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Plots of Δ(E) versus band gap energy and (inset) the corresponding spectra of the Kubelka–Munk function F(E) for the potassium polytitanates modified in aqueous solutions of copper, nickel and zinc salts.
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Here we present the data on the energy-band-gap characteristics of composite nanoparticles produced by modification of the amorphous potassium polytitanate in aqueous solutions of different transition metal salts. Band gap characteristics are investigated using diffuse reflection spectra of the obtained powders. Calculated logarithmic derivative qu...
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... measured diffuse reflection spectra has been processed to obtain the Kubelka-Munk functions F(E) and corresponding Δ(E) functions for different PPT powders modified in aqueous solutions of transition metal salts (PPTM). The insets in Fig. 1 present the typical examples of F(E) functions. Fig. 2 Fig. 1 shows Δ(E) dependences obtained for different PPTM. In order to minimize the influence of noise in the initial spectral data on the results of Δ(E) calculations, these data have been preliminarily smoothed using the Savitzky-Golay second-order filter with a 15-point window. The applied spectral method does not allow estimating ...Similar publications
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In this present work, we synthesized a yolk-shell shaped CuCo2S4 by a simple anion exchange method. The morphological and structural properties of the as-synthesized sample were characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM)...
This paper presents the results pertaining to studying the properties of the photocatalytically active composition of strontium bismuthate SrBi 2.70 O 5.05 , SrBi 2.90 O 5.35 , and SrBi 3.25 O 5.88 and bismuth carbonate (BiO) 2 CO 3 in molar ratios 1/0.67, 1/0.56, and 1/0.37, respectively. These compositions are obtained through pyrolytic synthesis...
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... The mineral is a composite of several elements and oxides present of natural form, therefore, it is not possible to determine its bandgap because of the presence of particles characterized with varied structure and composition such as amorphous and quasi-amorphous structures [53]. The spectra (Fig. 5) reveal the absorption characteristics in the ultraviolet region for TiO 2 , while the minerals absorb slightly energy in UV/Vis spectra [54]. ...
Black sand from coastal deposits composed by a mixture containing oxides (Fe2O3, TiO2, SiO2, ZrO2, MnO, Al2O3, etc.) and metals (V, Cr, Ni, Sr, Ce, etc.). Both this mineral, as well as a fraction obtained from it, have been used as a photocatalyst for hydrogen production from EDTA (electron donor agent) solutions under UV/Vis irradiation. The physical, chemical and optical properties of materials were studied by X-ray fluorescence, scanning electron microscopy/energy-dispersive X-Ray analysis, BET area, thermal gravimetric analysis, X-ray diffraction patterns, Fourier transform infrared and UV–Vis spectroscopy techniques. The effect of several variables, such as chemical composition (Fe/Ti atomic ratio), catalyst dosage, initial pH of suspension, and sacrificial agent (EDTA) concentration on photocatalytic hydrogen production using these minerals were evaluated. The hydrogen production rate was favored by the high content of iron and low initial pH. Catalyst dosage and sacrificial agent concentration show a synergistic effect due to free radicals generated by the photocatalytic mechanism and the turbidity of the suspension (optical depth). In acidic conditions, M1 fraction produced 35,459.78 µmol g⁻¹ (0.5 g l⁻¹ catalyst and 10 mM EDTA), while lowest hydrogen production (350.294 µmol g⁻¹) was obtained using the same sacrificial agent concentration but employing 0.1 g l⁻¹ of M1 at natural pH suspension (pH 4.8). The results are promising since the hydrogen levels produced by this natural ore are close to yields obtained under similar conditions, using synthetized semiconductors. It’s highlight, that in this study a natural catalyst (principle of the geocatalysis), that not was substantially modified.
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... These results indicated that the thermal stability of the SiO 2 /CNOs/TiO 2 (3%) composites was quite good. The band gap energies were estimated using the Tauc formula (αhν) 1/2 ∝ (hυ-Eg), where α is the absorption coefficient, ν is the frequency of the light, h is Planck's constant and Eg is the band gap [44,45]. In Figure 7, the absorbance of SiO2/CNOs/TiO2(3%) in the visible region was stronger than TiO2, in which the band gap energies were found to be 2.90 eV and 2.22 eV for TiO2 and SiO2/CNOs/TiO2(3%). ...
... where χ is the absolute electronegativity of the semiconductor (χ is 5.81 eV for TiO2 ), E C is the energy The band gap energies were estimated using the Tauc formula (αhν) 1/2 ∝ (hυ-Eg), where α is the absorption coefficient, ν is the frequency of the light, h is Planck's constant and Eg is the band gap [44,45]. In Figure 7, the absorbance of SiO 2 /CNOs/TiO 2 (3%) in the visible region was stronger than TiO 2 , in which the band gap energies were found to be 2.90 eV and 2.22 eV for TiO 2 and SiO 2 /CNOs/TiO 2 (3%). ...
... In Figure 7, the absorbance of SiO 2 /CNOs/TiO 2 (3%) in the visible region was stronger than TiO 2 , in which the band gap energies were found to be 2.90 eV and 2.22 eV for TiO 2 and SiO 2 /CNOs/TiO 2 (3%). The band gap energies were estimated using the Tauc formula (αhν) 1/2 ∝ (hυ-Eg), where α is the absorption coefficient, ν is the frequency of the light, h is Planck's constant and Eg is the band gap [44,45]. In Figure 7, the absorbance of SiO2/CNOs/TiO2(3%) in the visible region was stronger than TiO2, in which the band gap energies were found to be 2.90 eV and 2.22 eV for TiO2 and SiO2/CNOs/TiO2(3%). ...
A silicon dioxide/carbon nano onions/titanium dioxide (SiO2/CNOs/TiO2) composite was synthesized by a simple sol-gel method and characterized by the methods of X-ray diffraction (XRD), scanning electronic microscope (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR), thermogravimetric analysis (TG), differential scanning calorimeter (DSC) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). In this work, the photocatalytic activity of the SiO2/CNOs/TiO2 photocatalyst was assessed by testing the degradation rate of Rhodamine B (RhB) under visible light. The results indicated that the samples exhibited the best photocatalytic activity when the composite consisted of 3% CNOs and the optimum dosage of SiO2/CNOs/TiO2(3%) was 1.5 g/L as evidenced by the highest RhB degradation rate (96%). The SiO2/CNOs/TiO2 composite greatly improved the quantum efficiency of TiO2. This work provides a new option for the modification of subsequent nanocomposite oxide nanoparticles.
... Compared with pure Bi 2 MoO 6 , B-V4 and 5 wt%-A/B-V4 composites have stronger and wider visible-light absorption, which is beneficial for the catalyst to absorb more photons and further improve photocatalytic activity. In addition, the band gap energy (Eg) of the photocatalyst can be calculated by kubelka-munk function [47,48] and the results are expressed in Figure 6b. It can be calculated that the Eg of Bi 2 MoO 6 is 2.56 eV which is close to the previous research. ...
A novel efficient AgI‐Bi2MoO6/vermiculite adsorption‐photocatalyst is successfully synthesized by sol‐gel method and precipitation method. The structure and properties of AgI‐Bi2MoO6/vermiculite were analyzed by XRD, FT‐IR, XPS, SEM, TEM, BET, and DRS. All the AgI‐Bi2MoO6/vermiculite composites with different AgI content show enhanced photocatalytic performance for malachite green (MG) dye degradation compared to pure Bi2MoO6 and Bi2MoO6/vermiculite composites. The highest degradation efficiency for MG (30 mg/L) via 5 wt%‐AgI‐Bi2MoO6/vermiculite composite (AgI content 5 wt%) photocatalyst (1 g/L) reaches 98.89% in 60 min at pH 9 without salt. The enhanced performance can be attributed to the uniform dispersion of Bi2MoO6 and AgI on the surface of vermiculite, the stable structure, the enhanced adsorption and the widened visible‐light absorption range as well as the faster separation of electron‐hole pairs. Besides, the photocatalyst still shows relatively high adsorption and photocatalytic performance after three times recycling. In addition, the possible photocatalytic mechanism is proposed at the end.
... Potassium polytitanate (K2O nTiO2) is a class of compounds presenting a layered crystal of a scaled form, with the thickness of 20-80 nm [15,22,23]. Potassium polytitanate has the layered structure, analogical to the structure of graphite and molybdenum disulfide. ...
The article presents the results of the investigations on the development of new method of hardening and reconditioning of resource-determining parts of hydraulics aggregates of various purpose machinery by composite electroless nickel coatings. It is proved, that by obtaining the composite chemical coatings the most efficient are nanodispersed particles of aluminum oxide and potassium polytitanate. The tribological testing testified, that the wear of the samples which were deposited with the nickel based composite coating, is 1.4 times less than the wear of the samples with the base nickel coating. The bench testing determined that in spool and sleeves of the hydraulic distributors hardened by the composite electroless nickel deposition, leakage value is 1.4 times less than in commercial ones, and 1.3 times less compared with the pairs being reconditioned by ironing.
... The Kubelka-Munk (KM) model [16] has been used to describe the optical properties of inhomogeneous materials consisting of light scattering and absorbing particles in a matrix. Zimnyakov et al. [17], applied the KM theory to composite systems. In the KM model, the properties of the optically dense systems are characterized by the Kubelka-Funk function F(E) which is related to the diffuse refection coefficient R(E) through the relationship F(E) ...
Titania decorated reduced graphene oxide (TiO2∙x%rGO (x = 0, 1, 05, 10, 15, 20 and 25) nanocomposites (NC’s) were fabricated using a hydrothermal process. Scanning electron microscope (SEM) images show that the rGO surfaces were covered with TiO2 nanoparticles whose average sizes increased as x is increased. X Ray Diffraction (XRD) of all the NP’s exhibits the diffractions peaks of the anatase phase of the TiO2. The Fourier-Transform Infrared (FT-IR) spectra of these NC’s indicate an increase in the Ti-O-C interfacial chemical bond vibration signals as x increases. A decrease in the energy of the band (energy) gap as the amount of rGO is increased is determined from the UV–vis light absorption spectra. The use of these TiO2∙x%rGO NC’s to reduce toxic Cr⁶⁺ ions to nontoxic Cr³⁺ ions is studied. The photo-catalytic reduction of the toxic Cr⁶⁺ is seen in general to increase as x is increased.
... The Kubelka-Munk (KM) model [16] has been used to describe the optical properties of inhomogeneous materials consisting of light scattering and absorbing particles in a matrix. Zimnyakov et al. [17], applied the KM theory to composite systems. In the KM model, the properties of the optically dense systems are characterized by the Kubelka-Funk function F(E) which is related to the diffuse refection coefficient R(E) through the relationship F(E) ...
... depending the synthesis conditions. It was recognized earlier that PPT is a semiconductor ceramic material with a band-gap about of 3 eV, which can be reduced and regulated by the modification in transition metal salts [18,19]. The modified PPT have been already reported for a use as solid state ionic conductors [20] and photocatalysts [18,21,22]. ...
... The modified PPT have been already reported for a use as solid state ionic conductors [20] and photocatalysts [18,21,22]. Recently we have shown that modification of the PPT by the transition metals and their oxides/hydroxides allows adjustment of its band-gap [19,23]. It is assumed that introduction of the system based on two transition metal ions, Me 2+ and Me 3+ , can greater contribute to the energy band-gap characteristics due to more substantial changes of the electronic structure of the material, i.e. appearance of impurity levels and/or formation of nanoparticles of the corresponding layered double hydroxide decorating the PPT surface (multiple p-n junction). ...
... SEM images of the electrophoretically deposited ceramic layers are depicted in the Fig. 2. The structure of the obtained layers is characterized by the typical morphology of PPT generally represented by rod-shaped and spherical agglomerates characterized with effective diameter of 1.5-3.5 μm. These agglomerates are covered by ultrafine quasi-amorphous particles which, presumably, in accordance with [18,19], are represented by oxide-hydroxide complexes of the transition metals used for the treatment. ...
The ceramic layers of the potassium polytitanates modified by transition metal salts were electrophoretically deposited onto the surface of glassy substrate coated with indium-tin oxide. The deposition allows obtaining a dense ceramic layer formed by composite agglomerates consisting of nanoscale particles with average size of 130-190 nm. The optical absorption spectra of the coatings modified in the mixtures of aqueous solutions of different transition metal salts were investigated. It was recognized that a bandgap value of these composites can be adjusted in a range from 1.4 to 2.3 eV depending the chemical composition of layered double hydroxide obtained during modification. This might be very promising for optoelectronic applications of such coatings due to an explicit control of optical properties.
A nanostructured material from black sand, whose structure is composed by Fe2O3 and TiO2 oxides, was prepared via hydrothermal treatment (at 120 °C for 72 h), The starting mineral (as‐synthesized nanostructure) was characterized by XRF spectroscopy and thermogravimetric analysis (TGA/DTA) whereas the calcined nanostructures were analyzed by scanning electron microscopy/EDX, BET single point measurements, X‐ray diffraction, FTIR spectroscopy, and UV‐Vis spectrophotometry. The effect of thermal treatment on structural, morphological and redox properties of nanostructured samples (NS) have been thoroughly studied in the samples calcined at 400, 700 and 1000 °C, together with a non‐treated sample (M1). Their photocatalytic activity toward hydrogen production in the presence of EDTA as sacrificial agent has been tested. The as‐synthetized samples calcined at 1000 °C (NS‐1000) showed a higher photocatalytic activity for hydrogen production, possibly due to the transformation of magnetite into more active photocatalytical phases (hematite) driven by the changes in surface morphology (such as reduction of crystallite and pore size reduction) according to thermal equilibrium of its phases. The highest activity for photocatalytic hydrogen production was achieved by the materials calcined at 1000 °C (M1‐1000 and NS‐1000), while the sample calcined at lower values (<700 °C) were the least active. The catalyst activity was assigned to the appearance of a new active phase (α‐Fe2O3), which improves the electronic mobility during the photocatalytic mechanism.
A new route of purification/revalorization of nickel electroplating wastewaters is proposed. It is shown that chemical treatment of different nickel-electroplating wastewaters with aqueous dispersion of layered structure amorphous potassium polytitanate (PPT) successfully removed the nickel from the effluents. Moreover, the resulting solid products, obtained with optimal PPT doses, showed excellent and consistent photocatalytic properties in the visible range of solar radiation, which are independent on the characteristics of the wastewater i.e. pH, nickel contents or the presence of other heavy metals. On the other hand, after proper dilution, the resulting treated effluents can be returned to the municipal wastewater collectors. The mechanisms of the processes taking place during the treatment are analyzed.
