Thermal Degradation Studies on PMMA–HET Acid Based Oligoesters Blends

Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO2, H2O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented

PHYSICOCHEMICAL CHARACTERISTICS OF RASAMANIKYA-AN AYURVEDIC ARSENICAL FORMULATION

Objective: The objective of this study was standardization and Chemical characterization of rasamanikya prepared as per standard operating procedures (SOP) mentioned in the classical text. Methods: Rasamanikya was prepared by putting churnodaka shodhita haratala (Orpiment-As2S3) between two abhraka (white mica) sheets which are heated for a while to obtain a red colored finished product. The Ayurvedic specifications for the analysis of rasamanikya were performed through qualitative and quantitative analysis. Physicochemical analysis, assay of elements by atomic absorption spectrometer (AAS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) were carried out and some other tests such as x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray analyzer (EDAX) were also performed to ensure the quality of the drug. Results: In the finished drug Arsenic and Sulphur are present in the form of As4S4, As2S3, As2S5. On the basis of XPS survey scans, scanning electron microscopy-energy dispersive x-ray analyzer (SEM-EDAX) and carbon, hydrogen, nitrogen, sulphur (CHNS) analysis the Arsenic to Sulphur (As to S) ratio is thus standardized as 39-47: 53-61. In addition to this powder, XRD shows a major conversion into an amorphous phase. Conclusion: The results could be used to lay down a new set of pharmacopoeial standards for the preparation of rasamanikya for getting optimal efficacy of medicine. Therefore, the information will help the Scientists and Researchers to build comprehensive standards, to screen the compounds responsible for different bioactivities, and to elucidate the molecular mechanism of action

Cobalt Phthalocyanine Immobilized on Graphene Oxide: An Efficient Visible-Active Catalyst for the Photoreduction of Carbon Dioxide

International audienceNew graphene oxide (GO)-tethered–Co II phthalo-cyanine complex [CoPc–GO] was synthesized by a stepwise procedure and demonstrated to be an efficient, cost-effective and recyclable photocatalyst for the reduction of carbon dioxide to produce methanol as the main product. The developed GO-immobilized CoPc was characterized by X-ray diffraction (XRD), FTIR, XPS, Raman, diffusion reflection UV/ Vis spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), scanning electron mi-croscopy (SEM), and transmission electron microscopy (TEM). FTIR, XPS, Raman, UV/Vis and ICP-AES along with elemental analysis data showed that Co II –Pc complex was successfully grafted on GO. The prepared catalyst was used for the pho-tocatalytic reduction of carbon dioxide by using water as a solvent and triethylamine as the sacrificial donor. Methanol was obtained as the major reaction product along with the formation of minor amount of CO (0.82 %). It was found that GO-grafted CoPc exhibited higher photocatalytic activity than homogeneous CoPc, as well as GO, and showed good recoverability without significant leaching during the reaction. Quantitative determination of methanol was done by GC flame-ionization detector (FID), and verification of product was done by NMR spectroscopy. The yield of methanol after 48 h of reaction by using GO–CoPc catalyst in the presence of sacrificial donor triethylamine was found to be 3781.8881 mmol g À1 cat., and the conversion rate was found to be 78.7893 mmol g À1 cat. h À1. After the photoreduction experiment , the catalyst was easily recovered by filtration and reused for the subsequent recycling experiment without significant change in the catalytic efficiency

Physicochemical and textural properties of amino-functionalised mesoporous silica nanomaterials from different silica sources

A series of MCM-41 nanomaterials that could serve various scientific applications was synthesised from two silica sources, tetraethyl ortho silicate and sodium silicate. Calcination and solvent extraction were employed as surfactant removal methods, while surface functionalisation was done via co-condensation and post-grafting methods. The synthesised nanomaterials were characterised, and their physicochemical properties were compared using X-ray powder diffraction (XRD), Brunauer Emmett Teller (BET) analysis, Fourier Transform Infra-red spectroscopy (FTIR), Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results showed that the surfactant removal and surface functionalisation methods affected the synthesised nanomaterials’ 2θ values, d-spacing, and unit cell parameters. However, surfactant removal methods did not affect the morphology of amino-functionalised nanomaterials. Mesoporous silica nanomaterials of specific surface areas (884.0–17.1 m2/g), pore volumes (1.0–0.1 cm3/g), pore size diameters (7.2–1.5 nm), and less orderly mesoporous structures were produced with co-condensation and amino functionalisation using both silica sources. These methods can produce mesoporous silica nanostructures with different morphologies for wastewater remediation, catalysis, bio-catalysis, drug delivery, CO2 capture, indoor air cleaning, bioanalytical sample preparation, and pervaporation membrane improvement

Nanostructured AgBr loaded TiO2: An efficient sunlight active photocatalyst for degradation of Reactive Red 120

The AgBr loaded TiO2 catalyst was prepared by a feasible approach with AgBr and tetraisopropyl orthotitanate and characterized by BET surface area measurement, diffuse reflectance spectra (DRS), scanning electron microscope (SEM), energy dispersive spectra (EDS), X-ray diffraction (XRD), transmission electron microscope (TEM) and atomic force microscope (AFM) analysis. The results of characterization reveal that AgBr loaded TiO2 has a nanostructure. Formation of the nanostructure in AgBr loaded TiO2 results in substantial shifting of the absorption edge of TiO2 to red and enhancement of visible light absorption. Electrochemical impedance spectroscopy measurements reveal that AgBr loaded TiO2 has a higher photoconductivity than prepared TiO2 due to higher separation efficiency of electron-hole pairs. Cyclic voltammetric studies reveal enhanced conductivity in AgBr loaded TiO2, which causes an increase in its photocatalytic activity. AgBr loaded TiO2 exhibited a higher photocatalytic activity than TiO2-P25 and prepared TiO2 in the photodegradation of Reactive Red 120 (RR 120)

Recyclable heterogeneous supported copper-catalyzed coupling of thiols with aryl halides: base-controlled differential arylthiolation of bromoiodobenzenes

Alumina-supported copper sulfate efficiently catalyzes the S-arylation of aromatic, heteroaromatic and aliphatic thiols with aryl as well as heteroaryl halides under aerobic, ligand-free conditions. This protocol provides an easy access to a variety of thioethers as well as unsymmetrical bis-thioethers by base-controlled differential coupling of thiols with iodo- and bromo-substituents in an aromatic halide. The catalyst is inexpensive, non-air sensitive, environmentally friendly and recyclable

Molecular sieves-supported palladium(II) catalyst: Suzuki coupling of chloroarenes and an easy access to useful intermediates for the synthesis of irbesartan, losartan and boscalid

Palladium(II) chloride supported on 4 Å molecular sieves efficiently catalyzes the Suzuki coupling reactions of chlorobenzenes in presence of tetrabutylammonium bromide without any ligand. The useful intermediates for the synthesis of bioactive compounds such as irbesartan, and losartan have been prepared in one step following this reaction. The preparation of this catalyst is very simple. The FE-SEM image shows a cube shape ordered structure. The catalyst does not exhibit any nanoparticles as indicated by TEM. EDS and XPS demonstrate anchoring of Pd on molecular sieves in +2 oxidation state. This heterogeneous catalyst is stable, non-air sensitive and recyclable

Synthesis, characterization and photocatalytic activity of alkaline earth metal doped titania

1189-1196The synthesis of beryllium doped titania (Be2+–TiO2) at different percentages (0.25, 0.5, 0.75 and 1.0 wt %) by sol-gel method and its characterization by XRD, UV-visible absorption spectroscopy, XPS, SEM and FT-IR techniques are reported. Diffraction peaks of anatase crystalline phase have been observed both in synthesized TiO2 as well as in Be2+–TiO2. Presence of Be2+ ions in the TiO2 structure causes significant absorption shift towards the visible region. FT-IR and XPS data show the interstitial presence of Be2+ ion in TiO2. The photocatalytic efficiency of the synthesized Be2+–TiO2 and unsubstituted TiO2 has been evaluated by the degradation of monocrotophos pesticide under visible light irradiation, wherein the degradation rate of MCP by Be2+–TiO2 is found to be higher than by unsubstituted TiO2. This may be attributed to the more efficient electron-hole creation in Be2+–TiO2 in visible light, as compared to unsubstituted TiO2 which can be excited only by UV irradiation. The effect of dopant concentration, pH, catalyst dosage and pollutant concentration have been studied for obtaining optimal degradation conditions