Sharif Digital Repository

A new Zinc phosphating bath, which produces coatings at relatively lower temperatures within a reasonable time by using of chemical accelerators has been devised. Improvement of the bath performance by the addition of divalent cations like calcium, nickel has been studied. Bath formulation and operating conditions have been optimized by coating weight determinations. Stable samples of phosphating formulations with and without calcium and nickel salts were prepared and the structure and morphology of the phosphate coatings were determined by using X-ray diffraction (XRD) techniques, scanning electron microscopy. ASTMB117 salt spray test and electrochemical impedance spectroscopy (EIS) were... 

The effect of the bath chemistry and operating conditions on the chemical composition, microstructure and properties of NiWmdashB alloys deposited from tartrate baths on working electrode was studied for the first time by the pulsed current method. The investigations included the measurement of the current efficiencies and determination of the tungsten content in the electrodeposits. UV spectrometry was used for characterisation of complex formation. The grain size of deposits was determined by XRD. Also, the morphology of the deposits was studied by SEM. Amorphous NimdashWB alloys were successfully obtained by electrodeposition from the tartrate bath. The corrosion behaviour of NiWmdashB... 

In this study, crumpled-shape nanocomposite of nitrogen and sulfur co-doped ZnO–CeO2 (NSZC) was deposited on FTO substrate using one-step ultrasonic spray pyrolysis. Zinc acetate, cerium nitrate, and thiourea were dissolved in deionized water and used as starting solution. The samples were characterized using FESEM, XRD, UV–vis spectroscopy, EIS, and PL. The as-prepared nitrogen and sulfur co-doped ZnO–CeO2 nanocomposites were evaluated as high photocatalysts for degradation of methyl orange. Nearly 100% photocatalytic degradation of methyl orange was achieved for 180 min. The photoluminescence and electrochemical impedance spectroscopy revealed that co-doping of nitrogen and sulfur could... 

In a nutshell, this study outlines the efficacy of mixed dimensional (2D/3D) hybrid perovskites by developing a new class of triple-cation quasi-2D perovskites having (S0.97S′0.03)2[Cs0.05(FA0.97MA0.03)0.95]n-1Pbn(I0.07Br0.03)3n+1 general composition, in which a mixture of ý5-ammonium valeric acid ýiodideý (S) and tetra-n-octylammonium ýbromide (S′) was employed ýas a spacer.ý The effect of the 2D and 3D structures molar ratios (i.e., C=2D/2D+3D) in the range of 0-100 % on photovoltaic performance of the deposited photoanodes was systemically studied. Drawing a comparison between such compounds and an analogous triple-cation 3D counterpart (i.e., Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3) as... 

The ability of an active protective organic coating to restore its protection functionality in case of a coating defect is of pivotal importance to ensure durable performance under demanding corrosive conditions. In this paper, a self-healing epoxy system is fabricated by separate encapsulation of epoxy and polyamine in carbon hollow spheres (CHSs) and the autonomous healing performance of the system applied on mild steel is investigated. CHSs were synthesized via a silica templating method using carbonization of polysaccharide shells formed on the surface of silica templates. Consequently, epoxy and polyamine were loaded in separate capsules by dispersion of CHSs into the dilute solutions... 

In this article, the synthesis procedure of mesoporous carbon nanospheres (MCNSs) using silica hard-templates, doping of the nanospheres with walnut extract, and their impact on active protective properties of an epoxy coating are presented. Field emission scanning electron microscope (FE-SEM) results showed that the synthesis of these nanocontainers was successfully done in spherical form. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) results showed that walnut extract as a green inhibitor was doped into the pores of nanocapsules. Corrosion resistance of the mild steel samples in the 3.5 wt.% NaCl solution in the presence and absence of walnut extract... 

In the field of energy storage by high-rate supercapacitors, there has been an upper limit for the total interfacial capacitance of carbon-based materials. This upper limit originates from both quantum and electric double-layer capacitances. Surpassing this limit has been the focus of intense research in this field. Here, we precisely investigate the effect of chemical functional groups and physical confinement on the electrochemical performance of graphene nanoribbons. We present the results of a quasi-one-dimensional single-layer graphene nanoribbon (120 nm in width and -100 μm in length) microelectrode fabricated by mechanical exfoliation of graphite, followed by electron beam lithography... 

SnS2-SnO2 nano-heterostructures are synthesized with two different precursors of thioacetamide (TAA) and thiourea (TU) at various solvent ratios (SR) of ethanol and water by using a facile, economical, scalable, and cost-effective solvothermal method. The obtained products have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and Brunauer–Emmet–Teller (BET) techniques. It is found that different precursors and various SR values have an influence on the composition and morphologies of the prepared nanostructures, leading to variation in capacitive behavior of the fabricated electrodes.... 

Carbon nanocapsules doped separately with epoxy and polyamine were used to fabricate an epoxy nanocomposite coating. Carbon nanospheres with dual-encapsulated epoxy/polyamine were dispersed uniformly in the epoxy resin at concentrations of 2, 5, and 10 wt %. The mechanical properties of the nanocomposites were studied by tensile testing and scratch hardness measurements. Furthermore, nanocomposites were applied on mild steel substrates, and their corrosion protection and barrier performance were evaluated using electrochemical impedance spectroscopy (EIS). Adhesion loss measurements of coatings after 240 h exposure to 3.5 wt % NaCl solution were performed by pull-off adhesion testing. Also,... 

A new poly (acrylonitrile) (PAN)-based gel polymer electrolyte (GPE) is fabricated to study the effect of carbon nanotube (CNT) on dye-sensitized solar cell (DSSC) efficiency. The GPEs are examined using electrochemical impedance spectroscopy (EIS) to analyze ionic conductivity. A maximum of 4.45 mS cm −1 ionic conductivity is achieved at room temperature with incorporation of 11 wt.% CNT. Performance of DSSC is examined with a solar simulator, and the highest energy conversion efficiency of 8.87% is achieved with the addition of 11 wt.% CNT. All GPE samples are found to follow Arrhenius model with temperature-dependent ionic conductivity testing. Structural properties are also characterized... 

The reduced graphene oxide-Fe2O3 (rGO-Fe2O3) nanocomposites were synthesized by a facile and low-cost hydrothermal method employing rGO and Iron (III) nitrate precursors. The synthesis parameters including the reduction time and presence of reduction aid are studied. The structural and morphological studies of the nanocomposites were investigated by using Raman spectra, Fourier transform infrared spectroscopy, X-ray diffraction, and field emission scanning electron microscopy. The results indicate that Fe2O3 nanoparticles with average particle size of 25 nm are well anchored on graphene sheets and the weight percent of the nanoparticles in the nanocomposites was influenced by the reduction... 

In this study, a novel inorganic/organic hybrid pigment based on zinc cations/Ferula Asafoetida leaves extract (Zn-FALE) was synthesized, and its corrosion protection properties were investigated in a saline solution and an organic coating. Interactions of components between Zn2+ cations and FALE were assessed by thermo-gravimetric analysis (TGA) and ultraviolet-visible (UV–visible) spectroscopy. Corrosion inhibitive performance of FALE and Zn-FALE pigments in the solution phase and coating phase was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). TGA and UV–visible results revealed the proper chelation between inorganic and organic components of... 

In this research, a novel, rapid, and non-immune electrochemical method was used to detect cardiac troponin I (cTnI) using a double recognition approach. Amine terminus cTnI aptamers immobilized on COOH-ZnO nanoparticles (COOH-ZnONPs) modified GCE surface were applied to capture cTnI for imprinting recognition. The COOH-ZnONPs were synthesized in a biological manner. Then, the methylene blue (MB) monomers were electro-polymerized around the cTnI-aptamer complexes. Following the removal of cTnI, cavities were constructed and converted to a new aptamer and molecular imprinted polymer (MIP) hybrid receptor (aptamer/MIP/ZnONPs). FT-IR spectra, SEM images, XRD patterns, and electrochemical... 

Designing a novel epoxy composite system with dual self-healing/barrier anti-corrosion functions using graphene oxide (GO) nano-platforms decorated by polypyrrole (PPy) nanoparticles doped with zinc metal ions is the major objective of this research attempt. GO-PPy-Zn nanoplatform was fabricated via one-pot polymerization of pyrrole monomers on GO and two direct/indirect methods of zinc doping. In order to verify the PPy nanoparticles synthesis on GO sheets several analyses such as UV–visible, XPS, HR-TEM and FE-SEM were performed. The epoxy nanocomposite coatings containing GO-PPy and GO-PPy-Zn nanoplatforms were fabricated and applied on carbon steel. The nanocomposite coatings... 

A novel AC impedance study on three-dimensional hybrid structures of graphene sheets/MoS2 nanorose (GMS) toward ethanol vapor detection is presented in this work. These defective 3D hybrid porous structures are sensitive to the presence of different gases as a result of charge transfer with gas species, as well as a change in the effective capacitance of the system. The sensing behavior of the samples is investigated throughout time-dependent impedance measurement and electrochemical impedance spectroscopy (EIS). The sensor response is estimated at about 20% to 10 ppm ethanol vapor, with the response and recovery times about 3.2 s and 0.8 s, respectively. Sensing mechanism proposed to... 

In planar perovskite solar cells (PSCs), engineering the extraction and recombination of electron–hole pairs by modification of the electron transport layer (ETL)/perovskite interface is very vital for obtaining high performance. The main idea here is to improve properties of the TiO2/perovskite interface by inserting an ultra-thin layer (UTL) of WO3 or SnO2 with the thickness of less than 10 nm by RF magnetron sputtering method. The structural and electrical characteristics of the samples were tested by XRD, AFM, FE-SEM, Mott-Schottky analysis, UV–Vis spectroscopy, J-V characterization and electrochemical impedance spectroscopy (EIS). It was found that the bilayer structured ETLs exhibit... 

Among the various approaches, ZnS treatment is the most convenient method for reducing the charge recombination in quantum dot-sensitized solar cells (QDSSCs). Here an improved method of ZnS treatment is explained for efficiency enhancement in QDSSCs. To get to the goal of device performance improvement, it is essential to have a uniform deposited layer. We utilized Triton X-100 (TX-100) as a surfactant to the convenient aqueous precursors during ZnS deposition by successive ionic layer adsorption and reaction method. It helps to decrease in contact angle and increase in wettability of the aqueous precursor and results in a more uniform deposited layer. The effect of modified ZnS treatment... 

The high charge carrier recombination rate and weak oxygen evolution kinetics have impeded the efficiency of WO3 photoelectrodes for water splitting. We present a novel type II heterojunction semiconductor based on mixed WS2 and MoS2 nanosheets on WO3 nanoflakes hydrothermally grown on highly porous W skeletons. The chemically exfoliated transition metal dichalcogenide (TMD) sheets with submicrometric lateral sizes were deposited on the surface of WO3 nanoflakes by the electrophoretic technique to fabricate a staggered gap heterojunction. The photoanode exhibited an impressive current density of 14.9 mA cm−2 at 1.23 VRHE which comprised ∼1.7 mA cm−2 photocurrent under 100 mW cm−2 simulated... 

TiO2 deposited on a membrane of Ag fibers was prepared as a photoelectrochemical cell electrode. Ag fibers were made by reduction of Ag complexes on cellulose fibers, followed by burning out the template. TiO 2 photocatalyst layers were grown on the fibers by electrophoretic deposition of TiO2 nanoparticles. Ag fibers could be uniformly deposited. Photocatalytic tests by dye decomposition and electrochemical impedance spectroscopy (EIS) under UV illumination demonstrate that Ag fibers act as a good substrate that provides both high surface area and good separation of photogenerated electron-hole pairs and causes the enhancement of photocatalytic activity in comparison with a thin film of... 

In this study, we have investigated the use of electrodeposited Au-Pt nanoparticles (AuPtNPs) on indium tin oxide (ITO) for the detection of Hg2+ heavy ions in water samples. The mechanism of AuPtNP electrocrystallization on ITO glass in an aqueous solution containing 0.5 mM HAuCl4 + 0.5 mM H2PtCl6 is described for the first time. The nucleation mechanism of monometallic AuNPs on ITO was found to be progressive; however, a transition from progressive to instantaneous was observed for bimetallic AuPtNPs at elevated overpotentials. The modified ITOs were then assessed for the electrodetection of Hg2+ in aqueous media. It was shown by differential pulse voltammetry (DPV) that the sensitivity of...