Effect of electron beam irradiation on the structural properties of poly(vinyl alcohol) formulations with triphenyl tetrazolium chloride dye (TTC)

Films of poly(vinyl alcohol) (PVA) composites with triphenyl tetrazolium chloride (TTC) dye were prepared and exposed to various radiation doses delivered by accelerated electrons. The results showed that at a low dose of 50 kGy, the colour difference (ΔE^*) of PVA/TTC films was increased by ∼10 times of the initial value. However, the change in colour differences did not go systematically with increasing the TTC content, in which the composite with 1.5 wt% displayed higher value than that with 3.5 wt%. The differential scanning calorimetry (DSC) showed that the presence of the TTC dye caused a depression in the melting point (T_m) and heat of fusion (ΔH_f) of the PVA bulk polymer. However, the thermogravimetric analysis (TGA) showed that the presence of the TTC dye improved the thermal stability of PVA. Also, the tensile strength at break of PVA/TTC composites was improved after electron beam irradiation.     

Nanocomposite of CeVO4/BiVO4 Loaded on Reduced Graphene Oxide for the Photocatalytic Degradation of Methyl Orange

A facile procedure, involving one-pot synthesis of CeVO₄/BiVO₄ and in-situ reduction of graphene oxide (GO), has been used to prepare CeVO₄/BiVO₄/rGO nanocomposites. Different ratios of the CeVO₄–BiVO₄ were prepared to afford composites represented as CBVG3, CBVG5, and CBVG7. The ternary nanocomposite materials were characterized by using powder X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), photoluminescence and UV–vis spectroscopic techniques. Photocatalytic efficiency of the as-prepared ternary nanocomposites was investigated through the photo degradation of methyl orange under a visible light irradiation at 470 nm. The photocatalytic performance was enhanced by loading the CeVO₄/BiVO₄ nanoparticles on reduced graphene oxide (rGO), given MO degradation rate of 57, 65, 80, and 90% for BVG, CBVG3, CBVG5, and CBVG7, respectively after exposure to visible light for 120 min. Effects of experimental process parameters including initial dye concentration, catalysts loading and effect of different modification regimes were studied using CBVG7, which exhibited the highest efficiency. The improvement in the photocatalytic efficiency may be attributed to increased surface area of the nanocomposites, enhanced light absorption capacity and improved charge separation. The study showed a one-pot synthesis route to prepare promising CeVO₄/BiVO₄/GO nanocomposites for the photo-enhanced degradation of dye contaminants.

     

Effect of sunset yellow dye on morphological,optical, dielectric,thermal and mechanical properties of KDP crystal

Herein, we describe the growth and morphology of well-defined dyed crystals of KH₂PO₄ (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping.     

Enhanced Thermal Decomposition Properties and Catalytic Mechanism of Ammonium Perchlorate over CuO/MoS2 Composite

In this report, CuO/MoS₂ composites were successfully prepared by the hydrothermal method where nano‐sized CuO was uniformly distributed on the surface of hierarchical MoS₂ substrates (CuO/MoS₂ composites). Their physicochemical properties and catalytic performance in ammonium perchlorate (AP) decomposition were investigated and characterized by XRD, SEM, TEM, BET, XPS, TG/DSC and combustion measurement. The results showed that it could decrease AP decomposition temperature at high decomposition stage from 416.5 °C to 323.5 °C and increase the heat release from 378 J/g (pure AP) to 1340 J/g (AP with catalysts), which was better than pure CuO nanoparticles (345.5 °C and 1046 J/g). Meanwhile, it showed excellent performance in combustion reaction either in N₂ or air atmosphere. The results obtained by photocurrent spectra, photoluminescence spectra and time‐resolved fluorescence emission spectra indicated that loading CuO mediated the generation rate and combination rate of electrons and holes, thus tuning the catalytic performance on AP decomposition. This study proved that employing the supports that can synergistically interact with CuO is an efficient strategy to enhance the catalytic performance of CuO.     

Photocatalytic Degradation of Organic Reactive Dyes over MnTiO3/TiO2 Heterojunction Composites Under UV‐Visible Irradiation

In this study, the photocatalytic degradation of organic reactive dyes have been investigated using MnTiO₃/TiO₂ heterojunction composites in the presence of electron acceptors under UV‐Visible light irradiation. This MnTiO₃/TiO₂ heterojunction composites were prepared by annealing different mass ratios of pyrophanite MnTiO₃ (3–11 wt%) and TiO₂ at 300°C. All the MnTiO₃/TiO₂ heterojunction composites were characterized by spectral techniques like X‐ray diffraction (XRD), scanning electron microscope (SEM) and diffused reflectance UV‐visible spectroscopic analysis (DRS). Among them, 9 wt% MnTiO₃/TiO₂ heterojunction composites exhibited higher photocatalytic activity for the degradation of Reactive Blue 4 (RB 4). The photocatalytic efficiency of 9 wt% MnTiO₃/TiO₂ heterojunction composites was further enhanced by the addition of substantial amount of electron acceptors like hydrogen peroxide (H₂O₂) and ammonium peroxydisulfate ([NH₄]₂S₂O₈). The presence of oxidants (electron acceptors) facilitates the fast degradation of dye solution even in higher concentration upto 200 mg/L. The photocatalytic activity of MnTiO₃/TiO₂ heterojunction composites was also studied for the degradation of other four different structured reactive dyes. The extent of mineralization of these organic reactive dyes during photocatalytic degradation was estimated from COD analysis. MnTiO₃/TiO₂ heterojunction composites was also found to have good photostability in the presence of oxidants.     

Synthesis of Pr<Superscript>3+</Superscript> doped or Tb<Superscript>3+</Superscript>–Mg codoped CaSnO<Subscript>3</Subscript> perovskite phosphor by the polymerized complex method

Pr³⁺ doped or Tb³⁺–Mg codoped CaSnO₃ phosphor powder with perovskite structure was synthesized by the polymerized complex method. Powder samples crystallized into the perovskite phase at approximately 600 °C, which is 400 °C lower than the crystallization temperature for the solid-state reaction method. Uniform-sized powders with average particle sizes of 1–2 μm were obtained after heat treatment at 1,400 °C. Although the samples heat-treated at 600 °C did not exhibit photoluminescence, white photoluminescence of Pr³⁺ doped CaSnO₃ or green photoluminescence of Tb³⁺–Mg codoped CaSnO₃ was observed from the sample heat-treated above 800 °C. The intensity of the photoluminescence increased with increase of the heat-treatment temperature and reached a maximum for heat treatment at 1,400 °C. The maximum photoluminescence intensity for the samples prepared by the polymerized complex method was larger than those prepared by solid-state reaction method, which is probably due to the homogeneous mixing of the doped rare earth ions.     

Optical,piezoelectric and mechanical properties of xylenol orange doped ADP single crystals for NLO applications

Single crystals of pure and xylenol orange (XO; C₃₁H₃₂N₂O₁₃S) dye doped (0.01, 0.05 and 0.1 mol%) ammonium dihydrogen phosphate (ADP; NH₄H₂PO₄) were grown by slow evaporation method with the vision to improve the properties of pure ammonium dihydrogen phosphate crystal. The theoretical morphology of the grown crystals was drawn using Bravais–Friedel–Donnay–Harker (BFDH) law. The selective nature of xylenol orange dye to selectively stain the particular growth sectors of ADP crystal was studied. The structural analysis of as grown crystals was carried out using powder XRD study. The identification of the functional groups present in the ADP material was done using Fourier transform infrared (FTIR) spectroscopy. The linear optical study on pure and dye doped crystals was carried out using UV–vis–NIR spectroscopy. The optical band gap, extinction coefficient, refractive index and optical conductivity were calculated using the transmittance spectra for all the samples. In photoluminescence studies, the blue emission intensity got quenched and an orange emission at 597 nm was seen as a result of XO doping. The thermal stability and decomposition temperature of ADP crystal were found to decrease as an effect of dye doping. The piezoelectric charge coefficient, SHG conversion efficiency, mechanical strength and wettability were also enhanced as a result of XO dye doping.     

Chemiluminescence and laser photoluminescence of some diatomic metal halides

Several diatomic metal halides, BaBr, BaCl, BiBr, BiCl, CuBr, CuCl, PbBr, and PbCl, were produced by reacting metal vapor with Br₂ or Cl₂. Molecules were identified from chemiluminescence and laser induced photoluminescence. Using a pulsed, tunable dye laser, the radiative lifetimes of the C² II state of BaBr and BaCl were found to be 8 and 22 nsec, respectively.     

In situ electrochemically tuned photoluminescence of [Ru(bpy)<Subscript>2</Subscript>(dppz)]<Superscript>2+</Superscript> aggregates with single-walled carbon nanotubes and DNA monitored by guanine oxidation

A classical ruthenium(II) complex [Ru(bpy)₂(dppz)]²⁺ (bpy = 2,2′-bipyridine, dppz = dipyrido[3,2-a:2′,3′-c]phenazine) was combined with guanine and single-walled carbon nanotubes dispersed with DNA (SWCNTs-DNA) to prepare electrochemically tunable photoluminescence materials. These multi-component aggregates were found to show enhanced luminescence by the electrocatalytic oxidation of guanine under the excitation of a continuous wave green laser at a constant anodic potential via an electrode-solution interface. The results from this study provide a significant foundation for better understanding of DNA-based luminescent devices.     

New laser dye based on the 3-styryl analog of the BODIPY dye PM567

We report the synthesis, photophysical properties and evaluation of laser dye of a new BODIPY dye with a 3-styryl substituent, PMS, and with the rest of the substituents as in the commercial dye PM567. PMS shows an emission band at 584 nm in methanol, i.e. displaced ca. 50 nm to longer wavelengths with regard to the green-emission band of PM567, as well as a high-fluorescence quantum yield (0.82) and also a high-molar absorption coefficient (10⁵ M⁻¹ cm⁻¹) in the same solvent. The laser action of the new dye has been analyzed under transversal pumping at 532 nm, 5.5 mJ pulse⁻¹ and up to 10 Hz repetition rate, in both liquid phase and incorporated into solid polymeric matrices of methyl methacrylate copolymerized with crosslinking or fluorinated monomers. Lasing emission at 602–610 nm, with maximum efficiencies of 18%, were reached in these media. In solid-fluorinated matrices, good lasing photostabilities were established, with 30% of the initial laser output remaining after 100,000 pump pulses at 10 Hz.     

The effect of different substrate temperatures on the structure and luminescence properties of Y2O3:Bi3+ thin films

Y₂O₃:Bi³⁺ phosphor thin films were prepared by pulsed laser deposition in the presence of oxygen (O₂) gas. The microstructure and photoluminescence (PL) of these films were found to be highly dependent on the substrate temperature. X-ray diffraction analysis showed that the Y₂O₃:Bi³⁺ films transformed from amorphous to cubic and monoclinic phases when the substrate temperature was increased up to 600 °C. At the higher substrate temperature of 600 °C, the cubic phase became dominant. The crystallinity of the thin films, therefore, increased with increasing substrate temperatures. Surface morphology results obtained by atomic force microscopy showed a decrease in the surface roughness with an increase in substrate temperature. The increase in the PL intensities was attributed to the crystallinity improvement and surface roughness decrease. The main PL emission peak position of the thin films prepared at substrate temperatures of 450 °C and 600 °C showed a shift to shorter wavelengths of 460 and 480 nm respectively, if compared to the main PL peak position of the powder at 495 nm. The shift was attributed to a different Bi³⁺ ion environment in the monoclinic and cubic phases.     

Electrochemical synthesis of orientation-ordered ZnO nanorod bundles

The high density and orientation-ordered ZnO nanorod bundles with wurtzite structures were prepared on Cu substrates by electrochemical deposition in solution of ZnCl₂ + tartaric acid at a temperature of 90 °C. This approach is a unique and size controlled synthetic method for the large-scale preparation of ZnO nanorod bundles. Cyclic voltammogram measured in solution of the mixture of ZnCl₂ and tartaric acid shows a restraining role of tartaric acid for the electro-reduction of Zn(II). The formation mechanism of ZnO on the surface of the cathode can be explained that the high temperature (⩾90 °C) promotes the corrosion of electrodeposited Zn via reacting with H₂O and O₂ to form the stable passive phase of ZnO. The compositions of the nanorod bundles can be entirely ZnO or Zn and ZnO composites determined by the temperature and deposition rate. The photoluminescence (PL) properties indicate that these ZnO deposits are highly crystallized and of excellent optical quality.     

Sol-Gel Processing of Sm2+-Doped Glass and Its Spectral Hole Burning at Room Temperature

The sol-gel process was applied to the preparation of Sm²⁺ ion-doped silicate glasses, which show persistent spectral hole burning at room temperature. The gels synthesized by the hydrolysis of metal alkoxides and SmCl₃·6H₂O were heated in air at 500°C, were then reacted with H₂ gas to form the Sm²⁺ ion. The Al₂O₃−SiO₂2 glasses are appropriate to reduce the Sm³⁺ ion with H₂ gas and show intense photoluminescence of Sm²⁺ ion. Persistent spectra hole burning was observed in the excitation spectrum for the⁷F₀→⁵D₀ transition of the Sm²⁺ ion by the irradiation of DCM dye laser. The hole width and depth were ∼16 cm⁻¹ and ∼10% of the total intensity, respectively, at 20°C.     

Synthesis,characterization, and visible light–induced photocatalytic evaluation of WO3/NaNbO3 composites for the degradation of 2,4-D herbicide

In this research study, WO₃/NaNbO₃-coupled photocatalysts were synthesized at three WO₃ mass ratios (15, 85, and 95 wt%) and characterized. These composites were characterized via X-ray powder diffraction, N₂ physisorption, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and photoluminescence techniques. For comparison, bare WO₃ and NaNbO₃ were also synthesized and characterized. 2,4-Dichlorophenoxyacetic acid (2,4-D) was degraded under visible light to evaluate its photocatalytic performance. The WO₃ (95 wt%)/NaNbO₃ composite showed higher photocatalytic activity than pure WO₃ and NaNbO₃ and even than the 15 and 85 wt% coupled materials; thus, the combination with the highest ratio of WO₃ with respect to NaNbO₃ showed increased photocatalytic activity compared with the bare materials.     

Photodegradation of orange II dye using p-n junction NiO/TiO2 composite,and assessment of its biological activities

The chemical reduction method was used to synthesize nickel oxide particles (NiO) and NiO supported on titanium dioxide (NiO/TiO₂ nanocomposite). The composites were characterized through scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The morphological investigation showed that pseudocubic NiO are present in dispersed as well as agglomerated forms. Whereas NiO particles (<200 nm) are evenly deposited over the surface of TiO₂ in NiO/TiO₂ composite. The formation of NiO and NiO/TiO₂ was also verified by XRD analysis. The synthesized NiO and NiO/TiO₂ were used as photocatalysts for the degradation of Orange II (OII) dye. According to the degradation investigation, both NiO and NiO/TiO₂ composite degraded OII dye more efficiently when exposed to UV light. The results indicated that NiO degraded 93% and NiO/TiO₂ composites degraded approximately 96% of OII dye within 30 min. Both photocatalysts are highly sustainable and have significant OII dye degradation recyclability. Moreover, NiO and NiO/TiO₂ exhibited promising bioactivities (antioxidant activity of 80%) against the pathogenic bacteria Citrobacter and Providencia, which is comparable with the standard ascorbic acid (88%).     

Poly(o-phenylenediamine)/MWNTs composite film as a hole conductor in solid-state dye-sensitized solar cells

All solid-state dye-sensitized solar cells were fabricated using in situ electrochemically polymerized poly(o-phenylenediamine)/MWNTs (PoPD/MWNTs) as a hole transport materiel. The electrochemical behaviors of PoPD/MWNTs indicated that the electron exchange efficiency improves obviously of PoPD after the addition of carbon nanotubes. The PoPD/MWNTs composite film was deposited on the dye anchored porous TiO₂ electrode and I–V characterization was performed under simulated AM 1.5 illumination. Fabricated devices for the PoPD/MWNT composites prepared in 0.1 g/L MWNTs showed a photoresponse with an open-circuit voltage V_OC of 479 mV and a short-circuit current density (I_SC) of 0.572 mA/cm² with the overall conversion efficiency of 0.13%, higher than those of the cell with only PoPD (i.e., I_SC = 0.275 mA/cm², V_OC = 462 mV, FF = 0.35, η = 0.04%). It is obvious that the introduction of MWNTs to PoPD composites could improve the cell performance.     

Comparative investigation on structure and luminescence properties of fluoride phosphors codoped with Er/Yb

This paper reports on comparative investigation of structure and luminescence properties of tetragonal LiYF₄ and BaYF₅, and hexagonal NaYF₄ phosphors codoped with Er³⁺/Yb³⁺ by a facile hydrothermal synthesis. The products were characterized by X-ray diffractometer, scanning electron microscope, and photoluminescence spectroscopy. Intense visible emissions centered at around 525, 550 and 650 nm, originated from the transitions of ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 of Er³⁺, respectively, have been observed in all the samples upon excitation with a 980 nm laser diode, and the involved mechanisms have been explained. Based on the green up-conversion emission performance, the Yb³⁺ concentrations of Er³⁺/Yb³⁺-codoped LiYF₄, BaYF₅, and NaYF₄ phosphors have been optimized to be 10, 20, and 20 mol.%, respectively. The quadratic dependence of fluorescence on excitation laser power has confirmed that two-photon contribute to up-conversion of the green–red emissions.     

Synthesis of carbon nanotube/anatase titania composites by a combination of sol-gel and self-assembly at low temperature

A simple method is described for the synthesis of carbon nanotube/anatase titania composites by a combination of a sol-gel method with a self-assembly technique at 65 °C. This method makes use of polyelectrolyte for wrapping multi-walled carbon nanotube (MWCNT) and providing them with adsorption sites for electrostatically driven TiO₂ nanoparticle deposition. The composites were characterized using X-ray diffraction, transmission electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy, and photoluminescence for analyzing their crystal phase, microstructure, particle size, and other physicochemical properties. The results showed that MWCNT were covered with an anatase TiO₂ thin layer or surrounded by an anatase TiO₂ thick coating, which is constructed of TiO₂ particles about 6 nm in size. The composites were rich in surface hydroxyl groups. The excited e⁻ in conduction band of TiO₂ may migrate to MWCNT. Concerning the potential applicability, MWCNT/TiO₂ composites showed excellent photocatalytic activity toward the photodegradation of methyl orange.     

One-pot synthesis of graphene–cuprous oxide composite with enhanced photocatalytic activity

In this paper, graphene–cuprous oxide (G–Cu₂O) composites were synthesized at room temperature using graphene oxide (GO) as two-dimensional support. From Zeta potential analysis, the surface charge of G–Cu₂O composites altered from positive to negative, which favors the adsorption and photodegradation of positively charged dyes. Compared with Cu₂O under similar synthesis condition, the G–Cu₂O composites demonstrated improved photodegradation activity for methylene blue (MB) dye under visible light. Controlled experiments indicated that the G–Cu₂O composite synthesized with 80 mg GO in the reaction system possessed more negative Zeta potential, highest specific surface area and thus presented the highest photocatalytic activity. Electrons mechanism for the improved photocatalytic performance of G–Cu₂O composite was proposed in the degradation of MB.     

Structural analysis of reactive dye species retained by the basic alumina surface

The alumina-dye composites were prepared by treating the basic alumina with the water solutions of Reactive Red 120 (RR 120) and Reactive Blue 15 (RB 15) dyes. The bands of low intensities in the 1400–1600 cm⁻¹ region and at 783 cm⁻¹ in the IR spectra of these composites point out that the dye species is bound weakly to the surface. In the case of mechanochemical adsorption of dye molecules, the asymmetric and symmetric S(=O)₂ and the S-O-C stretching bands together with the vibrations of aromatic ring revealed that dye types under dry conditions interacted effectively with alumina surface. After the heating of the alumina dye complexes in the temperature range 150–350°C, the intensities of the IR and XRD peaks for adsorbed types decreased. The endothermic peaks over 200°C and the bigger total mass losses for the alumina-dye composites can be ascribed to the decomposition of dye species retained by the alumina surface. The mass losses on TG curves of the alumina-dye complexes up to ∼800°C exhibit the removal of black residues occurred by decomposition of first adsorbed products. The thermal analysis data also point out that the water molecules bonded strongly to the alumina surface and dye types compete to accommodate at the surface active sites.