Search for: nanoclusters
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    A novel 12-molybdovanadate nanocluster: synthesis, structure investigation and its application as an efficient heterogeneous sulfoxidation catalyst

    , Article Inorganic Chemistry Communications ; Volume 83 , 2017 , Pages 103-108 ; 13877003 (ISSN) Amini, M ; Sheykhi, A ; Naslhajian, H ; Bayrami, A ; Bagherzadeh, M ; Holynska, M ; Sharif University of Technology
    Tetraethylammonium salt of a new keggin-type 12-molybdovanadate nanocluster, [(C2H5)4N]4[VMo12O40] (1) was synthesized via reaction between sodium tungstate, ammonium vanadate and tetraethylammonium bromide in acidic medium. Compound 1 was characterized by X-ray crystallography, FT-IR, UV–Vis and cyclic voltammetry and then applied as an efficient heterogeneous catalyst to oxidation of various organosulfides to sulfoxides with H2O2 at room temperature with 81–100% conversion and 60–99% selectivity. Nanocluster 1 was also shown to display excellent recyclability – it can be reused more than 10 times. © 2017 Elsevier B.V  

    Selective oxidation of organosulfurs with a sandwich-type polyoxometalate/hydrogen peroxide system

    , Article Polyhedron ; Volume 186 , 1 August , 2020 Naslhajian, H ; Amini, M ; Dastyar, M. A ; Bayrami, A ; Bagherzadeh, M ; Farnia, S. M. F ; Janczak, J ; Sharif University of Technology
    Elsevier Ltd  2020
    A dimeric tungstophosphate, Na14[Co4(PW9O35)2].28H2O (1), was synthesized via a simple one-pot method and characterized by single-crystal X-ray crystallography. Nanocluster 1 was exhibited to be able to selective oxidation of aliphatic and aromatic sulfides to sulfoxides in the presence of hydrogen peroxide at room temperature with high performance. Further investigations showed that this catalyst could reuse four times without a significant reduction in its activity for the oxidation of methyl phenyl sulfide. © 2020 Elsevier Ltd  

    Theoretical study of the thermodynamic parameters of (CaO)n nanoclusters with n = 2–16 in the gas and solution phases: proton affinity, molecular basicity, and pKb values

    , Article Structural Chemistry ; Volume 30, Issue 5 , 2019 , Pages 1805-1818 ; 10400400 (ISSN) Zobeydi, R ; Nazari, P ; Rahman Setayesh, S ; Sharif University of Technology
    Springer New York LLC  2019
    Thermodynamic quantities such as proton affinity (PA) and molecular basicity (GB) for (CaO)n nanoclusters with n = 2–16 have been calculated using three computational models of the density functional theory (DFT) (Becke, 3-parameter, Lee-Yang-Parr (B3LYP), Minnesota 2006, Perdew-Wang 1991 (PW91), Coulomb attenuated method-B3LYP, and ωB97XD functionals); Møller-Plesset perturbation theory; and Hartree-Fock with the cc-PVNZ (n = D and T) basis set in the gas phase. Absolute deviation error (AAD%) indicates that obtained PA and GB values using DFT model and the B3LYP method with mean percentage errors of 0.77 and 0.90%, respectively, have the higher accuracy than the other methods and models.... 

    Effects of ligands on (de-)enhancement of plasmonic excitations of silver, gold and bimetallic nanoclusters: TD-DFT+TB calculations

    , Article Physical Chemistry Chemical Physics ; Volume 23, Issue 33 , 2021 , Pages 17929-17938 ; 14639076 (ISSN) Asadi Aghbolaghi, N ; Pototschnig, J ; Jamshidi, Z ; Visscher, L ; Sharif University of Technology
    Royal Society of Chemistry  2021
    Metal nanoclusters can be synthesized in various sizes and shapes and are typically protected with ligands to stabilize them. These ligands can also be used to tune the plasmonic properties of the clusters as the absorption spectrum of a protected cluster can be significantly altered compared to the bare cluster. In this paper, we computationally investigate the influence of thiolate ligands on the plasmonic intensity for silver, gold and alloy clusters. Using time-dependent density functional theory with tight-binding approximations, TD-DFT+TB, we show that this level of theory can reproduce the broad experimental spectra of Au144(SR)60 and Ag53Au91(SR)60 (R = CH3) compounds with... 

    Planar molecular dynamics simulation of Au clusters in pushing process

    , Article International Journal of Nanomanufacturing ; Vol.5, No.3/4 , 2010 , pp.288-296 Mahboobi, S. H ; Meghdari, A. (Ali) ; Jalili, N. (Nader) ; Amiri, F. (Farshid) ; Sharif University of Technology
    Based on the fact that the manipulation of fine nanoclusters calls for more precise modelling, the aim of this paper is to conduct an atomistic investigation for interaction analysis of particle-substrate system for pushing and positioning purposes. In the present research, 2D molecular dynamics simulations have been used to investigate such behaviours. Performing the planar simulations can provide a fairly acceptable qualitative tool for our purpose while the computation time is reduced extremely in comparison to 3D simulations. To perform this study, Nose-Hoover dynamics and Sutton-Chen interatomic potential will be used to investigate the behaviour of the aforementioned system. Pushing of... 

    Investigations for gas-phase deprotonation of the silica-propyl-SO3H catalyst using cage-like nanocluster modeling technique

    , Article Journal of the Iranian Chemical Society ; Volume 12, Issue 11 , November , 2015 , Pages 1991-1997 ; 1735207X (ISSN) Vafaeezadeh, M ; Hashemi, M. M ; Sharif University of Technology
    Springer Verlag  2015
    Exploring deprotonation properties of silica-functionalized propylsulfonic acid catalyst (silica-propyl-SO3H) is the subject of various experimental and theoretical researches. In the current study, the structure of the silica-propyl-SO3H has been simulated using density functional theory (DFT) methods by mimicking the surface of the silica in the form of cubic cage-like nanoclusters of silicon and oxygen. The values of ΔHacidity for gas-phase deprotonation are calculated considering various possible interactions of the propylsulfonic acid on the surface of the silica. Our investigations indicate that interactions of sulfonic acid (-SO3H) head... 

    Wireless electrochemical preparation of gradient nanoclusters consisting of copper(II), stearic acid and montmorillonite on a copper wire for headspace in-tube microextraction of chlorobenzenes

    , Article Microchimica Acta ; Volume 185, Issue 1 , 2018 ; 00263672 (ISSN) Enteshari Najafabadi, M ; Bagheri, H ; Sharif University of Technology
    Springer-Verlag Wien  2018
    This work introduces a new gradient fiber coating for microextraction of chlorobenzenes. Nanoclusters of organoclay-Cu(II) on a copper wire were fabricated by wireless electrofunctionalization. The resultant gradient coatings are more robust, and thermally and mechanically stable. Wireless electrofunctionalization was carried out in a bipolar cell under a constant deposition potential and using an ethanolic electrolyte solution containing stearic acid and montmorillonite. Stearic acid acts as an inexpensive and green coating while montmorillonite acts as a modifier to impart thermal stability. The gradient morphology of the nanoclusters was investigated by scanning electron microscopy,... 

    Wide color-varying visualization of sulfide with a dual emissive ratiometric fluorescence assay using carbon dots and gold nanoclusters

    , Article Microchemical Journal ; Volume 157 , September , 2020 Farahmand Nejad, M. A ; Bigdeli, A ; Hormozi Nezhad, M. R ; Sharif University of Technology
    Elsevier Inc  2020
    Development of visual detection methods regarding water pollutants can effectively facilitate water resource monitoring programs. A wide color-varying ratiometric approach has been developed for sensitive determination of sulfide by mixing orange emissive glutathione stabilized gold nanoclusters (AuNCs) and blue emissive urea stabilized carbon dots (CDs) in an appropriate ratio. Under a single excitation wavelength of 365 nm, the ratiometric fluorescence (RF) probe exhibited two distinct emission bands at 452 and 607 nm corresponding to CDs and AuNCs, respectively. Owing to the high affinity of sulfide ions to AuNCs in alkaline medium, the fluorescence (FL) of AuNCs was turned-off while the... 

    Interaction of ionic liquids with the surface of silica gel using nanocluster approach: A combined density functional theory and experimental study

    , Article Journal of Physical Organic Chemistry ; Vol. 27, issue. 2 , 2014 , pp. 163-167 ; ISSN: 08943230 Vafaeezadeh, M ; Fattahi, A ; Sharif University of Technology
    Silica gel-confined ionic liquid (IL) is a class of heterogeneous catalysts with broad catalytic applications. Leaching of the IL from the surface of the support is the major drawback of these catalysts, which reduce the catalyst efficiency during the chemical reactions. To investigate the effect of the hydrogen bonding on the leaching phenomena, the interaction between the 1-ethyl-3-methylimidazolium-based IL with various anions (Cl-, Br-, HSO4 -, NO3 -, BF 4 -, and PF6 -) and the surface of the silica gel were studied using density functional theory. Hence, a hydroxylated cage-like cluster of silica gel, Si4O6(OH), was selected to mimic the surface. The values of ÎEinteraction show that... 

    Simulation of vacancy diffusion in a silver nanocluster

    , Article Chemical Physics Letters ; Volume 498, Issue 4-6 , 2010 , Pages 312-316 ; 00092614 (ISSN) Taherkhani, F ; Negreiros, F. R ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
    The formation and diffusion of a vacancy in a silver nanocluster are studied via a combination of first-principles and statistical mechanics simulations. A 38-atom truncated-octahedral (TO) arrangement and its homologue with 37 Ag atoms and one vacancy are considered, and density-functional calculations are performed to derive the energies of the local minima and the energy barriers connecting them. These data are then used as an input for a study of the system dynamics via a kinetic Monte Carlo algorithm, evaluating site occupancies, diffusion coefficient and equilibration time. It is found that vacancy formation and diffusion represents a viable path for atom-atom exchange in these... 

    Molecular dynamics study of success evaluation for metallic nanoparticles manipulation on gold substrate

    , Article Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009, 30 August 2009 through 2 September 2009 ; Volume 6 , August–September , 2010 , Pages 345-346 ; 9780791849033 (ISBN) Mahboobi, S. H ; Meghdari, A ; Jalili, N ; Sharif University of Technology
    Using molecular dynamics, the behavior of nanoparticles during manipulation process is investigated in this paper. The system consists of a tip, cluster and substrate. The focus of the present research is on ultra-fine metallic nanoclusters. The system of concern is made of different transition metals. Two criteria have been proposed for evaluation of success in a pushing process. Such criteria describe the intactness of nanoparticle/substrate pair. The effects of cluster material and manipulation speed on the success of the process are investigated by atomistic simulations. Such qualitative simulation studies can evaluate the level of success of manipulation regarding different working... 

    Calculation of thermodynamic properties of Ni nanoclusters via selected equations of state based on molecular dynamics simulations

    , Article Solid State Communications ; Volume 151, Issue 14-15 , 2011 , Pages 965-970 ; 00381098 (ISSN) Akbarzadeh, H ; Abroshan, H ; Taherkhani, F ; Parsafar, G. A ; Sharif University of Technology
    We present an approach for constant-pressure molecular dynamics simulations. This approach is especially designed for finite systems, for which no periodic boundary condition applies. A molecular dynamics (MD) simulation for Ni nanoclusters is used to calculate their pressurevolumetemperature (pvT) data for the temperature range 200 K≤T≤400 K, and pressures up to 600 kbar. Isothermal sets of pvT data were generated by the simulation; each set was fitted by three equations of state (EoSs): Linear Isotherm Regularity-II (LIRII), BirchMurnaghan (BM), and EOS III. It is found that the MD data are satisfactorily reproduced by the EoSs with reasonable precision. Some features of the EoSs criteria,... 

    A wide-color-varying ratiometric nanoprobe for detection of norepinephrine in urine samples

    , Article Analytica Chimica Acta ; Volume 1039 , 2018 , Pages 124-131 ; 00032670 (ISSN) Farahmand Nejad, M. A ; Ghasemi, F ; Hormozi Nezhad, M. R ; Sharif University of Technology
    Elsevier B.V  2018
    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)... 

    A molecular-dynamics study of thermal and physical properties of platinum nanoclusters

    , Article Fluid Phase Equilibria ; Volume 280, Issue 1-2 , 2009 , Pages 16-21 ; 03783812 (ISSN) Akbarzadeh, H ; Parsafar, G. A ; Sharif University of Technology
    Metallic nanoclusters are interesting because of their utility in catalysis and sensors. The thermal and physical characteristics of metallic Pt nanoclusters with different sizes were investigated via molecular-dynamics simulations using Quantum Sutton-Chen (QSC) potential. This force field accurately predicts solid and liquid states properties as well as melting of the bulk platinum. Molecular dynamic simulations of Pt nanoclusters with 256, 456, 500, 864, 1372, 2048, 2916, 4000, 5324, 6912, 8788 atoms have been carried out at various temperatures. The Pt-Pt radial distribution function, internal energy, heat capacity, enthalpy, entropy of the nanoclusters were calculated at some... 

    Molecular Dynamic Simulation of the Straining of Nano Cluster Aggregate

    , M.Sc. Thesis Sharif University of Technology Nayebzadeh, Payam (Author) ; Khoei, Amir Reza (Supervisor)
    We carry out computer simulations in the hope of understanding the properties of assemblies of molecules in terms of their structure and the microscopic interactions between them. This serves as a complement to conventional experiments, enabling us to learn something new, something that cannot be found out in other ways. One of the main families of simulation technique are molecular dynamics (MD). Over the last decade , nanoscience and nanotechnology have emerged as two of the pillars of the research that will lead us to the next industrial revolution. The fundamental entities of interest to nanoscience and nanotechnology are the isolated individual nanostructures and their assemblies. Nano... 

    Theoretical Investigation of Hydrogen Bonding Effects on Interaction of Metal Nanoclusters with Histidine, Oxidation of Olefins by MnO4– & Acidity Enhancement of Alcohols

    , Ph.D. Dissertation Sharif University of Technology Jebeli Javan, Marjan (Author) ; Fattahi, Alireza (Supervisor) ; Mahmoodi Hashemi, Mohammad (Supervisor) ; Jamshidi, Zahra (Supervisor)
    This thesis is divided into three parts: In part I, interactions of neutral and anionic forms of histidine with coinage metal nano clusters M3 (M = Au, Ag and Cu) are investigated. Results demonstrate that nonconventional M…H-O hydrogen bonds and M-X bonds (X = N, O) play stabilization roles in interactions of histidine and metal nano clusters. Presence of negative charge in ligand leads to increase of binding energy of complexes. In the next step, the effects of coinage metal nano clusters on the gas-phase acidity of weak organic acid (histidine) have been explored. The acidity of isolated histidine is compared with the acidity of its Au3–, Ag3– and Cu3–complexed species. Moreover, pKa... 

    Molecular dynamics study of success evaluation for metallic nanoparticles manipulation on gold substrate

    , Article Proceedings of the ASME Design Engineering Technical Conference, 30 August 2009 through 2 September 2009, San Diego, CA ; Volume 6 , 2009 , Pages 345-346 ; 9780791849033 (ISBN) Mahboobi, S. H ; Meghdari, A ; Jalili, N ; Sharif University of Technology
    Using molecular dynamics, the behavior of nanoparticles during manipulation process is investigated in this paper. The system consists of a tip, cluster and substrate. The focus of the present research is on ultra-fine metallic nanoclusters. The system of concern is made of different transition metals. Two criteria have been proposed for evaluation of success in a pushing process. Such criteria describe the intactness of nanoparticle/substrate pair. The effects of cluster material and manipulation speed on the success of the process are investigated by atomistic simulations. Such qualitative simulation studies can evaluate the level of success of manipulation regarding different working... 

    Kinetics formation of bimetallic nanoalloys at different simulation times

    , Article Journal of Molecular Liquids ; Volume 240 , 2017 , Pages 468-475 ; 01677322 (ISSN) Akbarzadeh, H ; Taherkhani, F ; Mehrjouei, E ; Masoumi, A ; Sharif University of Technology
    Elsevier B.V  2017
    MD simulations were used for investigation on the kinetic formation of Ni-Pd nanoalloys at different simulation times. We have examined excess energies and bond order parameters for initial gas phase compositions including pure Ni, and Pd, and also Ni0.2Pd0.8, Ni0.4Pd0.6, Ni0.6Pd0.4, Ni0.8Pd0.2 concentrations. Excess energies for created Ni-Pd nanoalloys exhibit more instabilities for larger nanoparticles. Also, bond order results demonstrate amorphous structures for all of created nanoclusters. Moreover, number of formed clusters for pure Ni at 5 ns is more than pure Pd nanoclusters and number of formed clusters decreases when Pd is doped in pure Ni nanocluster. © 2017 Elsevier B.V  

    A DFT study of carbon monoxide adsorption on a Si4 nano-cluster

    , Article Molecular Physics ; Volume 107, Issue 17 , 2009 , Pages 1805-1810 ; 00268976 (ISSN) Nahali, M ; Gobal, F ; Sharif University of Technology
    Using the gradient-corrected hybrid density functional method of Predew, Burke, and Ernzerhof (PBEPBE) and the new hybrid meta-density functional method of Truhlar (MPW1B95), the geometry, adsorption energy, vibrational frequency, and charge distribution of carbon monoxide adsorption on a Si4 nano-cluster has been studied. Taking into account spin multicipility in the calculations, a new stable structure of CO absorbed on the Si4 cluster has been found, in addition to the previously reported structures. Exhaustive vibrational frequency analysis of optimized structures shows that some of the formerly reported structures have imaginary vibrational frequencies and are not proper stable... 

    Optical nanoprobes for chiral discrimination

    , Article Analyst ; Volume 145, Issue 20 , 2020 , Pages 6416-6434 Bigdeli, A ; Ghasemi, F ; Fahimi Kashani, N ; Abbasi Moayed, S ; Orouji, A ; Jafar Nezhad Ivrigh, Z ; Shahdost Fard, F ; Hormozi Nezhad, M. R ; Sharif University of Technology
    Royal Society of Chemistry  2020
    Chiral discrimination has always been a hot topic in chemical, food and pharmaceutical industries, especially when dealing with chiral drugs. Enantiomeric recognition not only leads to better understanding of the mechanism of molecular recognition in biological systems, but may further assist in developing useful molecular devices in biochemical and pharmaceutical studies. By emerging nanotechnology and exploiting nanomaterials in sensing applications, a great deal of attention has been given to the design of optical nanoprobes that are able to discriminate enantiomers of chiral analytes. This review explains how engineering nanoparticles (NPs) with desired physicochemical properties allows...