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gold
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Anti-aggregation of gold nanoparticles for metal ion discrimination: a promising strategy to design colorimetric sensor arrays
, Article Sensors and Actuators, B: Chemical ; Volume 270 , 2018 , Pages 545-551 ; 09254005 (ISSN) ; Ghasemi, F ; Hormozi Nezhad, M. R ; Sharif University of Technology
Abstract
The first report of anti-aggregation-based sensor arrays is presented. The strategy is based on the competitive interaction of citrate-capped gold nanoparticles (AuNPs) and heavy metal ions (i.e., Hg(II), Ag(I), Fe(III), and Pb(II)) with three aggregation reagents (i.e., cysteine, melamine, and arginine). In the presence of aggregation reagent, the color and UV–vis spectra of AuNPs are changed indicating the aggregation of AuNPs. Addition of the aggregation reagents which are firstly treated with the ions, causes AuNPs turn from the aggregation to the dispersion state. The anti-aggregation capability of ions towards various aggregation reagents is different because of distinct stability...
Enhanced thermal stability and biocompatibility of gold nanorods by graphene oxide
, Article Plasmonics ; Volume 13, Issue 5 , 2018 , Pages 1585-1594 ; 15571955 (ISSN) ; Hatamie, S ; Tabatabaei, S. N ; Salimi, M ; Saber, R ; Sharif University of Technology
Abstract
In the present study, the effect of nanosized graphene oxide layer on thermal stability and biocompatibility of gold nanorods has been examined. The graphene oxide-wrapped gold nanorods were prepared by electrostatic interaction between negatively charged graphene oxide and positively charged nanorods. The resulting nanohybrids were then heated at different time intervals to 95 °C in a water bath to assess the effect of heat on the rods morphology. The structural changes in gold nanorods were monitored via UV-Vis spectroscopy measurements and transmission electron microscopy images. In similar experiments, the graphene oxide used to wrap gold nanorods was reduced by ascorbic acid in a 95 °C...
Magnetic nanocomposite of cross-linked Mmelamine groups decorated with large amounts of gold NPs: reduction of nitro compounds and Suzuki–Miyaura coupling reactions in aqueous media
, Article ChemistrySelect ; Volume 3, Issue 10 , March , 2018 , Pages 2716-2722 ; 23656549 (ISSN) ; Keshavarzi, N ; Matloubi Moghaddam, F ; Hosseini, S. H ; Sharif University of Technology
Wiley-Blackwell
2018
Abstract
A magnetic nanocomposite was prepared based on magnetic Fe3O4 nanoparticles entrapped into a cross-linked nitrogen rich polymer which has high loading capacity for immobilization of gold nanoparticles. The synthesized catalyst was characterized using various methods including Atomic absorption spectroscopy (AAS), Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDX), Thermogravimetric analysis (TGA), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), VSM and X-ray diffraction (XRD) techniques. The catalyst was proven to be highly efficient for reduction of nitroarenes as well as Suzuki–Miyaura...
Effects of catalyst preparation conditions on nano-gold deposited on ZSM-5 for CO oxidation
, Article International Journal of Modern Physics B ; Volume 22, Issue 18-19 , 2008 , Pages 3278-3288 ; 02179792 (ISSN) ; Kazemeini, M ; Kazemian, H ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2008
Abstract
Calcined Na-ZSM-5 zeolite was directly reacted with the chloroauric acid solution in different concentrations and pH for gold loading process. The synthesized Au/ZSM-5 catalyst was then characterized using XRD, BET, SEM, TEM and EDS techniques. In order to evaluate its catalytic activity, effect of temperature on CO conversion was investigated. © 2008 World Scientific Publishing Company
Gold Nanowaste Reduction and Recycling Using Chemical Methods
, M.Sc. Thesis Sharif University of Technology ; Hormozi-Nezhad, Mohammad Reza (Supervisor) ; Alamolhoda, Ali Asghar (Supervisor)
Abstract
The growing use of nanomaterials leads to causing harm to the aquatic environment resulting in a demand for effective methods to remove these nanomaterials from aquatic environment. On the other hand, the high cost of raw materials used for the production of noble metal nanomaterial limits their use or requires the development of recycling and recovery methods. In this study, we found that citrate capped gold nanoparticles (cit-AuNPs) could be removed effectively from waste water using aluminum chloride (AlCl3) coagulant. The effect of pH, of coagulant concentration, and alkalinity on the performance of this coagulant was investigated. It has...
Raman active jagged-shaped gold-coated magnetic particles as a novel multimodal nanoprobe
, Article Chemical Communications ; Volume 47, Issue 37 , Aug , 2011 , Pages 10404-10406 ; 13597345 (ISSN) ; Amiri, H ; Shokrgozar, M. A ; Sasanpour, P ; Rashidian, B ; Laurent, S ; Casula, M. F ; Lascialfari, A ; Sharif University of Technology
2011
Abstract
The creation of novel engineered multimodal nanoparticles (NPs) is a key focus in bionanotechnology and can lead to deep understanding of biological processes at the molecular level. Here, we present a multi-component system made of gold-coupled core-shell SPIONs, as a new nanoprobe with signal enhancement in surface Raman spectroscopy, due to its jagged-shaped gold shell coating
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) ; Nejat Pishkenari, H ; Meghdari, A ; Ge, S. S ; Sharif University of Technology
American Chemical Society
2019
Abstract
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...
Electrodeposition of long gold nanotubes in polycarbonate templates as highly sensitive 3D nanoelectrode ensembles
, Article Electrochimica Acta ; Volume 75 , 2012 , Pages 157-163 ; 00134686 (ISSN) ; Ghorbani, M ; Dolati, A ; Sharif University of Technology
Elsevier
2012
Abstract
Electrodeposition of long and well-defined gold nanotubes in polycarbonate (PC) templates is still a major concern due to pore blockage problems. In the present study, we introduce a novel method for electrodeposition of long gold nanotubes within the pores of PC templates for the first time. In order to deposit gold atoms onto the pore walls preferentially, pore walls were functionalized with a coupling agent. Short and thin Ni nanotubes were then electrodeposited at the bottom of the pores. Gold nanotubes were subsequently electrodeposited at constant potentials and low solution concentrations. The morphology of nanotubes was characterized by electron microscopy and their formation...
Self-assembly of tryptophan-capped gold nanoparticles onto DNA network template
, Article Journal of Dispersion Science and Technology ; Volume 30, Issue 2 , 2009 , Pages 254-258 ; 01932691 (ISSN) ; Vosoughi, M ; Alemsadeh, I ; Sharif University of Technology
2009
Abstract
In this study, a simple route to the formation of DNA-gold complex has been reported, using immobilized DNA as a template. The nanoporous gold films have been prepared by the electrostatic self assembly of gold nanoparticles capped with tryptophan. Tryptophan would improve surface properties of gold nanoparticles for strongly attaching to DNA. Fourier transform infrared spectroscopy confirmed that gold nanoparticles have been capped by tryptophan. Also measured zeta potential shows that there are positive charges on the surface of gold nanoparticles. Investigations by atomic force microscopy substantially confirm that tryptophan-capped gold nanoparticles can be bonded to DNA template...
Activated layered manganese oxides with deposited nano-sized gold or silver as an efficient catalyst for epoxidation of olefins
, Article RSC Advances ; Volume 3, Issue 46 , 2013 , Pages 24069-24074 ; ISSN: 20462069 ; Amini, M ; Sedigh, D. J ; Rahimi, F ; Bagherzadeh, M ; Sharif University of Technology
2013
Abstract
Activated layered manganese oxides with deposited nano-sized gold or silver were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy and energy-dispersive X-ray mapping. Here, we report that Au or Ag nanoparticles deposited on layered Mn oxides improve the catalytic activity of the Mn oxides toward the epoxidation of olefins in the presence of H2O2 and NaHCO3
Comparison of different strategies for the assembly of gold colloids onto Fe3O4@SiO2 nanocomposite particles
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 49 , 2013 , Pages 30-38 ; 13869477 (ISSN) ; Yaghmaei, S ; Roostaazad, R ; Arpanaei, A ; Sharif University of Technology
2013
Abstract
Three strategies were employed for the assembly of gold nanoparticles on silica-coated magnetite particles (SCMPs). In strategy I, citrate-coated gold nanoparticles were attached on the surface of amine-SCMPs. In strategy II, amine-SCMPs were coated with carboxylated gold nanoparticles via amide bond formation. In strategy III, the thiol-SCMPs surface was coated with gold nanoparticles. Among the above examined strategies, coating amine-SCMPs with gold nanoparticles via strategy I resulted in a better coverage and stronger intensity of absorption bands. Furthermore, results obtained through strategy I showed that decreasing the pH of the solution from 7 to 3 leads to a further red-shift of...
A close look at the motion of C60 on gold
,
Article
Current Applied Physics
;
Volume 15, Issue 11
,
November
,
2015
,
Pages 1402-1411
;
15671739 (ISSN)
; Nemati, A
; Meghdari, A
; Sohrabpour, S
;
Sharif University of Technology
Elsevier
2015
Abstract
In this paper, we have studied the motion of buckminsterfullerene (C60 ) on a gold surface by analyzing its potential energy and using classical molecular dynamics method. The results can be employed to investigate the motion of C60 -based nanocars which have been made in recent years. For this purpose, we have studied the translational and rotational motions of C60 molecule independently. First, we have calculated the potential energy of a C60 molecule on a gold surface in different orientations and positions and employed this data to predict fullerene motion by examining its potential energy. Then we have simulated the motion of C60 at...
Gold immobilized onto poly(ionic liquid) functionalized magnetic nanoparticles: A robust magnetically recoverable catalyst for the synthesis of propargylamine in water
, Article RSC Advances ; Volume 5, Issue 43 , Apr , 2015 , Pages 34502-34510 ; 20462069 (ISSN) ; Ayati, S. E ; Hosseini, S. H ; Pourjavadi, A ; Sharif University of Technology
Royal Society of Chemistry
2015
Abstract
Supported gold(III) on poly(ionic liquid) coated on magnetic nanoparticles produced a highly active, stable, recoverable and high loading for the synthesis of propargylamines (A3 coupling reaction) under green conditions. The reaction of aldehyde, secondary amine and alkyne were followed in aqueous media. The catalyst was characterized by TEM, TGA, AAS, FT-IR, XRD and EDX. A broad diversity of aldehydes, secondary amines, and alkynes, and a good to excellent yield of corresponding propargylamines were synthesized using 1.0% Au. The catalyst was easily recovered and reused 10 times without significant loss of activity
Developing a time series model based on particle swarm optimization for gold price forecasting
, Article Proceedings - 3rd International Conference on Business Intelligence and Financial Engineering, BIFE 2010, 13 August 2010 through 15 August 2010, Hong Kong ; August , 2010 , Pages 337-340 ; 9780769541167 (ISBN) ; Ghanbari, A ; Abbasian Naghneh, S ; Sharif University of Technology
2010
Abstract
The trend of gold price in the market is the most important consideration for the investors of the gold, and serves as the basis of gaining profit, so there are scholars who try to forecast the gold price. Forecasting accuracy is one of the most important factors involved in selecting a forecasting method. Besides, nowadays artificial intelligence (AI) techniques are becoming more and more widespread because of their accuracy, symbolic reasoning, flexibility and explanation capabilities. Among these techniques, particle swarm optimization (PSO) is one of the best AI techniques for optimization and parameter estimation. In this study a PSO-based time series model for the gold price...
Development of a paper-based plasmonic test strip for visual detection of methiocarb insecticide
, Article IEEE Sensors Journal ; Volume 17, Issue 18 , 2017 , Pages 6044-6049 ; 1530437X (ISSN) ; Ghasemi, F ; Hormozi Nezhad, M. R ; Sharif University of Technology
Abstract
This paper describes a simple and low-cost test strip for on-site monitoring of methiocarb insecticide. Hydrophilic filter paper soaked in agarose solution was bounded by hydrophobic solid wax and then was coated with unmodified gold nanoparticles (AuNPs). AuNPs aggregation caused by methiocarb served as colorimetric response. We demonstrated detection capability of methiocarb both in solution- and substrate-based sensor. A good linear relationship was obtained between the colorimetric response and the concentration of methiocarb ranging from 20 to 80 ng mL -1 with a limit of detection of 5 ng mL -1. Excellent selectivity toward methiocarb was observed among various pesticides and cationic...
Electrodeposition of well-defined gold nanowires with uniform ends for developing 3D nanoelectrode ensembles with enhanced sensitivity
, Article Materials Chemistry and Physics ; Volume 213 , 2018 , Pages 67-75 ; 02540584 (ISSN) ; Ghorbani, M ; Dolati, A ; Hosseini, D ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Fabrication of well-defined gold nanowires (GNWs) is of significant importance in many fields such as sensing applications. In this study, the electrodeposition of well-defined GNWs inside polycarbonate (PC) template has been discussed in detail. GNWs were potentiostatically electrodeposited at different filling rates. The growth of GNWs at different stages of pore filling was monitored by electrochemical measurements and field-emission scanning electron microscopy (FE-SEM). It was confirmed that under growth rates between 2.5 and 4 nm/s, GNWs with smooth ends grew uniformly inside the template without any imperfections or corrugations. The length of GNWs was electrochemically controlled to...
Nanoporous gold as a suitable substrate for preparation of a new sensitive electrochemical aptasensor for detection of salmonella typhimurium
, Article Sensors and Actuators, B: Chemical ; Volume 255 , 2018 , Pages 1536-1544 ; 09254005 (ISSN) ; Shahrokhian, S ; Nurmohammadi, F ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Nowadays, achievement to easy, fast, reliable and cost-effective techniques and tools is one of the most important challenges in detection of microorganisms. Salmonella typhimurium is one of the most important pathogenic bacteria that affect the human health and environmental infections. In this work we report a new, stable, biocompatible and cost-effective platform for construction of an aptasensor based on nanoporous gold (NPG) for detection of S. typhimurium. Nanoporous gold is electrochemically synthesized using Au-Cu alloy at the surface of Au/GCE. Thiol functionalized aptamer is used for effective linking to the surface of NPG/Au/GCE via self-assemble monolayers (SAMs) formation....
Influence of scalar-relativistic and spin-orbit terms on the plasmonic properties of pure and silver-doped gold chains
, Article Journal of Physical Chemistry C ; Volume 123, Issue 14 , 2019 , Pages 9331-9342 ; 19327447 (ISSN) ; Asadi Aghbolaghi, N ; Jamshidi, Z ; Sharif University of Technology
American Chemical Society
2019
Abstract
The unique plasmonic character of silver and gold nanoparticles has a wide range of applications, and tailoring this property by changing electronic and geometric structures has received a great deal of attention. Herein, we study the role of the quantum properties in controlling the plasmonic excitations of gold and silver atomic chains and rods. The influence of relativistic effects, scalar as well as spin-orbit, on the intensity and energy of plasmonic excitations is investigated. The intensity quenching and the red shift of energy in the presence of relativistic effects are introduced via the appearance of d orbitals directly in optical excitations in addition to the screening of...
Synthesis of fulvene vinyl ethers by gold catalysis
, Article Chemistry - A European Journal ; Volume 26, Issue 23 , 2020 , Pages 5280-5287 ; Schwarz, J ; Lustosa, D. M ; Pourkaveh, R ; Hoffmann, M ; Rominger, F ; Rudolph, M ; Dreuw, A ; Hashmi, A. S. K ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
Gold-catalyzed cyclization of 1,5-diynes with ketones as reagents and solvent provides diversely substituted vinyl ethers under mild conditions. The regioselectivity of such gold-catalyzed cyclizations is usually controlled by the scaffold of the diyne. Herein, we report the first solvent-controlled switching of regioselectivity from a 6-endo-dig- to 5-endo-dig-cyclization in these transformations, providing fulvene derivatives. With respect to the functional-group tolerance, aryl fluorides, chlorides, bromides, and ethers are tolerated. Furthermore, the mechanism and selectivity are put to scrutiny by experimental studies and a thermodynamic analysis of the product. Additionally,...
The effect of liquid environment on size and aggregation of gold nanoparticles prepared by pulsed laser ablation
, Article Journal of Nanoparticle Research ; Volume 9, Issue 5 , 2007 , Pages 853-860 ; 13880764 (ISSN) ; Iraji zad, A ; Mahdavi, S. M ; Sharif University of Technology
2007
Abstract
The effects of liquid environment on nucleation, growth and aggregation of gold nanoparticles were studied. Gold nanoparticles were prepared by pulsed laser ablation in deionised water with various concentrations of ethanol and also in pure ethanol. UV/visible extinction and TEM observations were employed for characterization of optical properties and particle sizes respectively. Preparation in water results in smaller size, shorter wavelength of maximum extinction and stable solution with an average size of 6 nm. Nanoparticles in solution with low concentration ethanol up to 20 vol% are very similar to those prepared in water. In the mixture of deionised water and 40 up to 80 vol% ethanol,...