Search for: spectroscopy
Total 1296 records
Article Physica Status Solidi (B) Basic Research ; Volume 248, Issue 11 , OCT , 2011 , Pages 2639-2643 ; 03701972 (ISSN) ; Petaccia, L ; Wang, Y ; Quian, H ; Farjam, M ; Jafari, S. A ; Sachdev, H ; Federov, A. V ; Usachov, D ; Vyalikh, D. V ; Liu, X ; Vilkov, O ; Adamchuk, V. K ; Irle, S ; Knupfer, M ; Büchner, B ; Grüneis, A ; Sharif University of Technology
Tailoring the electronic properties of graphene is of fundamental interest regarding its application in electronic devices. One of the key strategies is chemical functionalization which modifies the p-electron system and thus can induce band gaps. However, in order to control the degree of functionalization it is crucial to know the exact amount of the chemisorbed species. We show with angle-resolved photoemission spectroscopy (ARPES) the formation of a band gap in graphene and estimate the hydrogen coverage from the scattering rate. Using X-ray photoemission spectroscopy (XPS) we identify the chemical environments in hydrogenated graphene and determine the total hydrogen to carbon...
Synthetic study of symmetrical and unsymmetrical schiff base complexes of VO(IV) and Mn(III) derived from 2,2′-diaminobiphenyl, Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 35, Issue 4 , 2005 , Pages 261-267 ; 15533174 (ISSN) ; Behzad, M ; Sharif University of Technology
The symmetrical and unsymmetrical Schiff base complexes of VO(IV) and Mn(III) derived from 2,2′-diaminobiphenyl and derivatives of salicylaldehyde and 1-hydroxy-2-napnthaldehyde have been synthesized and characterized by elemental analysis, NMR, infrared and electronic absorption spectroscopies, and conductivity measurements. The reaction of the ligands with oxovanadium(IV) was found to be kinetically unfavored, probably due to the small ionic radius of the metal ion, which is not in accordance with the cavity size of the ligands. Copyright © 2005 Taylor & Francis, Inc
Effect of concentration on hydrodynamic size of magnetite-based ferrofluid as a potential MRI contrast agent, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; 2013 ; 09277757 (ISSN) ; Gu, N ; Sharif University of Technology
In this work, ferrofluids containing dextran coated magnetite nanoparticles have been synthesized via co-precipitation method. FT-IR results verified presence of dextran molecules on the particles surface. TEM results showed that mean particle size is 7.23 nm, while mean hydrodynamic size determined via PCS technique varies between 39.8 and 125.8 nm depending on the ferrofluid concentration. The maximum hydrodynamic size was obtained in mid concentrations. To the best of our knowledge, effect of concentration on mean hydrodynamic size has not been systematically studied before. VSM results confirmed the superparamagnetic behavior of the synthesized nanoparticles with saturation magnetization...
Article Vacuum ; Volume 84, Issue 4 , 8 December , 2009 , PP. 469-473 ; Iraji Zad, A. (Azam) ; Ahadian, M. M. (Mohammad M.) ; Sharif University of Technology
We report experimental evidence of Cu surface segregation in Ni/Cu system, during deposition of Ni film onto Cu substrate at room temperature and during heat treatment in vacuum. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) by Tougaard's analysis results show that surface segregation defeats in competition with increase in Ni thickness and terminates when thickness of Ni increase to more than 4 nm. Surface energy and concentration were calculated using contact angle measurements and the results confirm that segregation reduces the surface energy. Surface segregation during heat treatment at 150–220 °C range as a function of time initially shows linear mass...
Article Journal of Solid State Electrochemistry ; Volume 14, Issue 4 , 2010 , Pages 643-650 ; 14328488 (ISSN) ; Gobal, F ; Raissi, H ; Moghiminia, S ; Sharif University of Technology
Nanostructured molybdenum oxide was potentiodynamically deposited onto a stainless steel surface from an aqueous bath by cycling the potential between 0 and -0.75 V vs. Ag/AgCl. The deposit consisted of particulates in the range of 30 to 80 nm. Electrochemical studies under galvanostatic charge/discharge and also impedance spectroscopy revealed capacitive behavior in the potential range of -0.3 to -0.55 V vs. Ag/AgCl with the value of 477 F g-1 at 0.1 mA/cm2. An equivalent circuit comprising of three parallel branches consisting of double-layer capacitance, Warburg impedance, and a constant phase element signifying pseudo-capacitance each coupled with their corresponding resistances was...
Reproducible electrochemical analysis of nanostructured Cu2O using a non-aqueous 3-methoxypropionitrile-based electrolyte, Article Electrochemistry Communications ; Volume 86 , 2018 , Pages 1-5 ; 13882481 (ISSN) ; Iraji zad, A ; Mohammadpour, R ; Sharif University of Technology
Elsevier Inc 2018
Cu2O is an attractive material in terms of semiconducting properties and is considered a leading candidate in all-oxide photovoltaics. Electrochemical analysis of Cu2O, including Mott-Schottky (MS) and impedance spectroscopy (IS), provides a wealth of data on charge carriers, Fermi level and interface properties. MS and IS are usually measured in aqueous solutions. However, Cu2O is easily reduced or oxidized to Cu or CuO in aqueous solutions, the layer peels off after the analysis and there is a small voltage window for the tests. In some cases, an anti-corrosive n-type barrier layer is employed on top of the bare Cu2O electrode to make the measurement possible, which could result in...
Synthesis, characterization, electrochemical studies and catecholase-like activity of a series of mononuclear Cu(II), homodinuclear Cu(II)Cu(II) and heterodinuclear Cu(II)Ni(II) complexes of a phenol-based compartmental ligand, Article Journal of Molecular Catalysis A: Chemical ; Volume 241, Issue 1-2 , 2005 , Pages 1-7 ; 13811169 (ISSN) ; Behzad, M ; Bezaatpour, A ; Sharif University of Technology
A series of previously reported mononuclear Cu(II) and homodinuclear Cu(II)Cu(II) complexes, as well as, novel mononuclear Cu(II), homodinuclear Cu(II)Cu(II), and heterodinuclear Cu(II)Ni(II) complexes of a phenol-based dinucleating ligand with two different N(amine)2O2 and N(imine)2O2 coordination sites, were synthesized and characterized by elemental analyses, infrared and electronic absorption spectroscopies and conductivity measurements. The electrochemical behavior and catecholase-like activity of the complexes were also studied using cyclic voltammetry and UV-vis spectrophotometry, respectively. Our results show that the dinuclear complexes are more effective catalysts in the oxidation...
Formation of carbon nanotubes in Iron-catalyzed arcing method: Effect of iron-ion charge in the aqueous medium [electronic resource], Article International Journal of Modern Physics B Condensed Matter Physics; Statistical Physics; Atomic, Molecular and Optical Physics ; 30 December 2011, Volume 25, Issue 32, PP. 4411-4417 ; Gheytani, S ; Simchi, A. (Abdolreza) ; Sharif University of Technology
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
Synthesis and thermogravimetric analysis of inclusion complexes of O2N2-donor Aza-crown macrocyclic ligands with fullerene, Article Journal of Thermal Analysis and Calorimetry ; Volume 118, Issue 3 , 2014 , pp 1631-1637 ; ISSN: 13886150 ; Gholamnezhad, P ; Hatami, M ; Sharif University of Technology
A simple method for the formation of inclusion complex of fullerene with two O2N2-donor aza-crown macrocyclic ligands was introduced. The products were characterized using UV-vis and IR spectroscopies as well as HPLC, and ESI mass spectrometry. The ESI mass and elemental analysis data revealed that the ratio of macroring:fullerene were not the same. The binding capability of the macrorings as well as the number of the macroring addends to fullerene were investigated using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Considering percentage mass loss in different steps of TG and the enthalpy changes in DSC found for each of these products, the number...
Formation of carbon nanotubes in iron-catalyzed liquid arcing method: Effect of iron-ion charge in the aqueous medium, Article International Journal of Modern Physics B ; Volume 25, Issue 32 , 2011 , Pages 4411-4417 ; 02179792 (ISSN) ; Gheytani, S ; Simchi, A ; Sharif University of Technology
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
Article Iranian Journal of Physics Research ; Volume 14, Issue 4 , 2015 , Pages 351-360 ; 16826957 (ISSN) ; Irjizad, A ; Samadpoor, M ; Sharif University of Technology
Isfahan University of Technology 2015
In this research, solar cells sensitized with CdS and PbS Nanocrystalline metal sulfides, chemically grown by SILAR, were fabricated and characterized. PV experiments including I-V test in the presence of light and dark,Vocdecay, and Electrochemical impedance spectroscopy were performed on the Cells made through this method in the presence of light and dark and in the time period of 2, 3, 6 and 10 days. From these experiments, the changes in indicators including fill factor, efficiency, open-circuit voltage, short-circuit current, lifetime of electrons in nanostructured anode electrode, recombination resistance and capacitance of the anode electrode-electrolyte interface were observed. Also,...
Article Materials Research Express ; Volume 5, Issue 4 , April , 2018 ; 20531591 (ISSN) ; Iraji Zad, A ; Berahman, M ; Aghakhani Mahyari, F ; Hosseini Shokouh, S. H ; Sharif University of Technology
Institute of Physics Publishing 2018
Due to high surface to volume ratio and tunable band gap, two dimensional (2D) layered materials such as MoS2, is good candidate for gas sensing applications. This research mainly focuses on variation of Density of States (DOS) of MoS2 monolayes caused by ethanol adsorption. The nanosheets are synthesized by liquid exfoliation, and then using Scanning Tunneling Spectroscopy (STS) and Density Functional Theory (DFT), local electronic characteristic such as DOS and band gap in non-vacuum condition are analyzed. The results show that ethanol adsorption enhances DOS and deform orbitals near the valence and conduction bands that increase transport of carriers on the sheet. © 2018 IOP Publishing...
A green and efficient route for P − S − C bond construction using copper ferrite nanoparticles as catalyst: a TD-DFT study, Article Phosphorus, Sulfur and Silicon and the Related Elements ; 26 October , 2020 ; Daneshfar, M ; Azaryan, R ; Sharif University of Technilogy
Taylor and Francis Ltd 2020
Magnetic nanoparticles of CuFe2O4 were applied as catalyst system for one-pot thiophosphate synthesis via the reaction of aryl sulfonyl chlorides with H-phosphonates under conventional heating conditions. This is an extremely efficient and green method for thiophosphate synthesis under base- and solvent-free conditions. Various thiophosphates were obtained in good to excellent yields under the optimized reaction conditions in a short time. The catalyst can be easily recycled from the reaction by an external magnetic field and reused for the next run. In this study, TD-DFT B3LYP/6-31 + G(d) calculations are in good accord with the experimental results. A comparison between experimental and...
Theoretical simulation of surface-enhanced resonance Raman spectroscopy of cytosine and its tautomers, Article Journal of Raman Spectroscopy ; Volume 51, Issue 1 , 2020 , Pages 55-65 ; Mohammadpour, M ; Ramazani, S ; Jamshidi, Z ; Sharif University of Technology
John Wiley and Sons Ltd 2020
The primary challenge of spectroscopic techniques in selective detection and characterization of tautomeric structures of DNA and RNA bases, and moreover, the accurate interpretation and explanation of the experimental results are the main motives of theoretical studies. Surface-enhanced Raman spectroscopy (SERS) can be a powerful approach to distinguish cytosine in the presence of its tautomers. For this respect, herein, the theoretical simulation of the SERS spectra of cytosine and its three most stable tautomers adsorbed on silver clusters is carried out. The calculations of SERS spectra is based on the excited-state energy gradient approximation as a well-established approach that gives...
Role of herzberg-teller vibronic coupling in surface-enhanced resonance raman spectra of 4,4′-diaminotolane with nearly close molecular and charge-transfer transitions, Article Journal of Physical Chemistry C ; Volume 125, Issue 31 , 2021 , Pages 17202-17211 ; 19327447 (ISSN) ; Ashtari Jafari, S ; Smirnov, A ; Solovyeva, E. V ; Sharif University of Technology
American Chemical Society 2021
We have investigated the surface-enhanced resonance Raman spectroscopy (SERRS) for 4,4′-diaminotolane absorbed on silver experimentally and theoretically. Experimental observation shows greatly enhanced bg symmetric modes ν26 and ν27, which are silent in normal Raman spectroscopy and SERS on gold. The dependence of the surface-enhanced Raman spectroscopy (SERS) spectra on five excitation lines has also been registered and classified for single bands into three profiles referring to the different contributions of resonant transitions. Theoretical calculations based on the time-dependent path integral formalism by including the Herzberg-Teller correction reproduce the experimental spectra with...
Simultaneous determination of theophylline and caffeine by proton magnetic resonance spectroscopy using partial least squares regression techniques, Article Analytical Sciences ; Volume 19, Issue 7 , 2003 , Pages 1079-1082 ; 09106340 (ISSN) ; Maesum, S ; Jalali Heravi, M ; Shamsipur, M ; Sharif University of Technology
Japan Society for Analytical Chemistry 2003
A 1H-NMR procedure based on an analysis of its data by a multivariate calibration method was conducted for the simultaneous determination of theophylline and caffeine in synthetic and real samples. Partial least squares regression (PLS) was chosen as the calibration method. The methyl signals of theophilline at 3.36 and 3.54 ppm that overlapped with those of caffeine were significant characteristics which were employed in this study for their analyses. The proposed method was successfully applied to recovery studies of theophylline and caffeine from real tablet samples
Article Journal of Electroanalytical Chemistry ; Volume 542 , 2003 , Pages 67-74 ; 15726657 (ISSN) ; Hosseini, M ; Arshadi, M. R ; Ritson, D ; Young, K. L ; Nichols, R. J ; Sharif University of Technology
The specific adsorption of citrate from perchloric acid electrolytes, has been investigated using in-situ FTIR spectroscopy at Au(1 1 1) electrodes. For comparison IR spectra for formate adsorption are also presented. Clear voltammetric peaks have been observed positive of the pzc and these are shown by FTIR spectroscopy to be associated with the adsorption of citrate. Models for the surface co-ordination of the citrate anion are discussed. © 2002 Elsevier Science B.V. All rights reserved
Article Starch/Staerke ; Volume 59, Issue 11 , 2007 , Pages 557-562 ; 00389056 (ISSN) ; Seidi, F ; Salimi, H ; Sharif University of Technology
Eight new chitin derivatives have been synthesized via SN2 reaction of primary and secondary amines with tosylchitin. The products were characterized using FTIR and 1H NMR spectroscopy. A degree of substitution ∼ 1 was achieved through this process. These materials are soluble in water at room temperature, which enable their further applications in the future. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA
CMC-g-poly (sodium acrylate)/kaolin superabsorbent hydrogel composites: Synthesis, characterization and swelling behaviour, Article Polymers and Polymer Composites ; Volume 14, Issue 7 , 2006 , Pages 701-712 ; 09673911 (ISSN) ; Ghasemzadeh, H ; Sharif University of Technology
Rapra Technology Ltd 2006
A novel superabsorbent composite system based on carboxymethyl cellulose (CMC) was prepared by graft copolymerization of acrylic acid (AA) in the presence of kaolin powder using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. The effect of reaction variables, such as MBA, AA, and APS concentration and CMC/kaolin ratio on the water absorbency of the composite were studied. Evidence of grafting and kaolin interaction was obtained by comparing the FT-IR spectra of the initial substrates with that of the superabsorbent composite. The results indicated that with increasing amount of kaolin, the swelling capacity was increased and then...
Ugi four-component assembly process: An efficient approach for one-pot multifunctionalization of nanographene oxide in water and its application in lipase immobilization, Article Chemistry of Materials ; Volume 28, Issue 9 , 2016 , Pages 3004-3016 ; 08974756 (ISSN) ; Akhavan, O ; Hashemi, E ; Shamsara, M ; Sharif University of Technology
American Chemical Society 2016
Graphene-based materials are revealing the leading edge of advanced technology for their exceptional physical and chemical properties. Chemical manipulation on graphene surface to tailor its unique properties and modify atomic structures is being actively pursued. Therefore, the discovery of robust and general protocols to anchor active functionality on graphene basal plane is still of great interest. Multicomponent reactions promise an enormous level of interest due to addressing both diversity and complexity in combinatorial synthesis, in which more than two starting compounds react to form a product derived from entire inputs. In this article, we present the first covalent...