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Ammonium persulphate promoted synthesis of polyethylene glycol entrapped potassium tribromide and its application in acylation and bromination of some selective organic compounds

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Chinese Chemical Letters 2013年第10期24卷 866-868页

作者： Rupa Rani Dey siddhartha sankar dhar Department of Chemistry National Institute of Technology

In this study, a new method of synthesis of polyethylene glycol supported potassium tribromide （PEG KBr3） and its application in acylation and bromination reactions are reported. Ammonium persulphate oxidizes I（Br to the corresponding tribromide which is entrapped by polyethylene glycol leading to stable PEG KBr3. The reagent is proved to be highly efficient for the acylation of variety of alcohols and bromination of activated aromatic substrates. The method is a mild, one pot reaction and involves no use of toxic reagents.

关键词： Potassium bromide Polyethylene glycol (PEG) Ammonium per sulphate Acylation Bromination

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α-Fe2O3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

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Chinese Chemical Letters 2016年第11期27卷 1725-1730页

作者： Bappi Paul Sethumathavan Vadivel siddhartha sankar dhar Department of Chemistry National Institute of Technology Silchar Silchar-788010 Assam India Department of Chemistry PSC College of Technology Peelamedu Coimbatore-641004 Tamilnadu India

Nanostructured ot-Fe2O3 were prepared by precipitation followed by calcination method. Cetyltrimethylammonium bromide （CRAB） was used as surfactant. The nano α-Fe2O3 was then silanized with （3-chloropropyl）-triethoxysilane （CPTES） by room temperature mixing ofα-Fe2O3 and CPTES to produce silane coated ct-Fe2O3 （CIPr-Si@Fe2O3）. As-synthesized CIPr-Si@Fe2O3 was functionalized via covalent grafting of benzimidazole to produce 3-（1-benzimidazole）Pr-Si@Fe2O3. This was further reacted with bromine to afford α-Fe2O3 immobilized benzimidazolium tribromide （α-Fe2O3-BIM tribromide）. This ionic liquid （IL） α-Fe2O3 BIM tribromide was characterized by FT-IR, XRD, TEM, SEM, TGA, VSM, EDX and BET analysis. The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines. The method is greener in terms of solvent selection, recovery of the catalyst and efficiency.

关键词： Nano α-Fe2O3 Covalent grafting Ionic liquid Multicomponent reaction

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VO(acac)_2 catalyzed condensation of o-phenylenediamine with aromatic carboxylic acids/aldehydes under microwave radiation affording benzimidazoles

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Chinese Chemical Letters 2011年第3期22卷 296-299页

作者： Madhudeepa Dey Krishnajyoti Deb siddhartha sankar dhar Department of Chemistry National Institute of TechnologySilcharSilchar 788010AssamIndia

Vanadyl acetylacetonate,VO（acac）_2,has been found to be very effective catalyst for synthesis of a variety of benzimidazoles under solvent-free *** methodology involves the exposure of a mixture of o-phenylenediamine and a selected aromatic carboxylic acid/aldehyde to microwave radiation without the use of any solvent or supporting *** benzimidazoles were obtained in quick time with high yields.

关键词： Vanadyl acetylacetonate o-Phenylenediamine Microwave irradiation Solvent-free

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Preparation and Antibacterial Activity of Silver Nanoparticles

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Journal of Biomaterials and Nanobiotechnology 2011年第4期2卷 472-475页

作者： Ratan Das Sneha Gang siddhartha sankar Nath 不详

Uniform silver nanoparticles have been prepared through the chemical reduction of silver ions by ethanol in presence of sodium linoleate. TEM micrograph shows a uniform distribution of the particles with an average size of 12 nm. Further, the antimicrobial activity of silver nanoparticles shows that these nanoparticles can be used as effective growth inhibitors against Staphylococcus Basillus, Staphylloccoccus Aureus, and Pseudimonas Aureginosa.

关键词： Linoleic Acid Absorption Band Colloid Antimicrobial Microorganisms

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Fatigue Failure of Notched Specimen—A Strain-Life Approach

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Materials Sciences and Applications 2011年第12期2卷 1730-1740页

作者： Bikash Joadder Jagabandhu Shit Sanjib Acharyya sankar dhar 不详

Failure cycles of notched round specimens under strain controlled cyclic loading are predicted using strain—life relations obtained from experiment for plain fatigue round specimens. For notched specimens, maximum strain occurs at notch root and is different from applied controlled strain. The maximum strain is computed by appropriate Finite element analysis using the FE software ABAQUS. FE model and material parameters are validated by comparing the FE results and experimental results of LCF tests of round specimens. This value of maximum strain is used for prediction of failure cycles. Prediction is compared with the experimental results. The results show good matching.

关键词： Strain Life Equation Failure Cycle Notched Specimen LCF Cyclic Plasticity

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ZnO: PVP Quantum Dot Ethanol Sensor

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Journal of Sensor Technology 2011年第3期1卷 86-90页

作者： Madhuchhanda Choudhury siddhartha sankar Nath Rajarshi Krishna Nath 不详

We prepare of ZnO quantum dots embedded in polyvinylpyrrolidone (PVP) matrix and report it’s working as ethanol sensor. The samples have been prepared via quenching technique where bulk ZnO powder is calcined at very high temperature of 1200°C and then quenched into ice cold polyvinylpyrrolidone solution. Thee acteiut the samples specimen have been characterized by using UV/VIS spectroscopy, X-ray diffracttion study and high resolution transmission electron microscopy (HRTEM). These studies indicate the sizes of quantum dots to be within 10 nm. The prepared quantum dot samples have been examined for ethanol vapour sensing by exploring the variation of their resistance with time at different operating temperatures. It has been revealed that ZnO quantum dots can sense ethanol at low operating (230°C) temperature with less response time.

关键词： Quantum Dot Ethanol Sensor Polyvinylpyrrolidone Quenching

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