Sharif Digital Repository

Designing efficient and inexpensive catalysts toward the oxygen evolution reaction (OER) is vital for achieving sustainable and green hydrogen fuel production through water electrolysis. Herein, we have synthesized several bi- and trimetallic metal–organic frameworks (MOFs) composed of Co, Ni, and Mn metals and benzene-1,3,5-tricarboxylic acid linker. The MOFs were prepared via a simple hydrothermal method, and their electrocatalytic performances in alkaline OER were investigated. A battery of analytical techniques was employed to characterize the as-synthesized materials, including field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM),... 

The oxygen evolution reaction (OER) with its sluggish kinetics has imposed a significant barrier to the sustainable and green generation of hydrogen fuel (via electrolysis of water) and the development of metal-air batteries. In this study, we report an efficient and novel OER electrocatalyst based on NiSe2nanoparticles (NPs) and the naturally abundant halloysite clay mineral. The NiSe2/halloysite nanocomposite (NiSe2/H) was prepared by a simple one-step hydrothermal route. The electrocatalytic performance of the as-synthesized nanocomposite and its components (pristine NiSe2and halloysite) toward OER in 1.0 KOH solution was examined. The NiSe2/H nanocomposite exhibited a significantly... 

This study investigates the synthesis of CuCo2O4, BiVO4, and CuCo2O4/BiVO4 nanocomposite by the solvothermal method. The Physico-chemical properties of the samples were verified through Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Transmission Electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET). Evaluation of catalytic efficiency of the synthesized samples were done in promoting the 4-Nitrophenol reduction to 4-Aminophenol in the existence of high amount of sodium borohydride (NaBH4) as a reducing agent, and the progress of the catalytic reaction was monitored... 

La-MOF-NH2@Fe3O4 (magnetic-MOF) was used as an efficient, ultrafast, and selective adsorbent for the separation of Congo Red (CR) with 92.02% removal after 2 min. The magnetic-MOF was identified by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, Zeta Potential analysis, analysis of the magnetic hysteresis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Kinetics, isotherms, the effect of pH, thermodynamic, and selectivity of CR adsorption were investigated. The results confirmed that the adsorption kinetics complied with the pseudo-second-order model. The... 

Novel Bi2S3/NiCo2O4 nanocomposites (BS/NCO) with various mass ratios were prepared using NiCo-MOF as precursor. The morphology, composition and structure of the as-prepared catalysts were studied by different techniques such as FE-SEM, EDX, XRD, FT-IR, VSM and BET. The as-synthesized composite with 20 % Bi2S3 (%20 BS/NCO) demonstrated the best performance in reduction reaction of 4-nitrophenol (4-NP). The enhanced catalytic activity of %20 BS/NCO composite compared to the Bi2S3 and NiCo2O4 can be assigned to the optimized synergistic effects between the two pristine materials. Thermodynamic parameters and the activation energy of the reaction in the presence of %20 BS/NCO composite were... 

In this study, a series of Zirconium-based MOF and chitosan composites (MOF-808/chitosan) were synthesized as efficient adsorbent for Cr(VI) ions elimination from aqueous solution. MOF-808/chitosan structure and morphology was characterized by FE-SEM, EDX, XRD, BET, zeta potential analysis, FT-IR, XPS techniques. The kinetic studies ascertained that Cr(VI) adsorption over MOF-808/chitosan followed pseudo-second-order kinetic model. The adsorption isotherms fitted the Langmuir isotherm model, implying on homogeneously adsorption of Cr(VI) on the surface of MOF-808/chitosan. According to the Langmuir model, the maximum capacity was obtained to be 320.0 mg/g at pH 5. Thermodynamic investigation... 

In this study, a series of heteroatoms including nitrogen, oxygen, and sulfur were added to different positions of the model asphaltene structure to study the effect of the heteroatom presence in the self-aggregation of the model asphaltenes. Molecular Dynamics was used to calculate Solubility Parameters, Radial Distribution Function, and Relative Solubility Parameters. Additionally, Reactivity Parameters, Electrostatic Potential, Reduced Density Gradient, and Independent Gradient Model were calculated using the Density Functional Theory to further investigate the Molecular Dynamics results. This study indicated that heteroatoms' diversity and their positions in the model asphaltene... 

In this work Halloysite nanotubes were used to synthesis a series of modified acrylamide/Quince seeds-based hydrogels (Poly (AAm-co-QS)/Haln). The as-prepared Poly (AAm-co-QS)/Haln hydrogels displayed improved performance as adsorbent in elimination of methylene blue (MB) from aqueous solution. The structures of the prepared Poly (AAm-co-QS)/Haln hydrogels were identified by XRD, FT-IR, FE-SEM, BET, TGA and EDX. Effect of pH value on the swelling behavior and dye adsorption performance of as-prepared hydrogels was explored. The adsorption MB results suggested that the adsorption kinetics fitted the pseudo-second-order model. The adsorption experiments at various pH condition indicated that... 

The electric field of the modes of semiconductor microring lasers (SMRLs) in the presence of bus waveguide reflections are linear combinations of the clock wise (CW) and the counter clock wise (CCW) electric fields. The mode structures can be controlled by the waveguide reflection coefficients. The power ratio and phase difference of the CW and CCW fields of one mode is proportional to the ratio of the reflection coefficients of the left and right waveguides. It is shown that the degenerate CW and CCW modes in the presence of bus waveguide reflections are split into two modes with different frequencies. Employing these new modes, SMRL can be used as an element to design flip-flops used in... 

Silver-doped indium tin oxide thin films were synthesized using sol-gel dip-coating technique. The influence of different silver-dopant contents and annealing temperature on the electrical, optical, structural, and morphological properties of the films were characterized by means of four-point probe, UV-Vis spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscope (XPS). XRD analysis confirmed the formation of cubic bixbyte structure of In2O3with silver nanoparticles annealed at 350 °C. XPS analysis showed that divalent tin transformed to tetravalent tin through oxidization, and silver nanoparticles embedded into ITO... 

Abstract: This study aimed to understand the microstructural, optical, and electrical properties of tin-doped indium oxide (ITO) prepared with tetravalent and divalent tin salts. The influence of tin valence on the electrical, optical, structural, and morphological properties of the films were characterized by the mean of four-point probe, thermogravimetric analysis, differential thermal analysis (DTA), UV–Vis spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscope. XRD results revealed formation of cubic bixbyite structure of In2O3 with a small shift in major peak position toward lower angles with... 

The endurance time method (ET) is a dynamic analysis procedure in which intensifying dynamic excitations are used as the loading function. Seismic performance is evaluated over the entire range of equivalent seismic intensities of interest in each response history analysis, considerably reducing computational demand. In this paper, a general methodology for performance-based retrof itting of typical steel frames by the ET method is discussed. A baseline steel momentresisting frame is considered, and its seismic performance is evaluated by the ET method, considering viscous dampers and shear wall panels as strengthening alternatives. Each retrof itting option includes several design... 

In the Endurance Time (ET) method, structures are subjected to a calibrated intensifying accelerogram and their performance is assessed based on their response at various equivalent intensity levels. Application of the ET method in performance-based design of structures has been studied by introducing a continuous performance target curve, which expresses the limit of the proper seismic performance of a structure along various times of the ET accelerogram. The correlation between time in the ET method and the return period for different structural periods is investigated. The procedure is based on the coincidence of response spectra obtained from the ET accelerogram at different times and...