Photocatalytic degradation of Rhodamine B dye using ZnO–SnO2 electrospun ceramic nanofibers

ZnO–SnO₂ nanofibers were fabricated by the electrospinning technique combined with calcination at 600 °C. Their structural and morphological properties were analyzed by X-ray diffraction and scanning/transmission electron microscopy, and their photocatalytic activity was investigated by the degradation of Rhodamine B (RhB) dye by visible light irradiation. UV–vis spectral data were used to estimate the photodegradation efficiency of the metal oxide nanocomposites. All the RhB dye samples were tested for six hours of degradation the highest efficiency being obtained for a molar ratio Sn/Zn of 0.030.     

TiO2–SnO2 nanomaterials for gas sensing and photocatalysis

Nanopowders of TiO₂–SnO₂ over a full composition range extending from 100 mol% TiO₂ to 100 mol% SnO₂ are obtained by the sol–gel method from TTIP and SnCl₂·5H₂O precursors of Ti and Sn, respectively followed by calcination at 400 °C. The samples are characterized by means of BET, XRD and TEM. Optical properties of the prepared nanomaterials are studied as well. TEM images indicate that the nanoparticles are regular in shape. The specific surface area, SSA of TiO₂ is 95 m²/g while that of SnO₂ amounts to 129 m²/g. The highest SSA of 156 m²/g is achieved at 20 mol% of TiO₂. Occurrence of rutile, anatase and brookite polymorphic forms depends on the chemical composition of nanopowders. Formation of rutile-type solid solution of TiO₂–SnO₂ over the range of 0–80 mol% TiO₂ is confirmed by Vegard rule applied to lattice constants. Electronic band gap decreases with Ti content from 3.84 eV (100 mol% SnO₂) to 3.18 eV (100 mol% TiO₂).     

Sb2O3–ZnO nanospindles: A potential material for photocatalytic and sensing applications

This paper reports the facile synthesis, characterization and applications of Sb₂O₃–ZnO nanospindles. The nanospindles were synthesized by facile diethanolammine assisted hydrothermal process and characterized in detail in terms of their morphological, structural, compositional and optical properties. The detailed characterizations revealed that the prepared nanoellipsoids are well-crystalline, grown in high density and possessing good optical properties. Further, the as-synthesized Sb₂O₃–ZnO nanospindles were found to be an efficient photocatalyst for the degradation of methylene blue (MB) dye under UV light. Sb₂O₃–ZnO nanospindles were also used as an efficient electron mediator to fabricate a robust, highly sensitive and reproducible chemical sensor for the detection of thiourea in aqueous medium. The fabricated chemical sensor possesses high sensitivity of 6.54 µA mmol L⁻¹ cm⁻². The sensing calibration plot was found to be linear (R²=0.91423) over the large concentration range from 1.56 mmol L⁻¹ to 100 mmol L⁻¹. The obtained results confirmed that the Sb₂O₃–ZnO nanospindles may hold great potential for the removal of organic pollutants and for monitoring of thiourea in aqueous solution.     

Facile synthesis and investigation of NiO–ZnO–Ag nanocomposites as efficient photocatalysts for degradation of methylene blue dye

In the present study, NiO–ZnO–Ag photocatalytic nanocomposites were synthesized using two-stage precipitation method. The synthesized composite powders were investigated and characterized using different techniques including XRD, FESEM, FT-IR, TGA and UV–Vis. XRD results showed that by increasing the Ag content, the crystallite size of ZnO decreased. FESEM micrographs showed that addition of Ag could lead to formation of more uniform particles in the size range of 30–500 nm. Diffuse reflectance spectroscopy results confirmed that addition of Ag nanoparticles led to the increase of light absorption, which was attributed to the plasmon surface resonance of Ag. Band gap energies of NiO–ZnO, NiO–ZnO–5%Ag, NiO–ZnO–3%Ag, NiO–ZnO–1%Ag and ZnO–1%Ag were estimated to be 3.13, 3.14, 3.147, 3.19 and 3.17 eV, respectively. Investigation of degradation process showed that by adding up to 1 wt% Ag to NiO–ZnO composite led to the increase of methylene blue degradation from 67% to 94%, but further addition resulted in decrease of degradation.     

Sol–gel synthesis of Pd doped ZnO nanorods for room temperature hydrogen sensing applications

A sol–gel spin coating technique was described for the synthesis of Pd doped ZnO nanorods for hydrogen sensing applications. The nanorods were hexagonal in shape, 50–100 nm in diameter and uniform in distribution. They exhibited homogeneous surface morphology, c-axis orientation and excellent crystalline properties. The synthesized nanorods were used to sense and detect hydrogen in a homemade gas chamber. The fabricated sensor successfully detected as low as 40 ppm hydrogen at room temperature with a very low level of power supply (16.16 μA) under a mixed background. Dynamic and repeated responses were observed with a wide range of hydrogen concentrations (40–360 ppm) at 200 °C. The developed sensor was at least 25 fold more sensitive over the literature documented Pd doped ZnO nanorods in detecting hydrogen at ambient temperature. The simplicity, low-cost, high sensitivity and high stability of the sensor materials suggested that the synthesized Pd doped ZnO nanorods could be used in hydrogen and chemical sensing devices where Pd-mediated catalysis is involved.     

Ar plasma treatment on ZnO–SnO2 heterojunction nanofibers and its enhancement mechanism of hydrogen gas sensing

In this study, ZnO–SnO₂ heterojunction nanofibers were fabricated using electrospinning and treated by Ar plasma. The post treatment demonstrated the ability to regulate adsorbed oxygen of nanofibers and thus affecting the gas sensing performance. The results revealed that the gas sensing performances increased with the increase of plasma treatment time at first, then showed a downward trend. The setting for the best H₂ gas performance was 20 min of plasma treatment, under which the response of the sample was 80% higher and the response time was two thirds shorter than those of the untreated sample. The explanation can be that appropriate plasma treatment can increase the oxygen vacancy on the surface of heterojunction nanofibers as well as the resistance modulation range in the air; however, excessive plasma treatment can result in the reduction of the resistance modulation range in the air by reducing the metal oxide to metal.     

Photocatalytic degradation kinetics of cationic and anionic dyes using Au–ZnO nanorods: Role of pH for selective and simultaneous degradation of binary dye mixtures

Photocatalysis with ecofriendly and low cost materials is attractive for degradation of organic pollutants without aid of strong reagents. In this regard, Au nanoparticle decorated ZnO nanorods (Au–ZnO) with good crystalline quality was synthesized by cost-effective and scalable hydrothermal method followed by photo-reduction of Au salt. This study addresses variation of photocatalytic degradation kinetics of different nature of dyes with various scavengers and pH conditions. Further, the process versatility is demonstrated by selective or simultaneous degradation of binary dye mixtures with optimized parameters. From Langmuir-Hinshelwood kinetic model, dye concentration range for first order limiting case was determined, and further validated from measured surface area of photocatalyst and change in dye absorbance before irradiation. Better adsorption with faster degradation exhibited by Methylene Blue (MB) dye showed efficient mineralization, revealed from chemical oxygen demand measurements. In Au–ZnO photocatalysis, generation of hydroxyl radical and its significant role in dye degradation was demonstrated using different scavengers. Variation of dye adsorption with pH dependent surface charge characteristics of photocatalyst resulted about one order higher degradation rate constant of MB at high pH. Strong pH dependent MB degradation is shown to be useful for its selective or simultaneous degradation with other dyes. Results of this study are useful for designing photo-reactors and these nanoparticles are efficient for degradation of different dyes, their combinations and industrial effluents under low power UV lamp for treatment different organic pollutants.     

Physico-chemical characterization of IrO2–SnO2 sol-gel nanopowders for electrochemical applications

Mixed tin–iridium oxide (Sn_0.85Ir_0.15O₂) nanoparticles at low Ir content (15 mol%) were prepared by the sol–gel preparative route, varying calcination temperatures in the range 450–550 °C. The crystal structures, the phase composition and crystallite sizes were analyzed by X-ray powder diffraction (XRD). The local order of the materials was investigated by Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) analysis revealed the variation of the Ir surface state with the temperature of firing. The morphology of crystallites and the aggregates were analyzed by high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), respectively. Nitrogen physisorption by BET method was adopted to evaluate the particle surface area and the mesopore volume distribution. Electrochemical properties of the Ti-supported powders were evaluated by cyclic voltammetry (CV) and quasi steady-state voltammetry.     

Ceramic varistors based on ZnO–SnO2

Model ceramic varistor formulations based on 98% ZnO–SnO₂ (plus 2% oxides of Bi, Co and Mn) were prepared by conventional powder processing routes; specimens were sintered at 1150–1275 °C. The product density increased with SnO₂ content, but decreased with increase in sintering temperature. The microstructures contained ZnO, Zn₂SnO₄ spinel and very small bismuth rich phases; with increasing Sn content the spinel became the dominant phase. From I–V measurements, the non-linear coefficients were found to be in the range 24–32. For all compositions, the α values decreased with increasing sintering temperature; the maximum α value was obtained with samples containing 20 mol% SnO₂ sintered at 1200 °C. Breakdown fields were in the range 3000–11000 V/cm and increased with increasing tin content. Leakage currents were in the range 1–11 μA. Tin substitution for Zn appears to cause a strong donor effect.     

Polymer-Salt Synthesis of Photoactive Bactericide ZnO–Ag and ZnO–SnO2–Ag Nanopowders and a Study of Their Structure and Properties

Glass Physics and Chemistry - This paper describes the low-temperature polymer-salt synthesis of ZnO–Ag nanopowders and presents the results of studying their structure, morphology, and...     

Palygorskite and SnO2–TiO2 for the photodegradation of phenol

The photocatalytic removal of phenol was studied using palygorskite-SnO₂–TiO₂ composites (abbreviated as Paly-SnO₂–TiO₂) under ultraviolet radiation. The photocatalysts were prepared by attachment of SnO₂–TiO₂ oxides onto the surface of the palygorskite by in situ sol–gel technique. The products were characterized by XRD, TEM and BET measurements. SnO₂–TiO₂ nanoparticles, with an average diameter of about 10 nm, covered the surface of the palygorskite fibers without obvious aggregation. Compared with palygorskite-titania (Paly-TiO₂), palygorskite-tin dioxide (Paly-SnO₂), and Degussa P25, Paly-SnO₂–TiO₂ and SnO₂–TiO₂ exhibited much higher photocatalytic activity. The photodecomposition of phenol was as high as 99.8% within 1.5 h. The apparent rate constants (k_app) for Paly-SnO₂–TiO_2, TiO₂, and P25 were measured. Paly-SnO₂–TiO₂ showed the highest rate constant (0.03435 min^?1). The chemical oxygen demand (COD) of the phenol solution was reduced from 220.2 mg/L to 0.21 mg/L, indicating the almost complete decomposition of phenol. Reusability of the photocatalyst was proved.     

Synthesis and fluorescence properties of a waterborne polyurethane–acrylic hybrid polymeric dye

A waterborne polyurethane–acrylic hybrid polymeric dye was prepared depending on soap-free emulsion polymerization method. The resulting polymeric dye composed of methyl methacrylate (MMA) monomer which was polymerized into polymethyl methacrylate (PMMA) as cores and waterborne polyurethane-based dye was synthesized by anchoring dye monomers (6-amino-2-cyclohexyl-benz[de]isoquinone-1,3-dione) to polyurethane chains as shells. The average particle sizes of the hybrid polymeric dye emulsions were found to be increased with the increase in MMA contents for MMA monomers. Compared with dye monomers, the absorption intensities and fluorescence intensities of the hybrid polymeric dye were enhanced with the increase of particle sizes. This study revealed that enhanced fluorescence intensity of the hybrid polymeric dye was mainly attributed to the hindered formation of exciplexes among dye monomers and an augmented light absorption area. It was found that the fluorescence intensity of the hybrid polymeric dye was increased with increasing temperature and the trend first increased and then decreased with increase in concentration. Furthermore, the fluorescence of the hybrid polymeric dye emulsions was found to be very stable and not sensitive to the fluorescence quencher.     

In vitro degradation and apatite-formation of ZnO–CaO–SiO2–P2O5 glass–ceramics by substitution of zinc for calcium

A series of CaSiO₃–Ca₂ZnSi₂O₇-based glass–ceramics of the type ZnO–CaO–SiO₂–P₂O₅ were successfully obtained by the partial substitution of calcium with zinc. The effect of zinc addition on structure, dissolution behavior and apatite-forming ability of the resultant glass–ceramics was comprehensively investigated by X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry (TG/DSC), and scanning electron microscopy coupled to an energy dispersive X-Ray spectrometer (EDS). The data revealed that the zinc addition favored the generation of Ca₂ZnSi₂O₇ and induced the formation of ZnSiO₄ and SiO₂ phases. In addition, the excessive content of these compounds led to the attendant loss in the dissolution rate and apatite-forming ability, indicating that the incorporation of zinc into CaSiO₃ is a promising route to regulate the dissolution and apatite formation of CaSiO₃–Ca₂ZnSi₂O₇- based bioceramics.     

Nanostructure composite ZnFe2O4–FeFe2O4–ZnO immobilized on glass: Photocatalytic activity for degradation of an azo textile dye F3B

An efficient and scalable one-pot synthetic method to prepare nanostructure composite of ZnFe₂O₄–FeFe₂O₄–ZnO (ZFZ) has been investigated. This method is based on thermal decomposition of iron(III) acetate and zinc acetate in monoethanolamine (MEA) as a capping agent. Moreover, thermogravimetric analysis (TG-DTG) was performed to determine the temperature at which the decomposition and oxidation of the chelating agents took place. ZFZ was immobilized on glass using doctor blade method and calcinated at different temperatures. The properties of the ZFZ nanocomposite have been examined by different techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance (DRS). FESEM shows that nanocomposite is monocrystallines and a narrow dispersion in size of 48 nm. XRD confirms that the prepared nanocomposite is composed of franklinite, ZnFe₂O₄ (54%), magnetite, FeFe₂O₄ (8%) and wurtzite, ZnO (48%). Photocatalytic activity of ZFZ immobilized on glass was carried out by choosing an azo textile dye, Reactive Red 195 (F3B) as a model pollutant under UV irradiation with homemade photocatalytic apparatus and the results indicated that ZFZ exhibited good photocatalytic activity.     

High photonic effect of organic dye degradation by CdSe–graphene–TiO2 particles

Photocatalytic activity of CdSe (cadmium selenide) decorated graphene composites coupled with TiO₂ (titanium oxide) was investigated with organic dye solutions. The characterizations of composites were studied by X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscope (SEM), and with transmission electron microscope (TEM). The degradation of methyl orange (MO) and rhodamine B (RhB) was observed by measuring the decrease in the concentration by UV spectrophotometer. The synergistic effect of graphene on CdSe and TiO₂ was demonstrated by comparative study. The composites were tested for recyclability, investigating the stability of CdSe–graphene/TiO₂ composites.     

Nano Ca–Mg–Zn ferrites as tuneable photocatalyst for UV light-induced degradation of rhodamine B dye and antimicrobial behavior for water purification

We report the synthesis of Ca-doped Mg–Zn ferrite Mg_0.4Zn_(0.6-x)Ca_xFe₂O₄ nanomaterials with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 through citrate precursor approach and their structural, morphological, optical, photocatalytic, and antimicrobial properties were systematically studied. The prepared nanoferrites's cubic spinel structure with an average crystallite size of 15–38 nm was evaluated by the XRD examination. The spherical morphology of these ferrite nanoparticles was seen from scanning electron microscopy (SEM). The observed bands at 560 cm⁻¹ and 406 cm⁻¹ in the FTIR spectra confirmed the spinel structure of the synthesized nanoferrite. The optical study confirmed an optical band gap of 1.60 eV–1.86 eV. The photocatalysis was done for the degradation of rhodamine B dye solution under UV light. All the synthesized nano ferrites displayed a promising antimicrobial potential upon Candida albicans fungi. Mg_0.4Zn_0.1Ca_0.5Fe₂O₄ nanoparticles have a better photocatalytic response (99.5%) for the degradation of rhodamine B dye and show superior antimicrobial activity (96.1%) for the inhibition of Candida albicans fungi.     

Sintering densification behavior of ZnO–SnO2 binary ceramic targets

In this work, high-performance ZnO–SnO₂ binary ceramic targets for magnetron sputtering of transparent conductive oxide (TCO) films were prepared by pressureless oxygen atmosphere sintering. The sintering behavior and densification mechanism of the ZnO–SnO₂ binary targets were analyzed by systematically studying the oxide powder state, formation process of the solid reaction phase, and evolution of the target microstructure. The data revealed that the ZnO–SnO₂ powder treatment improved the sintering activity and the powder dispersion; furthermore, it promoted a mutual reaction between the different components during sintering and the homogeneity of the target composition. The densification of the pure SnO₂ ceramic target was difficult to achieve, and the addition of ZnO led to a continuous interaction between the ZnO and SnO₂ components. The Zn₂SnO₄ phase started to form, and a temporary shrinkage of the target occurred above 800°C. After formation of the stable Zn₂SnO₄ and SnO₂ phases, the target shrunk rapidly with increasing temperature, densification occurred during growth, and the two phases started to interact. The sintering temperature provided the driving force for the target densification, with the densification activation energy of the ZnO–SnO₂ binary ceramic target estimated to be 580 kJ/mol based on the master sintering curve. A binary ceramic target with a high density (99.78% relative density), a fine grain size, and a homogeneous phase structure was achieved at a temperature of 1600°C. These findings are promising for the further improvement and performance enhancement of SnO₂-based materials.     

Sol–gel hydrothermal synthesis of bismuth–TiO2 nanocubes for dye-sensitized solar cell

Bismuth–TiO₂ nanocubes were synthesized via a facile sol–gel hydrothermal method with titanium tetraisopropoxide as the precursor. The influence of the bismuth on the size, morphology, crystallinity and optical behavior of TiO₂ nanocubes were investigated. The samples were characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), field emission scanning electron microscopy (FESEM) and UV–visible spectroscopy (UV–vis). Photovoltaic behavior of dye-sensitized solar cells (DSSCs) fabricated using Bi–TiO₂ nanocubes was studied. The DSSCs had an open-circuit voltage (V_oc) of 590 mV, a short-circuit current density (J_sc) of 7.71 mA/cm², and the conversion efficiency (η) of 2.11% under AM 1.5 illumination, a 77% increment as compared to pure TiO₂ nanocubes.     

SnO2–polyaniline composites for the desensitization of Al/SnO2 thermite composites

Nanothermites consisting of a reducing metal and a metal oxide nanopowder represent a new generation of energetic materials in pyrotechnics due to their impressive reactive properties. However, their extreme sensitivity regarding electrostatic discharge appears to be detrimental to their future practical applications. Herein, the mitigation of the sensitivity thresholds of the aluminium/tin (IV) oxide energetic nanocomposite is successfully achieved by using a conducting polymer, polyaniline (PAni). PAni was introduced within the thermite by the chemical polymerization of an oxidizer/PAni hybrid matrix. The SnO₂–PAni composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, electrical conductivity measurements, and transmission electron microscopy. The derived Al/SnO₂–PAni thermites were investigated in terms of sensitivities and reactivity. Results revealed gradual desensitization of the Al/SnO₂ thermite as a function of the concentration of PAni for both the electrostatic discharge (0.14–1212 mJ) and friction (216–360 N) tests while maintaining reactive energetic composites. This work presents a way for the preparation of insensitive and reactive energetic formulations. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48947.     

Influence of doped platinum nanoparticles on photocatalytic performance of CuO–SiO2 for degradation of Acridine orange dye

Preparation of cupric oxide-silicon dioxide nanoparticles was carried out using a sol-gel method. Cupric oxide-silicon dioxide nanoparticles were decorated by different weight percent of platinum (0.5, 1.0, 3.0 and 5.0 wt %) using method of photoassisted deposition. XRD remarks revealed that XRD patterns for all samples are composed of cupric oxide. Therefore, silicon dioxide is amorphous and decoration of cupric oxide-silicon dioxide nanoparticles by platinum has no effect on the formed phase. Also, due to low percent of platinum there are no peaks for platinum oxide or platinum. Cupric oxide has bandgap energy absorb in visible region but has high e-h recombination rate. Decoration of cupric oxide-silicon dioxide nanoparticles by platinum was decreased bandgap energy from 2.38 to 1.91 eV and also decrease rate of e-h recombination rate. The photocatalytic activity of platinum decorated cupric oxide-silicon dioxide nanoparticles was measured under visible light for Acridine orange dye degradation. 100% of Acridine orange dye can be degraded using 3.0 wt % of platinum decorated cupric oxide-silicon dioxide photocatalyst, 1.2 g/L dose of platinum decorated cupric oxide-silicon dioxide photocatalyst and 30 min reaction time. 3.0 wt % of platinum decorated cupric oxide-silicon dioxide photocatalyst has photocatalytic stability for five times.