Methane sensor based on palladium/MWNT nanocomposites

Methane gas sensor was fabricated based on electrocatalytic properties of the Pd/MWNT nanocomposites on indium tin oxide (ITO)glass substrates.A linear response for methane was obtained in the range of 0-16%(v/v)with a detection limit of 0.167%(v/ v)and R.S.D.of 4.1%.After 100 times sensing or stable stored more than 12 months in atmosphere,unconspicuous measurable decrease was observed.The response time was less than 60s at room temperature and ambient pressure.Some common potential interferents in samp...     

A Versatile and Practical Synthesis of 1,1‐Diacetates from Aldehydes Catalyzed by Cyanuric Chloride

Structurally diverse aldehydes are successfully converted into 1,1‐diacetates with acetic anhydride using cyanuric chloride as a mild, convenient and inexpensive catalyst under solvent‐free conditions. The noteworthy features of the present system are shorter reaction times, and mild and solvent‐free conditions. Furthermore, it offers chemoselective protection of aldehydes.     

Citrinal A,a novel tricyclic derivative of citrinin,from an algicolous fungus Penicillium sp.i-1-1

Citrinal A(1),a novel tricyclic compound with a rare tetrahydro-2H-benzofuro[7-b][1,4]dioxin-9(3H)-one skeleton,along with two known related compounds,citrinin(2) and 2,3,4-trimethyl-5,7-dihydroxy-2,3-dihydrobenzofuran(3) were isolated from an algicolous fungus Penicillium sp.i-1-1.The structure and stereochemistry of 1 were determined by comprehensive spectral and biogenic analysis.Its cytotoxic effects on the A-549 and HL-60 cell lines were evaluated.     

“Green synthesis” of benzothiazepine library of indeno analogues and their in vitro antimicrobial activity

A novel series of indeno-benzothiazepine derivatives was synthesised via a “green” route. Synthesis of these compounds involves the treatment of dinucleophiles such as 2-aminobenzenethiols with α,β-unsaturated ketones in poly(oxyethylene) (poly(ethylene glycol), PEG-400) catalysed by acetic acid. The synthone α,β-unsaturated ketones were obtained by Claisen-Schmidt condensation of indan-1-one with substituted pyrazole-2-carbaldehydes prompted by bleaching earth (pH 12.5) as catalyst and PEG-400 as “green” reaction solvent. Screening of all the synthesised compounds for antimicrobial activity revealed that most of these compounds exhibited moderate to significant antimicrobial activity.     

Synergistic liquid-liquid extractive spectrophotometric determination of gold(III) using 1-(2′,4′-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol

Synergistic liquid-liquid extractive spectrophotometric determination of gold(III) using 1-(2′,4′-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydro pyrimidine-2-thiol [2′,4′-dinitro APTPT] has been described. Equal volumes (5 cm³) of the 2′,4′-dinitro APTPT (0.02 mol L⁻¹) in the presence of pyridine (0.5 mol L⁻¹) form an orange-red coloured ternary complex with gold(III) of molar ratio 1:1:1 at pH 1.8-2.4 with 5 min of shaking. The absorbance of coloured organic layer in 1,2-dichloroethane is measured spectrophotometrically at 445 nm against reagent blank. A pronounced synergism has been observed by the binary mixture of 2′,4′-dinitro APTPT and pyridine, which shows that the enhancement in the absorbance is observed in the presence of pyridine by the adduct formation in the organic phase. Beer's law was obeyed in the concentration range 2.5-20.0 μg mL⁻¹, with molar absorptivity and Sandell's sensitivity values of 8.7 × 10³ dm³ mol⁻¹ cm⁻¹ and 0.023 μg cm⁻² respectively. A repetition of the method was checked by finding relative standard deviation (R.S.D.) (n = 10) which was 0.17%. The composition of the gold(III)-2′,4′-dinitro APTPT-pyridine adduct was established by slope analysis, molar ratio and Job's method. The ternary complex was stable for more than 48 h. The influence of various factors such as pH, 2′,4′-dinitro APTPT concentration, solvent and pyridine on the degree of complexation has been established. A number of foreign ions tested for their interferences and use of suitable masking agents wherever necessary are tabulated, which show that selectivity of the method has been enhanced. The method is successfully employed for the determination of gold(III) in binary, synthetic mixtures and ayurvedic samples. The reliability of the method is assured by inter-comparison of experimental values, using an atomic absorption spectrometer.     

Fourier transform infrared and quasielectron neutron scattering studies on the binding modes of methanol molecules in the confined spaces of HMCM-41 and HZSM-5: role of pore structure and surface acid sites

Quasielastic neutron scattering (QENS) and Fourier transform infrared spectroscopic studies were carried out on methanol molecules adsorbed in HMCM-41 and HZSM-5 molecular sieves to monitor the effect of pore structure on their occluded state under the conditions of ambient temperature and 5-250 mbar pressures. The QENS results have shown that the pore geometry of the host matrix and the dipolar character of the adsorbate are together responsible for the binding state of guest molecules in the confining medium. Thus, neither translational nor free rotational motion was noticed for methanol molecules adsorbed in HZSM-5, in contrast to benzene and cyclohexane molecules of almost similar size that are reported to undergo a rotational motion under the identical conditions of loading (Phys. Chem. Chem. Phys. 2001, 3, 4449; 2003, 5, 3066). In the case of HMCM-41, a translational motion of occluded methanol molecules was clearly observed with a diffusion constant D approximately 1.5 x 10(-5) cm2 s(-1), as compared to a value of D approximately 2.6 x 10(-5) cm2 s(-1) for its liquid state. These results indicate that the adsorbed methanol experiences a considerable extent of supercooling due to capillary condensation in zeolitic pores, giving rise to formation of a metastable state even at room temperature. In HZSM-5, entrapped methanol exists in an almost solidlike state, whereas in HMCM-41, its density lies between that of the solid and the liquid phases. Infrared spectroscopic study conducted using deuterium-labeled adsorbate and host matrixes have given evidence for different kinds of interactions between the methanol molecules and the host matrix, depending upon the loading. For small loadings the internal hydroxy groups within the pore system get perturbed first, giving rise to formation of the methoxy groups. Multilayer adsorption and capillary condensation of methanol occur for a loading of 0.05 mmol per gram and above, within the pore system and also at the external surface, giving rise to a highly compressed state due to strong intermolecular bonding. At the same time, a considerable amount of exchange occurred between the hydroxy groups of the adsorbed methanol and those of the host matrix. Such exchange of hydroxy groups may play an important role in the catalytic properties of the porous aluminosilicates.     

Schisanlactone G,a new 3,4-seco-lanostane triterpenoid from Schisandra sphenanthera

A new 3,4-seco-lanostane triterpenoid,schisanlactone G (1),was isolated from the fruits of Schisandra sphenanthera.Its structure was established on the basis of extensive spectroscopic analysis.2009 Rong Tao Li.Published by Elsevier B.V.on behalf of Chinese Chemical Society.All fights reserved.     

FeCl_3 catalyzed diarylmethanes formations

Under mild condition,using FeCl3 as catalyst,a series of functionalized diarylmethanes were prepared efficiently from the reactions of arenes with paraformaldehyde.This catalytic system is not sensitive to air and moisture.     

Selectively colorimetric detection of cysteine with triangular silver nanoprisms

Triangular silver nanoprisms were prepared and applied to make colorimetric detection of cysteine based on our findings that cysteine could lead to the blue shift of the dipole plasmon resonance absorption,but other 19 kinds of natural amino acids could not.Cysteine with a concentration 160 nmol/L can result in a color change that can be discerned with naked eyes.     

Studies on the oxygen sensitivity and microstructure of sol–gel based organic–inorganic hybrid coatings doped with platinum porphyrin dye

Hybrid organic–inorganic nanocomposite coatings were prepared by copolymerizing tetraethylorthosilicate with ethyltriethoxysilane with an acid catalysis process. Oxygen sensor coatings were fabricated by doping the hybrid sol with platinum meso-tetra(pentfluorophenyl) porphyrin. Photophysical properties and oxygen sensitivity of the sensor coatings were studied. The microstructure of the coatings was examined using optical microscopy and scanning electron microscopy. The effect of sol–gel process conditions like precursor silane molar ratio, acid concentration and stirring time of the sol on the oxygen sensitivity and surface microstructure of the sensor coating was studied. Oxygen sensitivity and surface morphology of the coatings were dependent on the sol–gel process parameters.