysteine on Cu–5Ni (−37.81 kJ mol−1) reveals a strong physical adsorption of the inhibitor on the alloy surface.

The corrosion and passivation behaviors of alloys with different Cu–Ni ratios were investigated in acidic sulfate solutions. The corrosion rate was calculated and the corrosion inhibition process was investigated using different amino acids as corrosion inhibitors. For these investigations conventional electrochemical techniques and electrochemical impedance spectroscopy (EIS) were used. Fitting of the experimental impedance data to theoretical values enables understanding of the corrosion inhibition mechanism and the suggestion of a suitable electrical model to explain the behavior of the alloys under different conditions. The investigation of the electrochemical behavior of alloys before and after the corrosion inhibition processes has shown that some amino acids like lysine have promising corrosion inhibition efficiency at very low concentrations. A model for the electrode/electrolyte interface during the corrosion inhibition processes was suggested and the validity of the model for the explanation of the corrosion inhibition phenomena was discussed.

The effect of systematic increase of Ni content on the electrochemical behavior of the Cu–Ni alloys in neutral chloride solutions was investigated. The pitting corrosion behavior of Cu–Ni alloys with different Ni contents, namely, 5, 10, 30 and 65 mass% Ni, in a stagnant 0.6 mol dm−3 NaCl solution of pH 7.0 was studied. The effect of chloride ion concentration on the electrochemical behavior of these alloys was also investigated. The results show that the increase in nickel content decreases the corrosion rate of the alloys in the neutral chloride solution. The increase of chloride concentration up to 0.3 mol dm−3 increases the corrosion rate. At higher concentrations ([Cl−] > 0.3 mol dm−3) the corrosion rate decreases due to the hydrolysis of Cu(I) chloride to form the passive Cu(I) oxide film. The breakdown potential depends on the chloride ion concentration and the nickel content of the alloy. For these investigations conventional electrochemical techniques and electrochemical impedance spectroscopy (EIS) were used. The impedance measurements have shown that the increase of the Ni content and the immersion time of the alloys in the chloride solution increase the corrosion resistance of the alloys. The experimental impedance data were fitted to theoretical values according to a proposed equivalent circuit model.

The effect of Ni content on the corrosion and passivation behaviors of copper-nickel alloys with different Cu to Ni ratios was investigated in neutral sulfate solutions. The influence of working conditions (e.g., immersion time, sulfate ions concentration, and temperature) on the electrochemical behavior of the different alloys was also studied. In this respect, conventional electrochemical methods like open-circuit potential (OCP) measurements, polarization techniques, and electrochemical impedance spectroscopy (EIS) were used. It was found that the initial corrosion resistance is relatively low for alloys with high nickel content. An increase in the nickel content and long immersion time in the neutral sulfate solution increases the corrosion resistance of the alloy and improves its stability. The stability of the alloy was considered to be due to the formation of a stable passive film on its surface. The impedance data were fitted to theoretical data obtained according to an equivalent circuit...

The electrochemical behaviour of copper–nickel alloys with different Ni content (5–65%) in sulphate solutions of pH 12 was investigated. The effects of temperature, immersion time, and concentration of sulphate ions were also studied. Different electrochemical methods such as open-circuit potential measurements, polarization techniques and electrochemical impedance spectroscopy (EIS) were used. Potentiodynamic measurements reveal that the increase in nickel content increases the corrosion rate of the alloy in sulphate solution linearly. Nevertheless, an increase in the nickel content along with increase in immersion time improves the stability of the Cu–Ni alloys due to the formation of a stable passive film. An equivalent circuit model for the electrode/electrolyte interface under different conditions was proposed. The experimental impedance data were fitted to theoretical data according to the proposed model. The relevance of the model to the corrosion/passivation phenomena occurring at the electrode/solution interface was discussed.