Synthesis and characterization of Pb<Subscript>2</Subscript>SiO<Subscript>4</Subscript> nanostructure: study of photo-catalytic behavior of reactive Red198 and reactive Orange16 dyes as pollutants

Pure Pb₂SiO₄ nanostructures were fabricated using amines as alkaline agents by sol–gel method and characterized via X-ray powder diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS). The average crystallite size of the products in presence and absence of the alkaline agent in the reaction was calculated about 18 and 34 nm by XRD technique, respectively. The type of alkaline agent was evaluated to achieve the optimized nanostructure. The results showed that the ethylenediamine as an alkaline agent has a better performance than the other alkaline agents (ammonia, triethylenetetramine, and tetraethylenepentamine). Optical property of optimized nanostructure was studied by diffuse reflectance spectroscopy (DRS) and its band gap was estimated to about 3.3 eV. It is the first time that photo-catalytic behavior of Pb₂SiO₄ nanostructure was investigated. The photo-catalytic performance of optimized Pb₂SiO₄ nanostructure was evaluated in the presence of various concentrations of Reactive Red198 and Reactive Orange16 dyes. The degradation percentage of dyes in various concentrations (5, 7, and 9 ppm) was obtained for Reactive Red198 and Reactive Orange16 about 100, 57, and 52% and also 100, 52, and 42% after 75 min ultraviolet irradiation, respectively. At 5 ppm concentration, Reactive Orange16 pollutant destruction was faster than Reactive Red198.     

Novel D-π-A dye sensitizers of polymeric metal complexes with phenylethyl or carbazole derivatives as donors for dye-sensitized solar cells: synthesis,characterization, and photovoltaic application

Four novel polymeric metal complexes containing D-π-A type structures were synthesized, characterized and applied as dye sensitizers in dye-sensitized solar cells (DSSCs). The alkoxy benzene or carbazole (CZ) derivative acts as an electron donor (D), C=C acts as π-bridge (π) and the 8-hydroxyquinoline derivative complex acts as electron acceptor. Bipyridine derivative was ancillary ligand as well as providing anchoring group. FT-IR, gel permeation chromatography, thermogravimetric analyses, differential scanning calorimetry, UV–Vis absorption spectroscopy, Elemental analysis, cyclic voltammetry, J-V curves and input photon to converted current efficiency plots were introduced to investigate the four dyes. These dyes exhibit good thermal stability with 5 % weight loss at temperatures (T_d) of around 300 °C. For the DSSCs devices using dyes with CZ derivatives as electron D (P2, P4) exhibited higher power conversion efficiency (PCE) than that with alkoxy benzene (P1, P3). The DSSC based on P4 exhibited the highest PCE value of 2.42 % (J _sc  = 4.93 mA/cm², V _oc  = 0.73 V, FF = 67.2 %) under AM 1.5G solar irradiation. This indicates a new way to design dye sensitizers for DSSCs.     

Solar/UV-induced photocatalytic degradation of three commercial textile dyes.

The photocatalytic degradation of three commercial textile dyes with different structure has been investigated using TiO(2) (Degussa P25) photocatalyst in aqueous solution under solar irradiation. Experiments were conducted to optimise various parameters viz. amount of catalyst, concentration of dye, pH and solar light intensity. Degradation of all the dyes were examined by using chemical oxygen demand (COD) method. The degradation efficiency of the three dyes is as follows: Reactive Yellow 17(RY17) > Reactive Red 2(RR2) > Reactive Blue 4 (RB4), respectively. The experimental results indicate that TiO(2) (Degussa P25) is the best catalyst in comparison with other commercial photocatalysts such as, TiO(2) (Merck), ZnO, ZrO(2), WO(3) and CdS. Though the UV irradiation can efficiently degrade the dyes, naturally abundant solar irradiation is also very effective in the mineralisation of dyes. The comparison between thin-film coating and aqueous slurry method reveals that slurry method is more efficient than coating but the problems of leaching and the requirement of separation can be avoided by using coating technique. These observations indicate that all the three dyes could be degraded completely at different time intervals. Hence, it may be a viable technique for the safe disposal of textile wastewater into the water streams.     

Shifting mechanisms in the initial stage of dye photodegradation by hollow TiO2 nanospheres

Hollow TiO₂ (HT) sphere aggregates were prepared using carbon spheres as templates. The photocatalytic activity of HT was determined by degradation of two nitrogen-containing dyes, methylene blue (MB) and methyl orange (MO). The adsorption isotherms and the photocatalytic degradation kinetics of the two dyes were studied and compared using different concentrations of dyes for the pure, isopropanol-added, and KI-added systems. Isopropanol was used as a OH^? radical scavenger, while KI was added as a valance band hole scavenger. The results showed that the reaction mechanism of the photocatalytic process of MB was first governed by OH^? radicals, and then by valence band holes, whereas holes played a major role in the whole photodegradation process of MO. The photocatalytic adsorption constant K _V has a positive correlation with the reaction constant k _ov in all systems. The photodegradation efficiencies of the dyes were discussed considering the surface characteristics of HT and the structure of the dyes with different catalyst loads (0.25–2 g L^?1) and under different pH (3–10) conditions. Compared with solid TiO₂, HT exhibited enhanced performance in photocatalytic degradation of both MB and MO.     

Irradiation effects on AlGaN HFET devices and GaN layers

AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with protons as well as carbon, oxygen, iron and krypton ions of high (68 and 120 MeV) and low (2 MeV) energy with fluences in the range from 1 × 10⁷ to 1 × 10¹³ cm^?2. High energy irradiation with protons, carbon and oxygen produced no degradation in devices while krypton irradiation at the fluence of 1 × 10¹⁰ cm^?2 resulted in a small reduction of 2% in the transconductance. Similarly, for GaN samples irradiated with protons, carbon and oxygen at high energy no changes were seen by XRD, PL and Hall effect, while changes in lattice constant and a reduction in PL intensity were observed after irradiation with high energy krypton. Low energy irradiation with carbon and oxygen at a fluence of 5 × 10¹⁰ cm^?2 results in small change in the device performance while remarkable changes in device characteristics are seen at a fluence of 1 × 10¹² cm^?2 for carbon, oxygen, iron and krypton irradiation. Similarly changes are also observed by XRD, PL and Hall effect for the thick GaN layer irradiated at the fluence of 1 × 10¹² cm^?2. The device results and GaN layer properties are strongly correlated.     

Photocatalytic performance of pure anatase nanocrystallite TiO2 synthesized under low temperature hydrothermal conditions

Photocatalytic performance of a hydrothermally synthesized pure anatase TiO₂ with 8 nm average crystallite size for decomposition of Reactive Red 141 was examined by investigating the effects of UV-light irradiation time, irradiation power, amount of TiO₂ and initial dye concentration. Change in the UV absorbance of the dye during irradiation was monitored. One wt.% TiO₂ in 30 mg/l Reactive Red 141 aqueous solution was found adequate for complete decolorization in 70 min at 770 W/m² irradiation power. It was realized that, compared to Degussa P-25, the synthesized nano-TiO₂ can be repeatedly used as a new catalyst. The results also proved that Reactive Red 141 is decomposed catalytically due to the pseudo first-order reaction kinetics.     

Kinetics of the decoloration of reactive dyes over visible light-irradiated TiO(2) semiconductor photocatalyst

Photocatalytic decoloration kinetics of triazine (Reactive Red 11, Reactive Red 2, and Reactive Orange 84) and vinylsulfone type (Reactive Orange 16 and Reactive Black 5) of reactive dyes have been studied spectrophotometrically by following the decrease in dye concentration with time. At ambient conditions, over 90-95% decoloration of above dyes have been observed upon prolonged illumination (15 h) of the reacting system with a 150 W xenon lamp. It was found that the decoloration reaction followed first-order kinetics. The values of observed rate constants were found to be dependent of the structure of dyes at low dye concentration, but independent at higher concentration. It also reports for the first time the decoloration of two different dyes together in a binary dye mixture using visible light-irradiated TiO(2) photocatalyst. Rate of decoloration of two different dyes together in a binary dye mixture using visible light-irradiated TiO(2) photocatalyst is governed by the adsorptivity of the particular dye onto the surface of the TiO(2) photocatalyst.     

Alpha and deuteron irradiation effects on silica nanoparticles

We present an experimental investigation focused on the effects of alpha and deuteron irradiation on different silica nanoparticles. The study has been devoted also to characterize the induced point defects and the eventual structural modifications to evaluate the effects of the different irradiation source in comparison with the bulk materials. After irradiation up to about 10¹⁶ ions cm^?2, we performed electron paramagnetic resonance (EPR), photoluminescence (PL), infrared (IR) absorption, Raman, and atomic force microscopy (AFM) measurements. We found that the two types of irradiation qualitatively induce comparable effects. Furthermore, irradiation generates the so-called twofold coordinated Si and the H(I) point defects, originating from the reaction of the former with hydrogen atoms. The occurrence of these defects is a not trivial and interesting finding due to its connection to irradiation-induced oxygen deficiency, not yet evidenced by other irradiation of silica nanoparticles. We also detected the E′Si paramagnetic centers and found that their lineshape at the highest fluence, independently from the nanoparticles size and irradiation source, is different from the one observed in the bulk. Furthermore, the integral of the E′Si signal does not depend significantly on the nanoparticles size differing from previous irradiation with β-ray of the same nanoparticles. AFM images indicate the absence of significant radiation induced sintering between the nanoparticles in the plan orthogonal to the irradiation direction suggesting the absence of morphological changes, whereas IR measurements suggest the occurrence of some structural modifications in all the nanoparticles, which consist in the decrease of the peak value of the Si–O–Si angle distribution. Finally, irradiation effects are induced not uniformly along the irradiation direction, as supported also by micro-Raman investigation of an irradiated bulk silica material and simulations of ions penetration profiles. These results suggest the occurrence of some irradiation effects due to light ion bombardment specific of nanoparticles.     

γ Irradiation of Bulk MgB2 Superconductor

Current–voltage (I–V) characteristics of MgB₂ bulk sintered superconductor, prepared from the commercially available powder (Alfa-Aesar), have been investigated before and after several γ irradiations up to 5000 MR. A minor increase in the normal state resistance of the sample was observed up to 5000 MR without any change in its critical temperature (T _c ). I–V characteristics before and after γ irradiation with different doses up to 5000 MR were shown and fitted to the expression V∝I ^β(T,B) where β approaches unity near T _c before and after γ irradiation. A decrease in the critical currents (I _c ) with γ irradiation up to 1000 MR was observed; after which they start to increase with higher irradiations up to 5000 MR without exceeding the critical currents before irradiation.     

Swift heavy ion irradiation induced modification of structure and surface morphology of BiFeO3 thin film

BiFeO₃ (BFO) thin films of thickness about 800 nm deposited on Si (100) substrates by sol–gel spin coating method were irradiated by 200 MeV Ag ions. Modification of structure and surface morphology of the films under irradiation was studied using glancing incidence X-ray diffraction (GIXRD) and atomic force microscope (AFM). Fluence dependence of GIXRD peak intensity indicated formation of 10 nm diameter cylindrical amorphous columns in crystalline BFO due to 200 MeV Ag ion irradiation. AFM analysis indicated that the pristine film consists of agglomerated grains with diffuse grain boundary. Irradiation led to reduced agglomeration of the grains with the formation of sharper grain boundaries. The rms roughness (σ _rms) estimated from AFM analysis increased from 6·2 in pristine film to 12·7 nm when the film irradiated at a fluence of 1 × 10¹¹ ions cm ^???2 . Further irradiation led to decrease of σ _rms which finally saturated at a value of 7–8 nm at high ion fluences. The power spectral density analysis indicated that the evolution of surface morphology of the pristine film is governed by the combined effect of evaporation condensation and volume diffusion processes. Swift heavy ion irradiation seems to increase the dominance of volume diffusion in controlling surface morphology of the film at high ion fluences.     

Decolorization of reactive textile dyes using water falling film dielectric barrier discharge

Decolorization of reactive textile dyes Reactive Black 5, Reactive Blue 52, Reactive Yellow 125 and Reactive Green 15 was studied using advanced oxidation processes (AOPs) in a non-thermal plasma reactor, based on coaxial water falling film dielectric barrier discharge (DBD). Used initial dye concentrations in the solution were 40.0 and 80.0 mg/L. The effects of different initial pH of dye solutions, and addition of homogeneous catalysts (H₂O₂, Fe²⁺ and Cu²⁺) on the decolorization during subsequent recirculation of dye solution through the DBD reactor, i.e. applied energy density (45-315 kJ/L) were studied. Influence of residence time was investigated over a period of 24 h. Change of pH values and effect of pH adjustments of dye solution after each recirculation on the decolorization was also tested. It was found that the initial pH of dye solutions and pH adjustments of dye solution after each recirculation did not influence the decolorization. The most effective decolorization of 97% was obtained with addition of 10 mM H₂O₂ in a system of 80.0 mg/L Reactive Black 5 with applied energy density of 45 kJ/L, after residence time of 24 h from plasma treatment. Toxicity was evaluated using the brine shrimp Artemia salina as a test organism.     

Growth of thin metallic films on insulating substrates in the presence of electron irradiation

The condensation parameters for Ag and Sb films on amorphous dielectric substrates have been studied under electron irradiation conditions (J = 400 μcm^-2, V_e = 1 kV). With the help of Auger spectroscopy it was shown that the irradiation activated additional condensation centres, whose lifetimes on Sitall substrates were 1 h or more. Optimum doses of irradiation were determined (14 × 10^-3 A s cm^-2).From critical flux measurements for Ag condensation on polymeric surfaces, it was determined that irradiation increased the number of condensation centres by 2–2.5 times without influencing the film formation energy. It was shown that irradiation changed the process of Ag film condensation, causing earlier coalescence.     

Lyoluminescence in Ce3+ activated (KNa)Br phosphor for ionizing radiation dosimetry

The lyoluminescence (LL) in γ-ray irradiated (KNa)Br : Ce^3?+? phosphors are reported in this paper. LL of (KNa)Br : Ce^3?+? have been recorded for different γ-ray doses. The nature of variations of LL peak intensities is found to be linear with γ-ray irradiation dose and LL peak intensity is found to be dependent on concentrations (0·1–10 mol%) of added Ce^3?+? ions in the (KNa)Br host lattice. Negligible fading in the prepared sample is observed.     

Facile synthesis of Bi2S3 nanocrystalline-modified TiO2: Fe nanotubes hybrids and their photocatalytic activities in dye degradation

Interface-induced effects and large specific area of heteronanostructures are attracting much attention due to applications in photocatalysis. In this work, ultrafine bismuth sulfide (Bi₂S₃) nanocrystalline-modified Fe-doped TiO₂ nanotubes (NTs) were fabricated with facile methods. The effect of the ratio of Bi₂S₃ to the Fe-doped TiO₂ NTs on the microstructural, optical, and photocatalytic properties of the NTs and hybrids was studied. The NTs showed an actual Fe content of ～ 2.93 at.%. The optical bandgap of the NTs and hybrids was ～2.90 eV and ～2.46–2.88 eV, respectively, and decreased with increasing Bi₂S₃/NTs ratio. The specific surface area of the NTs was ～333 m² · g^?1; whereas the hybrids showed obviously larger specific surface area of ～ 527–689 m² · g^?1 than the NTs because of well-controlled formation process of Bi₂S₃ nanoparticles. The sunlight-excited degradation experiments of dyes in the water indicated that the photocatalytic activity of the hybrids was higher than that of the NTs and increased with increasing Bi₂S₃/NTs ratio. Moreover, the degradation rates of two dyes at different initial pH values were very different. The high photocatalytic activity of the hybrids was mainly ascribed to the narrow bandgap, large specific surface area, and effective heterojunction.     

Improving photochemical properties of Ipomea pescaprae,Imperata cylindrica (L.) Beauv,and Paspalum conjugatum Berg as photosensitizers for dye sensitized solar cells

This paper reports on the improving photochemical properties of natural dye using acid treatment, coadsorber addition, and dye combination. The natural pigments have been extracted from Ipomea pescaprae, Imperata cylindrica (L.) Beauv, and Paspalum conjugatum Berg containing quercetin 3-O-β-d-glucofuranoside, graminone B, and chlorophyll a. The dyes have been successfully sensitized on TiO₂ anatase nanoparticles as photoelectrodes for the dye-sensitized solar cell. The cells were illuminated under 100 mW/cm² AM 1.5 condition. It is investigated that the acidic treatments have been successfully improving the cell efficiencies of I. pescaprae dye from 0.45 to 0.53 %, I. cylindrica dye from 0.44 to 0.48 %, and P. conjugatum dye from 0.50 to 0.69 %. The acidic treatment leads to broaden the dye spectrum absorption and cell efficiency. Moreover, the addition of coadsorber into I. pescaprae dye is able to improve its cell efficiency from 0.53 to 0.55 % with J _sc of 3.738 mA/cm², V_oc of 0.393 V, and the FF of 0.377. The combination of dyes from I. pescaprae with efficiency of 0.27 % and P. conjugatum with efficiency of 0.55 % could be improved to be 0.76 %. In conclusion, we prove that the acidic treatment, coadsorber addition, and dyes combination play a significant role in improving the photochemical properties of natural dye sensitized solar cell.     

Adsorbents made from textile scraps: preparation,characterization and application for removal of reactive dye

Textile scraps from the clothing industry were used to prepare a low-cost adsorbent to remove anionic dye from textile effluents. Adsorbents were prepared through pyrolysis and chemical activation with K₂CO₃. These samples were characterized through thermogravimetric analysis, scanning electron microscopy, N₂ adsorption/desorption isotherms, Fourier transform infrared spectroscopy, point of zero charge, isoelectric point, elemental composition and proximate analysis. Batch kinetic experiments and adsorption isotherm modeling were conducted in different conditions. The surface properties of the adsorbents were significantly influenced by the activation process. The highest BET surface area (S_BET = 358.55 m² g^?1) was attributed to the sample with chemical treatment. The results indicate that activation process raised 700% the adsorption capacity. The adsorption was strongly dependent on the pH. For the activated adsorbent, 6 g L^?1 was sufficient for the complete removal of 40 mg L^?1 Reactive Black 5 (RB5) solution. The monolayer capacity was up to 10.3 mg g^?1 and was higher than a commercial activated carbon commonly used in textile sector, which was 9.7 mg g^?1.     

Fabrication of graphene-decorated Al2O3 heterojunction nanocomposites for enhanced photocatalytic degradation of high-molecular weight textile reactive dyes

Development of efficient and stable photocatalyst is an urgent need for detoxification of industrial waste water. Herein we synthesized a novel nanohybrid of graphene/Al₂O₃ nanocomposite via ultrasonication route. The crystalline phase, morphological, and optical information identified by XRD, SEM, TEM, Raman, and UV techniques demonstrated the high crystallinity and purity of the hybrid materials. Three highly reactive and high-molecular weight dyes, such as Reactive Violet 5, Reactive Blue 5, and Reactive Red 195, were chosen to demonstrate the photocatalytic activity of nanohybrid material under solar irradiation. It was found that graphene-decorated Al₂O₃ exhibited high performance to degrade all the three dyes. The maximum degradation efficiency of 91%, 87%, and 93% was achieved for RB5, RV5, and RR195, respectively. The photocatalytic mechanism for superior photocatalytic efficiency of nanohybrid composite was proposed on the basis of surface area, synergic effect, and band gap energy. Reusability tests showed excellent stability of composite. Based on the results, graphene-decorated Al₂O₃ nanocomposite is a promising new class of materials that can be used as efficient photocatalytic material for industrial wastewater applications.

     

Preparation of hemicellulose-containing latex and its application as absorbent toward dyes

The removal of hazardous dyes from process water has become one of the most important tasks for water clarification. In this work, a novel type of latex, prepared by the emulsion polymerization of butyl acrylate (BA) and acrylamide (AM) in the presence of hemicellulose, was developed. Under the optimal polymerization conditions, the conversion of monomers reached as high as 97.6 %. The resulting hemicellulose-containing latex (HCL) was assessed as an absorbent toward dyes, methylene blue (MB) in particular. Much effort was made to revealing the impact of adsorption conditions of the dye removal induced by HCL. The maximum removal of the dye by HCL was about 93.8 %, much higher than that of the control sample. The dye adsorption isotherm was determined to further understand the adsorption mechanism. The adsorption data were found to fit Langmuir model well (R ²=0.99904). The maximum adsorption capacity obtained at 25 °C was 42.7 mg g^?1, suggesting that the HCL is promising as an excellent absorbent for the removal of dyes from effluents.     

Strengthening mechanisms in solution treated Mg–yNd–zZn–xZr alloy

A number of solution treated Mg–0.52Nd–0.08Zn–xZr (x = 0, 0.01, 0.03, 0.07, 0.12, and 0.14), Mg–yNd–0.08Zn–0.12Zr (y = 0, 0.17, 0.34, and 0.52) and Mg–0.52Nd–zZn–0.12Zr (z = 0, 0.08, 0.19, and 0.38) (at.%) cast alloys were investigated in terms of grain boundary and solid solution strengthening in this study. The hardness and yield strength of these alloys are determined by the average grain size (Zr content) and the concentration of Nd and Zn elements. The hardness can be predicted as HV₅ ≈ 23 + 3.07 d ^?0.5 (m^?0.5) + 26.5 C _Nd (at.%) + 10.5 C _Zn (at.%), with the average error of about 1.3 %. When the interactions among different solution atoms were not considered, the yield strength can be expressed as σ_0.2 (MPa) = 21 + 0.42 d ^?0.5 (m^?0.5) + (813^3/2 C _Nd (at. %) + 964^3/2 C _Zn (at. %))^2/3, with the average error of about 2.0 %. When the interactions among different solution atoms were considered, more exact yield strength prediction could be obtained with the average error of about 1.6 %.     

Effect of gamma irradiation on the optical properties of amorphous GeSe films

We have studied the influence of gamma irradiation in a ⁶⁰Co source (1.25 MeV, gamma doses from 10² to 10⁶ Gy) and subsequent storage for a year on the structure, fundamental absorption edge, and refractive index of a-GeSe films prepared by flash evaporation in vacuum on silica substrates (T _s = 293 K). The high-energy irradiation has been shown to stimulate structural transformations and to produce changes in the electron-defect subsystem of the films.