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Lee R Penn - One of the best experts on this subject based on the ideXlab platform.
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size dependent anatase to rutile phase transformation and Particle growth
Chemistry of Materials, 2013Co-Authors: Kairat Sabyrov, Nathan D Burrows, Lee R PennAbstract:Phase transformation and Particle growth are fundamental processes that govern Final Particle size and morphology, as well as phase composition. At the nanoscale, these processes can be significantly affected by initial Particle size. Rates of anatase growth and its transformation to rutile increase with decreasing initial size under hydrothermal conditions at pH 1 and pH 3. Overall, rates are slower at the higher pH. At pH 1, the data fit well to a kinetic model developed based on a dissolution–precipitation mechanism. However, at pH 3, it deviates substantially from the model, indicating that the transformation occurs via a different mechanism or a mixture of dissolution–precipitation and another mechanism, which likely involves aggregation. Finally, the compactness of the aggregates affects the processes significantly. That is, densely aggregated Particles show higher transformation and growth rates, compared to loosely aggregated ones.
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size dependent anatase to rutile phase transformation and Particle growth
Chemistry of Materials, 2013Co-Authors: Kairat Sabyrov, Nathan D Burrows, Lee R PennAbstract:Phase transformation and Particle growth are fundamental processes that govern Final Particle size and morphology, as well as phase composition. At the nanoscale, these processes can be significant...
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zinc oxide nanoParticle growth from homogenous solution influence of zn oh water concentration and surfactant additives
Materials Research Bulletin, 2009Co-Authors: Anthony S Ratkovich, Lee R PennAbstract:Zinc oxide Particle growth from homogeneous solution was monitored using in situ UV-vis spectroscopy. Final Particle size and overall growth rate increased with increasing zinc to hydroxide concentration ratio and were both sensitive to the surfactant added. Particle growth was fit using two models: (1) the classic coarsening model and (2) the simultaneous coarsening and oriented aggregation model. Results demonstrate that using adamantane carboxylic acid as a surfactant additive inhibits ZnO nanoParticle growth both by coarsening and oriented aggregation as compared to using other monocarboxylates (e.g., acetate and tribromoacetate). In addition, ZnO nanoParticle growth was independent of water concentration within the range of 40-100 mM for the conditions studied here (1 mM zinc perchlorate, 1.6 mM hydroxide, and 0.38 mM adamantane carboxylic acid). High-resolution transmission electron micrographs confirm inhibited growth by oriented aggregation for ZnO grown with adamantane carboxylic acid. Results are compared to previous work and generally show that ZnO growth by coarsening and oriented aggregation can be selectively inhibited or promoted by judicious selection of the surfactant additive.
Kairat Sabyrov - One of the best experts on this subject based on the ideXlab platform.
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size dependent anatase to rutile phase transformation and Particle growth
Chemistry of Materials, 2013Co-Authors: Kairat Sabyrov, Nathan D Burrows, Lee R PennAbstract:Phase transformation and Particle growth are fundamental processes that govern Final Particle size and morphology, as well as phase composition. At the nanoscale, these processes can be significant...
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size dependent anatase to rutile phase transformation and Particle growth
Chemistry of Materials, 2013Co-Authors: Kairat Sabyrov, Nathan D Burrows, Lee R PennAbstract:Phase transformation and Particle growth are fundamental processes that govern Final Particle size and morphology, as well as phase composition. At the nanoscale, these processes can be significantly affected by initial Particle size. Rates of anatase growth and its transformation to rutile increase with decreasing initial size under hydrothermal conditions at pH 1 and pH 3. Overall, rates are slower at the higher pH. At pH 1, the data fit well to a kinetic model developed based on a dissolution–precipitation mechanism. However, at pH 3, it deviates substantially from the model, indicating that the transformation occurs via a different mechanism or a mixture of dissolution–precipitation and another mechanism, which likely involves aggregation. Finally, the compactness of the aggregates affects the processes significantly. That is, densely aggregated Particles show higher transformation and growth rates, compared to loosely aggregated ones.
Laszlo Pusztai - One of the best experts on this subject based on the ideXlab platform.
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reverse monte carlo modeling of liquid water with the explicit use of the spc e interatomic potential
Journal of Chemical Physics, 2017Co-Authors: Ildiko Pethes, Laszlo PusztaiAbstract:Reverse Monte Carlo (RMC) modeling of liquid water, based on one neutron and one X-ray diffraction data set, applying also the most popular interatomic potential for water, extended simple point charge (SPC/E), has been performed. The strictly rigid geometry of SPC/E water molecules had to be loosened somewhat, in order to be able to produce a good fit to both sets of experimental data. In the Final Particle configurations, regularly shaped water molecules and straight hydrogen bonding angles were found to be consistent with diffraction results. It has been demonstrated that the explicit use of interatomic potentials in RMC has a role to play in future structural modeling of water and aqueous solutions.
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reverse monte carlo modeling of liquid water with the explicit use of the spc e interatomic potential
arXiv: Soft Condensed Matter, 2017Co-Authors: Ildiko Pethes, Laszlo PusztaiAbstract:Reverse Monte Carlo modeling of liquid water, based on one neutron and one X-ray diffraction data set, applying also the most popular interatomic potential for water, SPC/E, has been performed. The strictly rigid geometry of SPC/E water molecules had to be loosened somewhat, in order to be able to produce a good fit to both sets of experimental data. In the Final Particle configurations, regularly shaped water molecules and straight hydrogen bonding angles were found to be consistent with diffraction results. It has been demonstrated that explicit use of interatomic potentials in RMC has a role to play in future structural modeling of water and aqueous solutions.
Younes Moussaoui - One of the best experts on this subject based on the ideXlab platform.
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tuning Particle morphology of mesoporous silica nanoParticles for adsorption of dyes from aqueous solution
Journal of Saudi Chemical Society, 2017Co-Authors: Sana Kachbouri, Najib Mnasri, Elimame Elaloui, Younes MoussaouiAbstract:Abstract Spherical and rod mesoporous silica nanoParticles with hexagonal mesostructure were prepared using the modified Stober method. The morphology, size and internal pore structure can be controlled by simple changing of surfactant concentration and water:ethanol molar ratio. Monodispersed spheroid MCM-41 was obtained at 40 °C under basic conditions using cetyltrimethylammonium bromide (C 16 TAB) as template. Obtained materials were characterized by X-ray diffraction (XRD), nitrogen physisorption (BET), transmission electron microscopy (TEM) and scanning electronic microscopy (SEM). The results reveal that the pore volume and surface area increase when the amount of C 16 TAB increases whereas the pore diameter and Particle size decrease. However, the use of ethanol as cosolvent led to an increase in the Particles’ size. Moreover, the addition of a 3-aminopropyltriethoxysilane greatly influenced the Final Particle shape. The material was effectively used for the removal of two fluorescent dyes (Hoechst 33342 and rhodamine 6g) from aqueous solution. Adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. The Langmuir model was found to fit the experimental data better than others models.
Jörg Polte - One of the best experts on this subject based on the ideXlab platform.
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fundamental growth principles of colloidal metal nanoParticles a new perspective
CrystEngComm, 2015Co-Authors: Jörg PolteAbstract:In the past few decades, much effort was put into the development of synthetic strategies to produce nanoParticles of different sizes and morphologies and a large number of scientific contributions is dedicated to the characterization and application of metal nanoParticles. In contrast, only few studies deal with Particle formation mechanisms. As a consequence, theoretical concepts that describe Particle growth processes are very rare and the few existing models are hardly able to explain how synthesis parameters influence the Final Particle size distribution. This contribution discusses recent experimental results from which a novel growth concept based on colloidal stability is deduced. The growth concept is in contrast to nucleation models and allows a description of colloidal growth processes from a different perspective. It states that for most syntheses the minimal Particle size is rather determined by colloidal than thermodynamic stability making a nucleation model irrelevant.
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illustrating the formation of metal nanoParticles with a growth concept based on colloidal stability
Physical Chemistry Chemical Physics, 2015Co-Authors: Maria Wuithschick, Steffen Witte, Frieder Kettemann, Klaus Rademann, Jörg PolteAbstract:A large number of scientific contributions is dedicated to syntheses, characterization and applications of metal nanoParticles. In contrast, only few studies on their formation mechanisms have been reported. In general, concepts to describe Particle growth processes are rare. Commonly used models are not able to explain the influences of reaction parameters on the growth and the Final Particle size. In this contribution it is shown how the growth of colloidal metal nanoParticles can be illustrated using an approach based on colloidal stability. In the first part, investigations of various syntheses of colloidal nanoParticles (including Rh, Pd, Pt, Cu, Ag and Au) show that growth due to aggregation and coalescence is the governing principle of nanoParticle formation if the monomer supply is faster than the actual growth. In the second part of this contribution, the influences of various parameters on the growth of Au nanoParticles are studied and it is demonstrated how the colloidal stability approach can illustrate the impact of synthesis parameters on the Final Particle size.