Sol-gel synthesis,characterisation, and photocatalytic activity of porous spinel Co3O4 nanosheets

Mesoporous spinel Co₃O₄ nanosheets were synthesised via a simple sol-gel route using the Pluronic P123 triblock copolymer as the stabilising agent. Their structural, morphological, and textural properties were characterised. FTIR spectrum revealed the formation of cobalt oxide without any surface adsorbed impurities. Face centered cubic phase of spinel Co₃O₄ with the mean crystalline size of 26 nm was assigned by the X-ray diffraction analysis without the formation of other phases. Porous nanosheets and cave-like morphologies were identified from the scanning electron microscopy (SEM) images. Highly agglomerated more or less spherical particles with well separated lattice fringes, representing the oriented growth of nanocrystals, were noticed on the transmission electron microscopy photographs. Surface area analysis revealed that the spinel has high surface area of about 25 m² g^?1 with monomodal mesoporosity. The average pore size distribution was found to be about 15.8 nm. The as-prepared spinel photocatalyst showed a mild photocatalytic activity in the degradation of methylene blue (2.5 mg L^?1) under UV light irradiation with air as the oxidising agent. Photocatalytic activity of the as-prepared reusable Co₃O₄ was found to be higher than that of the commercial spinel powder.     

Novel preparation method of nanosilver doped sol gel TiO2 photocatalysts for dye pollutant degradation

In the present study, a novel method for the silver nanoparticle incorporation into TiO₂ sol is reported which provides efficient dispersion of inserted metal in the calcined gel. Glucose mediated metal nanoparticle synthesis eliminates the additional steps for the introduction of dopant over the support. Ag nanoparticle acts as competent trapping centers preventing the recombination of electron?Chole pairs. Thus, in spite of the low UV intensity present in the sunlight, considerable enhancement in the catalytic efficiency was observed for the degradation of dye pollutants over nanosilver loaded TiO₂. Transmission electron microscopic images display the well isolated nanoparticles of silver having uniform dimensions of less than 5?nm over the best system, 2?wt% nanosilver loaded TiO₂, which is accountable for its effectiveness as a photocatalyst. Anatase is found to be the photocatalytic active phase, as evident from the X-ray diffraction studies.     

Hydrogen production by steam reforming of glycerol over Ni/Ce/Cu hydroxyapatite-supported catalysts

Hydroxyapatite-supported Ni-Ce-Cu catalysts were synthesised and tested to study their potential for use in the steam reforming of glycerol to produce hydrogen. The catalysts were prepared by the deposition-precipitation method with variable nickel, cerium, and copper loadings. The performance of the catalysts was evaluated in terms of hydrogen yield at 600°C in a tubular fixed-bed microreactor. All catalysts were characterised by the BET surface area, XRD, TPR, TEM, and FE-SEM techniques. The reaction time was 240 min in a fixed-bed reactor at 600°C and atmospheric pressure with a water-to-glycerol feed molar ratio of 8: 1. It was found that the Ni-Ce-Cu (3 mass %-7.5 mass %-7.5 mass %) hydroxyapatite-supported catalyst afforded the highest hydrogen yield (57.5 %), with a glycerol conversion rate of 97.3 %. The results indicate that Ni/Ce/Cu/hydroxyapatite has great potential as a catalyst for hydrogen production by steam reforming of glycerol.     

Threshold reduction of stimulated Brillouin scattering in photonic crystal fiber

A simple configuration for the reduction of stimulated Brillouin scattering threshold in photonic crystal fiber is presented. The threshold reduction is contributed by the bidirectional pumping scheme through the reflection of transmitted Brillouin pump back to the gain medium. The pump recycling scheme has greatly reduced the Brillouin threshold of a 200-m long of photonic crystal fiber from 50 to 30 mW of Brillouin pump power.     

Influence of natural organic matter on the screening of pharmaceuticals in water by using liquid chromatography with full scan mass spectrometry

The influence of natural organic matter on the screening of pharmaceuticals in water was determined by using high resolution liquid chromatography (HRLC) combined with full scan mass spectrometry (MS) techniques like time of flight (ToF) or Orbitrap MS. Water samples containing different amount of natural organic matter (NOM) and residues of a set of 11 pharmaceuticals were analyzed by using Exactive Orbitrap? LC-MS. The samples were screened for residues of pharmaceuticals belonging to different classes like benzimidazoles, macrolides, penicillins, quinolones, sulfonamides, tetracyclines, tranquillizers, non-steroidal anti-inflammatory drugs (NSAIDs), anti-epileptics and lipid regulators. The method characteristics were established over a concentration range of 0.1-500 μg L(-1). The 11 pharmaceuticals were added to two effluent and two influent water samples. The NOM concentration within the samples ranged from 2 to 8 mg L(-1) of dissolved organic carbon. The HRLC-Exactive Orbitrap? LC-MS system was set at a resolution of 50,000 (FWHM) and this selection was found sufficient for the detection of the list of pharmaceuticals. With this resolution setting, accurate mass measurements with errors below 2 ppm were found, despite of the NOM concentration of the different types of water samples. The linearities were acceptable with correlation coefficients greater than 0.95 for 30 of the 51 measured linearities. The limit of detection varies between 0.1 μg L(-1)and 100 μg L(-1). It was demonstrated that sensitivity could be affected by matrix constituents in both directions of signal reduction or enhancement. Finally it was concluded that with direct shoot method used (no sample pretreatment) all compounds, were detected but LODs depend on matrix-analyte-concentration combination. No direct relation was observed between NOM concentration and method characteristics. For accurate quantification the use of internal standards and/or sample clean-up is necessary. The direct shoot method is only applicable for qualitative screening purposes. The use of full scan MS makes it possible to search for unknown contaminants. With the use of adequate software and a database containing more than 50,000 entries a tool is available to search for unknowns.     

Novel synthesis of 3-cyano-2-pyridones derivatives catalyzed by Au–Co/TiO2

Research on Chemical Intermediates - The current work described a new and highly selective method for the synthesis of substituted 3-cyano-2-pyridones scaffolds using gold-cobalt supported on TiO2...     

Effects of polyvinylpyrrolidone on structural and optical properties of willemite semiconductor nanoparticles by polymer thermal treatment method

Journal of Thermal Analysis and Calorimetry - Willemite is an inorganic semiconductor material used for optoelectronic applications. The present study purposes a new polymer thermal treatment...     

Efficient multicomponent synthesis of 2-aminopyridines catalysed by basic mesoporous materials

Research on Chemical Intermediates - An efficient and green procedure for the synthesis of 2-aminopyridines derivatives via four-component reaction of acetophenone, malononitrile, triethoxymethane...