Improvement of Orange II Photobleaching by Moderate Ga 3+

Highly photoactive Ga3+-doped anatase modification of titania was prepared by homogeneous hydrolysis of aqueous solutions mixture of titanium oxo-sulphate TiOSO4 and gallium(III) nitrate with urea. Incorporation of Ga3+ into the anatase lattice has a clear positive effect on the photocatalytic activity under UV and Vis light irradiation up to a certain extent of Ga. Ga3+ doping decreased the size of the crystallites, increased surface area, and affected texture of the samples. Higher amount of gallium leads to the formation of a nondiffractive phase, probably photocatalytically inactive. The titania sample with 2.18 wt.% Ge3+ had the highest activity during the photocatalysed degradation in the UV and visible light regions; the total bleaching of dye Orange II was achieved within 29 minutes. Ga concentration larger than 5% (up to 15%) significantly inhibited the growth of the anatase crystal domains which formed the nondiffractive phase content and led to remarkable worsening of the photobleaching efficiency

Hmotnostni spektrometrie plazmatu a vytvareni tenkych vrstev Si-C-N.

Although many results have been reported on the sputtered C-N and Si-C-N films in the literature, deposition mechanisms of such films have not yet been explained in a consistent way. This is due to the lack of knowledge about complex physical and chemical processes occurring on the magnetron target surface, in the plasma bulk and in the sheath region near the powered substrate holder, and on the surface or in the subsurface region of the growing film.Summary in English and GermanAvailable from STL, Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Composite Fe3O4/humic acid magnetic sorbent and its sorption ability for chlorophenols and some other aromatic compounds

A composite magnetic sorbent with a relatively high content of humic substances (above 35% of organic carbon) was prepared by co-precipitation of Fe2+/Fe3+ salts with commercially available alkaline humate concentrate. Magnetite (Fe3O4) was identified as the main crystalline phase bearing the magnetic properties of the sorbent. Scanning electron microscope (SEM) images revealed the presence of uniform sub-micron structures on the surface of the sorbent grains. Due to the presence of humic substances, the sorbent exhibited good sorption ability towards low-polarity organic pollutants, namely chlorophenols. The sorption efficiency increased in the order of 4-mono- < 2,4-di- < 2,4,5-trichlorophenol in accordance with growing hydrophobicity of these compounds, confirming a hydrophobic nature of the interactions involved in the sorption process. Similar trends were found in the desorption study utilizing water and methanol as leachants. Some polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene, fluoranthene, pyrene) were also retained on the sorbent. The chemical composition as well as the main physical characteristics (surface area, phase composition) of the sorbent remained virtually unchanged during the sorption process. The sorbent retained its magnetic properties during the sorption of organic substances from aqueous solutions, which provides an opportunity for its regeneration.Web of Science48132035202

Comparison of the Influence of Two Types of Plasma Treatment of Short Carbon Fibers on Mechanical Properties of Epoxy Composites Filled with These Treated Fibers

The interfacial interface between fibers and matrix plays a key role for epoxy matrix composites and short recycled randomly arranged fibers. This study used short recycled carbon fiber (RCF) as a filler. Plasma treatment was used for carbon fiber surface treatment. This treatment was performed using radio (RF) and microwave (MW) frequencies at the same pressure and atmosphere. Appropriate chemical modification of the fiber surfaces helps to improve the wettability of the carbon fibers and, at the same time, allows the necessary covalent bonds to form between fibers and the epoxy matrix. The effect of the plasma treatment was analyzed and confirmed by X-ray photoelectron spectroscopy, Raman microscopy, scanning electron microscopy, transmission electron microscopy and wettability measurements. Composite samples filled with recycled carbon fibers with low concentrations (1 wt%, 2.5 wt% and 5 wt%) and high concentrations (20 wt% and 30 wt%) were made from selected treated fibers. The mechanical properties (impact toughness, 3PB) were analyzed on these samples. It was found that the modulus of elasticity and bending stress increase with the increasing content of recycled carbon fibers. A more significant change in impact strength occurred in samples with low concentration

Synthesis and properties of nanocomposites of WO3 and exfoliated g-C3N4

The nanocomposites of WO3 nanoparticles and exfoliated graphitized C3N4 (g-C3N4) particles were prepared and their properties were studied. For this purpose, common methods used for characterization of solid samples were completed with dynamic light scattering (DLS) method and photocatalysis, which are suitable for study of aqueous dispersions. The WO3 nanoparticles of monoclinic structures were prepared by a hydrothermal method from sodium tungstate and g-C3N4 particles were prepared by calcination of melamine forming bulk g-C3N4, which was further thermally exfoliated. Its specific surface area (SSA) was 115 m(2) g(-1). The nanocomposites were prepared by mixing of WO3 nanoparticles and g-C3N4 structures in aqueous dispersions acidified by hydrochloric acid at pH = 2 followed by their separation and calcination at 450 degrees C. The real content of WO3 was determined at 19 wt%, 52 wt% and 63 wt%. It was found by the DLS analysis that the g-C3N4 particles were covered by the WO3 nanoparticles or their agglomerates creating the nanocomposites that were stable in aqueous dispersions even under intensive ultrasonic field. Using transmission electron microscopy (TEM) the average size of the pure WO3 nanoparticles and those in the nanocomposites was 73 nm and 72 nm, respectively. The formation of heterojunction between both components was investigated by UV Vis diffuse reflectance (DRS) and photoluminescence (PL) spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photocatalysis and photocurrent measurements. The photocatalytic decomposition of phenol under the LED source of 416 nm identified the formation of Z-scheme heterojunction, which was confirmed by the photocurrents measurements. The photocatalytic activity of the nanocomposites decreased with the increasing content of WO3, which was explained by shielding of the g-C3N4 surface by bigger WO3 agglomerates. This study also demonstrates a unique combination of various characterization techniques working in solid and liquid phase.Web of Science4316135911358

Composites g-C3N4 and BiOIO3 for photocatalytic decomposition of N2O

The composites of graphitic carbon nitride (g-C3N4) and BiOIO3 with different weight ratios of both components (1:1, 2:1, 4:1 and 6:1) were prepared by heating of their mechanical mixtures. Bismuth iodate was prepared by hydrothermal treatment of aqueous solutions of Bi(NO3)(3)center dot 5H(2)O and I2O5. Pure g-C3N4 was prepared by thermal polycondenzation of melamine at 620 degrees C. All of the samples were characterized using X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), UV-VIS diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, X-ray photoelectron (XPS) and Fourier transformed infrared (FTIR) spectroscopy. The measurement of photocurrents was used for the study of photogenerated charge carriers and nitrogen physisorption for the evaluation of specific surface area (SSA) and pore size distribution of the samples. The photodegradation activity of the samples was tested by the UVA light photocatalytic decomposition of N2O. The highest photodegradation activity was observed for the 1:1 composite, which was 2 and 2.5 times higher in comparison to pure BiOIO3 and g-C3N4, respectively. The enhanced photocatalytic activity was explained by a significant reduction of charge carriers' recombination due to the formation of a heterojunction between g-C3N4 and BiOIO3.Web of Science10012211

C18-functionalized Fe3O4/SiO2 magnetic nano-sorbent for PAHs removal from water

Magnetic sorbents represent very promising materials for environmental applications due to their simple synthesis, separability in a magnetic field, low toxicity, wide range of possible modifications, and usability in heterogeneous systems. We report on the synthesis, characterization, and application of magnetically separable Fe3O4/SiO2 sorbent surface-modified with octadecyl chains (C18). Preparation of Fe3O4 cores by co-precipitation from Fe2+ and Fe3+ chlorides in an alkaline aqueous solution was followed by SiO2 shell synthesis and functionalization with C18. Fe3O4, Fe3O4/SiO2, and Fe3O4/SiO2-C18 samples were characterized by SEM, TOC, XRD, BET, and tested for purification of water contaminated by various polycyclic aromatic hydrocarbons (PAHs). Since PAHs are formed as by-products of pyrolysis, a rapidly evolving technology for transformation of waste into green chemicals, there is a need for efficient sorbents suitable for PAHs removal from the environment. The use of Fe3O4/SiO2-C18 for adsorption of 16 different PAHs has not yet been reported. The adsorption was examined by gas chromatography with mass spectrometry and studied using molecular modeling. Comparison of adsorption efficiency 7.7 for Fe3O4, Fe3O4/SiO2, and Fe3O4/SiO2- C18 revealed a positive effect of C18. When averaging all Fe3O4/SiO2-C18 doses tested (1-8 g/L), 7.7 > 80% and > 90% was found for 14 and 7 PAHs, respectively, out of a total of 16 tested PAHs. The highest 7.7 values were found for medium-heavy PAHs (178.2-228.2 g/mol). Exhibiting high efficiency and average capacity of similar to 1 mu g/g, the Fe3O4/SiO2-C18 is suitable for pre-concentration purposes of PAHs in analytical sample extractions from water.Web of Science24art. no. 10190

Structural Characterization of Nanopatterned Surfaces

In this work, chemically and topographically nanopatterned surfaces were produced by a top-down processing approach for biosensing devices. The nanopatterning was the result of the combination of plasma polymerisation (pp) of biofunctional materials and colloidal lithography techniques. The morphological and chemical properties induced by the plasma deposition–etching treatment were characterised by optical method combining ellipsometry and Fourier Transform Infrared spectroscopy studies. This method supported by atomic force microscopy measurements, allowed the full optical characterization of each step of the top-down process. The optical characterization of the end-up nanopatterned samples demonstrated that the chosen process is able to produce well-defined nanostructured surfaces with controlled chemical and morphological properties.JRC.I.4-Nanotechnology and Molecular Imagin

The effect of Zr loading in Zr/TiO2 prepared by pressurized hot water on its surface, morphological and photocatalytic properties

Zr/TiO2 anatase photocatalysts with 0.5, 1, 2, 5 and 7.5mol.% Zr were prepared using pressurized hot water crystallization and their photocatalytic activity was explored in acid orange 7 photodegradation. Parent TiO2 was also prepared and tested. From all tested photocatalysts, 2mol.% Zr/TiO2 showed the highest photoactivity, and 7.5mol.% Zr/TiO2 showed the lowest photoactivity. The poor photoactivity of 7.5mol.% Zr/TiO2 can be explained by the amorphous ZrO2 present in the surface layer (similar to 1-3m depth) of TiO2 anatase nanocrystallite agregates which changed the aggregate morphology and shielded the anatase nanocrystallite surface. The type and amount of defects (e.g., oxygen vacancies, lattice defects) did not effect the photoactivity of Zr/TiO2 in AO7 photodegradation. The addition of Zr to TiO2 significantly affects the photocatalyst morphology and the location where amorphous ZrO2 forms. The optimal Zr loading in TiO2 was determined to be 2mol.%.Web of Science90237936