The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Serge Stoll - One of the best experts on this subject based on the ideXlab platform.
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Dielectric Discontinuity effects on the adsorption of a linear polyelectrolyte at the surface of a neutral nanoparticle
The Journal of chemical physics, 2009Co-Authors: Marianne Seijo, Serge Ulrich, Martin Pohl, Serge StollAbstract:The formation of complexes between nanoparticles and polyelectrolytes is a key process for the control of the reactivity of manufactured nanoparticles and rational design of core shell nanostructures. In this work, we investigate the influence of the nanoparticle Dielectric constant on the adsorption of a linear charged polymer (polyelectrolyte) at the surface of a neutral nanoparticle. The polyelectrolyte linear charge density, as well as the image charges in the nanoparticle due to the Dielectric Discontinuity, is taken into account. Monte Carlo simulations are used to predict the adsorption/desorption limits and system properties. Effects of the nanoparticle size and polyelectrolyte length are also investigated. The polyelectrolyte is found adsorbed on the nanoparticle when the Dielectric constant of the nanoparticle is greater than the Dielectric constant of the medium. Attractive interactions induced by the presence of opposite sign image charges are found strong enough to adsorb the polyelectrolyte showing that the reaction field contribution has to be considered. The affinity between the polyelectrolyte and the nanoparticle is found to increase in magnitude by increasing the nanoparticle size and Dielectric constant. The reaction field magnitude is also found to depend in a nonlinear way from the polyelectrolyte length.
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modeling the surface charge evolution of spherical nanoparticles by considering Dielectric Discontinuity effects at the solid electrolyte solution interface
Journal of Colloid and Interface Science, 2008Co-Authors: Marianne Seijo, Serge Ulrich, Montserrat Filella, Jacques Buffle, Serge StollAbstract:It is well known that the electrostatic repulsions between charges on neighboring sites decrease the effective charge at the surface of a charged nanoparticle (NP). However, the situation is more complex close to a Dielectric Discontinuity, since charged sites are interacting not only with their neighbors but also with their own image charges and the image charges of all neighbors. Titrating site positions, solution ionic concentration, Dielectric Discontinuity effects, and surface charge variations with pH are investigated here using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach is used to calculate the interaction potentials between the discrete charged sites. Homogeneous, heterogeneous, and patch site distributions are considered to reproduce the various titrating site distributions at the solid/solution interface of spherical NPs. By considering Coulomb, salt, and image charges effects, results show that for different ionic concentrations, modifications of the Dielectric constant of NPs having homogeneous and heterogeneous site distributions have little effect on their charging process. Thus, the reaction field, due to the presence of image charges, fully counterbalances the Coulomb interactions. This is not the case for patch distributions, where Coulomb interactions are not completely counterbalanced by the reaction field. Application of the present model to pyrogenic silica is also performed and comparison is made with published experimental data of titration curves at various ionic concentrations.
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Modeling the surface charge evolution of spherical nanoparticles by considering Dielectric Discontinuity effects at the solid/electrolyte solution interface.
Journal of colloid and interface science, 2008Co-Authors: Marianne Seijo, Serge Ulrich, Montserrat Filella, Jacques Buffle, Serge StollAbstract:It is well known that the electrostatic repulsions between charges on neighboring sites decrease the effective charge at the surface of a charged nanoparticle (NP). However, the situation is more complex close to a Dielectric Discontinuity, since charged sites are interacting not only with their neighbors but also with their own image charges and the image charges of all neighbors. Titrating site positions, solution ionic concentration, Dielectric Discontinuity effects, and surface charge variations with pH are investigated here using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach is used to calculate the interaction potentials between the discrete charged sites. Homogeneous, heterogeneous, and patch site distributions are considered to reproduce the various titrating site distributions at the solid/solution interface of spherical NPs. By considering Coulomb, salt, and image charges effects, results show that for different ionic concentrations, modifications of the Dielectric constant of NPs having homogeneous and heterogeneous site distributions have little effect on their charging process. Thus, the reaction field, due to the presence of image charges, fully counterbalances the Coulomb interactions. This is not the case for patch distributions, where Coulomb interactions are not completely counterbalanced by the reaction field. Application of the present model to pyrogenic silica is also performed and comparison is made with published experimental data of titration curves at various ionic concentrations.
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Effects of surface site distribution and Dielectric Discontinuity on the charging behavior of nanoparticles. A grand canonical Monte Carlo study
Physical chemistry chemical physics : PCCP, 2006Co-Authors: Marianne Seijo, Serge Ulrich, Montserrat Filella, Jacques Buffle, Serge StollAbstract:The surface site distribution and the Dielectric Discontinuity effects on the charging process of a spherical nanoparticle (NP) have been investigated. It is well known that electrostatic repulsion between charges on neighbouring sites tends to decrease the effective charge of a NP. The situation is more complicated close to a Dielectric breakdown, since here a charged site is not only interacting with its neighbours but also with its own image charge and the image charges of all its neighbours. Coexistence of opposite charges, titration sites positions, and pH dependence are systematically studied using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach has been applied to describe the interaction potentials between explicit discrete ampholytic charging sites. Homogeneous, heterogeneous and patch site distributions were considered to reproduce the titration site distribution at the solid/solution interface of natural NPs. Results show that the charging process is controlled by the balance between Coulomb interactions and the reaction field through the solid–liquid interface. They also show that the site distribution plays a crucial role in the charging process. In patch distributions, charges accumulate at the perimeter of each patch due to finite size effects. When homogeneous and heterogeneous distributions are compared, three different charging regimes are obtained. In homogeneous and heterogeneous (with quite low polydispersity indexes) distributions, the effects of the NP Dielectric constant on Coulomb interactions are counterbalanced by the reaction field and in this case, the Dielectric breakdown has no significant effect on the charging process. This is not the case in patch distributions, where the Dielectric breakdown plays a crucial role in the charging process.
Rajeev Ahuja - One of the best experts on this subject based on the ideXlab platform.
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shallow donor inside core shell spherical nanodot effect of nanostructure size and Dielectric environment on energy spectrum
Superlattices and Microstructures, 2017Co-Authors: A Chafai, F Dujardin, I Essaoudi, A Ainane, Rajeev AhujaAbstract:Abstract We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The Dielectric Discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.
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Shallow donor inside core/shell spherical nanodot: Effect of nanostructure size and Dielectric environment on energy spectrum
Superlattices and Microstructures, 2017Co-Authors: A Chafai, F Dujardin, I Essaoudi, A Ainane, Rajeev AhujaAbstract:We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The Dielectric Discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.
Marianne Seijo - One of the best experts on this subject based on the ideXlab platform.
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Dielectric Discontinuity effects on the adsorption of a linear polyelectrolyte at the surface of a neutral nanoparticle
The Journal of chemical physics, 2009Co-Authors: Marianne Seijo, Serge Ulrich, Martin Pohl, Serge StollAbstract:The formation of complexes between nanoparticles and polyelectrolytes is a key process for the control of the reactivity of manufactured nanoparticles and rational design of core shell nanostructures. In this work, we investigate the influence of the nanoparticle Dielectric constant on the adsorption of a linear charged polymer (polyelectrolyte) at the surface of a neutral nanoparticle. The polyelectrolyte linear charge density, as well as the image charges in the nanoparticle due to the Dielectric Discontinuity, is taken into account. Monte Carlo simulations are used to predict the adsorption/desorption limits and system properties. Effects of the nanoparticle size and polyelectrolyte length are also investigated. The polyelectrolyte is found adsorbed on the nanoparticle when the Dielectric constant of the nanoparticle is greater than the Dielectric constant of the medium. Attractive interactions induced by the presence of opposite sign image charges are found strong enough to adsorb the polyelectrolyte showing that the reaction field contribution has to be considered. The affinity between the polyelectrolyte and the nanoparticle is found to increase in magnitude by increasing the nanoparticle size and Dielectric constant. The reaction field magnitude is also found to depend in a nonlinear way from the polyelectrolyte length.
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modeling the surface charge evolution of spherical nanoparticles by considering Dielectric Discontinuity effects at the solid electrolyte solution interface
Journal of Colloid and Interface Science, 2008Co-Authors: Marianne Seijo, Serge Ulrich, Montserrat Filella, Jacques Buffle, Serge StollAbstract:It is well known that the electrostatic repulsions between charges on neighboring sites decrease the effective charge at the surface of a charged nanoparticle (NP). However, the situation is more complex close to a Dielectric Discontinuity, since charged sites are interacting not only with their neighbors but also with their own image charges and the image charges of all neighbors. Titrating site positions, solution ionic concentration, Dielectric Discontinuity effects, and surface charge variations with pH are investigated here using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach is used to calculate the interaction potentials between the discrete charged sites. Homogeneous, heterogeneous, and patch site distributions are considered to reproduce the various titrating site distributions at the solid/solution interface of spherical NPs. By considering Coulomb, salt, and image charges effects, results show that for different ionic concentrations, modifications of the Dielectric constant of NPs having homogeneous and heterogeneous site distributions have little effect on their charging process. Thus, the reaction field, due to the presence of image charges, fully counterbalances the Coulomb interactions. This is not the case for patch distributions, where Coulomb interactions are not completely counterbalanced by the reaction field. Application of the present model to pyrogenic silica is also performed and comparison is made with published experimental data of titration curves at various ionic concentrations.
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Modeling the surface charge evolution of spherical nanoparticles by considering Dielectric Discontinuity effects at the solid/electrolyte solution interface.
Journal of colloid and interface science, 2008Co-Authors: Marianne Seijo, Serge Ulrich, Montserrat Filella, Jacques Buffle, Serge StollAbstract:It is well known that the electrostatic repulsions between charges on neighboring sites decrease the effective charge at the surface of a charged nanoparticle (NP). However, the situation is more complex close to a Dielectric Discontinuity, since charged sites are interacting not only with their neighbors but also with their own image charges and the image charges of all neighbors. Titrating site positions, solution ionic concentration, Dielectric Discontinuity effects, and surface charge variations with pH are investigated here using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach is used to calculate the interaction potentials between the discrete charged sites. Homogeneous, heterogeneous, and patch site distributions are considered to reproduce the various titrating site distributions at the solid/solution interface of spherical NPs. By considering Coulomb, salt, and image charges effects, results show that for different ionic concentrations, modifications of the Dielectric constant of NPs having homogeneous and heterogeneous site distributions have little effect on their charging process. Thus, the reaction field, due to the presence of image charges, fully counterbalances the Coulomb interactions. This is not the case for patch distributions, where Coulomb interactions are not completely counterbalanced by the reaction field. Application of the present model to pyrogenic silica is also performed and comparison is made with published experimental data of titration curves at various ionic concentrations.
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Effects of surface site distribution and Dielectric Discontinuity on the charging behavior of nanoparticles. A grand canonical Monte Carlo study
Physical chemistry chemical physics : PCCP, 2006Co-Authors: Marianne Seijo, Serge Ulrich, Montserrat Filella, Jacques Buffle, Serge StollAbstract:The surface site distribution and the Dielectric Discontinuity effects on the charging process of a spherical nanoparticle (NP) have been investigated. It is well known that electrostatic repulsion between charges on neighbouring sites tends to decrease the effective charge of a NP. The situation is more complicated close to a Dielectric breakdown, since here a charged site is not only interacting with its neighbours but also with its own image charge and the image charges of all its neighbours. Coexistence of opposite charges, titration sites positions, and pH dependence are systematically studied using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach has been applied to describe the interaction potentials between explicit discrete ampholytic charging sites. Homogeneous, heterogeneous and patch site distributions were considered to reproduce the titration site distribution at the solid/solution interface of natural NPs. Results show that the charging process is controlled by the balance between Coulomb interactions and the reaction field through the solid–liquid interface. They also show that the site distribution plays a crucial role in the charging process. In patch distributions, charges accumulate at the perimeter of each patch due to finite size effects. When homogeneous and heterogeneous distributions are compared, three different charging regimes are obtained. In homogeneous and heterogeneous (with quite low polydispersity indexes) distributions, the effects of the NP Dielectric constant on Coulomb interactions are counterbalanced by the reaction field and in this case, the Dielectric breakdown has no significant effect on the charging process. This is not the case in patch distributions, where the Dielectric breakdown plays a crucial role in the charging process.
A Ainane - One of the best experts on this subject based on the ideXlab platform.
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shallow donor inside core shell spherical nanodot effect of nanostructure size and Dielectric environment on energy spectrum
Superlattices and Microstructures, 2017Co-Authors: A Chafai, F Dujardin, I Essaoudi, A Ainane, Rajeev AhujaAbstract:Abstract We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The Dielectric Discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.
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Shallow donor inside core/shell spherical nanodot: Effect of nanostructure size and Dielectric environment on energy spectrum
Superlattices and Microstructures, 2017Co-Authors: A Chafai, F Dujardin, I Essaoudi, A Ainane, Rajeev AhujaAbstract:We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The Dielectric Discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.
F Dujardin - One of the best experts on this subject based on the ideXlab platform.
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shallow donor inside core shell spherical nanodot effect of nanostructure size and Dielectric environment on energy spectrum
Superlattices and Microstructures, 2017Co-Authors: A Chafai, F Dujardin, I Essaoudi, A Ainane, Rajeev AhujaAbstract:Abstract We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The Dielectric Discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.
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Shallow donor inside core/shell spherical nanodot: Effect of nanostructure size and Dielectric environment on energy spectrum
Superlattices and Microstructures, 2017Co-Authors: A Chafai, F Dujardin, I Essaoudi, A Ainane, Rajeev AhujaAbstract:We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The Dielectric Discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.
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Control of the binding energy by tuning the single dopant position, magnetic field strength and shell thickness in ZnS/CdSe core/shell quantum dot
Physica E: Low-dimensional Systems and Nanostructures, 2016Co-Authors: A. Talbi, F Dujardin, E. Feddi, A. Zouitine, M. El Haouari, M. Zazoui, A. Oukerroum, E. Assaid, M. AddouAbstract:Recently, the new tunable optoelectronic devices associated to the inclusion of the single dopant are in continuous emergence. Combined to other effects such as magnetic field, geometrical confinement and Dielectric Discontinuity, it can constitute an approach to adjusting new transitions. In this paper, we present a theoretical investigation of magnetic field, donor position and quantum confinement effects on the ground state binding energy of single dopant confined in ZnS/CdSe core/shell quantum dot. Within the framework of the effective mass approximation, the Schrödinger equation was numerically been solved by using the Ritz variational method under the finite potential barrier. The results show that the binding energy is very affected by the core/shell sizes and by the external magnetic field. It has been shown that the single dopant energy transitions can be controlled by tuning the dopant position and/or the field strength.