Highly dispersed Mn2O3−Co3O4 nanostructures on carbon matrix as heterogeneous Fenton-like catalyst

This work reports the synthesis of various carbon (Vulcan XC-72 R) supported metal oxide nanostructures, such as Mn₂O₃, Co₃O₄ and Mn₂O₃−Co₃O₄ as heterogeneous Fenton-like catalysts for the degradation of organic dye pollutants, namely Rhodamine B (RB) and Congo Red (CR) in wastewater. The activity results showed that the bimetallic Mn₂O₃−Co₃O₄/C catalyst exhibits much higher activity than the monometallic Mn₂O₃/C and Co₃O₄/C catalysts for the degradation of both RB and CR pollutants, due to the synergistic properties induced by the Mn−Co and/or Mn (Co)−support interactions. The degradation efficiency of RB and CR was considerably increased with an increase of reaction temperature from 25 to 45°C. Importantly, the bimetallic Mn₂O₃−Co₃O₄/C catalyst could maintain its catalytic activity up to five successive cycles, revealing its catalytic durability for wastewater purification. The structure–activity correlations demonstrated a probable mechanism for the degradation of organic dye pollutants in wastewater, involving •OH radical as well as Mn²⁺/Mn³⁺ or Co²⁺/Co³⁺ redox couple of the Mn₂O₃−Co₃O₄/C catalyst.     

Synthesis of 4-Arylidene-2-Phenyloxazol-5-Ones Using 1:1 Mixture of Al2O3 -H3BO3

Cyclodehydration-condensation of hippuric acid and arylaldehydes have been carried out using a 1:1 mixture of Al₂O₃-H₃BO₃ in the presence of stoichiometric quantity of acetic anhydride to give the target compound in good yield. This procedure can be used to synthesize the 4-alkylidene analogs also.     

"Click chemistry" inspired synthesis of pseudo-oligosaccharides and amino acid glycoconjugates

[reaction: see text] Various pseudo-oligosacchardies and amino acid glycoconjugates were synthesized via an intermolecular 1,3-dipolar cycloaddition ("click") reaction using easily accessible carbohydrate and amino acid derived azides and alkynes as building blocks. It is pertinent to mention that the conjugation reaction is highly regioselective and high yielding and can be carried out under mild reaction conditions.     

Propargyl glycosides as stable glycosyl donors: anomeric activation and glycoside syntheses

The advantages of stable glycosyl donors for saccharide coupling are many, and we describe herein the utility of propargyl glycosides for anomeric activation and glycoside synthesis exploiting the alkynophilicity of AuCl3. Various aglycones were reacted with propargyl glycosides, resulting in the formation of an alpha,beta-mixture of glycosides and disaccharides in good yields.     

Fiber-Bragg-grating-assisted surface plasmon-polariton sensor

A theoretical scheme for a new surface plasmon-polariton (SPP) fiber sensor with a fiber Bragg grating imprinted into the fiber core for SPP excitation is presented for the first time to our knowledge. In our scheme the energy in the fiber core mode can be transferred to a SPP with high efficiency by means of a properly designed short-period fiber Bragg grating (SPG). Developed for the cylindrical (fiber) geometry, our scheme without loss of generality can be applied to a planar geometry. Our simulations are based on the coupled-mode method and are performed at telecommunications wavelengths.     

Quantitative studies of pyrocarbon‐coated materials using synchrotron radiation

Phase‐contrast imaging provides enhanced image contrast and is important for non‐destructive evaluation of structural materials. In this paper, experimental results on in‐line phase‐contrast imaging using a synchrotron source (ELETTRA, Italy) for objects required in material science applications are discussed. Experiments have been carried out on two types of samples, pyrocarbon‐coated zirconia and pyrocarbon‐coated alumina microspheres. These have applications in both reactor and industrial fields. The phase‐contrast imaging technique is found to be very useful in visualizing and determining the coating thickness of pyrocarbon on zirconia and alumina microspheres. The experiments were carried out at X‐ray energies of 16, 18 and 20 keV and different object‐to‐detector distances. The results describe the contrast values and signal‐to‐noise ratio for both samples. A comprehensive study was carried out to determine the thickness of the pyrocarbon coating on zirconia and alumina microspheres of diameter 500 µm. The advantages of phase‐contrast images are discussed in terms of contrast and resolution, and a comparison is made with absorption images. The results show considerable improvement in contrast with phase‐contrast imaging as compared with absorption radiography.     

Solvent and Substituent Effects on the Spectra of Some Substituted Thioureas

A study on the effect of a number of solvents, covering a broad polarity range i.e. from dioxane (D=2.20) to acetonitrile (D=38.0), has been made on the electronic transitions of N-aryl, N′-2-(5-halo-pyridyl) thioureas (where aryl= -C₂H₅ or O-CH₃-C₆H₅-, and halo= -Cl, -Brand -I). Two intense absorption maxima in the regions 270-285 nm (assigned for thiocarbonyl π-π* transition) are exhibited by all the substituted thioureas studied. The excitation energies and oscillator strengths of these transitions have been calculated. A correlation between ‘E_T’ and ‘Z’ (an empirical measure of solvent polarity) has been attempted. Solvent sensitivities of these compounds have also been calculated. The effect of halo-substituents, in the pyridine ring, on the spectra of these substituted thioureas has also been studied. It has been proposed that there is a delocalization of electrons between the pyridine ring and the thiourea unit of these compounds. This delocalization of electronic charge is affected by the substitution of the halo-groups in the pyridine ring at para position to the thiourea unit which is reflected in the intensities and shifting of the absorption maxima.