Epitaxial growth by monolayer restricted galvanic displacement

The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD) was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV) and scanning tunneling microscopy (STM) are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111), Cu on Ag(111), and Cu on Au(111) by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process

TiO2 nanoparticles supported on natural zeolite clinoptilolite from Serbia for removal of bisphenol A from aqueous solution

Bisphenol A (BPA) is a well-known emerging contaminant that pose a severe threat to human health due to its negative effect on the body’s endocrine systems. BPA is widely used in the production of polycarbonate plastic and epoxy resins and therefore often detected in different water environments. Since the conventional wastewater treatments for BPA removal haven’t been proven efficient it is important to find a green and efficient method for its complete elimination. Therefore, the aim of this work was to prepare a cost-effective hybrid photocatalyst based on TiO2 nanoparticles and natural zeolite clinoptilolite and study its photocatalytic performance toward BPA. The TiO2/clinoptilolite, containing 20 wt% of TiO2, was prepared using ultrasound assisted solid-state dispersion method and characterized using a multi-technique approach by combining X-ray powder diffraction, FTIR, UV Vis DRS spectroscopy, atomic force microscopy (AFM), BET measurements and laser diffraction. The study showed complete removal of BPA (5 mg/L) after 180 minutes of simulated solar irradiation using 2 g/L of hybrid photocatalyst, at pH = 6.4. The addition of H2O2 led to a faster BPA removal after 120 minutes of irradiation. When BPA removal was tested in bottled drinking water a lower removal of 60 % after 180 minutes of irradiation was observed because of the presence of bicarbonate ions and its scavenger effect toward hydroxyl radicals. The reused photocatalyst showed good photocatalytic activity in repeated cycles (e. i. 70 % of BPA was still successfully removed at the end of the 4th cycle)

The Effect of Sintering Temperature on Mesoporous Structure of WO3 Doped Tio(2) Powders

In this study, WO3 doped TiO2 powders were synthesized via sol-gel method combined with a hydrothermal process. The effect of sintering temperature on mesoporous structure and catalytic activities of these powders were investigated. The physical analysis via X-ray diffraction indicates that prepared samples are a mixture of anatase and rutile TiO2 phases. X-ray peak analysis is used to evaluate the crystallite size and lattice strain by the Williamson-Hall analysis. Considering all the reflections of the anatase phase the lattice strain ranging from c = 9.505 to c = 9.548 is calculated, suggesting that microstrain decreases when calcination temperature increases. N-2 adsorption-desorption analysis shows that the surface area and pore volume decrease with increasing temperature and that WOx-TiO2 powders primarily consist of mesopores. Sintering temperature induced a change in textural properties causing a systematic shift towards larger mesopores. Simultaneously, photoactivity in decolorization of methyl orange increases with increasing calcination temperature up to 700 degrees C, followed by significant decrease with its further increase

Morphology and fractal dimension of tio2 thin films

The influence of annealing temperature on the morphology and surface fractal dimension of titanium dioxide (TiO2) films prepared via the spray deposition process was investigated. Thin films with various morphologies were obtained at different temperatures and characterized by X-ray diffraction and atomic force microscopy (AFM). It was found that the crystalline structure of TiO2 films depends strongly on annealing temperature. At higher temperatures, the partial phase transformation of anatase-to-rutile was observed. The morphology and surface fractal dimensions were evaluated by image analysis methods based on AFM micrographs. The results indicate that the value of surface roughness (the standard deviation of the height values within the given area of AFM image) of TiO(2)films increases with increasing annealing temperature. Fractal analysis revealed that the value of the fractal dimension of the samples decreases slowly from 2.23 to 2.15 following the annealing process

Mechanical Properties of Electrolytically Produced Copper Coatings Reinforced with Pigment Particles

Copper from sulfate baths without and with added inorganic pigment particles based on strontium aluminate doped with europium and dysprosium (SrAl2O4: Eu2+, Dy3+) was electrodeposited on a brass cathode by a galvanostatic regime. Morphological, structural, and roughness analysis of the pigment particles, the pure (pigment-free) Cu coating, and the Cu coatings with incorporated pigment particles were performed using SEM, XRD, and AFM techniques, respectively. Hardness and creep resistance were considered for the examination of the mechanical properties of the Cu coatings, applying Chicot–Lesage (for hardness) and Sargent–Ashby (for creep resistance) mathematical models. The wettability of the Cu coatings was examined by the static sessile drop method by a measurement of the water contact angle. The incorporation of pigment particles in the Cu deposits did not significantly affect the morphology or texture of the coatings, while the roughness of the deposits rose with the rise in pigment particle concentrations. The hardness of the Cu coatings also increased with the increasing concentration of pigments and was greater than that obtained for the pigment-free Cu coating. The presence of the pigments caused a change in the wettability of the Cu coatings from hydrophilic (for the pigment-free Cu coating) to hydrophobic (for Cu coatings with incorporated particles) surface areas

High photocatalytic activity of TiO2/Al2TiO5 coatings obtained by plasma electrolytic oxidation of titanium

In this work, it was shown that TiO2/Al2TiO5 coatings obtained by plasma electrolytic oxidation of titanium in alkaline electrolyte with added NaAlO2 show significantly better photocatalytic activity (PA) in degradation of methyl orange under simulated sunlight than anatase TiO2 coatings obtained in pure alkaline electrolyte. The TiO2/Al2TiO5 coating with the highest PA was obtained in alkaline electrolyte with the addition of 2.0 g/L NaAlO2, which has approximately 2.4 higher PA than anatase TiO2. Photoluminescence indicates that increased PA of TiO2/Al2TiO5 coatings is associated with increased number of oxygen vacancy and other defects

ZnO Particles Modified MgAl Coatings with Improved Photocatalytic Activity Formed by Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy in Aluminate Electrolyte

MgAl and MgAl/ZnO coatings were prepared by plasma electrolytic oxidation (PEO) of AZ31 magnesium alloy in aluminate electrolyte (5 g/L NaAlO2) without and with addition of ZnO particles in various concentrations. The MgAl coating was partially crystallized and contained MgO and MgAl2O4 phases. The addition of ZnO particles to aluminate electrolyte had no significant effect on the surface morphology of formed coatings, while the Zn content increased with ZnO particle concentrations. X-ray diffraction confirmed the incorporation of ZnO particles in the coatings. The photodegradation of methyl orange (10 cm3 of 8 mg/L) was used to measure the photocatalytic activity (PA) of MgAl and MgAl/ZnO coatings. The PA of MgAl coating after 8 h of irradiation was around 58%, while the PA of MgAl/ZnO coatings formed in aluminate electrolyte with the addition of ZnO particles in concentrations of 4 g/L, 8 g/L, and 12 g/L were around 69%, 86%, and 97%, respectively

Photoluminescent and Photocatalytic Properties of Eu3+-Doped MgAl Oxide Coatings Formed by Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy

The synthesis of Eu3+-doped MgAl oxide coatings containing MgO and MgAl2O4 was accomplished through plasma electrolytic oxidation of AZ31 magnesium alloy in aluminate electrolyte with the addition of Eu2O3 particles in various concentrations. Their morphological, structural, and above all, photoluminescent (PL) and photocatalytic activity (PA) were thoroughly investigated. PL emission spectra of MgAl oxide coatings feature characteristic emission peaks, which are ascribed to f–f transitions of Eu3+ ions from excited level 5D0 to lower levels 7FJ. The charge transfer state of Eu3+ or direct excitation of the Eu3+ ground state 7F0 into higher levels of the 4f-manifold are both attributed to the PL peaks that appear in the excitation PL spectra of the obtained coatings. The fact that the transition 5D0 → 7F2 (electrical dipole transition) in Eu3+-doped MgAl oxide coatings is considerably stronger than the transition 5D0 → 7F1 (magnetic dipole transition) indicates that Eu3+ ions occupied sites with non-inversion symmetry. Because of oxygen vacancy formation, the Eu3+-doped MgAl oxide coatings had a higher PA in the degradation of methyl orange than the pure MgAl oxide coating. The highest PA was found in Eu3+-doped MgAl oxide coating formed in an aluminate electrolyte with 4 g/L of Eu2O3 particles. The PA, morphology, and phase of Eu3+-doped MgAl oxide coatings did not change after several consecutive runs, indicating outstanding stability of these photocatalysts

One-pot plasma electrolytic oxidation synthesis of TiO2/Sb2O3 coatings for photocatalysis

Anatase TiO2 coatings modified by Sb2O3 particles were formed by plasma electrolytic oxidation of titanium in 10 g/L Na3PO4⋅10H2O with addition of Sb2O3 particles. The photodegradation of methyl orange under simulated sunlight was used to probe the photocatalytic potential of TiO2/Sb2O3 coatings. The photocatalytic activity (PA) of obtained coatings is higher than pure TiO2 for adding up to 2.0 g/L of Sb2O3 particles to electrolyte. The highest PA was observed for coatings formed in electrolyte with the addition of 0.75 g/L Sb2O3. Increased PA is related to a decrease of photogenerated electron/hole recombination rate as a result of TiO2 and Sb2O3 coupling

Photocatalytic degradation of bisphenol A in aqueous solution using TiO2/clinoptilolite hybrid photocatalyst

Photocatalytic degradation of bisphenol A (BPA) was investigated using commercial TiO2 P25 nanoparticles supported on natural zeolite clinoptilolite (Cli). Employing ultrasound assisted solid-state dispersion method hybrid photocatalyst containing 20 wt% of TiO2, marked TCli-20, was prepared. The structural, morphological and surface properties, and particle size distribution of TCli-20 were studied by X-ray powder diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, Brunner-Emmet-Teller method and laser diffraction. The results revealed a successful loading of TiO2 P25 nanoparticles on Cli surface and the preservation of both zeolitic structure and optical properties of TiO2. The influence of catalyst dose, pH value and the addition of hydrogen peroxide (H2O2) was evaluated. The optimal reaction conditions were 2 g/L of catalyst at near-neutral conditions (pH = 6.4) for complete BPA (5 mg/L) photodegradation after 180 min of exposure to simulated solar light. The addition of H2O2 was beneficial for the degradation process and led to the removal of BPA after 120 min of irradiation. BPA removal (60% for 180 min of irradiation) was reduced when TCli-20 was tested in bottled drinking water due to the presence of bicarbonate ions which acted as scavengers for hydroxyl radicals. Even though the photocatalytic activity of TCli-20 decreased after several cycles of usage, 70% of BPA was still successfully degraded during the fourth cycle. The reusability study showed easy separation, stability and good photocatalytic ability of investigated cost-effective hybrid photocatalyst. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature