Sharif Digital Repository

Zinc oxide nanoparticles were synthesized and modified by a three-stage method. Elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning and transmission electron microscopy, and Brunauer–Emmett–Teller method were applied to characterize the nanoparticles. These nanoparticles were evaluated for toluene adsorption from aqueous solutions as a representative of petroleum hydrocarbon removal. The optimum adsorption condition achieved at pH of 6 and contact time of 30 min. The adsorption isotherms were fitted to the Langmuir model. The measured adsorption capacity was 12.8 mg g−1. This study demonstrated that these nanoparticles could be used as an... 

The current study demonstrates homogenous decorating of zinc oxide quantum dots (QDs) onto graphene oxide (GO) surface via simple chemical method. The AFM image exhibited that the prepared graphene was 0.8 nm thick and hence practically monolayer. Average size of the ZnO QDs was estimated by transmission electron microscopy around 3 nm. Instrumental and chemical analyses demonstrated formation of a strong bond between ZnO QDs and GO, through C-O-Zn and C-Zn bridges. The UV-visible spectra displayed that the introduction of graphene sheets to ZnO QDs resulted in higher absorption intensity of UV as well as widening of adsorption window toward visible light for ZnO-Graphene due to chemical... 

Abstract: In this investigation, monodisperse CuGaS2 nanoparticles intended for use as visible-light-absorbing materials were synthesized using a facile one-step heating method that involved dissolving the precursors copper chloride, gallium acetylacetonate, and thiourea in a solvent consisting of either oleylamine alone or a combination of oleylamine, oleic acid, and 1-octadecene. The shapes of the resulting nanoparticles were either elongated, polygonal, or a mixture of both, depending on whether the crystal structure of the nanoparticles was predominantly wurtzite, predominantly chalcopyrite, or a more balanced mixture of both wurtzite and chalcopyrite (i.e., the nanoparticles were... 

The effects of thermal history on the microstructure and mechanical properties of a friction-stir-processed Al–Mg–TiO2 (3 vol.-%, 20 nm) nanocomposite were studied. It is shown that, with increases in peak temperature, a more uniform distribution of nanoparticles in the metal matrix, and a refined grain structure, are attained. Transmission electron microscopy indicated that the mechanism of grain refinement is influenced by the hard inclusions, changing from discontinuous to continuous dynamic recrystallisation. A fine-grained nanocomposite (average grain size of 3 µm) with a uniform distribution of nanoparticles is obtained after four fully-overlapping passes at 1200 rev min−1 and 100 mm... 

Polyurethane (PU) nanocomposites with 0, 1, 3, 5, and 7 wt-% nanoclay contents were prepared. X-ray diffraction patterns, transmission electron microscopy images, tensile test, and thermogravimetric analysis were utilised to reveal the morphological, mechanical, and thermal-resistant properties of the prepared nanocomposites. The exfoliated structure was obtained for nanoclay contents up to 3 wt-%. Incorporation of nanoclay to the PU matrix prompted the thermal stability of the polymer. A nanocomposite filled with 3 wt-% nanoclay showed the best tensile strength in the prepared nanocomposites. Subsequently, the nanocomposite with the 3 wt-% nanoclay was reinforced with carbon and glass... 

In this manuscript, synthesis of cobalt/poly vinyl alcohol (PVA)/gamma alumina nanocomposite via a simple room temperature, as well as its catalyst performance were explored. Brunauer–Emmett–Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were conducted. The surface area of the polymeric composite was obtained to be 280 m2/g. The cobalt loading on the nanocomposite was measured using inductivity couple plasma. Transmission electron microscopy analysis showed that the size of cobalt crystalline encapsulate inside the polymer was confined to 5 nm. Magnetic property analysis, using vibrating sample magnetometer, confirmed... 

Joining of Al-5083 alloy sheet to St-12 steel sheet was performed using a new friction stir spot welding (FSSW) technique in which the tool pin tip did not enter lower steel sheet. Effect of dwell time on the microstructure and mechanical properties of the joints was studied by various methods including microhardness measurements, shear test, stereo and light microscopy as well as scanning and transmission electron microscopy (SEM and TEM). Results indicated that compared to the conventional FSSW process, stronger joints can be achieved by this FSSW technique. Cross-sectional observation of the failed specimens indicated the occurrence of final fracture from the circumference of the tool pin... 

Platinum nanotubes (PtNTs) are fabricated by potentiostatic electrodeposition at various overpotentials (−200 up to −400 mV versus SCE) in polycarbonate templates (PCTs) with pore diameter of 200 nm in a solution containing 5 mM H2PtCl6 and 0.1 M H2SO4. The synthesized PtNTs are characterized by field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The electrochemical growth mechanism within nanoscopic pores and the relationship between morphological variations and kinetic parameters are investigated for the first time. It is shown that more porous structure of nanotubes forms at high overpotentials possibly due to preferably nucleation. The... 

Herein, an electrochemical technique as a cost-effective and one-step approach was utilized to fabricate graphene quantum dots (GQDs). Different amounts of GQDs (0, 0.2, 0.4, 0.8, and 1.2 wt %) were decorated uniformly on the surface of anodized ZnO nanowires (NWs) forming GQD/ZnO NWs. Transmission electron microscopy and atomic force microscopy confirmed formation of GQDs on the ZnO NWs, 12-22 nm in width and 1-3 graphene layers thick. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to verify the functional groups on the surface of GQDs, and the results indicated that GQDs readily anchored on the surface of ZnO NWs. The GQD/ZnO NWs exhibited a... 

In this study, initially graphene quantum dots (GQDs) were synthesized by an electrochemical technique and hierarchical porous TiO2 were made by a sol – gel method. Subsequently, GQDs/hierarchical porous TiO2 nanocomposites were prepared by two different methods for the purpose of comparison: spin coating (SC) and electrophoretic (EP) deposition. The GQDs/hierarchical porous TiO2 nanocomposites were characterized by various analytical methods including field emission scanning electron microscopy, atomic force microscopy, transmission electron microscopy, high resolution transmission electron microscopy, Fourier transform infra-red spectroscopy, photoluminescence spectroscopy and... 

Owing to its dual role as a hormone and neurotransmitter, norepinephrine (NE) detection is of great significance to biomedical diagnosis. In the present work, we have explored intense green fluorescence of poly (norepinephrine) (PNE) nanoparticles synthesized by oxidizing NE in alkaline condition, in combination with red fluorescent bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) for naked-eye detection of NE. The effect of sodium hydroxide on the emission behavior of NE was studied. The surface morphology and optical properties of PNE nanoparticles were characterized by UV–Vis, fluorescence, FTIR, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS)... 

This article reports the synthesis of a magnetic heterogeneous catalyst through the decoration of gold ions onto the cross-linked polymeric nanocomposite from 2,6-diaminopyridine. The activity of the resulting catalyst was then evaluated in the bromination of aromatic compounds. The nitrogen rich support showed a high affinity to gold ions, and the measured content of Au was 0.76 mmol g-1. The structure of the catalyst was fully characterized by using Fourier-transform infrared spectroscopy, thermogravimetric analysis, atomic absorption spectroscopy, transmission electron microscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller surface area... 

This work presents the catalytic graphitization process of phenolic resins (PR's) by addition of in situ nano-Fe particles as catalyst. Pyrolysis treatments of prepared compositions including various contents of nano-Fe particles were carried out at 600–1200 °C for 3 h under reducing atmosphere and graphitization process were evaluated by different techniques such as X-Ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Simultaneous Thermal Analysis (STA) and Raman spectroscopy that mainly performed to identify the phase and microstructural analysis, oxidation resistance and extend of graphitized carbon... 

Here in, reduced graphene oxide/g-C3N4/Ag2O nano structure (RGO/CAO) was decorated through a facile and simple chemical method. After that RGO/CAO nano structure combined with poly aniline electrochemically to form a composite electrode. Several physicochemical techniques were applied to characterize the composite electrode such as X-ray Diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, several electrochemical techniques were used to study the performance of composite electrode as an electrochemical capacitor. Results show that RGO/CAO nano... 

We synthesized by electrostatic self-assembly route in basic solution Fe3O4–cysteine/RGO and Fe3O4/RGO–cysteine nanocomposites. In this method, electrostatic interaction was created via negatively charged surface of the reduced graphene oxide and reduced graphene oxide–cysteine sheets and positively charged surface of the Fe3O4 and Fe3O4–Cys nanoparticles in aqueous solution. The structural and magnetic properties of the prepared samples were analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM), respectively. The dependences of magnetization as a function of... 

Supercritical water was used for simultaneous fragmentation and reduction of graphene oxide (GO) sheets into water-dispersible graphene quantum dots (GQDs) with tunable sizes. Transmission electron microscopy (TEM) demonstrated that by increasing the temperature above the critical point of water, the average size and thickness of the GQDs were decreased and the size uniformity and production yield were increased. The results of thermal conductivity measurement of GQD nanofluids with different weight fractions indicated that the GQDs prepared at supercritical condition could enhance the thermal conductivity of water by 65% as compared to 35% for the GQDs synthesized at sub-critical... 

Magnetic micelle nanoparticles with thermoresponsive behavior were designed for thermo-triggered paclitaxel delivery. For this purpose, thermoresponsive triblock copolymer poly(N-isopropyl acrylamide)-b-polycaprolactone-b-poly(N-isopropyl acrylamide) was prepared. The magnetic micelle was formed by self-assembly of triblock copolymer on the magnetite which was coated by oleic acid. The size of the magnetic micelle was between 30–40 nm reported by transmission electron microscopy. Also, dynamic light scattering indicated the hydrodynamic diameter was thermal dependent. Moreover, the drug release profile showed thermo-triggered release of paclitaxel. Thus, the smart nanocarrier has potential... 

Chalcostibite copper antimony sulfide (CuSbS2) micro- and nanoparticles with a different shape and size have been prepared by a new approach to hot injection route. In this method, sulfur in oleylamine (OLA) is employed as a sulfonating agent providing a simple route to control the shape and size of the particles, which enables the optimization of CuSbS2 for a variety of applications. The sulfur to metallic precursor ratio appears to be one of the most effective parameters along with the temperature and time for controlling the size and morphology of the particles. The growth mechanism study shows in addition to the CuSbS2 phase the presence of not previously observed intermediate phases... 

This paper presents a compact and cost effective method for on-chip separation of silica-coated magnetic nanoparticles (SMNPs) with different hydrodynamic size. Three types of SMNPs (Fe3O4@SiO2) with the same magnetic core but with different thickness of silica shells were successfully separated using the developed microfluidic platform. The innovative aspect of the presented separation method is that the induced velocity on the three different types of SMNPs while imposed to the same magnetic field gradient in a static fluid is inversely proportional to their overall, non-magnetic volume. This is due to the enhanced Stokes’ drag force exerted on the nanoparticles (NPs) resulting from their... 

Core-Shell structures of Ag@Pt Nanoparticles (NPs) dispersed on different carbon base supports such as Graphene Oxide (GO), Multiwall Carbon Nanotubes (MWCNT) and Carbon black (CB) Vulcan applied to the oxygen reduction reaction (ORR) in a Proton Exchange Membrane Fuel Cell (PEMFC). Electrocatalysts synthesized through the ultrasonic treatment method. The morphology of as prepared materials characterized through the High Resolution Transmission Electron Microscopy (HRTEM) and X-ray diffraction (XRD) analyses. The ORR activities and stabilities of electrocatalysts studied through electrochemical measurements of Cyclic Voltammetry (CV) and single cell tests, respectively. Results revealed all...