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Article ; Online: Comment on the article Primary structure of gum arabic and its dynamics at oil/water interface by Isobe et al.: The primary structure of gum Arabic species is not two-dimensional.

Roger, Kevin

2020 Volume 253, Page(s) 117234

Language	English
Publishing date	2020-10-20
Publishing country	England
Document type	Journal Article ; Comment
ZDB-ID	1501516-6
ISSN	1879-1344 ; 0144-8617
ISSN (online)	1879-1344
ISSN	0144-8617
DOI	10.1016/j.carbpol.2020.117234
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: An Alkanethiol-Surfactant Bilayer To Prevent Shape Conversion of Anisotropic Silver Nanoparticles and Probe Their Formation Mechanisms.

El Amri, Nouha / Roger, Kevin

Langmuir : the ACS journal of surfaces and colloids

2023 Volume 39, Issue 25, Page(s) 8623–8628

Abstract: Anisotropic nanoparticles can be synthesized under kinetic control but may undergo subsequent shape changes due to atomic reorganization. Furthermore, their synthesis involves rapid steps, which are challenging to monitor in situ. Here, we show how a ... ...

Abstract	Anisotropic nanoparticles can be synthesized under kinetic control but may undergo subsequent shape changes due to atomic reorganization. Furthermore, their synthesis involves rapid steps, which are challenging to monitor in situ. Here, we show how a nanoemulsion of alkanethiols with an ethoxylated surfactant, easily prepared and metastable for months, can simultaneously prevent shape reorganization and arrest reaction kinetics. We illustrate this generic method on the silver nanoplates synthesized in concentrated acetic acid aqueous solutions, in which rapid shape reorganization occurs. We show that there exists an optimum thiol concentration corresponding to full coverage of all silver surface atoms, which can be simply calculated from particle dimensions. Furthermore, we demonstrate that arresting nanoparticle formation can be achieved within milliseconds using a tandem rapid mixers scheme in a continuous flow setup, allowing ex situ monitoring of the reaction.
Language	English
Publishing date	2023-06-12
Publishing country	United States
Document type	Journal Article
ZDB-ID	2005937-1
ISSN	1520-5827 ; 0743-7463
ISSN (online)	1520-5827
ISSN	0743-7463
DOI	10.1021/acs.langmuir.3c00398
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Article: Controlling nanoparticle formation from the onset of nucleation through a multi-step continuous flow approach

Roger, Kevin / El Amri, Nouha

Journal of colloid and interface science. 2022 Feb. 15, v. 608

2022

Abstract: Metallic nanoparticles of various shapes and sizes can be synthesised through a diversity of bottom-up pathways, such as precipitation induced by chemical reduction. Varying composition, by adjusting concentrations or adding/replacing species, is the ... ...

Abstract	Metallic nanoparticles of various shapes and sizes can be synthesised through a diversity of bottom-up pathways, such as precipitation induced by chemical reduction. Varying composition, by adjusting concentrations or adding/replacing species, is the predominant strategy to tune nanoparticles structures. However, controlling time down to the onset of precipitation, nucleation, should also provide a powerful means to control nanostructuration. We perform sequential reagent additions with a time resolution down to the millisecond. We use a millifluidic continuous flow setup consisting of tangential mixers in series, which allows flow rates up to dozens of litres per hour. We systematically vary both addition order and delay for each reagent involved in the synthesis of silver nanoplates. The resulting dispersions are compared using UV–visible spectroscopy, transmission electron microscopy and small-angle X-ray scattering. We show that synthesis pathways differing only in the order of sub-second additions lead to drastically different synthetic outcomes. Silver nanoparticles of different shapes and sizes, displaying an array of plasmonic colours, are synthesised at the same final composition by tuning the composition pathways along time. Our results unlock a previously inaccessible portion of the space of parameters, which will lead to an enhanced structural diversity, control and understanding of nanoparticles syntheses.
Keywords	chemical reduction ; nanosilver ; silver ; small-angle X-ray scattering ; transmission electron microscopy ; ultraviolet-visible spectroscopy
Language	English
Dates of publication	2022-0215
Size	p. 1750-1757.
Publishing place	Elsevier Inc.
Document type	Article
ZDB-ID	241597-5
ISSN	1095-7103 ; 0021-9797
ISSN (online)	1095-7103
ISSN	0021-9797
DOI	10.1016/j.jcis.2021.10.071
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Article ; Online: Nanoprecipitation through solvent-shifting using rapid mixing: Dispelling the Ouzo boundary to reach large solute concentrations.

Roger, Kevin / Shcherbakova, Nataliya / Raynal, Lison

Journal of colloid and interface science

2023 Volume 650, Issue Pt B, Page(s) 2049–2055

Abstract: Hypothesis: The addition of a non-solvent to a solute in good solvent solution leads to nanoprecipitation, which is the spontaneous formation of nanodomains. Yet, increasing solute concentration usually leads to the formation of macrodomains that ... ...

Abstract	Hypothesis: The addition of a non-solvent to a solute in good solvent solution leads to nanoprecipitation, which is the spontaneous formation of nanodomains. Yet, increasing solute concentration usually leads to the formation of macrodomains that quickly separate into a bulk phase, which is a severe process limitation. The corresponding concentration threshold, often termed as the Ouzo boundary, remains a mystery that could find its origin in the complex interplay between nanoprecipitation and mixing. Experiments: We performed a systematic investigation of nanoprecipitation thermodynamics and kinetics as well as its interplay with mixing hydrodynamics for the hexadecane-acetone-water system, in the presence of the non-ionic C Findings: We elucidate the nature of the Ouzo boundary that marks the maximal solute concentration leading to nanoobjects. Rather than a thermodynamic boundary, as evidenced by its uncorrelation to the spinodal curve, it results from the coupling of nanoprecipitation and mixing when both processes occur within the same time range, leading to heterogeneous conditions and the escape of some objects to the macroscale. Increasing the solute concentration speeds up nanoprecipitation and thus requires increasingly faster mixing times to uncouple both processes. Accordingly, if the mixing efficiency is large enough, it is possible to dispel the Ouzo boundary and reach very large solute concentrations. Implementing rapid mixing strategies in continuous flow approaches is thus the solution to overcome the most stringent condition of nanoprecipitation and open the way to scale-up, while also providing efficient means to probe its fast mechanism. Overall, the simultaneous control of hydrodynamics and physical chemistry is thus key to boost up the Ouzo effect.
Language	English
Publishing date	2023-07-24
Publishing country	United States
Document type	Journal Article
ZDB-ID	241597-5
ISSN	1095-7103 ; 0021-9797
ISSN (online)	1095-7103
ISSN	0021-9797
DOI	10.1016/j.jcis.2023.07.065
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Article ; Online: Using the Intrinsic Geometry of Binodal Curves to Simplify the Computation of Ternary Liquid-Liquid Phase Diagrams.

Shcherbakova, Nataliya / Gerbaud, Vincent / Roger, Kevin

Entropy (Basel, Switzerland)

2023 Volume 25, Issue 9

Abstract: Phase diagrams are powerful tools to understand the multi-scale behaviour of complex systems. Yet, their determination requires in practice both experiments and computations, which quickly becomes a daunting task. Here, we propose a geometrical approach ... ...

Abstract	Phase diagrams are powerful tools to understand the multi-scale behaviour of complex systems. Yet, their determination requires in practice both experiments and computations, which quickly becomes a daunting task. Here, we propose a geometrical approach to simplify the numerical computation of liquid-liquid ternary phase diagrams. We show that using the intrinsic geometry of the binodal curve, it is possible to formulate the problem as a simple set of ordinary differential equations in an extended 4D space. Consequently, if the thermodynamic potential, such as Gibbs free energy, is known from an experimental data set, the whole phase diagram, including the spinodal curve, can be easily computed. We showcase this approach on four ternary liquid-liquid diagrams, with different topological properties, using a modified Flory-Huggins model. We demonstrate that our method leads to similar or better results comparing those obtained with other methods, but with a much simpler procedure. Acknowledging and using the intrinsic geometry of phase diagrams thus appears as a promising way to further develop the computation of multiphase diagrams.
Language	English
Publishing date	2023-09-13
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2014734-X
ISSN	1099-4300 ; 1099-4300
ISSN (online)	1099-4300
ISSN	1099-4300
DOI	10.3390/e25091329
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Article ; Online: Nanoprecipitation through solvent-shifting using rapid mixing: Dispelling the Ouzo boundary to reach large solute concentrations

Roger, Kevin / Shcherbakova, Nataliya / Raynal, Lison

Journal of Colloid And Interface Science. 2023 Nov., v. 650 p.2049-2055

2023

Abstract: The addition of a non-solvent to a solute in good solvent solution leads to nanoprecipitation, which is the spontaneous formation of nanodomains. Yet, increasing solute concentration usually leads to the formation of macrodomains that quickly separate ... ...

Abstract	The addition of a non-solvent to a solute in good solvent solution leads to nanoprecipitation, which is the spontaneous formation of nanodomains. Yet, increasing solute concentration usually leads to the formation of macrodomains that quickly separate into a bulk phase, which is a severe process limitation. The corresponding concentration threshold, often termed as the Ouzo boundary, remains a mystery that could find its origin in the complex interplay between nanoprecipitation and mixing. We performed a systematic investigation of nanoprecipitation thermodynamics and kinetics as well as its interplay with mixing hydrodynamics for the hexadecane-acetone-water system, in the presence of the non-ionic C₁₆EO₈ surfactant. The binodal curve and its underlying tie-lines were obtained using Raman spectroscopy, allowing the computation of the spinodal curve. Kinetics were probed using a continuous flow setup that combines two sequential rapid mixers. The impact of mixing efficiency was probed systematically by varying the oil concentration for respectively slow and rapid mixing, while the uncoupling from mixing and nanoprecipitation was quantified by modifying systematically the flow rate in a continuous flow approach. We elucidate the nature of the Ouzo boundary that marks the maximal solute concentration leading to nanoobjects. Rather than a thermodynamic boundary, as evidenced by its uncorrelation to the spinodal curve, it results from the coupling of nanoprecipitation and mixing when both processes occur within the same time range, leading to heterogeneous conditions and the escape of some objects to the macroscale. Increasing the solute concentration speeds up nanoprecipitation and thus requires increasingly faster mixing times to uncouple both processes. Accordingly, if the mixing efficiency is large enough, it is possible to dispel the Ouzo boundary and reach very large solute concentrations. Implementing rapid mixing strategies in continuous flow approaches is thus the solution to overcome the most stringent condition of nanoprecipitation and open the way to scale-up, while also providing efficient means to probe its fast mechanism. Overall, the simultaneous control of hydrodynamics and physical chemistry is thus key to boost up the Ouzo effect.
Keywords	Raman spectroscopy ; hydrodynamics ; nanotechnology ; oils ; physical chemistry ; solutes ; solvents ; surfactants ; thermodynamics ; Nanoprecipitation ; Mixing ; Continuous flow ; Kinetics ; Phase diagram ; Ouzo ; Boundary ; Solvent-shifting
Language	English
Dates of publication	2023-11
Size	p. 2049-2055.
Publishing place	Elsevier Inc.
Document type	Article ; Online
ZDB-ID	241597-5
ISSN	1095-7103 ; 0021-9797
ISSN (online)	1095-7103
ISSN	0021-9797
DOI	10.1016/j.jcis.2023.07.065
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Controlling nanoparticle formation from the onset of nucleation through a multi-step continuous flow approach.

Roger, Kevin / El Amri, Nouha

Journal of colloid and interface science

2021 Volume 608, Issue Pt 2, Page(s) 1750–1757

Abstract: Hypothesis: Metallic nanoparticles of various shapes and sizes can be synthesised through a diversity of bottom-up pathways, such as precipitation induced by chemical reduction. Varying composition, by adjusting concentrations or adding/replacing ... ...

Abstract	Hypothesis: Metallic nanoparticles of various shapes and sizes can be synthesised through a diversity of bottom-up pathways, such as precipitation induced by chemical reduction. Varying composition, by adjusting concentrations or adding/replacing species, is the predominant strategy to tune nanoparticles structures. However, controlling time down to the onset of precipitation, nucleation, should also provide a powerful means to control nanostructuration. Experiments: We perform sequential reagent additions with a time resolution down to the millisecond. We use a millifluidic continuous flow setup consisting of tangential mixers in series, which allows flow rates up to dozens of litres per hour. We systematically vary both addition order and delay for each reagent involved in the synthesis of silver nanoplates. The resulting dispersions are compared using UV-visible spectroscopy, transmission electron microscopy and small-angle X-ray scattering. Findings: We show that synthesis pathways differing only in the order of sub-second additions lead to drastically different synthetic outcomes. Silver nanoparticles of different shapes and sizes, displaying an array of plasmonic colours, are synthesised at the same final composition by tuning the composition pathways along time. Our results unlock a previously inaccessible portion of the space of parameters, which will lead to an enhanced structural diversity, control and understanding of nanoparticles syntheses.
MeSH term(s)	Metal Nanoparticles ; Microscopy, Electron, Transmission ; Silver
Chemical Substances	Silver (3M4G523W1G)
Language	English
Publishing date	2021-10-17
Publishing country	United States
Document type	Journal Article
ZDB-ID	241597-5
ISSN	1095-7103 ; 0021-9797
ISSN (online)	1095-7103
ISSN	0021-9797
DOI	10.1016/j.jcis.2021.10.071
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: How the interplay of molecular and colloidal scales controls drying of microgel dispersions.

Roger, Kevin / Crassous, Jérôme J

Proceedings of the National Academy of Sciences of the United States of America

2021 Volume 118, Issue 46

Abstract: Bringing an aqueous dispersion or solution into open air leads to water evaporation. The resulting drying process initiates the buildup of spatial heterogeneities, as nonvolatile solutes and colloids concentrate. Such composition gradients associate with ...

Abstract	Bringing an aqueous dispersion or solution into open air leads to water evaporation. The resulting drying process initiates the buildup of spatial heterogeneities, as nonvolatile solutes and colloids concentrate. Such composition gradients associate with mesostructure gradients, which, in turn, impact flows within these multicomponent systems. In this work, we investigate the drying of microgel dispersions in respect to two reference systems, a colloidal dispersion and a polymer solution, which, respectively, involve colloidal and molecular length scales. We evidence an intermediate behavior in which a film forms at the air/liquid interface and is clearly separated from bulk by a sharp drying front. However, complex composition and mesostructure gradients develop throughout the drying film, as evidenced by Raman and small-angle X-ray scattering mapping. We show that this results from the soft colloidal structure of microgel, which allows them to interpenetrate, deform, and deswell. As a result, water activity and water transport are drastically decreased in the vicinity of the air/liquid interface. This notably leads to diffusional drying kinetics that are nearly independent on the air relative humidity. The interplay between water fraction, water activity, and mesostructure on water transport is generic and, thus, shown to be pivotal in order to master evaporation in drying complex fluids.
Language	English
Publishing date	2021-10-12
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.2105530118
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Article ; Online: Polyvinylpyrrolidone (PVP) impurities drastically impact the outcome of nanoparticle syntheses.

Amri, Nouha El / Roger, Kevin

Journal of colloid and interface science

2020 Volume 576, Page(s) 435–443

Abstract: Hypothesis: Polymer additives such as Polyvinylpyrrolidone (PVP) are ubiquitously used in wet chemical reduction methods to tune nanoparticle sizes and shapes. However, all polymers retain some traces of their synthetic history through their end-groups ... ...

Abstract	Hypothesis: Polymer additives such as Polyvinylpyrrolidone (PVP) are ubiquitously used in wet chemical reduction methods to tune nanoparticle sizes and shapes. However, all polymers retain some traces of their synthetic history through their end-groups and impurities. These impurities may thus impact redox and interfacial processes occurring during the formation of nanocolloids. Experiments: We report a systematic comparison of four representative silver nanoparticle syntheses in the presence of either commercial PVP or its purified version, obtained through dialysis or filtration. We characterized the resulting nanoparticle dispersions through UV-visible spectroscopy, electron microscopy, X-ray scattering and Raman spectroscopy. Findings: For all syntheses and methods, the simple removal of PVP molecular impurities drastically modifies nanoparticle size, shape and formation kinetic. Impurities from additives thus play a pivotal role in nanoparticle syntheses and must be systematically evaluated for relevant mechanistic investigations and robust process engineering.
Language	English
Publishing date	2020-05-05
Publishing country	United States
Document type	Journal Article
ZDB-ID	241597-5
ISSN	1095-7103 ; 0021-9797
ISSN (online)	1095-7103
ISSN	0021-9797
DOI	10.1016/j.jcis.2020.04.113
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Article ; Online: Assessing suspension and infectivity times of virus-loaded aerosols involved in airborne transmission.

Merhi, Tania / Atasi, Omer / Coetsier, Clémence / Lalanne, Benjamin / Roger, Kevin

Proceedings of the National Academy of Sciences of the United States of America

2022 Volume 119, Issue 32, Page(s) e2204593119

Abstract: Airborne transmission occurs through droplet-mediated transport of viruses following the expulsion of an aerosol by an infected host. Transmission efficiency results from the interplay between virus survival in the drying droplet and droplet suspension ... ...

Abstract	Airborne transmission occurs through droplet-mediated transport of viruses following the expulsion of an aerosol by an infected host. Transmission efficiency results from the interplay between virus survival in the drying droplet and droplet suspension time in the air, controlled by the coupling between water evaporation and droplet sedimentation. Furthermore, droplets are made of a respiratory fluid and thus, display a complex composition consisting of water and nonvolatile solutes. Here, we quantify the impact of this complex composition on the different phenomena underlying transmission. Solutes lead to a nonideal thermodynamic behavior, which sets an equilibrium droplet size that is independent of relative humidity. In contrast, solutes do not significantly hinder transport due to their low initial concentration. Realistic suspension times are computed and increase with increasing relative humidity or decreasing temperature. By uncoupling drying and suspended stages, we observe that enveloped viruses may remain infectious for hours in dried droplets. However, their infectivity decreases with increasing relative humidity or temperature after dozens of minutes. Examining expelled droplet size distributions in the light of these results leads to distinguishing two aerosols. Most droplets measure between 0 and 40 µm and compose an aerosol that remains suspended for hours. Its transmission efficiency is controlled by infectivity, which decreases with increasing humidity and temperature. Larger droplets form an aerosol that only remains suspended for minutes but corresponds to a much larger volume and thus, viral load. Its transmission efficiency is controlled by droplet suspension time, which decreases with increasing humidity and decreasing temperature.
MeSH term(s)	Humans ; Humidity ; Respiratory Aerosols and Droplets/virology ; Suspensions ; Virus Diseases/transmission ; Water
Chemical Substances	Suspensions ; Water (059QF0KO0R)
Language	English
Publishing date	2022-08-05
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.2204593119
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