The Experts below are selected from a list of 31998 Experts worldwide ranked by ideXlab platform
Mostafa A Elsayed - One of the best experts on this subject based on the ideXlab platform.
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catalysis with transition metal nanoparticles in Colloidal Solution nanoparticle shape dependence and stability
Journal of Physical Chemistry B, 2005Co-Authors: Radha Narayanan, Mostafa A ElsayedAbstract:While the nanocatalysis field has undergone an explosive growth during the past decade, there have been very few studies in the area of shape-dependent catalysis and the effect of the catalytic process on the shape and size of transition metal nanoparticles as well as their recycling potential. Metal nanoparticles of different shapes have different crystallographic facets and have different fraction of surface atoms on their corners and edges, which makes it interesting to study the effect of metal nanoparticle shape on the catalytic activity of various organic and inorganic reactions. Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials, but their surface atoms could be so active that changes in the size and shape of the nanoparticles could occur during the course of their catalytic function, which could also affect their recycling potential. In this Feature Article, we review our work on the effect of the shape o...
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shape dependent catalytic activity of platinum nanoparticles in Colloidal Solution
Nano Letters, 2004Co-Authors: Radha Narayanan, Mostafa A ElsayedAbstract:The activation energies and the average rate constants are determined in the 298 K−318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (III) and thiosulfate ions using 4.8 ± 0.1 nm tetrahedral, 7.1 ± 0.2 nm cubic, and 4.9 ± 0.1 nm “near spherical” nanocrystals. These kinetic parameters are found to correlate with the calculated fraction of surface atoms located on the corners and edges in each size and shape.
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effect of nanocatalysis in Colloidal Solution on the tetrahedral and cubic nanoparticle shape electron transfer reaction catalyzed by platinum nanoparticles
Journal of Physical Chemistry B, 2004Co-Authors: Radha Narayanan And, Mostafa A ElsayedAbstract:The stability of tetrahedral and cubic platinum nanoparticles during the catalysis of the electron-transfer reaction between hexacyanoferrate (III) and thiosulfate ions in Colloidal Solution at room temperature was studied by using TEM and HRTEM. Before the reaction, the dominantly tetrahedral nanoparticles have a shape distribution of 55 ± 4% regular tetrahedral, 22 ± 2% distorted tetrahedral, and 23 ± 2% spherical nanoparticles, and the dominantly cubic nanoparticles have an initial shape distribution of 56 ± 4% regular cubes, 13 ± 1% distorted cubes, and 31 ± 3% truncated octahedral nanoparticles. The amount of tetrahedral nanoparticles decreases by 60 ± 5% after the first cycle and by 62 ± 4% after the second cycle of the reaction. In the case of cubic nanoparticles, the amount of cubic nanoparticles decreases by 39 ± 5% after the first cycle and by 66 ± 5% after the second cycle compared to before the reaction. After the first and second cycles of the reaction, there are a greater percentage of disto...
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surface enhanced raman scattering of molecules adsorbed on gold nanorods off surface plasmon resonance condition
Chemical Physics Letters, 2002Co-Authors: Babak Nikoobakht, Jianping Wang, Mostafa A ElsayedAbstract:The Raman spectra of several molecules adsorbed on gold nanospheres (NSs) (12 nm in diameter) and nanorods (NRs) (25 nm � 10 nm) are studied using an off-plasmon resonance excitation condition.The studies are carried out in Colloidal Solution and on solid substrates.Enhancement factors on the order of 10 4 –10 5 are observed for the adsorbed molecules on the NRs, however, no such enhancement was observed on NSs under similar condition.These factors are two orders of magnitude larger than the calculated value using the Wang and Kerker electromagnetic model.This suggests a contribution from the chemical mechanism in the observed enhancement. 2002 Published by Elsevier Science B.V.
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observation of large changes in the band gap absorption energy of small cdse nanoparticles induced by the adsorption of a strong hole acceptor
Nano Letters, 2001Co-Authors: Christy F Landes, Markus Braun, Clemens Burda, Mostafa A ElsayedAbstract:When butylamine in relatively high concentrations (0.1−0.25 M) is added to a Colloidal Solution of CdSe nanoparticles (NPs) that are approximately 1.6 nm in diameter, the band gap absorption changes from a broad, relatively weak absorption centered at 445 nm to a narrow, relatively strong absorption centered at 414 nm. The effect of concentration on the observed spectrum shows an isobestic point, suggesting an equilibrium between two species. The possible mechanisms for such a transformation are discussed.
Catherine J Murphy - One of the best experts on this subject based on the ideXlab platform.
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applications of Colloidal inorganic nanoparticles from medicine to energy
Journal of the American Chemical Society, 2012Co-Authors: Samuel E Lohse, Catherine J MurphyAbstract:The synthesis of well-defined inorganic nanoparticles in Colloidal Solution, which evolved gradually from the 1950s onward, has now reached the point where applications in both the research world and the wider world can be realized. This Perspective explores some of the successes and still-remaining challenges in nanoparticle synthesis and ligand analysis, highlights selected work in the areas of biomedicine and energy conversion that are enabled by Colloidal nanomaterials, and discusses technical barriers that need to be overcome by chemists and other scientists in order for nanotechnology to achieve its promise.
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aspect ratio dependence on surface enhanced raman scattering using silver and gold nanorod substrates
Physical Chemistry Chemical Physics, 2006Co-Authors: Christopher J Orendorff, Latha A Gearheart, Nikhil R Jana, Catherine J MurphyAbstract:Silver and gold nanorods with aspect ratios from 1 to 16 have been used as substrates for surface enhanced Raman spectroscopy (SERS) in Colloidal Solution. The nanorod aspect ratio is varied to give different degrees of overlap between the nanorod longitudinal plasmon band and excitation source in order to determine its effect on overall surface enhancement. Results suggest that enhancement factors are a factor of 10–102 greater for substrates that have plasmon band overlap with the excitation source than for substrates whose plasmon bands do not.
Motoo Yumura - One of the best experts on this subject based on the ideXlab platform.
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gas phase synthesis of single wall carbon nanotubes from Colloidal Solution of metal nanoparticles
Journal of Physical Chemistry B, 2001Co-Authors: Hiroki Ago, Satoshi Ohshima, And Kunio Uchida, Motoo YumuraAbstract:Metal nanoparticles play an important role in chemical vapor deposition (CVD) synthesis of carbon nanotubes because nanoparticles not only catalyze the nanotube growth but also determine the structural characteristics of the nanotubes. We report on the synthesis of single-wall carbon nanotubes (SWNTs) on the basis of the gas-phase reaction of Colloidal Solutions of metal nanoparticles containing Co and Mo. The Colloidal Solution of the nanoparticles is prepared by a reverse micelle method and injected into a furnace, where the solvent serves as the carbon source while the nanoparticles act as the catalyst. We have found that addition of a small amount of thiophene leads to formation of the SWNTs. The formation mechanism of the SWNTs is discussed by comparing the present CVD and laser-ablation methods.
Radha Narayanan - One of the best experts on this subject based on the ideXlab platform.
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Catalysis with transition metal nanoparticles in Colloidal Solution: nanoparticle shape dependence and stability.
The journal of physical chemistry. B, 2005Co-Authors: Radha Narayanan, Mostafa A. El-sayedAbstract:While the nanocatalysis field has undergone an explosive growth during the past decade, there have been very few studies in the area of shape-dependent catalysis and the effect of the catalytic process on the shape and size of transition metal nanoparticles as well as their recycling potential. Metal nanoparticles of different shapes have different crystallographic facets and have different fraction of surface atoms on their corners and edges, which makes it interesting to study the effect of metal nanoparticle shape on the catalytic activity of various organic and inorganic reactions. Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials, but their surface atoms could be so active that changes in the size and shape of the nanoparticles could occur during the course of their catalytic function, which could also affect their recycling potential. In this Feature Article, we review our work on the effect of the shape of the Colloidal nanocatalyst on the catalytic activity as well as the effect of the catalytic process on the shape and size of the Colloidal transition metal nanocatalysts and their recycling potential. These studies provide important clues on the mechanism of the reactions we studied and also can be very useful in the process of designing better catalysts in the future.
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catalysis with transition metal nanoparticles in Colloidal Solution nanoparticle shape dependence and stability
Journal of Physical Chemistry B, 2005Co-Authors: Radha Narayanan, Mostafa A ElsayedAbstract:While the nanocatalysis field has undergone an explosive growth during the past decade, there have been very few studies in the area of shape-dependent catalysis and the effect of the catalytic process on the shape and size of transition metal nanoparticles as well as their recycling potential. Metal nanoparticles of different shapes have different crystallographic facets and have different fraction of surface atoms on their corners and edges, which makes it interesting to study the effect of metal nanoparticle shape on the catalytic activity of various organic and inorganic reactions. Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials, but their surface atoms could be so active that changes in the size and shape of the nanoparticles could occur during the course of their catalytic function, which could also affect their recycling potential. In this Feature Article, we review our work on the effect of the shape o...
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shape dependent catalytic activity of platinum nanoparticles in Colloidal Solution
Nano Letters, 2004Co-Authors: Radha Narayanan, Mostafa A ElsayedAbstract:The activation energies and the average rate constants are determined in the 298 K−318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (III) and thiosulfate ions using 4.8 ± 0.1 nm tetrahedral, 7.1 ± 0.2 nm cubic, and 4.9 ± 0.1 nm “near spherical” nanocrystals. These kinetic parameters are found to correlate with the calculated fraction of surface atoms located on the corners and edges in each size and shape.
P V Lebedevstepanov - One of the best experts on this subject based on the ideXlab platform.
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simulation of self assembly in an evaporating droplet of Colloidal Solution by dissipative particle dynamics
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013Co-Authors: P V Lebedevstepanov, Konstantin VlasovAbstract:Abstract A method of Brownian dissipative dynamics of charged Colloidal nanoparticles in microdroplet of Solution deposited on plane substrate is proposed for investigation of self-assembly and self-ordering of colloids during solute evaporation. Method is based on the numerical Solution of multi-scale Langevin equation for each particle, the hydrodynamic microflows approach, and droplet evaporation model. The method takes into account the DLVO-forces between the particles, their interaction with the substrate (adhesion, friction, roughness); Stokes’, Brownian, and capillary forces (wetting and depinning, outflow angles, surface tension). The self-assembled pattern morphology dependence on the model parameters is investigated. The nature of coffee ring effect was studied. It is shown that the hexagonal domain ordering of particles ensemble in pattern can be formed onto plane substrate as a result of interparticle repulsion and the capillary compression during evaporation of solvent. Numerical results are in good agreement with experiments on self-assembly in Colloidal droplet deposited by inkjet technology.
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effect of substrate temperature on the self assembly of particles in the evaporating droplet of Colloidal Solution
Nanotechnologies in Russia, 2010Co-Authors: S P Molchanov, P V Lebedevstepanov, M V AlfimovAbstract:It was shown that the morphology of the ensemble of Colloidal particles deposited on the substrate from the evaporating droplet of Colloidal Solution can be controlled by varying the temperature of the substrate relative to the temperature of the coated Solution and environment. The main driving forces of self-assembly in the presence of a temperature gradient inside the droplet are considered.