Search for: silver
0.043 seconds
Total 301 records

    Highly efficient hydroxyapatite/TiO2 composites covered by silver halides as E. coli disinfectant under visible light and dark media

    , Article Photochemical and Photobiological Sciences ; Volume 12, Issue 10 , October , 2013 , Pages 1787-1794 Azimzadehirani, M ; Elahifard, M ; Haghighi, S ; Gholami, M. R. (Mohammad Reza) ; Sharif University of Technology
    TiO2-based photocatalysts are seen as the most common agents for the photodegradation of bacteria. In this study, AgCl/TiO2, hydroxyapatite(Hp)/AgCl/TiO2, AgI/TiO2, and Hp/AgI/TiO2 were prepared by the deposition-precipitation method on P25 TiO2 nanoparticles and were characterized by XRD, SEM, FT-IR, EDX and BET methods. The prepared composites showed high efficiency for the inactivation of Escherichia coli (E. coli) bacteria under visible light and in dark media with different catalyst amounts of 12 and 24 mg, respectively. In less than 30 min, AgI/TiO2, prepared by the combination of cationic surfactant and PVPI2, disinfected 1 × 10(7) colony-forming units of E. coli completely. However,... 

    Controlling the diffusive motion of fullerene-wheeled nanocars utilizing a hybrid substrate

    , Article Journal of Physical Chemistry C ; Volume 123, Issue 42 , 2019 , Pages 26018-26030 ; 19327447 (ISSN) Nemati, A ; Nejat Pishkenari, H ; Meghdari, A ; Ge, S. S ; Sharif University of Technology
    American Chemical Society  2019
    In the previous years, a few types of nanocars have been built with the promising potential to transport other molecules, to provide bottom-up assembly, or to perform other mechanical tasks. In this study, we propose a method to convert the diffusive displacement of nanocars to a guided motion in a desired path by adding some impurity atoms in the substrate. We investigated the motion of C60 as well as the nanotruck and the nanocar on a flat gold substrate containing silver contamination and conversely a silver substrate containing gold contamination at the different temperatures. The results showed that silver impurity on the gold substrate act as a repellent obstacle in the path of C60... 

    Controlling the geometry of silver nanostructures for biological applications

    , Article Physics Procedia, Ancona ; Volume 40 , 2013 , Pages 76-83 ; 18753884 (ISSN) Ashkarran, A. A ; Estakhri, S ; Nezhad, M. R. H ; Eshghi, S ; Sharif University of Technology
    Noble metals nanostructures, particularly silver, have attracted much attention in the fields of electronics, chemistry, physics, biology and medicine due to their unique properties which are strongly dependent on the size and shape of metal nanomaterials. This study discusses on silver nanostructures with different geometries including wire, cube, sphere and triangle prepared using solution-phase method and applied for antibacterial activities. X-ray diffraction (XRD), Ultra Violet Visible (UV-Vis) spectroscopy, Dynamic Light Scattering (DLS) and electron microscopy studies of different types of silver nanostructures revealed distinct optical and structural properties of an individual... 

    Two new silver(I) complexes with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz): Preparation, characterization, crystal structure and alcohol oxidation activity in the presence of oxone

    , Article Polyhedron ; Volume 29, Issue 14 , September , 2010 , Pages 2837-2843 ; 02775387 (ISSN) Najafpour, M. M ; Hołyńska, M ; Amini, M ; Kazemi, S. H ; Lis, T ; Bagherzadeh, M ; Sharif University of Technology
    Two new silver(I) complexes ((tptz)Ag2(NO3) 2 and [Ag5(tptz)4](NO3)5) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) have been synthesized and characterized by X-ray diffraction, elemental analysis, 1H NMR, IR, fluorescence, UV-Vis spectroscopy and electrochemistry. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted with one of the Ag complexes as a catalyst, soluble enough in organic solvent, using oxone (2KHSO5·KHSO4·K2SO4) as an oxidant under biphasic reaction conditions (CH2Cl 2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature  

    Novel keggin-type polyoxometalate nanocatalysts for michael addition polymerizations

    , Article Materials Chemistry and Physics ; Volume 199 , 2017 , Pages 79-87 ; 02540584 (ISSN) Karimi Ahmadabad, F ; Pourayoubi, M ; Bakhshi, H ; Sharif University of Technology
    Keggin-type polyoxometalate (POM) nanoparticles based on [PW12O40]3- and [SiW12O40]4- with Ag+ and (ZrO)2+ cations were prepared under ultrasound irradiation. The results of SEM and XRD revealed the average size of particles in the range of 24–95 nm. The moles of crystallization water per mole of nanocatalysts were in the range of 3–9. EDX spectra confirmed the successful replacement of protons of H3PW12O40 and H4SiW12O40 with Ag+ and (ZrO)2+ cations. These nanoparticles were used as heterogeneous catalysts for the synthesis of a poly (amido-ester) at room temperature. All polymers were fully characterized. Although employing the nanocatalyst resulted in at least 22% improvement in the... 

    Oxidative transformation of organic compounds using bis(1,10- phenanthroline)silver(II) peroxydisulfate as a twin catalyst/oxidant

    , Article Journal of the Iranian Chemical Society ; Volume 5, Issue SUPPL.1 , 2008 , Pages S108-S112 ; 1735207X (ISSN) Joshaghani, M ; Bahadori, M ; Rafiee, E ; Bagherzadeh, M ; Sharif University of Technology
    Iranian Chemical Society  2008
    The mild and efficient oxidation of a variety of organic functional groups with a twin catalyst/oxidant, bis(phenanthroline)silver(II) peroxydisulfate, [Ag(phen)2]S2O8, is reported. This reagent shows high selectivity and the type of obtained products and the extent of oxidation are strongly dependent to the type of the functional groups and oxidant/substrate molar ratios  

    Production of silver nanometric powders via Inert Gas Condensation (IGC) method

    , Article Amirkabir (Journal of Science and Technology) ; Volume 16, Issue 61 C , 2005 , Pages 103-107 ; 10150951 (ISSN) Ahmadi, R ; Simchi, A ; Seyedreyhani, S ; Sharif University of Technology
    Nanopowders are powders with particle size less than 100 nanometer. The applications of nanopowders are in the production and processing of nanocomposites, microelectronic, industrial cathalists, coating, sintering at low temperature, lubricants, propellants, purification of aqiuos solutions, biomaterials and filtration. In this work, a reactor for production of nanopowder using IGC method was designed and manufactured. By changing the production parameters such as chamber temperature and pressure, evaporation rate, precursor and evaporation time, silver powders were produced. The characteristics of the produced powders were studied using EDX, SEM and TEM techniques. The results showed that... 

    Synthesis and Comparison Dissolution of Silver Nanopowder with Various Morphologie

    , M.Sc. Thesis Sharif University of Technology Godary, Toktam (Author) ; Halali, Mohammad (Supervisor)
    Silver nanopowder is of great importance for various medical and industrial applications. Due to the significance of the solubility of silver nanoparticles in these applications as well as the high impact of the nanophysical morphology of the powder on their solubility, we prepared nanoparticles with plate morphology by the chemical reduction of silver nitrate in a soluble phase. Then we measure its solubility in a phosphate buffer salt, which greatly resembles the human blood chemically. The size and shape of the resulting nanosilver powder and also the use of non-toxic materials in their synthesis are important factors in the production of nanosilver powder.We confirmed the successful... 

    Size tuning of Ag‐decorated TiO2 nanotube arrays for improved bactericidal capacity of orthopedic implants [electronic resource]

    , Article Journal of Biomedical Materials Research Part A ; Auguest 2014, Vol. 102, Issue 8, P.2625-35 Esfandiari, N ; Simchi, A. (Abdolreza) ; Bagheri, R ; Sharif University of Technology
    Surface modification of orthopedic implants using titanium dioxide nanotubes and silver nanoparticles (SNs) is a promising approach to prevent bacteria adhesion, biofilm formation, and implant infection. Herein, we utilized a straightforward and all-solution process to prepare silver-decorated TiO2 nanotube arrays with surface density of 10(3) to 10(4) per µm(2). With controlling the synthesis conditions, hexagonal closed-packed nanotubes with opening diameter of 30-100 nm that are decorated with SNs with varying sizes (12-40 nm) were prepared. Various analytical techniques were utilized to characterize the size, morphology, distribution, valance state, surface roughness, and composition of... 

    Nanodiamond Decorated with Silver Nanoparticles as a Sensitive Film Modifier in a Jeweled Electrochemical Sensor: Application to Voltammetric Determination of Thioridazine

    , Article Electroanalysis ; Volume 25, Issue 2 , 2013 , Pages 417-425 ; 10400397 (ISSN) Shahrokhian, S ; Hosseini Nassab, N ; Sharif University of Technology
    Nanodiamond-graphite (NDG) decorated with Ag nanoparticles (AgNPs-NDG) was prepared and used to construct a novel sensitive sensor for the voltammetric determination of thioridazine (TR). The results indicate a remarkable increase in the oxidation peak currents together with a negative shift in the oxidation peak potentials, in comparison to the bare pyrolytic graphite electrode. Remarkable enhancement in microscopic area of the electrode along with strong adsorption of TR on the surface of the modified electrode resulted in a considerable increase in the peak current of TR. The surface morphology and the nature of the composite film deposited on PGE were characterized by scanning electron... 

    Optical detection of some hydrazine compounds based on the surface plasmon resonance band of silver nanoparticles

    , Article Spectroscopy Letters ; Volume 46, Issue 1 , 2013 , Pages 73-80 ; 00387010 (ISSN) Tashkhourian, J ; Hormozi Nezhad, M. R ; Fotovat, M ; Sharif University of Technology
    An indirect colorimetric method is presented for spectrophotometric determination of hydrazine, phenylhydrazine, and isoniazid. Reduction of silver ions to silver nanoparticles (AgNPs) by these analytes as active reducing agents in the presence of polyvinylpyrrolidone (PVP) and also cetyltrimethylammonium chloride (CTAC) as a stabilizer is the basis of the proposed method. The changes in plasmon absorbance of the AgNPs at λ = 415 nm in the presence of PVP were proportional to concentration of hydrazine, phenylhydrazine, and isoniazid in the ranges of 4.0-150.0 μM, 1.0-55.0 μM, and 2.0-30.0 μM, respectively, and the detection limit obtained was 0.79 μM. In the presence of CTAC, the linear... 

    Photo-induced growth of silver nanoparticles using UV sensitivity of cellulose fibers

    , Article Applied Surface Science ; Volume 258, Issue 7 , 2012 , Pages 2373-2377 ; 01694332 (ISSN) Omrani, A. A ; Taghavinia, N ; Sharif University of Technology
    A simple method has been demonstrated to grow silver nanoparticles on the surface of cellulose fibers. The preparation is based on photo-activation of surface by ultraviolet (UV) photons, followed by chemical reduction of silver nitrate. It is found that the concentration of silver nitrate in the solution is not a determining factor, while UV intensity affects the rate of initial growth and determines the final concentration of the loaded silver. We explain the phenomena based on a model including the number of reducing sites on the surface of cellulose fibers activated by UV photons, and a release mechanism that causes a slow rate of dissolution of silver back into the solution  

    Silver selenide as a potential electro-catalyst for l-ascorbic acid electro-oxidation in alkaline solution

    , Article Electrocatalysis ; Volume 2, Issue 4 , December , 2011 , Pages 331-336 ; 18682529 (ISSN) Gobal, F ; Majari Kasmaee, L ; Sharif University of Technology
    Cathodically deposited Ag 2Se, to form a 1-μm-thick film, characterized by energy dispersive X-ray analysis and scanning electron microscopy, showed high electro-catalytic activity for l-ascorbic acid oxidation in alkaline solution. The onset of the process was about 80 mV cathodic of that previously observed on Ag under the same conditions and far superior over glassy carbon and Pt. The values of the exchange current density, standard heterogeneous rate constant, and transfer coefficient of the reaction were 1. 65 × 10 -4 A cm -2, 4. 35 × 10 -7 cm s -1, and 0. 60, respectively. Diffusion coefficient of l-ascorbate di-anion was also measured and was around 7. 00 × 10 -6 cm 2 s -1  

    Sensitive spectrophotometric detection of dopamine, levodopa and adrenaline using surface plasmon resonance band of silver nanoparticles

    , Article Journal of the Iranian Chemical Society ; Volume 7, Issue SUPPL. 1 , 2010 , Pages S83-S91 ; 1735207X (ISSN) Hormozi Nezhad, M. R ; Tashkhourian, J ; Khodaveisi, J ; Sharif University of Technology
    A simple and effective procedure is proposed for spectrophotometric determination of catecholamines; Dopamine (1), L-Dopa (2) and Adrenaline (3). It was found that the reduction of Ag+ to silver nanoparticles (Ag-NPs) by these catecholamines in the presence of polyvinylpyrrolidone (PVP) as a stabilizing agent produced very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs allows the quantitative spectrophotometric detection of the catecholamines. The calibration curves derived from the changes in absorbance at λ = 440 nm were linear with concentration of Dopamine, Levodopa and Adrenaline in the range of 3.2×10-6- 2.0x10-5 M, 1.6x10-7 - 1.0×10-5 M,... 

    Antimicrobial wound dressing containing silver sulfadiazine with high biocompatibility: In vitro study

    , Article Artificial Organs ; Volume 40, Issue 8 , 2016 , Pages 765-773 ; 0160564X (ISSN) Mohseni, M ; Shamloo, A ; Aghababaei, Z ; Vossoughi, M ; Moravvej, H ; Sharif University of Technology
    Blackwell Publishing Inc 
    Many patients all over the world suffer from acute wounds caused by traumas or burns. In most crucial cases, skin regeneration cannot be promoted spontaneously, and skin grafts are applied as the main treatment. However, this therapy has some drawbacks which motivate researchers to develop wound dressings. In this study, electrospun mats consisting of polycaprolactone (PCL) and polyvinyl alcohol (PVA) incorporated with silver sulfadiazine (SSD) are proposed to be used as antimicrobial wound dressings with the capability of cell seeding. Various amounts of SSD were loaded into PVA nanofibers, and the effects of SSD particles on the morphological characteristics of nanofibers, mechanical... 

    Modification of the electrode surface by ag nanoparticles decorated nano diamond-graphite for voltammetric determination of ceftizoxime

    , Article Electroanalysis ; Volume 28, Issue 3 , 2016 , Pages 469-476 ; 10400397 (ISSN) Shahrokhian, S ; Ranjbar, S ; Ghalkhani, M ; Sharif University of Technology
    Wiley-VCH Verlag  2016
    A modified glassy carbon electrode with a film of nano diamond-graphite nano mixture decorated with Ag nanoparticles (AgNPs-NDG/GCE) was constructed and used for sensitive voltammetric determination of ceftizoxime (CFX). Morphology of AgNPs-NDG/GCE has been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental variables such as deposited amount of the modifier suspension, pH of the supporting electrolyte and accumulation potential and time were optimized by monitoring of CV and LSV responses of CFX. The results illustrate that AgNPs-NDG/GCE exhibits an excellent electrocatalytic effect in the electro-oxidation of CFX that leads to a considerable... 

    A novel nanocomposite with superior antibacterial activity: a silver-based metal organic framework embellished with graphene oxide

    , Article Advanced Materials Interfaces ; Volume 5, Issue 11 , 3 April , 2018 ; 21967350 (ISSN) Dadashi Firouzjaei, M ; Arabi Shamsabadi, A ; Sharifian Gh, M ; Rahimpour, A ; Soroush, M ; Sharif University of Technology
    Wiley-VCH Verlag  2018
    Silver-based nanomaterials have attracted considerable attention due to their antimicrobial activities. In this work, a silver (Ag)-based metal organic framework (Ag-MOF) is embellished with graphene-oxide (GO), leading to the fabrication of a novel Ag-based nanocomposite (GO-Ag-MOF) whose biocidal activity is higher than those of Ag-MOF and GO nanomaterials. The nanocomposite is characterized using X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, Fourier transform infrared spectra, ultraviolet−visible absorption spectra, X-ray powder diffraction, dynamic light scattering, and nitrogen gas adsorption/desorption. The characterization shows that... 

    Efflux pump inhibitory activity of biologically synthesized silver nanoparticles against multidrug-resistant Acinetobacter baumannii clinical isolates

    , Article Journal of Basic Microbiology ; Volume 60, Issue 6 , 2020 , Pages 494-507 Behdad, R ; Pargol, M ; Mirzaie, A ; Karizi, S. Z ; Noorbazargan, H ; Akbarzadeh, I ; Sharif University of Technology
    Wiley-VCH Verlag  2020
    This study was carried out to investigate the possible efflux pump inhibitory activity of biologically synthesized silver nanoparticles (AgNPs) against multidrug-resistant (MDR) Acinetobacter baumannii isolates. In this study, the physicochemical characteristics of synthesized AgNPs were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectrophotometer (FTIR) methods. Subsequently, MDR A. baumannii isolates were recovered from clinical samples and the phenotypic cartwheel efflux assay and polymerase chain reaction (PCR) were used to elucidate the possible presence of efflux pump in MDR... 

    Simulation, design optimization, and experimental validation of a silver SPND for neutron flux mapping in the Tehran MTR

    , Article Nuclear Engineering and Technology ; Volume 52, Issue 12 , 2020 , Pages 2852-2859 Saghafi, M ; Ayyoubzadeh, S. M ; Terman, M. S ; Sharif University of Technology
    Korean Nuclear Society  2020
    This paper deals with the simulation-based design optimization and experimental validation of the characteristics of an in-core silver Self-Powered Neutron Detector (SPND). Optimized dimensions of the SPND are determined by combining Monte Carlo simulations and analytical methods. As a first step, the Monte Carlo transport code MCNPX is used to follow the trajectory and fate of the neutrons emitted from an external source. This simulation is able to seamlessly integrate various phenomena, including neutron slowing-down and shielding effects. Then, the expected number of beta particles and their energy spectrum following a neutron capture reaction in the silver emitter are fetched from the... 

    Atmospheric corrosion evaluation of silver coating using simulating technique test

    , Article European Corrosion Conference: Long Term Prediction and Modelling of Corrosion, EUROCORR 2004, Nice, 12 September 2004 through 16 September 2004 ; 2004 Nasirpouri, F ; Afshar, A ; Sharif University of Technology
    A standard simulating technique test was investigated to assess the atmospheric corrosion behavior of silver coating. The rates of formation of corrosion products were measured in the simulating atmospheres of 100% humidity containing SO 2,H 2S and a complex atmosphere consist of SO 2,H 2S and NO 2 gases ,based on the mass increase method. The concentrations of corrosive gases were chosen according to real world conditions. XRD, SEM and EDS were used to examine the morphology and to determine the composition of the corrosion products under different experimental conditions. Results revealed the formation of Ag 2SO 4 and Ag 2S on the silver coating surfaces in the SO 2 and H 2S containing...