Growth and properties of lead iodide thin films by spin coating

In this study, lead iodide (PbI2) thin films were deposited on glass substrates by spin coating a solution of 0.2 M PbI2 dissolved in dimethylformamide, varying the deposition time and the spin speed. The thickness of the thin films decreased with increase in spin speed and deposition time, as examined by profilometry measurements. The structure, morphology, optical and electrical properties of the thin films were analysed using various techniques. X-ray diffraction patterns revealed that the thin films possessed hexagonal structures. The thin films were grown highly oriented to [001] direction of the hexagonal lattice. Raman peaks detected at 96 and 136 cm−1 were corresponding to the characteristic vibration modes of PbI2. The X-ray photoelectron spectroscopy detected the presence of Pb and I with core level binding energies corresponding to that in PbI2. Atomic force microcopy showed smooth and compact morphology of the thin films. From UV–Vis transmittance and reflectance spectral analysis, the bandgap of the thin films ∼2.3 eV was evaluated. The dark conductivity of the thin films was computed and the value decreased as the deposition time and spin speed increase

Bionanocompósitos de carragenina κ con nanopartículas metálicas

En este trabajo se reporta la preparación de nanocompósitos a base de biopoliméricos de Carragenina tipo κ con nanopartículas metálicas de plata y oro. La síntesis de las nanopartículas se llevó a cabo in situ en presencia de Carragenina κ, seguida del secado de la dispersión coloidal por liofilización para la obtención de los nanocompósitos. La morfología de los nanocompósitos y de las nanopartículas fue analizada por microscopía electrónica de barrido (MEB) y microscopía electrónica de transmisión (MET). Las propiedades ópticas se evaluaron mediante espectroscopía de UV-vis mientras que la caracterización estructural se llevó a cabo mediante espectroscopía de infrarrojo. Las propiedades térmicas se estudiaron mediante calorimetría diferencial de barrido (CDB). Los resultados muestran nanocompósitos con propiedades ópticas similares a las NP metálicas y con propiedades térmicas mejoradas. Estos nanocompósitos presentan potenciales aplicación como soporte biodegradable

IrO2-Ta2O5|Ti electrodes prepared by electrodeposition from different Ir:Ta ratios for the degradation of polycyclic aromatic hydrocarbons

This work investigates the feasibility of producing IrO2-Ta2O5|Ti electrodes by electrodeposition. Using precursor solutions with Ir:Ta molar ratios from 0:100 to 100:0, followed by thermal treatment, the goal was to find the optimal composition for enhancing the formation of hydroxyl radicals and providing long service lives. Scanning electron microscopy (SEM), coupled with energy dispersive X-ray spectroscopy (EDX), revealed that the production of homogeneous coatings with a good surface coverage and absence of agglomerates was only possible for electrodes with 70% or 100% Ir. The potential for O2 evolution was similar for all the electrodes containing Ir, at about 0.90 V vs Ag|AgCl. However, the ability to produce M(¿OH) clearly increased with increasing Ir in the Ir:Ta ratios (100:0 > 70:30 > 30:70 > 0:100). This observation was confirmed by the transformation of coumarin to 7-hydroxycoumarin as determined by spectroscopic and chromatographic techniques after treatment. Once manufactured and characterized, the electrodes were tested, as anodes, for the electro-oxidation of polycyclic aromatic hydrocarbons in aqueous solutions at natural pH (i.e., without pH adjustment). The anodes prepared from 70:30 and 100:0 ratios produced the fastest and highest removal rates, reaching 86% and 93% for phenanthrene and naphthalene, respectively, after 120 min at 50 mA. This was accompanied by a high degree of mineralization, as the result of direct and M(¿OH)-mediated oxidation, with some refractory intermediates remaining in the final solutions. The interaction between IrO2 and Ta2O5 oxides appeared to be important. The 100:0 anode provided high electrocatalytic effectiveness, whereas the anode with the 70:30 ratio provided improved long-term stability, as confirmed by its service life of about 93 h

Use of Silica Tubes as Nanocontainers for Corrosion Inhibitor Storage

A new alkyd paint anticorrosion smart coating was developed by using silica nanoparticles as corrosion inhibitor nanocontainers. Silica particles were mixed with the paint at different concentrations to study their performance and ensure their free transportation to the damaged metal. The filling up of silica particles was done preparing three solutions: distilled water, acetone, and a mixture of both, with Fe(NO3)3 and silica particles immersed in each of the solutions to adsorb the inhibitor. Acetone solution was the best alternative determined by weight gain analysis made with the inhibitor adsorbed in silica nanocontainers. Steel samples were painted with inhibitor silica nanocontainer coatings and immersed in an aqueous solution of 3% sodium chloride. Polarization curves and electrochemical noise techniques were used to evaluate the corrosion inhibitor system behavior. Good performance was obtained in comparison with samples without inhibitor nanocontainer coatin

Assessment of IrO2-Ta2O5|Ti electrodes for the electrokinetic treatment of hydrocarbon-contaminated soil using different electrode arrays

In recent years, physicochemical processes such as the electrokinetic treatment (EKT) have gained acceptance as suitable alternatives to restore hydrocarbon (HC)-contaminated sites. EKT entails relatively short times, moderate operation costs and high removal efficiencies, being usually applied in heterogeneous soils with low permeability. In this work, 1D and 2D configurations, which require one sole pair of electrodes (facing each other) or six anodes around a central cathode (radial array), respectively, have been tested by employing Ti cathodes and anodes, as well as purpose-made IrO2-Ta2O5|Ti as dimensionally-stable anodes (DSA). The electrodes were partially introduced into a real Vertisol soil contaminated with heavy and intermediate fractions of HC. The distance between the cathode and each anode was of 6 cm at laboratory scale employing a 276 cm3 container with 2.2 kg of polluted soil and a 115 cm3 container with 87.8 g of polluted soil for the 2D and 1D arrays, respectively. From GC-MS analysis of fat and oil content, it has been found that the radial 2D array with one central Ti cathode and six IrO2-Ta2O5|Ti anodes performed better, reaching 58% HC removal near the anode applying 30 V and an electric field of 2.4 A cm-1. The effect of the treatment on the morphology of the anodes has been analyzed by SEM-EDX

Microstructure, vibrational and visible emission properties of low frequency ultrasound (42 kHz) assisted ZnO nanostructures

Size and shape tuneable ZnO nanostructures were prepared by a low frequency ultrasound (42 kHz) route using various organic solvents as the reaction media. The crystalline nature, lattice parameters and microstructural parameters such as microstrain, stress and energy density of the prepared ZnO nanostructures were revealed through X-ray diffraction (XRD) analysis. The organic solvents influenced the size and morphology of the ZnO nanostructures, and interesting morphological changes involving a spherical to triangular shaped transition were observed. The visible emission properties and lattice vibrational characteristics of the nanostructures were drastically modified by the changes in size and shape. Raman spectral measurements revealed the presence of multiphonon processes in the ZnO nanostructures. The intensity of the visible emission band was found to vary with the size and morphology of the structures. The strongest visible emission band corresponded to the structure with the largest surface/volume ratio and could be attributed to surface oxygen vacancies. The control over the size and morphology of ZnO nanostructures has been presented as a means of determining the intensity of the visible emission ban

Synthesis and characterization of calcium hydroxide obtained from agave bagasse and investigation of its antibacterial activity

ABSTRACT Calcium hydroxide (Ca(OH)2) is recognized as an efficient bactericide and is widely applied as a root canal filler in endodontic treatment. Ca(OH)2 is mainly produced by hydration of calcium oxide (CaO), a product of the thermal decomposition of calcium carbonate (CaCO3) from sources such as limestone. In this work, calcium hydroxide particles were synthetized by the thermochemical transformation of waste biomass from the tequila industry. Agave biomass processed at 600 °C was composed mostly of calcium carbonate (CaCO3), while calcination at 900 °C followed by hydration produced Ca(OH)2. The morphology and crystalline nature of the Ca(OH)2 particles were characterized by micro-Raman spectroscopy, scanning electron microscopy and X-ray diffraction analysis. Bactericidal activity of synthesized calcium hydroxide was evaluated with the agar diffusion assay. Our results provide evidence that Ca(OH)2 obtained from agave biomass is an effective bactericidal against Escherichia coli and Enterococcus faecalis. Biomass from agave is available in Mexico and the rest of the American continent, the use of processed bagasse for medical applications could provide a venue for the useful disposition of industrial waste. Palabras clave: recursos renovables, ceniza, bactericida, Ca(OH)2 RESUMEN El hidróxido de calcio (Ca(OH)2) es reconocido como un eficiente bactericida y es ampliamente utilizado como relleno de la raíz dental en tratamientos de endodoncia. El Ca(OH)2 es producido por la hidratación del óxido de calcio (CaO), un producto de la descomposición térmica del carbonato de calcio (CaCO3), obtenido principalmente de piedra caliza. En el presente trabajo, se sintetizaron partículas de hidróxido de calcio mediante la descomposición térmica de biomasa residual de la industria tequilera. La biomasa de agave se procesó a 600 °C, la cual se compone principalmente de carbonato de calcio (CaCO3), por lo que su calcinación a 900 °C y posterior hidratación producen el Ca(OH)2. La morfología y cristalinidad de las partículas de Ca(OH)2 se caracterizaron mediante el uso de espectroscopía Raman, microscopio electrónico de barrido y difracción de rayos X. La actividad bactericida del hidróxido de calcio obtenido, se evaluó mediante el ensayo de difusión en agar. Los resultados proveen evidencia de la efectividad del Ca(OH)2, obtenido de la biomasa de agave, contra Escherichia coli y Enterococcus faecalis. La biomasa de agave se encuentra ampliamente disponible en México y el resto del continente americano, por lo que el uso de bagazo de agave procesado en aplicaciones médicas, puede proveer una alternativa en la disposición y el uso de residuos agroindustriales

Removal of Tetracycline Pollutants by Adsorption and Magnetic Separation Using Reduced Graphene Oxide Decorated with Alpha-Fe₂O₃ Nanoparticles

Nanocomposites of reduced graphene oxide (RGO) with ferromagnetic alpha-Fe₂O₃ nanoparticles have been prepared in-situ by thermal treatment. The structure and morphology of the hybrid material were studied by X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and transmission electron microscopy. The results show a hybrid material highly modified with alpha-Fe₂O₃ nanoparticles distributed on the graphene surface. The adsorption kinetics show the presence of alpha-Fe₂O₃ nanoparticles on the RGO surface, and the amount of remaining functional groups dominated by ionization and dispersion. The adsorption kinetics of this adsorbent was characterized and found to fit the pseudo-second-order model. The alpha-Fe₂O₃ nanoparticles on RGO modify the electrostatic interaction of RGO layers and tetracycline, and adsorption properties decreased in the hybrid material. Adsorption isotherms fit with the Langmuir model very well, and the maximum capacity adsorption was 44.23 mg/g for RGO and 18.47 mg/g for the hybrid material. Magnetic characterization of the hybrid material shows ferromagnetic behavior due to the nanosize of alpha-Fe₂O₃ with a saturation magnetization, Ms = 7.15 Am/kg, a remanence Mr = 2.29 Am/kg, and a coercive field, Hc = 0.02 T.Rodolfo Cruz-Silva acknowledges the support from the Center of Innovation (COI) Program “Global Aqua Innovation Center for Improving Living Standards andWater-sustainability” from Japan Science and Technology Agency, JST. Authors thank M. Nava for the specific surface area measurements of the materials

Electro-oxidation of amoxicillin using titanium electrodes electrophoretically coated by iridium or ruthenium with tantalum oxides

© 2020 Society of Chemical Industry (SCI) BACKGROUND: Amoxicillin (AMX) is one of the pharmaceutical compounds in waters being targeted in wastewater decontamination studies, and some of the technological alternatives to degrade it involve using modified surfaces with transition metal oxides, such as IrO2/Ta2O5|Ti and RuO2/Ta2O5|Ti, for in situ production of hydroxyl radical (•OH) to oxidize AMX in aqueous media. RESULTS: The IrO2/Ta2O5|Ti 70:30 electrode was best suited for AMX electro-oxidation, with 99.23% removal measured by HPLC-UV–Vis, 81.13% by COD removal, and current efficiency of 41.1% in 0.1 mol L–1 Na2SO4 after applying 15 mA for 6 h. These results are due to a larger surface area (251.67 cm2) and a higher amount of •OH radicals being generated by cm2 in neutral pH (3.8 mol L–1 cm−2) compared to the other electrodes. CONCLUSION: This paper shows the simulation of the experimental data regarding the complete degradation of AMX (100%) by HPLC, comparing the experimental results and simulation results for AMX degradation using the IrO2/Ta2O5|Ti 70:30. The modeling predicts and validates the disengagement of COD obtained experimentally, considering the mechanism proposed by Trovó and collaborators for the electro-oxidation of AMX to product C6 (C16H22N3O7S) by generating •OH. © 2020 Society of Chemical Industry (SCI)