Sharif Digital Repository

A heterogeneous nanocatalyst containing polyoxomolybdate immobilized on the internal surface of amino-functionalized SBA-15 pores was prepared and fully characterized by several analytical techniques. The textural property of supported material was found to retain important mesoporous features, compatible with its potential use as heterogeneous catalysts. The catalyst SBA-15-NH3+•{Mo36}–shows excellent catalytic activity for the epoxidation of alkenes as compared to POM, which is attributed to the large specific surface area and highly ordered pore structure of SBA-15, allowing for easy access of reactants to the active sites and removal of products. The prepared catalyst has high... 

Growing nanocrystals in a matrix is a way to have separate, non-agglomerated nanoparticles, which are surface passivated and stabilized against environmental attacks. To create nanocrystals of the desired size and properties in a matrix, it is required that the growth parameters are properly tuned. In this work, we study the growth parameters for ZnS nanocrystals in an SiO2 matrix. Samples were prepared by cosputtering of SiO 2 and ZnS on a silica substrate, followed by annealing at different temperatures. Two categories of samples with low-content ZnS (4 mol%) and high-content ZnS (15 mol%) were examined. In the low-content samples, ZnS nanocrystals are not formed below 900°C annealing... 

Stoichiometric hydroxyapatite (HA) powder was synthesized by wet method using orthophosphoric acid and calcium hydroxide, as raw materials. In this regard, the time-depending changes of the precipitated particles and effects of heating on them were investigated. The as-precipitated and heated powder samples were examined using field emission electron microscopy (FESEM), XRD and Raman spectroscopy methods. The results revealed that the morphology and size of the precipitated particles change in each stage of the process. After drying, these nanoparticles tend to form small agglomerates. © 2003 Elsevier Science B.V. All rights reserved  

Carbon nanotubes (CNTs) were synthesized via arc discharge in aqueous solutions containing ferrous and ferric irons to reveal the effect of iron-charge mole ratio, R = [Fe2+]/[Fe3+], on the purity of CNTs and the process yield. Raman spectroscopy and transmission electron microscopy were used to analyze the cathodic deposits. It is shown that the nucleation of multi-walled CNTs is catalyzed by ferric irons while their growth is affected by ferrous ions. Well-graphitized CNTs with a high-yield are obtained at R = 1 and total iron concentration of 0.05 M. The effect of iron charge is described based on the two-stage formation mechanism  

Polycitric acid was conjugated onto the surface of carbon nanotubes (CNTs), and hybrid nanomaterials containing CNT axis and polycitric acid branches that were highly soluble in aqueous solutions were synthesized. In this work, pristine MWCNTs were opened and functionalized through treatment with acid, then polycitric acid was covalently grafted onto their surface by the "grafting from" approach based on polycondensation of citric acid in the melting state. The chemical structure, morphology, thermal properties and size of MWCNT-g-PCA hybrid materials were investigated by IR, 13C NMR, 1H NMR, TEM, TGA, DSC and DLS. To investigate the biocompatibility of the synthesized hybrid nanomaterials... 

Carbon nanotubes (CNTs) were synthesized via arc discharge in aqueous solutions containing ferrous and ferric irons to reveal the effect of iron-charge mole ratio, R = [Fe 2+]/[Fe 3+], on the purity of CNTs and the process yield. Raman spectroscopy and transmission electron microscopy were used to analyze the cathodic deposits. It is shown that the nucleation of multi-walled CNTs is catalyzed by ferric irons while their growth is affected by ferrous ions. Well-graphitized CNTs with a high-yield are obtained at R = 1 and total iron concentration of 0.05 M. The effect of iron charge is described based on the two-stage formation mechanism  

Highly fluorescent and water-soluble cadmium selenide quantum dots (QDs) functionalised by thio-cyclodextrin (HS-CD) and mercaptoacetic acid (MAA) as surface coating agents (QDs-CD-MAA) were synthesised successfully. The synthesised hybrid nanomaterials, QDs-CD-MAA, were able to form water-soluble complexes with paclitaxel and folic acid. QDs and their complexes were characterised by usual spectroscopy and microscopy methods. Size and morphology of functionalised QDs were dependent on their capping agents and guest molecules. Short-term in vitro cytotoxicity tests on mouse tissue connective fibroblast adhesive cells (L929) showed that conjugation of CD molecules onto the surface of QDs... 

Silver-based nanomaterials have attracted considerable attention due to their antimicrobial activities. In this work, a silver (Ag)-based metal organic framework (Ag-MOF) is embellished with graphene-oxide (GO), leading to the fabrication of a novel Ag-based nanocomposite (GO-Ag-MOF) whose biocidal activity is higher than those of Ag-MOF and GO nanomaterials. The nanocomposite is characterized using X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, Fourier transform infrared spectra, ultraviolet−visible absorption spectra, X-ray powder diffraction, dynamic light scattering, and nitrogen gas adsorption/desorption. The characterization shows that... 

Single-layer MoS2-MoO3-x heterojunction nanosheets with visible-light-sensitive band gap energy and average lateral dimensions of ~70 nm were synthesized by using a two-step combined exfoliation method. The exfoliation was initiated from pristine MoS2, while some sulfur sites in expanded MoS2 sheets during exfoliating were substituted by ambient non-thermal oxygen, resulting in formation of α-MoO3-x crystalline domains. The morphological features, crystalline structure, phase formation, number of layers, and optical properties of the MoS2-MoO3-x nanosheets were determined by atomic force microscopy; X-ray diffraction; field emission electron microscopy; transmission electron microscopy; and... 

Construction over problematic soils is a common problem in many parts of the world, and one of the effective procedures to tackle this problem is soil stabilization. Accordingly, the current study provides the finding of a laboratory investigation into the effect of three kinds of nanomaterials, including nano-silica (NS), nano-clay (NC) and nano-calcium carbonate (NCC) on the properties of a loessial collapsible soil. To accomplish this issue, reconstituted samples of the stabilized loessial soil were prepared for unconfined compression and consolidation tests. The results illustrated that an insignificant amount of nanomaterials (less than 1% of the total dry weight of the soil when is... 

According to the importance of polyanion cathode materials in intercalation batteries, they may play a significant role in energy-storage systems. Here, evaluations of LiMBO3 and NaMBO3 (M = Mn, Fe, Co, Ni) as cathode materials of Li-ion and Na-ion batteries, respectively, are performed in the density functional theory (DFT) framework. The structural properties, structural stability after deintercalation, cell voltage, electrical conductivity, and rate capability of the cathodes are assessed. As a result, Li compounds have more structural stability and energy density than Na compounds in the C2/c frame structure. Cell voltage is increased by increasing the atomic number of the transition... 

Construction over problematic soils is a common problem in many parts of the world, and one of the effective procedures to tackle this problem is soil stabilization. Accordingly, the current study provides the finding of a laboratory investigation into the effect of three kinds of nanomaterials, including nano-silica (NS), nano-clay (NC) and nano-calcium carbonate (NCC) on the properties of a loessial collapsible soil. To accomplish this issue, reconstituted samples of the stabilized loessial soil were prepared for unconfined compression and consolidation tests. The results illustrated that an insignificant amount of nanomaterials (less than 1% of the total dry weight of the soil when is... 

Regarding the importance of rheological properties of water based drilling fluids, the effects of silica nanospheres, multiwall carbon nanotubes (MWCNTs) and two types of their hybrid, i.e. H1 (80 wt.% silica nanosphere/20 wt.% MWCNT) and H2 (50 wt.% silica nanosphere/50 wt.% MWCNT) on the viscosity and density of distilled water were investigated. According to the results, viscosity and density of the nanofluids increased with the concentration, while they were reduced by increasing the temperature. At high concentrations, the least increase in the viscosity of distilled water by adding the nanomaterials is related to H2 (8.2% increase at 1.0 wt.%). Likewise, the optimum operating... 

Anodic aluminium oxide films were fabricated by well known two-step anodizing process in oxalic acid electrolyte. The ordering characteristics (ordered pore domains, average pore diameter size and through-pore arrangement) of anodic aluminium oxide films, obtained in different growth sequences, were identified by microscopic analysis such as ex situ contact-mode atomic force microcopy and scanning electron microscopy. Flattened areas in which some pits are seen mostly cover the electropolished surface of aluminium. Single anodizing of aluminium produces a broad distribution of nanopore size, whereas induces a highly ordered hemispherical pattern, which plays the ordered nucleation sites for...