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    A comparative study on hydrogen interaction with defective graphene structures doped by transition metals

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Vol. 60 , June , 2014 , pp. 104-111 ; ISSN: 13869477 Lotfi, R ; Saboohi, Y ; Sharif University of Technology
    Abstract
    In the present work, the interaction of hydrogen molecules with defective graphene structures doped by transition metal (TM) atoms is investigated by using first principles density functional theory (DFT). Defective graphene structures include Stone-Wales (SW), 585 and 555-777 and transition metals include early TMs, i.e. scandium (Sc), titanium (Ti) and vanadium (V). It is found that in comparison with the pristine graphene, presence of defects significantly enhances the metal binding. Among three defects, 585 divacancy leads to the strongest binding between graphene and metal. Hydrogen adsorption is then evaluated by sequential addition of hydrogen molecules to the system. The results... 

    Study on the catalytic activity and theoretical modeling of a novel dual acidic mesoporous silica

    , Article RSC Advances ; Volume 4, Issue 32, 2014 , 2014 , Pages 16647-16654 ; ISSN: 20462069 Vafaeezadeh, M ; Fattahi, A ; Sharif University of Technology
    Abstract
    A novel mesoporous silica-functionalized dual Brønsted acidic species has been introduced as an efficient catalyst for solvent-free esterification of fatty acids with ethanol. The structure of the catalyst has been characterized by FT-IR spectroscopy, thermal gravimetric analysis (TGA), TEM and N2 adsorption-desorption. TGA of catalyst 1 showed no weight loss before 200 °C, indicating a high degree of hydrophobicity of the surface of the mesoporous silica. TEM images and nitrogen adsorption-desorption showed no noticeable changes to the structure of the catalyst before and after acid treatment. pH metric analysis was performed for the catalyst to determine the loading of the acidic sites.... 

    Adsorption isotherms and ideal selectivities of hydrogen sulfide and carbon dioxide over methane for the Si-CHA zeolite: Comparison of carbon dioxide and methane adsorption with the all-silica DD3R zeolite

    , Article Adsorption ; Volume 19, Issue 5 , 2013 , Pages 1045-1053 ; 09295607 (ISSN) Maghsoudi, H ; Soltanieh, M ; Bozorgzadeh, H ; Mohamadalizadeh, A ; Sharif University of Technology
    2013
    Abstract
    Adsorption isotherms of H2S, CO2, and CH4 on the Si-CHA zeolite were measured over pressure range of 0-190 kPa and temperatures of 298, 323, and 348 K. Acid gases adsorption isotherms on this type of zeolite are reported for the first time. The isotherms follow a typical Type-I shape according to the Brunauer classification. Both Langmuir and Toth isotherms describe well the adsorption isotherms of methane and acid gases over the experimental conditions tested. At room temperature and pressure of 100 kPa, the amount of CO2 adsorption for Si-CHA zeolite is 29 % greater than that reported elsewhere (van den Bergh et al. J Mem Sci 316:35-45 (2008); Surf Sci Catal 170:1021-1027 (2007)) for the... 

    The effects of multi-walled carbon nanotubes graphitization treated with different atmospheres and electrolyte temperatures on electrochemical hydrogen storage

    , Article Electrochimica Acta ; Volume 55, Issue 16 , June , 2010 , Pages 4700-4705 ; 00134686 (ISSN) Reyhani, A ; Nozad Golikand, A ; Mortazavi, S. Z ; Irannejad, L ; Moshfegh, A. Z ; Sharif University of Technology
    2010
    Abstract
    Using multi-walled carbon nanotubes (MWCNTs), the present study focuses on their electrochemical hydrogen storage capacities. The results showed that the hydrogen desorption process is composed of two steps with voltages around -0.75 and -0.15 V. Hydrogen adsorption at -0.15 V took place at temperatures above 30 °C, and the amount of energy required for adsorbing hydrogen was 1.68 eV. The hydrogen storage capacity increased with increasing electrolyte temperature from 30 to 60 °C in both steps. The hydrogen storage capacity of the MWCNTs treated at different atmospheres showed that the decrease in the graphitization of MWCNTs led to the increase in hydrogen adsorption. The results also... 

    Kinetics of oxygen adsorption on ZnS nanoparticles synthesized by precipitation process

    , Article Materials Science- Poland ; Volume 34, Issue 2 , 2016 , Pages 260-265 ; 20831331 (ISSN) Ahmadi, R ; Sadrnezhad, S. K ; Namivandi Zangeneh, R ; Oghabian, M. A ; Sharif University of Technology
    Walter de Gruyter GmbH 
    Abstract
    ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD), ultraviolet (UV) visible absorption and photoluminescence (PL) spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate... 

    New insight into H2S sensing mechanism of continuous SnO2-CuO bilayer thin film: A theoretical macroscopic approach

    , Article Journal of Physical Chemistry C ; Volume 120, Issue 14 , 2016 , Pages 7678-7684 ; 19327447 (ISSN) Boroun, Z ; Ghorbani, M ; Moosavi, A ; Mohammadpour, R ; Sharif University of Technology
    American Chemical Society  2016
    Abstract
    SnO2-CuO is one the most promising systems for detection of detrimental H2S gas. Although previous experimental research has suggested a sulfidation reaction to explain selectivity toward H2S, little is known about the origin of change of electrical response of this system by changing the H2S gas concentration. In this study the relation between sensing response of continuous SnO2-CuO bilayer thin film and H2S gas concentration is computed based on changeability of chemical composition of covellite CuxS. For this purpose, chemical activity of sulfur as a function of atomic fraction in covellite copper sulfide is estimated using Gibbs energies of formation and chemical thermodynamics. By... 

    Study of Absorption Enhancement of CO2 by SiO2, Al2O3, CNT, and Fe3O4 Nanoparticles in Water and Amine Solutions

    , Article Journal of Chemical and Engineering Data ; Volume 61, Issue 4 , 2016 , Pages 1378-1387 ; 00219568 (ISSN) Rahmatmand, B ; Keshavarz, P ; Ayatollahi, S ; Sharif University of Technology
    American Chemical Society 
    Abstract
    In this work, the absorption process of carbon dioxide is performed in a custom designed high pressure experimental setup in which the gas and nanofluid are in direct contact at static state in a closed vessel. The initial condition of the tests are set at 20, 30, and 40 bar and 308 K. Nanoparticles of SiO2, Al2O3, Fe3O4, and carbon nanotubes (CNTs) are dispersed in pure water to form nanofluids at concentrations of 0.02, 0.05, and 0.1 wt %. Also, CNT nanoparticle has been dispersed in methyldiethanolamine and diethanolamine aqueous solutions at the concentration of 0.02 wt %. The absorption performances of different nanofluids are compared with the base solutions and with other nanofluids... 

    DFT study of nitrogen monoxide adsorption and dissociation on Rh[sbnd]Cu nano clusters

    , Article Journal of Alloys and Compounds ; Volume 695 , 2017 , Pages 1924-1929 ; 09258388 (ISSN) Arab, A ; Nahali, M ; Gobal, F ; Sharif University of Technology
    Abstract
    Adsorption and dissociation of NO on RhxCu4-x(x = 0–4) nano clusters were investigated using density functional theory. Adsorption energy, total charge on NO, NO bond length, and NO vibrational frequency for various modes of NO adsorption were analyzed. Adsorption from the nitrogen end of NO on the Rh atom(s) of the clusters are more favored and adsorption energies are in the −1.02 eV to −2.59 eV range. NO binds stronger to Rh-Cu mixed clusters compared to pure Cu4 cluster, so N[sbnd]O bond is significantly weakened upon adsorption on the former. NO binding to more atoms of the clusters results in a corresponding decrease of the N[sbnd]O vibrational frequency. Dissociation of NO was also... 

    Ethylenediamine grafting to functionalized NH2-UiO-66 using green aza-Michael addition reaction to improve CO2/CH4 adsorption selectivity

    , Article Industrial and Engineering Chemistry Research ; Volume 57, Issue 20 , April , 2018 , Pages 7030-7039 ; 08885885 (ISSN) Molavi, H ; Ahmadi Joukani, F ; Shojaei, A ; Sharif University of Technology
    American Chemical Society  2018
    Abstract
    Three versions of zirconium-based metal organic frameworks, NH2-UiO-66, GMA-UiO-66, and EDA-UiO-66, were synthesized and employed as adsorbent for CO2/CH4 separation. GMA-UiO-66 was synthesized via a ring opening reaction between the amine species in the framework and epoxy groups in glycidyl methacrylate (GMA), while the green aza-Michael addition reaction was used for the first time to functionalize GMA-UiO-66 with ethylenediamine (EDA). The products were characterized by BET, XRD, TGA, FESEM, ICP-OES, 1H NMR, mass spectroscopy, and FTIR-ATR methods to monitor their textural properties before and after functionalization. The results indicated that GMA was successfully grafted to the... 

    Synthesis, characterization, and cesium sorption performance of potassium nickel hexacyanoferrate-loaded granular activated carbon

    , Article Particulate Science and Technology ; Vol. 32, issue. 4 , 2014 , pp. 348-354 ; ISSN: 02726351 Dashtinejad, M ; Samadfam, M ; Fasihi, J ; Grayeli Fumeshkenar, F ; Sepehrian, H ; Sharif University of Technology
    Abstract
    GAC has been modified by loading of potassium nickel hexacyanoferrate (KNiCF) as a new adsorbent for cesium adsorption. The potassium nickel hexacyanoferrate-loaded granular activated carbon (KNiCF-GAC) was characterized using powder x-ray diffraction (XRD) and nitrogen adsorption-desorption isotherm data, infrared spectroscopy, and its cesium adsorption performance in aqueous solution was investigated. The effect of the various parameters such as initial pH value of the solution, contact time, temperature, and initial concentration of the cesium ion on the adsorption efficiencies of KNiCF-GAC have been studied systematically by batch experiments. The adsorption isotherm of KNiCF-GAC was... 

    First principles study of oxygen adsorption on nickel-doped graphite

    , Article Molecular Physics ; Volume 110, Issue 13 , Feb , 2012 , Pages 1437-1445 ; 00268976 (ISSN) Nahali, M ; Gobal, F ; Sharif University of Technology
    2012
    Abstract
    Density functional theory is used in a spin-polarized plane wave pseudopotential implementation to investigate molecular oxygen adsorption and dissociation on graphite and nickel-doped graphite surfaces. Molecular oxygen physisorbs on graphite surface retaining its magnetic property. The calculated adsorption energy is consistent with the experimental value of 0.1eV. It is found that substituting a carbon atom of the graphite surface by a single doping nickel atom (2.8% content) makes the surface active for oxygen chemisorption. It is found that the molecular oxygen never adsorbs on doping nickel atom while it adsorbs and dissociates spontaneously into atomic oxygens on the carbon atoms... 

    Van der Waals energy surface of a carbon nanotube sheet

    , Article Solid State Communications ; Volume 152, Issue 3 , February , 2012 , Pages 225-230 ; 00381098 (ISSN) Motahari, S ; Shayeganfar, F ; Neek Amal, M ; Sharif University of Technology
    Abstract
    The van der Walls interaction between a carbon nanotube sheet (CNTS) and a rare gas atom, is studied using both atomistic and continuum approaches. We present analytical expressions for the van der Waals energy of continuous nanotubes interacting with a rare gas atom. It is found that the continuum approach does not properly treat the effect of atomistic configurations on the energy surfaces. The energy barriers are small as compared to the thermal energy, which implies the free motion above the CNTS in heights about one nanometer. In contrast to the energy surface of a graphene sheet, the honeycomb lattice structure in the energy surface of a CNTS is imperceivable. Defects alter the energy... 

    Theoretical study of nitrogen monoxide adsorption on small Six (x = 3-5) clusters

    , Article Molecular Physics ; Volume 109, Issue 2 , 2011 , Pages 229-237 ; 00268976 (ISSN) Nahali, M ; Gobal, F ; Sharif University of Technology
    2011
    Abstract
    Theoretical study of nitrogen monoxide adsorption on small Six (x = 3-5) clusters has been carried out using the advanced hybrid meta-density functional method of Truhlar (MPW1B95). MG3 semi-diffuse basis sets were employed to improve the results. The geometry, adsorption energy, natural bond orbital charge, natural population analysis (NPA)-derived spin density and vibrational frequency of NO adsorption on all optimized nanoclusters were investigated. Also using the NPA, we have investigated the change of bond orders through adsorption. It has been found that NO is capable of making n-centre bonds (n = 1-4) from the nitrogen side but bonds to one site from the oxygen end. In the later case... 

    Synthesis of magnetic mesoporous nanocomposites: A promising candidate for diagnostic and therapeutic biomedical applications

    , Article Materials Chemistry and Physics ; Volume 167 , November , 2015 , Pages 201-208 ; 02540584 (ISSN) Bagherzadeh, E ; Hosseini, H. R. M ; Khakzadian, J ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    In the present research, iron oxide nanoparticles were synthesized through the hydrothermal method, and the influence of processing parameters such as pH of the initial coprecipitation reaction, time and temperature of hydrothermal treatment was studied. The magnetic iron oxide nanoparticles were coated with a negatively charged, thin layer of silica. The product is then coated with a layer of mesoporous silica. As a result of the electrostatic attraction between the cationic CTAB and the primary silica coating, the formation of mesoporous silica would be mainly localized on the surface of nanoparticles. Calcination was performed in an argon atmosphere tube furnace at 550 °C, through which... 

    Removal of the CO2 from flue gas utilizing hybrid composite adsorbent MIL-53(Al)/GNP metal-organic framework

    , Article Microporous and Mesoporous Materials ; Volume 218 , 2015 , Pages 144-152 ; 13871811 (ISSN) Pourebrahimi, S ; Kazemeini, M ; Ganji Babakhani, E ; Taheri, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    Abstract In this study, adsorption of the CO2 and N2 gases on the MIL-53(Al) and its hybrid composite with the graphene nano-plates (GNP), MIL-53(Al)/GNP, adsorbents were investigated. These materials were synthesized using the solvothermal reaction method. The prepared samples were characterized by means of the powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), N2 adsorption-desorption isotherms (BET-BJH surface area measurement) and Fourier transfer infrared (FT-IR) spectroscopy methods as well as; thermogravimetric analysis (TGA). Adsorption equilibrium of the CO2 and N2 on the sorbents were... 

    Ionic liquid-based ordered mesoporous organosilica-supported copper as a novel and efficient nanocatalyst for the one-pot synthesis of Biginelli products

    , Article Microporous and Mesoporous Materials ; Volume 204, Issue C , 2015 , Pages 269-275 ; 13871811 (ISSN) Elhamifar, D ; Hosseinpoor, F ; Karimi, B ; Hajati, S ; Sharif University of Technology
    Abstract
    The preparation, characterization and catalytic application of a novel copper-loaded ionic liquid-based periodic mesoporous organosilica (Cu@PMO-IL) are described. The mesoporous structure of the Cu@PMO-IL material is characterized by transmission electron microscopy (TEM) and nitrogen adsorption-desorption analysis. The thermal stability of the material is also determined by thermal gravimetric analysis (TGA). The presence of copper species in the material framework is confirmed by X-ray photoelectron spectroscopy (XPS) and elemental analysis (EA). The catalytic application of Cu@PMO-IL nanocatalyst is then investigated in the Biginelli condensation of different aldehydes with urea and... 

    Modeling hydrogen fluoride adsorption by sodium fluoride

    , Article Journal of Industrial and Engineering Chemistry ; Volume 16, Issue 6 , November , 2010 , Pages 978-985 ; 1226086X (ISSN) Afzal, S ; Rahimi, A ; Ehsani, M. R ; Tavakoli, H ; Sharif University of Technology
    2010
    Abstract
    In the current study, hydrogen fluoride (HF) adsorption onto the sodium fluoride pellets is modeled. For this purpose a two-dimensional, non-isothermal model was developed and the governing equations were solved numerically. The contributions of diffusion transport in axial and radial directions also were considered in mathematical formulations. The model results of effluent concentration and breakthrough curves of HF were compared with the experimental data obtained in a lab-scale adsorption unit, reported in our previous work [1]. The results indicate while the feed gas velocity decreases, the HF adsorption capacity on NaF is significantly enhanced and there is a delay in breakthrough... 

    Production of granulated-copper oxide nanoparticles for catalytic application

    , Article Journal of Materials Research ; Volume 25, Issue 10 , 2010 , Pages 2025-2034 ; 08842914 (ISSN) Hosseinpour, M ; Ahmadi, S. J ; Mousavand, T ; Outokesh, M ; Sharif University of Technology
    2010
    Abstract
    Ultra fine CuO nanoparticles In the range of 2 ± 0.2 nm were synthesized by the supercritical hiydrotliermal method in a batch reactor. Itwas demonstrated that elevating the pH of the Cu2+ precursor solution to around 6 (neutral condition) not only does not lead to excessive agglomeration of the particles, but also reduces particle size and in general promotes their nanoscale characteristics. Prepared nanoparticles were immobilized in the biopolymcric matrix of barium alginate and calcined at different temperatures resulting in micro spherical granules of high porosity and elevated mechanical strength. The fabricated samples were characterized using x-ray diffractometry (XRD), transmission... 

    A study on the effects of Fex/Niy/MgO(1-x-y) catalysts on the volumetric and electrochemical hydrogen storage of multi-walled carbon nanotubes

    , Article International Journal of Hydrogen Energy ; Volume 35, Issue 1 , 2010 , Pages 231-237 ; 03603199 (ISSN) Reyhani, A ; Mortazavi, S. Z ; Zaker Moshfegh, A ; Nozad Golikand, A ; Sharif University of Technology
    Abstract
    The effects of various ratios of Fe/Ni/MgO and growth temperatures on yield, diameter and quality of multi-walled carbon nanotubes (MWCNTs) were studied. Thermal gravimetric analysis (TGA) confirmed that the MWCNT yield depends on Fe/Ni ratio with the following order; Fe0.5 Ni0.5 > Fe > Fe0.75 Ni0.25 > Fe0.25 Ni0.75 > Ni. The results indicated that there is an optimum temperature (940 °C) for the MWCNT growth both from quality and quantity (yield) aspects as compared to other temperatures. Moreover, the changes on Fe/Ni to MgO ratio for the MWCNT growth revealed that Fe/Ni/MgO with the ratio of 17.5/17.5/65 had the highest quality and surface area as compared to the other ratios. The... 

    Solid state preparation and photocatalytic activity of bismuth oxybromide nanoplates

    , Article Research on Chemical Intermediates ; Volume 42, Issue 3 , 2016 , Pages 2429-2447 ; 09226168 (ISSN) Bijanzad, K ; Tadjarodi, A ; Akhavan, O ; Moghaddasi Khiavi, M ; Sharif University of Technology
    Springer Netherlands  2016
    Abstract
    A mechanochemical method was applied to prepare bismuth oxybromide (BiOBr) nanoplates using bismuth nitrate pentahydrate and potassium bromide for 15 (A15), 30 (A30) and 60 (A60) minutes. Scanning electron microscopy studies showed that all the products were comprised of nanoplates. Aggregated nanoplates along with microblocks were observed for A15 and A30 and the entire morphology was not homogenous. The morphology of A60 was uniform and consisted of thin and isolated nanoplates. Evaluation of the X-ray diffraction patterns showed that the purity and crystallinity of the products improved by increasing the milling time. The energy dispersive X-ray analysis confirmed the high purity of the...