Preparation of (5.0%)Er3+:Y3Al5O12/Pt-(TiO2-Ta2O5) nanocatalysts and application in sonocatalytic decomposition of ametryn in aqueous solution

(5.0%)Er³⁺:Y₃Al₅O₁₂/Pt-(TiO₂-Ta₂O₅) powder, as a high effective sonocatalyst, was prepared using sol-gel and calcination method. Then it was characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). In order to evaluate the sonocatalytic activity of the prepared (5.0%)Er³⁺:Y₃Al₅O₁₂/Pt-(TiO₂-Ta₂O₅) powder, the sonocatalytic decomposition of ametryn was studied. In addition, some influencing factors such as different Ti/Ta molar ratios on the sonocatalytic activity of the prepared (5.0%)Er³⁺:Y₃Al₅O₁₂/Pt-(TiO₂-Ta₂O₅) powder, catalyst added amount with ultrasonic irradiation time and used times on the sonocatalytic decomposition efficiency were examined by using ion chromatogram determination. The experimental results showed that the best sonocatalytic decomposition ratio of ametryn were 77.50% based on the N atom calculation and 95.00% based on the S atom calculation, respectively, when the conditions of 10.00 mg/L initial concentration, 1.00 g/L prepared (5.0%)Er³⁺:Y₃Al₅O₁₂/Pt-(TiO₂-Ta₂O₅) powder (Ti/Ta = 1.00:0.25 heat-treated at 550 °C for 3.0 h) added amount, 150 min ultrasonic irradiation (40 kHz frequency and 300 W output power), 100 mL total volume and 25–28 °C temperature were adopted. Therefore, the (5.0%)Er³⁺:Y₃Al₅O₁₂/Pt-(TiO₂-Ta₂O₅) composite nanoparticles could be considered as an effective sonocatalyst for decomposition of ametryn in aqueous solution.     

Electrical properties of yttrium doped strontium titanate with A-site deficiency as potential anode materials for solid oxide fuel cells

Yttrium doped strontium titanate with A-site deficiency ((Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ) was synthesized by conventional solid state reaction. The deficiency limit of A-site in (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ is below 6 mol% in Ar/H₂ (5%) at 1500 °C. The sinterability of (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ samples decreases slightly with increasing A-site deficiency level (x). The ionic conductivity of (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ samples increases while the electronic conductivity decreases with increasing A-site deficient amount. The defect chemistry analysis indicates that the introduction of A-site deficiency results in not only the increase of oxygen vacancy concentration but also the decrease of Ti³⁺-ion concentration. The latter plays the main role in the electrical conduction. (Y_0.08Sr_0.92)_1 ? xTiO_3 ? δ shows good thermal-cyclic performance in electrical conductivity and has an excellent chemical compatibility with YSZ electrolyte below 1500 °C.     

Sonophotocatalytic inactivation of E. coli using ZnO nanofluids and its mechanism

The present study evaluated inactivation efficiency of a sonophotocatalytic process using ZnO nanofluids including ultrasonic parameters such as power density, frequency and time. The result showed that inactivation efficiency was increased by 20% when ultrasonic irradiation was combined with photocatalytic process in the presence of natural light. Comparison of inactivation efficiency in photocatalytic, ultrasonic and sonocatalytic processes using Escherichia coli as a model bacteria identified that inactivation efficiencies are shown in the following order: ultrasonic irradiation < sonocatalysis < photocatalysis < sonophotocatalysis. Furthermore, inactivation mechanism of sonophotocatalysis was proposed. Studies of reactive oxygen species (ROS) and zinc ions (Zn²⁺) release evaluation revealed that ROS play a key role in bacterial inactivation rather than Zn²⁺. Permeability of outer membrane (OM) and inner membrane (IM) of E. coli bacterial cells were studied and exhibited that sonophotocatalysis increased the permeability of OM and IM significantly. The enhanced bacterial inactivation effect in sonophotocatalytic process contributed to acoustic cavitation, sonocatalysis of ZnO and sonoporation phenomenon.     

Preparation and photocatalytic degradation of erbium doped titanium dioxide nanorods

Photocatalytic degradation of methylene blue (MB) in water was examined using Er³⁺-doped TiO₂ (Er–TiO₂) nanorods prepared by a sol–gel derived electrospinning, calcination, and subsequent mechanical grinding. Different concentrations of Er dopant in the range of 0–1.0 mol% were synthesized to evaluate the effect of Er content on the photocatalytic activity of TiO₂. Among Er³⁺–TiO₂ catalysts, the 0.7 mol% Er³⁺–TiO₂ catalyst showed the highest MB degradation rate. The degradation kinetic constant (k) increased from 1.0 × 10^?3 min^?1 to 5.1 × 10^?3 min^?1 with the increase of Er³⁺ doping from 0 to 0.7 mol%, but decreased down to 2.1 × 10^?3 min^?1 when Er³⁺ content was 1.0 mol%. It can be concluded that the degradation of MB under UV radiation was more efficient with Er³⁺–TiO₂ catalyst than with pure TiO₂. The higher activity might be attributed to the transition of 4f electrons of Er³⁺ and red shifts of the optical absorption edge of TiO₂ by erbium ion doping.     

Advanced oxidation of Reactive Blue 181 solution: A comparison between Fenton and Sono-Fenton Process

In this work, the decolorization of C.I. Reactive Blue 181 (RB181), an anthraquinone dye, by Ultrasound and Fe²⁺ H₂O₂ processes was investigated. The effects of operating parameters, such as Fe²⁺ dosage, H₂O₂ dosage, pH value, reaction time and temperature were examined. Process optimisation [pH, ferrous ion (Fe²⁺), hydrogen peroxide (H₂O₂), and reaction time], kinetic studies and their comparison were carried out for both of the processes. The Sono-Fenton process was performed by indirect sonication in an ultrasonic water bath, which was operated at a fixed 35-kHz frequency. The optimum conditions were determined as [Fe²⁺] = 30 mg/L, [H₂O₂] = 50 mg/L and pH = 3 for the Fenton process and [Fe²⁺] = 10 mg/L, [H₂O₂] = 40 mg/L and pH = 3 for the Sono-Fenton process. The colour removals were 88% and 93.5% by the Fenton and Sono-Fenton processes, respectively. The highest decolorization was achieved by the Sono-Fenton process because of the production of some oxidising agents as a result of sonication. The paper also discussed kinetic parameters. The decolorization kinetic of RB181 followed pseudo-second-order reaction (Fenton study) and Behnajady kinetics (Sono-Fenton study).     

Degradation of orange-G by advanced oxidation processes

The degradation and mineralization of orange-G (OG) in aqueous solutions by means of ultrasound irradiation at a frequency of 213 kHz and its combination with a heterogeneous photocatalyst (TiO₂) were investigated. The effects of various operational parameters such as, the concentration of the dye and solution pH on the degradation efficiency were studied. The degradation of the dye followed first-order like kinetics under the conditions examined. The sonolytic degradation of OG was relatively higher at pH 5.8 than that at pH 12. However, an alkaline pH was favoured for the photocatalytic degradation of OG using TiO₂. Total organic carbon (TOC) measurements were also carried out in order to evaluate the mineralization efficiency of OG using sonolysis, photocatalysis and sonophotocatalysis. The hybrid technique of sonophotocatalytic degradation was compared with the individual techniques of photocatalysis and sonolysis. A simple additive effect was observed during the sonophotocatalytic oxidation of OG using TiO₂ indicating that the combined treatment offers no synergistic enhancement. TOC results also support the additive effect in the dual treatment process.     

M/Li+(M = Mg2+, Zn2+, and Mn2+) ion-exchange on lithium ion-conducting perovskite-type oxides and their properties

Lithium ions of perovskite-type lithium ion conductor La_0.55Li_0.35TiO₃ were replaced by divalent Mg²⁺, Zn²⁺, and Mn²⁺ ions in an ion-exchange reaction using molten chlorides. The polycrystalline Mg-exchanged and Zn-exchanged samples are solid electrolytes for divalent Mg²⁺ and Zn²⁺ ions, whose dc ionic conductivities (σ = 2.0 × 10^− 6 S cm^− 1 at 558 K for the Mg-exchanged sample, La_0.56(2)Li_0.02(1)Mg_0.16(1)TiO_3.01(2) and σ = 1.7 × 10^− 6 S cm^− 1 at 708 K for the Zn-exchanged samples, La_0.55(1)Li_0.0037(2)Zn_0.15(1)TiO_2.98(2)) were compared to those of the known highest Mg²⁺ and Zn²⁺ inorganic solid electrolytes. The Mn-exchanged sample, then, showed paramagnetic behavior in the temperature range of 2 to 300 K. The Mn ions in the exchanged sample are divalent and the spin configuration is in high spin state (S = 5/2).     

Synthesis and photoluminescence properties of YVO4:Eu3+, Al3+ phosphor

The Y_0.95?xAl_xVO₄:5%Eu³⁺ (0≤x≤0.1) phosphors were successfully synthesized by solid state reaction at 900 °C for 6 h, and their luminescence properties were investigated under UV and VUV excitation. Monitoring at 619 nm, a strong broad absorption was enhanced by co-doping of Al³⁺ into the YVO₄:Eu³⁺ lattices at 256 nm under UV excitation. The VUV excitation spectra also showed the enhanced excitation bands at about 156 and 200 nm. Under 254 or 147 nm excitation, it was found that Y_0.95?xAl_xVO₄:Eu³⁺(0≤x≤0.1) phosphors showed strong red emission at about 619 nm corresponding to the electric dipole ⁵D₀^–7F₂ transition of Eu³⁺. The improvement of luminescence intensity of YVO₄:Eu³⁺ was also observed after partial substituting Y³⁺ by Al³⁺ and the optimal luminescence intensity appeared with incorporation of 2.5 mol% Al³⁺.     

Electronic property and structure of double-doping Y1−2xPrxCaxBa2Cu3O7−δ with 0 ⩽ x ⩽ 0.14

Equal amount Pr and Ca double-doping Y_1?2xPr_xCa_xBa₂Cu₃O_7?δ with 0 ? x ? 0.14 have been investigated by X-ray diffraction, resistivity, and X-ray photoemission spectroscopy (XPS). The deviation of the linearly decreasing of T_c vs. x curve was observed when x < 0.10. The resistivity and the temperature coefficient of resistivity also exhibit abnormal behaviors around x = 0.10. It is revealed that the conductivity behavior of Y_1?2xPr_xCa_xBa₂Cu₃O_7?δ with low Pr content (x < 0.10) is different from that of the relative high Pr content (x > 0.10), which suggests a change of Pr valence with the Pr content. XPS measurement shows that the relative amount of Pr³⁺ and Pr⁴⁺ is closely related to the total Pr content x. The valence of Pr is close to +3 when x < 0.10 and increases towards +4 when x > 0.10, which implies a different mechanism for depression of superconductivity of Pr content x < 0.10 from that of Pr content x > 0.10 in Pr doping Y-123.     

Synthesis and cathodoluminescent properties of Y2SiO5:Tb3+ phosphors prepared from uniform precursor

The luminescent properties of phosphors are sensitive to the size of phosphor particles. The commercial Y₂SiO₅:Tb³⁺ phosphors usually show relatively larger particle size (5–10 μm) due to the irregular morphology of rare earth oxide precursor and thus degrade the luminescent properties. In this paper, we report the Y₂SiO₅:Tb³⁺ phosphors synthesized from the uniform Tb-doped Y₂O₃ precursor by a homogeneous precipitation method. Compared with the commercial phosphors, the obtained Y₂SiO₅:Tb³⁺ phosphors manifest the uniform morphology with much smaller particles distributing from 0.8 μm to 1.9 μm. Consequently, the cathodoluminescent intensity under low excitation voltage (1–5 kV) was increased, demonstrating a strong green emission with a dominant wavelength of 545 nm. Our results indicate an effective way to develop the high-quality phosphors for field emission display.     

Quantification of local oxygen defects around Yttrium ions for yttria-doped ceria–zirconia ternary system

Local coordination structure around Yttrium ions in CeO₂–Y₂O₃ binary and [(CeO₂)_x(ZrO₂)_1?x]_0.8(YO_1.5)_0.2 (x = 0.0 ~ 1.0) ternary system has been investigated by ⁸⁹Y MAS-NMR. NMR spectra are found to be consisted of multiple peaks that can be assigned to 6-, 7- and 8-oxygen coordinated Yttrium ions. Compositional dependence of the spectrum was observed and compared with the previous results for ZrO₂–Y₂O₃ binary system. The present investigation suggested the degree of localization of the oxygen vacancy around the cation is in the order of Zr⁴⁺ > Y³⁺ > Ce⁴⁺. The degree of the oxygen vacancy preference for each cation was quantitatively determined for CeO₂–ZrO₂–Y₂O₃ ternary system the first time.     

Fabrication of Fe-doped TiO2 nanoparticles and investigation of photocatalytic decolorization of reactive red 198 under visible light irradiation

In this research, Fe-doped TiO₂ nanoparticles with various Fe concentrations (0. 0.1, 1, 5 and 10 wt%) were prepared by a sol–gel method. Then, nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), BET surface area, photoluminescence (PL) spectroscopy and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the nano-particles was evaluated through degradation of reactive red 198 (RR 198) under UV and visible light irradiations. XRD results revealed that all samples contained only anatase phase. DRS showed that the Fe doping in the titania induced a significant red shift of the absorption edge and then the band gap energy decreased from 3 to 2.1 eV. Photocatalytic results indicated that TiO₂ had a highest photocatalytic decolorization of the RR 198 under UV irradiation whereas photocatalytic decolorization of the RR 198 under visible irradiation increased in the presence of Fe-doped TiO₂ nanoparticles. Among the samples, Fe-1 wt% doped TiO₂ nanoparticles showed the highest photocatalytic decolorization of RR198 under visible light irradiation.     

Ultrasound and heat enhanced persulfate oxidation activated with Fe0 aggregate for the decolorization of C.I. Direct Red 23

Effluents from the paper printing and textile industries are often heavily contaminated with azo dyes. Azo dyes are difficult to oxidize biologically. This work investigated the decolorization of an azo dye, C.I. Direct Red 23 (DR23), by persulfate (PS) activated with Fe⁰ aggregates (PS/Fe⁰). Ultrasound (US) and heat were used as enhancement tools in the PS oxidation system. Neither US-activated PS nor thermally activated PS was effective in oxidizing DR23. However, the decolorization was significantly enhanced by PS/Fe⁰ combined with US (PS/Fe⁰/US) or heat (PS/Fe⁰/55 °C). Approximately 95% decolorization of 1 × 10⁻⁴ M DR23 was achieved within 15 min in the PS/Fe⁰/US system at an initial pH of 6.0, PS of 5 × 10⁻³ M, Fe⁰ of 0.5 g/L and US irradiation of 106 W/cm² (60 kHz). Complete decolorization was achieved within 10 min in the Fe⁰/PS/55 °C system. The rate of decolorization doubled when US was introduced in the PS/Fe⁰ system during the treatment of different initial dye concentrations. The dependence of dye and true color (ADMI) depletion on PS concentration has been discussed. DR23 was completely degraded based on the disappearance of aromatic groups of UV–vis spectra and the variation of TOC mineralization. The observed pseudo-first-order decolorization rate was substantially enhanced by increasing temperature. The Arrhenius activation energy for the PS activated with Fe⁰ was estimated as 8.98 kcal/mol, implying that higher temperature is beneficial for the DR23 decolorization. The addition of US into the PS/Fe⁰ system did not incur a substantial increase in electricity, whereas the mineralization of DR23 occurred quickly. Thus, both PS/Fe⁰/US and heated PS/Fe⁰ systems are practically feasible for the effective degradation of the direct azo dye in textile wastewater.     

Intensification of sonochemical decolorization of anthraquinonic dye Acid Blue 25 using carbon tetrachloride

In this work, the influence of CCl₄ on the sonochemical decolorization of anthraquinonic dye Acid Blue 25 (AB25) in aqueous medium was investigated using high frequency ultrasound (1700 kHz). This frequency, reputed ineffective, was tested in order to introduce the ultrasound waves with high frequency in the field of degradation or removal of dyes from wastewater, due to its limited use in this field, and to increase the application of high frequency ultrasound wave in the field of environmental protection. The effects of various parameters such as the concentration of CCl₄, frequency (22.5 and 1700 kHz), solution pH, temperature and tert-butyl alcohol adding on the decolorization rate of AB25 was studied. The obtained results clearly demonstrated the significant intensification of AB25 decolorization in the presence of CCl₄. The enhancement effect of CCl₄ increased by decreasing temperature and by increasing the CCl₄ concentration. The pH has a significant influence on the bleaching of dye both in the absence and presence of CCl₄. The three investigated dosimeter methods (KI oxidation, Fricke reaction and H₂O₂ production) well corroborate the improvement of the sonochemical effects in the presence of CCl₄. The best sonochemical decolorization rate of AB25 in aqueous solution both in the absence and presence of CCl₄ is observed to occur at 1700 kHz compared to 22.5 kHz. The sonochemical oxidation of CCl₄ generates oxidizing species in the liquid phase that are highly beneficial for oxidation of hydrophilic and non-volatile pollutant, such as dyes, because they are less susceptible to free radical attack due to lower stability of the generated free radicals.     

Sonocatalyzed decolorization of synthetic textile wastewater using sonochemically synthesized MgO nanostructures

The present study focused on the synthesis of nanostructured MgO via sonochemical method and its application as sonocatalyst for the decolorization of Basic Red 46 (BR46) dye under ultrasonic irradiation. The sonocatalyst was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray microanalysis (EDX). In the following, the sonocatalytic removal of the dye under different operational conditions was evaluated kinetically on the basis of pseudo first-order kinetic model. The reaction rate of sonocatalyzed decolorization using MgO nanostructures (12.7 × 10⁻³ min⁻¹) was more efficient than that of ultrasound alone (2.0 × 10⁻³ min⁻¹). The increased sonocatalyst dosage showed better sonocatalytic activity but the application of excessive dosage should be avoided. The presence of periodate ions substantially increased the decolorization rate from 14.76 × 10⁻³ to 33.4 × 10⁻³ min⁻¹. Although the application of aeration favored the decolorization rate (17.8 × 10⁻³ min⁻¹), the addition of hydrogen peroxide resulted in a considerable decrease in the decolorization rate (9.5 × 10⁻³ min⁻¹) due to its scavenging effects at specific concentrations. Unlike alcoholic compounds, the addition of phenol had an insignificant scavenging effect on the sonocatalysis. A mineralization rate of 7.4 × 10⁻³ min⁻¹ was obtained within 120 min. The intermediate byproducts were also detected using GC–MS analysis.     

Studies of ion implantation conditions and magnetic properties of MnAs nanoparticles buried in GaAs substrate

We present here results obtained on the synthesis of ferromagnetic MnAs nanoclusters embedded in a GaAs matrix. These nanoclusters are formed by co-implanting Mn+As at a dose of 1×10¹⁶ ions cm⁻² for both species. MnAs nanoclusters are only synthezised after a two-step annealing process consisting in a pre-anneal at 600 °C, 60 s which favours the solid-phase epitaxy of the amorphous implanted area. The best magnetic properties have been obtained after a second annealing at 750 °C, 15 s.     

Synthesis of TiO2/WO3 nanoparticles via sonochemical approach for the photocatalytic degradation of methylene blue under visible light illumination

Through an ultrasound assisted method, TiO₂/WO₃ nanoparticles were synthesized at room temperature. The XRD pattern of as-prepared TiO₂/WO₃ nanoparticles matches well with that of pure monoclinic WO₃ and rutile TiO₂ nanoparticles. TEM images show that the prepared TiO₂/WO₃ nanoparticles consist of mixed square and hexagonal shape particles about 8–12 nm in diameter. The photocatalytic activity of TiO₂/WO₃ nanoparticles was tested for the degradation of a wastewater containing methylene blue (MB) under visible light illumination. The TiO₂/WO₃ nanoparticles exhibits a higher degradation rate constant (6.72 × 10⁻⁴ s⁻¹) than bare TiO₂ nanoparticles (1.72 × 10⁻⁴ s⁻¹) under similar experimental conditions.     

Interface Mn nanoclusters in YMnO3/Si ferroelectric gate structures revealed by electron magnetic resonance

In this work, systematic X-band electron magnetic resonance (EMR) studies for YMnO₃/Si ferroelectric gate structures were performed to trace a variation of interface characteristics as different sputtering condition of O₂/(Ar + O₂) ratio. Our result showed that the EMR signal intensities were increased with increasing O₂/(Ar + O₂) ratio. In addition, it was suggested from detailed analyses that the observed EMR signals could be originated from Mn nanoclusters existing in both the polycrystalline Y₂O₃ layer and the amorphous Si-enriched Y–Si interface layer in YMnO₃/Si thin film structure. And also, a correlation between the decrease of crystallinity in YMnO₃/Si film and the content of Mn nanoclusters within the polycrystalline Y₂O₃ layer and/or the amorphous Y–Si layer was discussed.     

Upconversion luminescence dynamics of Er-doped fluoride crystals for optical converters

Erbium (Er)-doped fluoride crystals (YLF, BYF, CaF₂, etc.) are well-known as active media for solid-state lasers emitting in IR and VIS spectral domains, and as materials for efficient near-IR to VIS upconversion. In this paper, we report on the study of conversion of IR light from an ～1.5 μm spectral region to an ～1 μm spectral domain in low-phonon RE-doped fluoride crystals CaF₂ (RE=Er³⁺ Yb³⁺). Energy transfer processes taking place at selective pulsed and CW laser excitation are investigated experimentally. It is shown that in the CaF₂:RE crystals efficient conversion of IR radiation from the ～1.5 μm region to the ～1 μm region occurs, and these crystals are perspective for using in spectral converters for enhancing solar cell efficiency.     

Acute effects of sono-activated photocatalytic titanium dioxide nanoparticles on oral squamous cell carcinoma

Sonodynamic therapy (SDT) is a new treatment modality using ultrasound to activate certain chemical sensitizers for cancer therapy. In this study, effects of high intensity focused ultrasound (HIFU) combined with photocatalytic titanium dioxide (TiO₂) nanoparticles on human oral squamous cell line HSC-2 were investigated. Viability of HSC-2 cells after 0, 0.1, 1, or 3 s of HIFU irradiation with 20, 32, 55 and 73 W cm⁻² intensities in the presence or absence of TiO₂ was measured immediately after the exposures in vitro. Immediate effects of HIFU (3 s, 73 W cm⁻²) combined with TiO₂ on solid tumors were also examined by histological study. Cytotoxic effect of HIFU + TiO₂ in vitro was significantly higher than that of TiO₂ or HIFU alone with the tendency to increase for higher HIFU intensity, duration, and TiO₂ concentration in the suspension. In vivo results showed significant necrosis and tissue damage in HIFU and HIFU + TiO₂ treated samples. However, penetration of TiO₂ nanoparticles into the cell cytoplasm was only observed in HIFU + TiO₂ treated tissues. In this study, our findings provide a rational basis for the development of an effective HIFU based sonodynamic activation method. This approach offers an attractive non-invasive therapy technique for oral cancer in future.