Azo dyes degradation using TiO2-Pt/graphene oxide and TiO2-Pt/reduced graphene oxide photocatalysts under UV and natural sunlight irradiation

The photocatalytic degradation of azo dyes with different structures (amaranth, sunset yellow and tartrazine) using TiO₂-Pt nanoparticles (TPt), TiO₂-Pt/graphene oxide (TPt-GO) and TiO₂-Pt/reduced graphene oxide (TPt-rGO) composites were investigated in the presence of UV and natural sunlight irradiation. The composites were prepared by a combined chemical-thermal method and characterized by Transmission Electron Microscopy (TEM), X-ray powder diffraction (XRD), Infrared (FTIR) and UV–Vis spectroscopy. The modification of TiO₂-Pt with graphene oxide shifted its optical absorption edge towards the visible region and increased its photocatalytic activity under UV and natural sunlight irradiation. The efficiency of catalysts on azo dyes degradation (in similar conditions) reached high values (above 99%) under sunlight conditions, proving the remarkable photocatalytic activities of obtained composites. TPt-GO nanocomposite exhibited higher photoactivity than TPt or TPt-rGO, demonstrating degradation efficiencies of 99.56% for amaranth, 99.15% for sunset yellow and 96.23% for tartrazine. The dye photodegradation process follows a pseudo-first-order kinetic with respect to the Langmuir-Hinshelwood reaction mechanism. A direct dependence between azo dyes degradation rate and chemical structure of dyes has been observed.     

Synthesis and electrical characterization of Li0.30Ca0.35TaO3 perovskite synthesized via a polymerized complex route

The synthesis of Li_0.30Ca_0.35TaO₃ perovskite by a Pechini-type polymerizable precursor method is carefully described. The thermal decomposition of the precursor and the formation of a pure perovskite phase were investigated by means of differential thermal analysis-thermogravimetric analysis (DTA-TGA) and XRD techniques. A pure and well-crystallized phase has been obtained at a lower temperature and with a much shorter synthesis time than the phase obtained by conventional solid-state reaction method. The morphology of the powder after heating at 1300 °C was observed by laser granulometry, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Impedance spectroscopy data allowed us to determine the electrical properties, i.e., permittivity and dc-conductivity, of the bulk and grain boundaries. The results are discussed on the assumption of the brick layer model.     

Cellulose ternary photonic crystal created by solution processing

For the first time, a multiplanar photonic crystal structure has been obtained using cellulose as a structural material. This all-polymer system, made of cellulose, polyvinyl alcohol and poly(N-vinylcarbazole) is a ternary planar photonic crystal composed by 7 repeated trilayers produced by spin coating. Trimethylsilyl cellulose is used as a precursor to be converted to cellulose. Transverse Transmission Electron Microscopy analysis of our systems confirms the multilayered structure whose optical response can be theoretically accounted for. Preliminary results on the response of the photonic crystal to water vapors envisage the use of this system for humidity optical sensing.     

Facile synthesis of ZnO/CuO/Eu heterostructure photocatalyst for the degradation of industrial effluent

Zinc oxide-based ternary heterostructure ZnO/CuO/Eu(1%, 3%, and 5% of Eu) nanoparticles were effectively produced by employing Vigna unguiculata (cowpea)waste skin extract as fuel in a simple one-pot combustion process. The as-synthesized heterostructure was analyzed by X-ray diffraction studies, ultraviolet-visible spectroscopy, Fourier Transform Infrared Spectroscopy, Field Emission Scanning Electron Microscopy, and High-Resolution Transmission Electron Microscopy techniques. Besides, the photocatalytic degradation efficiency of the as-obtained ternary nanocomposite was evaluated under UV light for the degradation of model organic pollutants including methylene blue (MB), Rhodamine-B (RB), and an effluent sample collected from the textile industrial waste. During this study, the effect of a variety of parameters on the photodegradation activity of the photocatalysts has been thoroughly evaluated, such as light source, catalyst dose, irradiation period, dye concentration, solution pH, etc. Under UV irradiation(100 mins), the ternary ZnO/CuO/Eu photocatalyst demonstrated excellent degradation activity of ～99 and ～93% for MB and RB, respectively, while for the industrial effluent, a decent degradation activity of 42% has been recorded. Further experiments have revealed a pH and concentration-dependent photocatalytic behavior of the heterostructure photocatalyst. Therefore, the results suggest that the heterostructure photocatalyst can be potentially applied for wastewater treatment and other environmental applications.     

Adsorption and inhibition properties of Tephrosia Purpurea as corrosion inhibitor for mild steel in sulphuric acid solution

Abstract

The present study investigated the adsorption and inhibition behavior of leaf extract of Tephrosia Purpurea (T. purpurea) on mild steel corrosion in 1?N H₂SO₄ solution using electrochemical and surface morphological methods. Techniques adopted for electrochemical studies were Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) technique; and surface morphological studies were carried out using Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The leaf extract of T. purpurea was characterized using UV-Visible spectroscopy (UV-Vis), Fourier-Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance Spectroscopy (NMR) and Gas Chromatography – Mass Spectrometry (GCMS). The results obtained from electrochemical studies exhibited the potential of T. purpurea as good corrosion inhibitor. And, it was found that, the inhibition efficiency (I.E in %) increases with increase in concentration of the inhibitor molecules, the optimum inhibitor concentration observed was 300?ppm and the inhibition efficiency of 93% was observed at this inhibitor concentration. Above 300?ppm, there was not much changes in inhibition efficiency. Polarization studies provided the information that the inhibition is of mixed type and EIS confirmed that the corrosion process is controlled by single charge transfer mechanism. And, it was obtained that, the adsorption of inhibitor molecules obeys Langmuir adsorption isotherm. The inhibition is mainly by the adsorption of inhibitor molecules on the mild steel electrode surface, which was confirmed by FT-IR, SEM and AFM studies. Through all the experimental results, it can be arrived that, the leaf extract of T. purpurea performed as a good corrosion inhibitor for mild steel in 1?N sulfuric acid medium.     

Synthesis of 2D Molybdenum Disulfide (MoS2) for enhancement of mechanical and electrical properties of polystyrene (PS) polymer

In this research article, ultrasound assisted exfoliation in a liquid phase production process has been adopted for synthesis of 2D Molybdenum Disulfide (MoS₂). The energetic governing dispersion of Nano sheets in a wide range of solvents has been studied. Nano sheets dispersion in an aqueous media has been prepared with the help of high surface tension solvents like N-Methyl-1, 2-Pyyrolidone (NMP) and Tetrahydrofuran (THF). The dispersion was composed of layers of MoS₂ with some quantities of mono and bi-layer materials were observed. Scanning Electron Microscopy (SEM), X-Rays Diffractometry (XRD), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) were used to characterize the samples; SEM clearly evident the microstructure of samples while XRD shows the peaks of filler in the polystyrene composite membrane. AFM confirmed the presence of 2D MoS₂ with 0.9–7 nm thickness range of MoS₂ flake. In order to get the surfactant stabilized dispersed material, the processing was enhanced using prolonged sonication to yield maximized concentration. Liquid phase exfoliation allows dispersion to be cast into thin film by using vacuum filtration assembly. The obtained film is dispersed in solvent and is used in polymers. Two sets of concentrations (0.01, 0.03, 0.05 and 0.07% by wt. and 0.1, 0.3, 0.7 and 0.9% by wt.) were analyzed and it was observed during tensile testing that modulus of elasticity (E), percentage elongation and ultimate tensile strength (UTS) of composite material increases maximum up to 741times, 374 times and 200 times as compared to base polymer (PS), respectively. Furthermore, dielectric constant, dielectric loss and electrical conductivity of PS-MoS₂ were also evaluated and finding clearly pointed out that filler loading of MoS₂ has considerable effects on these properties and maximum value of dielectric constant is 3.6 at 0.9% loading as compared with of pure PS (polystyrene) matrix. On the other hand, variation in dielectric loss from lower to higher frequency is 2.5 × 10⁻² on average which is not so significant. Electrical conductivity was also accounted, and measurement results are indicating that conductivity was almost constant at lower frequency in range of 10⁻¹⁰ due to low field strength, but it increases to 10⁻⁹ value at higher frequency due to hoping mechanism and network formation of filler.     

Doping induced magnetism in Co-ZnS nanoparticles

Zn_1−xCo_xS nanoparticles with x=0, 0.1, 0.2, and 0.3 were synthesized by the co-precipitation method using thiophenol as capping agent. The effect of Co doping on the structural, optical and magnetic properties are investigated. The X-ray diffraction patterns show single phase with cubic structure and the images of Transmission Electron Microscopy indicate an average particle size of 39 nm. Significant blue shift in the optical absorbing band edge was observed with increasing Co doping. In the Co doped samples, room-temperature (RT) magnetic hysteresis is observed and the magnetization reduces with increasing Co content. However, these samples show paramagnetic resonance instead of ferromagnetic resonance at both 300 and 80 K, suggesting that the origin of RT magnetization in these Zn_1−xCo_xS nanoparticles involves with the frustration of antiferromagnetic interactions.     

Improvement of Nd:GGG crystal growth process under dynamic atmosphere composition

In this paper, the temperature dependency of the required oxygen on the quality of Nd:GGG crystal during the growth process has been investigated. Based on the thermodynamic analysis, the oxygen partial pressure in the surrounding vapor phase should be as low as possible through heating the raw material at lower temperatures to prevent the oxidation of iridium to IrO₂ (s). In order to eliminate the volatilization of Ga₂O₃, the oxygen was charged into the gas atmosphere (N₂) near the Nd:GGG melting point. Powder X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) were employed to characterize the crystal quality under different growth atmosphere. The experimental results confirm the validity of thermodynamic calculations. It was predicted that charging the required oxygen at about 1950 K could reduce the iridium loss rate to about 36%. Consequently, it would be expected to acquire more favorable Nd:GGG crystals with quite improved properties by applying the accurate growth conditions.     

SiO2 nanospheres with tailorable interiors by directly controlling Zn and NH3·H2O species in an emulsion process

SiO₂ nanospheres with tailorable interiors were synthesized by a facile one-spot microemulsion process using TEOS as silica source, wherein cyclohexane including triton X-100 and n-octanol as oil phase and Zn²⁺ or NH₃·H₂O aqueous solution as dispersive phase, respectively. The products were characterized by Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Powder Diffraction. It was suggested that the as-synthesized silica nanospheres possessed grape-stone-like porous or single hollow interior, and also found that the ammonia dosage and aging time played key roles in controlling the size and structure of silica nanospheres. Furthermore, the comparative results confirmed that in-situ zinc species [ZnO/Zn(OH)₂] acted as the temporary templates to construct grape-stone-like interior, and a simultaneously competing etching process occurred owing to the soluble Zn(NH₃)₄²⁺ complex formation while the additional excessive ammonia was introduced. With the aging time being extended, the in-situ nanocrystals tended to grow into bigger ones by Ostwald Ripening, producing single hollow interior.     

Adhesion of small particles of palladium on Al2O3

The adhesion of small particles of palladium prepared by thermal evaporation onto a substrate of Al₂O₃ was studied. Al₂O₃ was obtained by oxidation of a pollycristalline aluminum strip. The deposit of palladium was observed by Transmission Electron Microscopy which allowed to determine the size and the density of particles according to the average deposition thickness. The adhesion of particles was determined by two methods: the study of particle number density, and the study of the particle shapes.     

Potential application of termite mound for adsorption and removal of Pb(II) from aqueous solutions

The morphological and mineralogical composition of a termite mound from Ilorin, Nigeria was investigated with a view to understand its sorption properties. The termite hill soil was subjected to some spectroscopic analyses such as X-ray fluorescence (XRF) and Scanning Electron Microscopy. The XRF results revealed that the adsorbent contains a large fraction of Silicon, Iron and Aluminium minerals. The organic matter (OM) content expressed as percentage carbon was 3.45% while the high value of cation exchange capacity of 14.0?meq/100?g is in agreement with high percentage OM, which signifies high availability of exchangeable ions. The maximum Pb(II) adsorption capacity of the mound was found to be 15.5?mg/g. Batch adsorption experiments were carried out as a function of contact time, ionic strength and pH. Maximum and constant adsorption was observed in the pH range of 2?C5.5. The experimental results of Pb(II) adsorption were analyzed using Langmuir, Freundlich, and Temkin isotherms. The Langmuir and Temkin isotherms were found to fit the measured sorption data better than Freundlich. The constants obtained from the Langmuir model are maximum sorption value, Q _m?=?18.18 and Langmuir energy of adsorption constant, b?=?0.085, while the constants of the Freundlich model are the intensity of adsorption constant, n?=?0.134, and maximum diffusion constant, K _f?=?1.36. The adsorption data for Pb(II) was found to fit well into the pseudo-second order model. Desorption experiment was conducted using different concentrations of leachant and this was repeated three times to determine the life span of the adsorbent. It was observed that 0.2?M HCl had the highest desorption efficiency for reuse.     

Immobilized Au nanoparticles on chitosan-biguanidine modified Fe3O4 nanoparticles and investigation of its anti-human lung cancer activity

In current nanoscience bioengineered magnetic nanoparticles (NPs) have come into prominence with considerable impact. These advanced functional materials find outstanding applications in chemical science in catalysis, environmental issues, sensing etc, as well as in biology as drug delivery agent, chemical therapeutics and others. We have been prompted to architect and synthesize a novel Au NP adorned over chitosan-biguanidine polyplex modified core–shell type magnetic nanocomposite (Fe₃O₄/CS-biguanidine/Au NPs). The bioshells facilitate to protect the core ferrite NPs as well as provides stability to the synthesized Au NPs by capping. The material was characterized using different analytical techniques like Fourier Transformed Infra-Red spectroscopy (FT-IR), Inductively Coupled Plasma-Optical Emission Microscopy (ICP-OES), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray spectroscopy (EDX), Transmission Electron Microscopy (TEM), Vibrating Sample Magnetometer (VSM) and X-ray Diffraction (XRD) studies. We explored the biological application of the nanocomposite in determining cytotoxicity of three adenocarcinoma cell lines (PC-14, LC-2/ad, HLC-1) through the MTT assay. The material showed very good activity by exhibiting very low % cell viability over the cell lines dose-dependently. The IC50 of Fe₃O₄/CS-biguanidine/Au NPs were observed 503, 398 and 475 µg/mL respectively against the three cell lines. The best output was observed at a concentration of 1000 µg/mL of catalyst in terms of cytotoxicity and inhibition of lung cancer growth. The anti-cancer potential was found in close relation to their antioxidant potential.     

Biosynthesis of Zinc Oxide Nanoparticles Using Leaf Extract of Passiflora subpeltata: Characterization and Antibacterial Activity Against Escherichia coli Isolated from Poultry Faeces

The current study was undertaken to investigate the antibacterial (against molecular characterized E. coli isolated from poultry faeces) potential of biosynthesized zinc oxide nanoparticles (ZnO-NPs) from Passiflora subpeltata Ortega aqueous leaf extract. The biosynthesized nanoparticles were subjected to physico-chemical characterization to study shape, size and purity by UV–Vis spectroscopy, X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Transmission Electron Microscopy (TEM). The molecular identification of isolated E. coli from faeces samples was carried out by using 16–23s rRNA primers. The results of the physico-chemical characterization revealed that the biosynthesized nanoparticles were of 93.7% purity with an average size between 45 and 50 nm. The ZnO-NPs offered significant inhibition against the isolated Gram-negative E. coli with MIC at 62.5 µg mL^?1 concentration. The antibacterial potential of ZnO NPs against E. coli has also been investigated by the cell viability test, and further the effects of ZnO NPs on bacterial morphological structures was analysed by SEM and TEM.

     

Thermal degradation studies of polystyrene sulfonic and polyacrylic carboxylic cationites

The thermal degradation of polyacrylic carboxylic and polystyrene sulfonic cationites was investigated using thermal analysis (TG) combined with Scanning Electron Microscopy (SEM). Fourier Transform Infrared Spectroscopy (FTIR) was used to characterize the resins degradation steps. The carboxylic cationite undergoes degradation through dehydration forming polyanhydrides, decomposition of polyanhydrides through decarboxylation with elimination of CO₂ and CO. The sulfonic cationite undergoes degradation through dehydration, followed by decomposition of sulfonic acid functional groups liberating SO₂. It was observed that strong acid (−SO₃H⁺) cationite shows small mass loss of 55%, as against 88% mass loss shown by low-acidity carboxylic cationite. The possible reason for small mass loss of sulfonic cationite is discussed. The text was submitted by the authors in English.     

Sunlight Photocatalytic Performance of ZnO Nanoparticles Synthesized by Green Chemistry Using Different Botanical Extracts and Zinc Acetate as a Precursor

In this work, the assessment of Azadirachta indica, Tagetes erecta, Chrysanthemum morifolium, and Lentinula edodes extracts as catalysts for the green synthesis of zinc oxide nanoparticles (ZnO NPs) was performed. The photocatalytic properties of ZnO NPs were investigated by the photodegradation of methylene blue (MB) dye under sunlight irradiation. UV-visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Thermogravimetric (TGA), and Brunauer-Emmett-Teller analysis (BET) were used for the characterization of samples. The XRD results indicate that all synthesized nanoparticles have a hexagonal wurtzite crystalline structure, which was confirmed by TEM. Further, TEM analysis proved the formation of spherical and hemispherical nanoparticles of ZnO with a size in the range of 14–32 nm, which were found in aggregate shape; such a size was well below the size of the particles synthesized with no extract (~43 nm). ZnO NPs produced with Tagetes erecta and Lentinula edodes showed the best photocatalytic activity, matching with the maximum adsorbed MB molecules (45.41 and 58.73%, respectively). MB was completely degraded in 45 min using Tagetes erecta and 120 min using Lentinula edodes when subjected to solar irradiation.     

Planar ZrO2 Waveguides Prepared by the Sol-Gel Process: Structural and Optical Properties

ZrO₂ waveguides are prepared by the sol-gel process from a solution containing zirconiumn-propoxide and acetylacetone in propanol-2. Structural characterizations are investigated for different annealing temperatures using suitable techniques including Waveguide Raman Spectroscopy, Electron Microscopy and Atomic Force Microscopy. Films are amorphous at 300°C and the pure ZrO₂ tetragonal crystalline phase appears beyond 400°C. Crystallized films present a dense, uniform and polycrystalline structure made up by randomly oriented nanocrystallites, the diameter of which increases from 38 Å at 400°C to 53 Å at 600°C. Waveguides are at least monomode TE₀ at 632.8 nm. At this wavelength, optical losses are about, 0.8±0.2dB/cm for amorphous layers and increase up to 2.5±0.4 dB/cm for 600°C heat-treated waveguides.     

Effect of the AACVD based synthesis atmosphere on the structural properties of multi-walled carbon nanotubes

The synthesis of multi-walled carbon nanotubes (MWCNT_S) has been the focus of considerable research effort for more than twenty-five years and it continues to receive increasing attention because of its importance to produce carbon nanotubes with suitable parameters for future applications. To the best of our knowledge this study presents for the first time the complex studies concerning the effect of aerosol-assisted chemical vapour deposition (AACVD) process conditions (including temperature (750–1200 °C) and the composition of the carrier gas (N₂, Ar, He, 5% H₂-95% Ar, 3% H₂O-97% Ar)) on the conversion of the carbon source and on the properties of the carbon nanotubes. In addition, it was also found that oxidative or reductive atmosphere applied during the AACVD process have a great impact on the quality and the degree of toluene conversion into the carbon solids obtained during the synthesis. X-ray Diffraction (XRD), Specific Surface Area and Porosity analysis (BET), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), Transmission Electron Microscopy (TEM), Raman spectroscopy and Thermo-gravimetric Analysis (TG) were used to characterize the carbon nanotubes.     

Microwave-assisted preparation and enhanced photocatalytic activity of Bi2WO6/BiOI heterojunction for organic pollutants degradation under visible-light irradiation

In this research, we adopted morphology control and constructing p-n heterojunction to boost the photocatalytic performance of BiOI. BiOI with three morphologies (nanoplate, micro-flower, microsphere) was fabricated via a wet-chemical method at room temperature using different solvents. And Bi₂WO₆/BiOI microspheres were successfully prepared by a microwave-assisted synthetic method. The as-synthesized samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive Spectroscopy (EDS) and High-resolution Transmission Electron Microscopy (HRTEM). The results of photo-degradation experiment demonstrated that BiOI-3 and BWOI-3 show high photocatalytic performance towards methyl orange (MO) and bisphenol A (BPA) degradation due to the high specific surface area, synergistic effect between p-type BiOI and n-type Bi₂WO₆ and high separation efficiency of electron-hole pairs, which is verified by Brunauer-Emmett-Teller (BET), Photocurrent (PC) and Electrochemical Impedance Spectroscopy (EIS) analysis. Moreover, the repeated photocatalytic experiment was carried out by using MO as the representative organic pollutant, manifesting the good durability of the sample.     

Picosecond study of an electron transfer in the first excited state of dodci

Electron transfer from the first excited singlet state of a polymethine cyanine dye. DODCI, to various electron acceptors (p-benzoquinone,p-dinitrobenzene and methylviologen) was investigated using picosecond fluorescence and absorption spectroscopy. The electron transfer to methylviologen was confirmed by conventional nanosecond laser spectroscopy. Its efficiency, as expressed by the ratio k₅/(k₄ + k₅) = 0.07. can be explained by coulombic repulsion in the initial radical pair. On the other hand, although fluorescence quenching by p-BQ and p-DNB is very efficient, no electron transfer was observed.     

Green synthesis of silver nanoparticles by bloom forming marine microalgae Trichodesmium erythraeum and its applications in antioxidant,drug-resistant bacteria,and cytotoxicity activity

In the present study, we developed an eco-friendly method of stable silver nanoparticles (AgNPs) production using the aqueous extract of Trichodesmium erythraeum. The biosynthesized AgNPs were characterized using UV–Vis spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy-Dispersive X-ray (EDX), and X-ray diffraction (XRD). The results affirmed that synthesized AgNPs were crystalline in nature, cubical in shape, and the average size of T. erythraeum silver nanoparticles (TENPs) was 26.5 nm. The antioxidant potential of synthesized AgNPs (500 µg/ml) was 77.01 ± 0.17% in DPPH, 67.5 ± 0.22% in Deoxy-ribose, 52.77 ± 0.42% in ABTS and 88.12 ± 0.26% in nitric oxide radical scavenging assays. The antibacterial results showed excellent inhibition against the clinical strains (Staphylococcus aureus and Proteus mirabilis) and drug-resistant bacterial strains such as E. coli (Amikacin^R), S. aureus (Tetracycline^R) and S. pneumoniae (Penicillin^R). The maximum anti-proliferative effect of TENPs was seen using 50 µg concentration against He La and MCF-7 cell lines, and IC₅₀ values were 25.0 ± 0.50 µg/ml and 30.0 ± 0.50 µg/ml, respectively, at 24 h.