Sharif Digital Repository

An eco-friendly gold-based catalyst supported on proline decorated montmorillonite was synthesized. The catalyst was characterized by combination of Fourier-transform infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmett Teller (BET) surface area analysis, Ultraviolet–visible spectroscopy (UV-Vis), Energy-dispersive X-ray spectroscopy (EDX), thermo gravimetric analysis (TGA) and atomic absorption spectroscopy (AAS) techniques. The synthesized catalyst was found to be a highly efficient heterogeneous nanocatalyst for multi component A3 coupling reaction of aldehyde, amine and alkyne... 

Herein, we demonstrate a facile low temperature approach to prepare a gel polymer electrolyte (GPE) based on the triiodide/iodide redox couple in a quasi-solid-state dye-sensitized solar cell (DSSC). Only one polymeric agent (i.e., hydroxypropyl cellulose (HPC)) is used for the preparation of a non-volatile GPE system for the standard liquid electrolyte containing 1-methyl-3-propylimidazolium iodide (MPII). The prepared GPE completely penetrates into a TiO2 photoanode at room temperature due to the uniform distribution of Ti, Ru and I elements in the cross-section of the electrode, forming an interpenetrating GPE/TiO2 network to access all dye molecules. The GPE with the optimum HPC : MPII... 

Perovskite solar cells with an inverted p-i-n architecture were constructed under ambient conditions by employing materials of lower cost than standard cells. Thus, graphene oxide was used as a hole transporting material and Li-modified graphene oxide as an electron transporting material, while Al was used as a counter electrode. A maximum solar conversion efficiency of 10.2% was achieved by adding a Ti-based sol on the top of the Li-modified graphene oxide layer. © The Royal Society of Chemistry  

In the present work, a simple, green, rapid, and catalyst-free procedure for the synthesis of benzamide derivatives by ring opening of azlactones with diamines such as ethylene diamine and 1,3-propylenediamine is described. The present method offers several advantages such as short reaction times, easy work-up, and mild reaction conditions in the absence of catalyst and any toxic solvent and material. In addition, the structure obtained by X-ray crystallography was compared with the theoretical results obtained by density functional theory using the B3LYP functional and cc-pVDZ basis sets  

Abstract A visible-light-active Ag3PO4/BiPO4 nanocomposite with a p-n heterojunction structure was fabricated via a co-precipitation hydrothermal process using 2-hydroxylethylammonium formate (RTIL) as a room-temperature ionic liquid. The resulting catalysts were characterized by various techniques. The photocatalytic activity of the photocatalysts was evaluated by the photodegradation of phthalocyanine Reactive Blue 21 (RB21) under both visible and UV light irradiations. The results reveal that the heterojunction composite prepared in RTIL noticeably exhibited an improvement in both efficiency and rate of RB21 photodegradation in comparison with pure Ag3PO4 and BiPO4. The enhanced... 

Pursuing a sensing structure with a large effective surface area, partial ordered arrays of ZnO nanorods with flower-like structures are introduced for gas sensing applications. Room temperature H2S response of the grown structure shows significant enhancement after modification with Au nanoparticles. High response (about 1270 at 6 ppm H2S gas) and selectivity were achieved by depositing an Au layer with nominal thickness ∼6 nm. X-ray photoelectron spectroscopy (XPS) was utilized to describe the H2S sensing mechanism  

Abstract A visible light active Ag2CO3/TiO2/2-hydroxylethylammonium formate (RTIL) nanocomposite has been synthesized via loading Ag2CO3 flower-like particles on TiO2/RTIL by a simple precipitation method. TiO2 nanoparticles were prepared by the modified sol-gel method using 2-hydroxylethylammonium formate (RTIL) as an ionic liquid. The prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform-infra red spectroscopy (FTIR) and Diffuse reflectance UV-vis spectroscopy (DRS) techniques. The photocatalytic performance of the synthesized photocatalysts... 

Site reactivity of some enol-imines derived from N-aryl formamides with pentachloropyridine under basic conditions in dry CH3CN was investigated. The aromatic nucleophilic substitution of pentachloropyridine with enol-imines occurs at the 4-position of pyridine ring by both oxygen and nitrogen site of enol-imines. Nucleophilic attack by the oxygen of enol-imine gave corresponding oximino compounds as a mixture of E- and Z-isomers. In contrast, nucleophilic attack by the nitrogen of enol-imine gave the unexpected N,N-di-substituted aryl compounds. The structures of all the compounds were confirmed by IR, 1H NMR, 13C NMR and 19F NMR spectroscopy as well as elemental analysis and... 

Mn-doped ZnO nanoparticles, Zn1−xMnxO, were synthesised by a polyethylene glycol (PEG) sol–gel method and the physicochemical properties of compounds were characterised by atomic absorption spectroscopy (AAS), energy-dispersive X-ray analysis, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The catalytic degradation of an organic dye, methylene blue (MB), in the presence of Zn1−xMnxO as the catalyst and hydrogen peroxide (H2O2) as the oxidant at room temperature in water has been studied. Effects of oxidant, catalyst amount, catalyst composition, pH value of the solution and an OH-radical... 

The comprehensive optical-electrical-gain-thermal self-consistent model of the 1.55 μm AlGaInAs Photonic Crystal vertical cavity surface emitting diode lasers (PhC VCSELs) with buried tunnel junction (BTJ) has been applied to optimize its threshold characteristics. It shows that, for 5 μm devices, the room temperature (RT) threshold current equal to only 0.59 mA and maximum operating temperature equal to as much as 380 K. Results suggest that, the 5 μm AlGaInAs PhC VCSELs seem to be the most optimal ones for light sources in high performance optical communication systems  

Two room temperature liquid salts containing molybdenum(VI), [BMIM] 2[MoO2(NCS)4] (1) and [DMIM] 2[MoO2(NCS)4] (2), were immobilized on ionic liquid-modified silica leading to materials which showed notable catalytic activity for the reduction of sulfoxides into sulfides with triphenylphosphine (PPh3). The molybdenum liquid salts immobilized on the supported ionic liquid phase could be reused at least for three catalytic cycles without significant loss of activity  

An environmentally benign, aqueous synthesis of 1,2-azidoalcohols via regioselective ring opening of their epoxides using magnetic imidazolium based dicationic room temperature ionic liquid, [pbmim](FeCl4)2, as an efficient magnetic phase transfer catalyst in water has been described. The present approach offers the advantages of clean reaction, simple methodology, short reaction time, high yield, easy purification and reusable catalyst  

Tungsten oxide thin films (deposited by thermal evaporation or sol gel method) were used for photocatalytic reduction of graphene oxide (GO) platelets (synthesized through a chemical exfoliation method) on surface of the films under UV or visible light of the environment, in the absence of any aqueous ambient at room temperature. Atomic force microscopy (AFM) technique was employed to characterize surface morphology of the GO sheets and the tungsten oxide films. Moreover, using X-ray photoelectron spectroscopy (XPS), chemical state of the tungsten oxide films and the photocatalytic reduction of the GO platelets were quantitatively investigated. The better performance of the sol-gel tungsten... 

This work presents a procedure for functionalization of graphene sheets from edges by polyglycerol. Hyperbranched polyglycerol with a bi-dentate aromatic segment in its focal point was synthesized and used to sandwich graphene sheets from the cut-edges. Due to the hydrophobicity of the flat surface of the edge-functionalized graphenes and hydrophilicity of their edges, they changed their conformation from the extended- to the closed-state and formed nanocapsules in aqueous solutions. Spectroscopy and microscopy evaluations showed that the average size for nanocapsules is 300 nm. They were able to encapsulate hydrophobic molecules such as doxorubicin in aqueous solutions with a high loading... 

In this work, a novel heterogeneous organocatalyst was synthesized by immobilization of hydroxide ions on the modified salep as a natural polymer. Because of the grafting of ionic polymer chains onto the salep backbone, catalyst has high loading level of hydroxide ions (3.01 mmol/g). The resulting catalyst shows excellent activity in the synthesis of 4H-benzo[b]pyrans in water at room temperature in short reaction times. The present catalyst and protocol represent a simple, ecologically safe and cost-effective route to synthesize 4H-benzo[b]pyrans with high product yield, as well as easy catalyst recycling  

A uniformly distributed ZnO nanowire array has been grown on silicon (100) substrates by catalyst-free chemical vapor transport and condensation. The effect of growth conditions including source heating temperature, substrate temperature, and gas flow rate on growth properties of ZnO nanowire arrays are studied. Scanning electron microscopy, X-ray diffraction, and room temperature photoluminescence are employed to study the structural features and optical properties of the samples. The results show a correlation among experimental growth parameters. There is a zone for substrate temperature, by controlling gas flow rate, that uniformly distributed and well aligned ZnO nanowire arrays can be... 

Fiber bending and temperature loss mechanisms in plastic optical fibers are reported.A simple arrangement is used to monitor the fiber bending and temperature by output power variation. Powers in the fibers in bend-free situation at room temperature and under rolling deforming force at different water bath temperatures (20-60°C) are measured and compared. Reported arrangements can be used as a temperature sensor  

In the present paper, the heat treatment effect on A356.0, a cast aluminum alloy which has been widely used in diesel engine cylinder heads, is investigated under out-of-phase thermo-mechanical fatigue and low cycle fatigue (at different temperatures) loadings. A typical heat treatment is applied to the material including 8. h solution at 535 °C, water quench and 3. h ageing at 180 °C. The experimental fatigue results show that the heat treatment process has considerable influence on mechanical and low cycle fatigue behaviors, especially at room temperature, but its effect on thermo-mechanical fatigue lifetime is not significant. The improvement in the strength can be explained by the... 

Ferrite-bainite-martensite triple phase (TP) microstructures with different volume fractions of martensite were obtained by changing heat treatment time during austempering at 300 C. Room temperature impact properties of TP steels with different martensite volume fractions (VM) were determined by means of Charpy impact testing. The effects of test temperature on impact properties were also investigated for two selected microstructures containing 0 (the DP steel) and 8.5 vol.% martensite. Test results showed reduction in toughness with increasing VM in TP steels. Fracture toughness values for the DP and TP steels with 8.5 vol.% martensite were obtained from correlation between fracture... 

Hydrolysis of titanium isopropoxide alcoholic solution has been used to prepare the crystallized TiO2 nanoparticles at low temperature. Concentration ratio was used to control the pathway of sol-gel process and change the physical characteristics of TiO2 nanopowders. The crystallinity, morphology and size of aged TiO2 nanopowders were studied by X-ray diffraction and Scanning Electron Microscopy (SEM). FTIR and, Thermo-Gravimetric (TG) analysis were used to identify the functional groups and thermal behavior of prepared samples. Experimental results have shown that high crystalline TiO2 nanomaterial with anatase polymorph can be obtained at room temperature. It has been found that the...