Papers by Désert Anthony
Faraday Discuss., 2015
Silica particles with a controlled number of entropic patches, i.e. dimples, are synthesized thro... more Silica particles with a controlled number of entropic patches, i.e. dimples, are synthesized through the growth of the silica core of binary multipods that have been produced by a seeded-growth emulsion polymerization reaction. Transmission electron microscopy studies indicate that the silica surface conforms to the shape of the polystyrene (PS) nodules of the multipods while growing, allowing good control of the final shape of the dimpled silica particles. The PS nodules are also used as protecting masks to regioselectively graft amino groups, as revealed by the adsorption of gold markers. After dissolution of the PS nodules, some polymer chains remain grafted onto the silica surface, forming organic bumps. These residues are also selectively functionalized, leading to silica particles with both entropic and enthalpic patches.
New luminescent poly(methylmethacrylate) (PMMA) nanocomposites with high content of different hex... more New luminescent poly(methylmethacrylate) (PMMA) nanocomposites with high content of different hexanuclear octahedral cluster building blocks, namely [Mo6I8(C2F5COO6)]2−, [Re6Se8(CN)6]4− and [W6Cl14]2− have been prepared by free-radical polymerisation. To do so, cluster complexes bearing a polymerisable ammonium counter-cation have been synthesised. In this way, we demonstrate that ionic assembling is a powerful tool to functionalise easily any type of anionic cluster units to be introduced in a PMMA organic matrix. All samples remain homogeneous, stable during several months, and retain the luminescence properties of the cluster precursor.
Large amounts of regular tetrapods and hexapods made of a central silica core and four or six pol... more Large amounts of regular tetrapods and hexapods made of a central silica core and four or six polystyrene satellite nodules were prepared with yields over 80\% from 55 nm and 85 nm silica seeds, respectively. The robustness of the process is supported by extensive statistical analyses and large-field transmission electron microscopy images.
Silica/PS and silica/PMMA heterodimers were obtained in very good yields using 80 nm silica parti... more Silica/PS and silica/PMMA heterodimers were obtained in very good yields using 80 nm silica particles first functionalized with a polymerizable alkoxysilane and then used as seeds for the emulsion polymerization of either styrene or methyl methacrylate. Aiming at a one-pot and scalable process, a commercial silica sol was used and the grafting reaction of silica with the functional silane was directly performed in the mixture of surfactants subsequently used for the polymerization. The effect of silica content, nature and concentration of the surfactant, of the reactive alkoxysilane or of the monomer, on the formation of the silica/PS heterodimers was investigated. Either dumbbell- or snowman-like dimers were obtained depending on monomer conversion. The typical morphological yield reached 60\% with respect to all morphologies. The synthesis of silica/PMMA dumbbell-like dimers was also successful. In addition to TEM and DLS, the emerging technique of charge detection mass spectrometry (CD-MS) was used to provide the mass distribution and the sample composition in terms of morphologies. Finally, this system also proved to be efficient for the synthesis of dimpled polymer particles.
We describe an easy procedure to regioselectively coat binary tetrapod-like silica/polystyrene cl... more We describe an easy procedure to regioselectively coat binary tetrapod-like silica/polystyrene clusters with silica. First we show that the addition of tetraethoxysilane into a basic hydroalcoholic suspension of binary tetrapods induces the preferential growth of their silica core, which conforms to the shape of the polystyrene nodules while growing. On the contrary, we show that the formation of a continuous silica shell around the clusters is promoted if silanol groups have been incorporated at the surface of the polystyrene nodules before the addition of tetraethoxysilane. The thickness and the roughness of the silica coating can be tuned by varying several experimental parameters.
The past decade has been witness to the development of new chemical and physical methods allowing... more The past decade has been witness to the development of new chemical and physical methods allowing the synthesis of colloidal particles of different shapes with a good size and shape selectivity.
Binary colloidal particles of polyhedral morphology, obtained by an emulsion polymerization of st... more Binary colloidal particles of polyhedral morphology, obtained by an emulsion polymerization of styrene in the presence of silica seeds, are studied. Because of kinetic effects, composite particles usually exhibit polydispersity in size, shape, and composition. Thus, accurate techniques aiming at characterizing the size and the shape, as well as the composition and surface properties of such objects, are required. In this work, we use charge detection mass spectrometry (CD-MS) as a tool for the characterization of nanometer-sized composite (clusters of) particles. CD-MS measures both the mass and the charge for each ion. This single ion mass spectrometry technique enables one to construct a histogram of mass, yielding the mass distribution. CD-MS for molar mass determination and composition of composite particles is demonstrated to be complementary to transmission electron microscopy. The study of the charging capacity of these composite particles in the gas phase also appears as a valuable approach to probe the surface area of such complex nano-objects, thus giving some insight about their structure and morphology.
Multipod-like clusters composed of a silica core and PS satellites are prepared according to a se... more Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80\%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the history of the cluster growth and the final composition of the cluster mixture. Finally, using the model as a predictive tool and varying the extra experimental conditions, e.g. the composition of the surfactant mixture and the styrene concentration, result in trapping other cluster morphologies, such as tripods.
Integration of stable emissive entities into organic waveguide with minimum scattering is essenti... more Integration of stable emissive entities into organic waveguide with minimum scattering is essential to design efficient optically active devices. Here we present a new class of doped nanocomposite waveguides exploiting 1-nm diameter metallic cluster-based building blocks as red-NIR luminescent dyes embedded in a SU8 polymeric matrix, a reference photoresist for organic photonics. These building blocks are [Mo6Ii8(OOCC2F5)a6]2− cluster anionic units with unique chemical and physical features well suited for optical nanocomposites such as a ligand-promoted dispersibility, a large Stokes shift with a broad absorption window and an emission window in the range 600–900 nm. A whole investigation of the nanocomposite has been first performed. Optical characterizations of Cs2[Mo6Ii8(OOCCnF2n+1)a6]@SU8 nanocomposites thin film and waveguiding structures show their relevance as active layers in integrated structures with a significant increase of the refractive index of 3 × 10−2 when the cluster concentration increases up to 4 wt\%, while keeping high values for the transmitted power, as shown for different waveguide dimensions and clusters concentrations. The efficiency of photoluminescence propagation is investigated as a function of clusters concentration in the excitation area for several waveguides dimensions. Attenuation coefficient ranges between 5 and 18 dB/cm, values of the same order of magnitude as those obtained in polymeric waveguide doped with QDs or organic dyes. This original, stable and efficient nanocomposite is promising for downscaling complex nanosources and active waveguides in the visible and NIR range.
The production of highly monodisperse nanoparticles of precisely controlled size is a very import... more The production of highly monodisperse nanoparticles of precisely controlled size is a very important research field. It has important applications notably for the optical properties of nanoparticles (e.g. quantum dot) or nanoparticle assemblies (e.g. photonic band gap crystals) and for electromagnetic properties (e.g. information storage). Understanding monodisperse nanoparticle synthesis mechanism is based mostly on the Classical Nucleation Theory (CNT). It has been shown in the literature and in this work that CNT is able to predict the nanoparticle concentration and average size correctly. However, until recently only a few models based on CNT were able to predict the size distribution of the synthesized objects. In this work, we show that a CNT based model is not able to predict the size distribution of silica nanoparticles formed in a pure La Mer like nucleation growth process. Reasons for this discrepancy are discussed and should be taken into account to develop more complete models able to predict the size distribution especially if it is desired to use them as tools to optimize monodispersity.
The effect of ionic liquid (IL) constituents and other monovalent salts on the stability of polys... more The effect of ionic liquid (IL) constituents and other monovalent salts on the stability of polystyrene latex particles was studied by electrophoresis and light scattering in dilute aqueous suspensions. Surface charge and aggregation rate were both sensitive to the type of ions leading to different critical coagulation concentration (CCC) values. Systematic variation of the type of IL cations and anions allows us to place these ions within the Hofmeister series. We find that the dicyanoamide anion should be placed between iodide and thiocyanate, while all 1-alkyl-3-methylimidazolium cations can be positioned to the left of the tetramethylammonium and ammonium ions. The hydrophobicity of 1-butyl-1-methylpyrrolidinium (BMPL+) ion is intermediate between 1-ethyl-3-methylimidazolium (EMIM+) and 1-butyl-3-methylimidazolium (BMIM+). With increasing alkyl chain length, the 1-alkyl-3-methylimidazolium cations adsorb on the latex particles very strongly, and 1-hexyl-3-methylimidazolium (HMIM+) and 1-octyl-3-methylimidazolium (OMIM+) lead to pronounced charge reversal and to an intermediate restabilization region.
Aggregation of sub-micron and nano-sized polystyrene latex particles was studied in room temperat... more Aggregation of sub-micron and nano-sized polystyrene latex particles was studied in room temperature ionic liquids (ILs) and in their water mixtures by time-resolved light scattering. The aggregation rates were found to vary with the IL-to-water molar ratio in a systematic way. At the water side, the aggregation rate is initially small, but increases rapidly with increasing IL content, and reaches a plateau value. This behaviour resembles simple salts, and can be rationalized by the competition of double-layer and van der Waals forces as surmised by the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). At the IL side, aggregation slows down again. Two generic mechanisms could be identified to be responsible for the stabilization in ILs, namely viscous stabilization and solvation stabilization. Viscous stabilization is important in highly viscous ILs, as it originates from the slowdown of the diffusion controlled aggregation due to the hindrance of the diffusion in a viscous liquid. The solvation stabilization mechanism is system specific, but can lead to a dramatic slowdown of the aggregation rate in ILs. This mechanism is related to repulsive solvation forces that are operational in ILs due to the layering of the ILs close to the surfaces. These two stabilization mechanisms are suspected to be generic, as they both occur in different ILs, and for particles differing in surface functionalities and size. ; Tel: +41 22 379 6405 † Electronic supplementary information (ESI) available. See
ABSTRACT We use evaporation within a microfluidic device to extract the solvent of a (possibly ve... more ABSTRACT We use evaporation within a microfluidic device to extract the solvent of a (possibly very
dilute) dispersion of nanoparticles and concentrate the dispersion until a solid made of densely packed
nanoparticles grows and totally invades the microfluidic geometry. The growth process can be rationalized
as an interplay between evaporation-induced flow and kinetic and thermodynamic coefficients which are
system-dependent; this yields limitations to the growth process illustrated here on two main cases:
evaporation- and transport-limited growth. Importantly, we also quantify how colloidal stability may hinder the growth and show that care must be taken
as to the composition of the initial dispersion, especially regarding traces of ionic species that can destabilize the suspension upon concentration. We define
a stability chart, which, when fulfilled, permits us to grow and shape-up solids, including superlattices and extended and thick arrays of nanoparticles made
of unary and binary dispersions, composites, and heterojunctions between distinct types of nanoparticles. In all cases, the geometry of the final solid is
imparted by that of the microfluidic device.
KEYWORDS: densley packed nanoparticles . microfluidic-induced growth . extended arrays
Hybrid organic-inorganic nanoparticles with well-controlled morphology are currently of great int... more Hybrid organic-inorganic nanoparticles with well-controlled morphology are currently of great interest for numerous applications. Synthetic routes leading to robust aggregates made of nanoparticles of different chemical natures which are associated in a controlled manner (i.e. number of nanoparticles and geometrical arrangement) are especially investigated.
Chemical Society Reviews, 2011
The concept of colloidal molecules was first evoked by van Blaaderen in 2003 for describing small... more The concept of colloidal molecules was first evoked by van Blaaderen in 2003 for describing small non-spherical colloids made of the aggregation of a small number of particles. He predicted original properties to the complex assemblies of such colloids, in particular in optics. This critical review deals with the different strategies reported for creating robust clusters of spherical particles which could mimic the space-filling models of simple conventional molecules. These routes concern either the controlled clustering of preformed colloids directed by coalescence, physical routes, chemical routes, or 2-D/3-D geometrical confinement, or strategies starting from a single colloid which is decorated by satellite colloids by taking advantage of controlled phase separation or nucleation and growth phenomena. These routes are compared from the viewpoint of the accessible shapes, their tunability and scalability (146 references).
Through the heterogeneous nucleation of polymer nodules on a surface-modified silica particle, th... more Through the heterogeneous nucleation of polymer nodules on a surface-modified silica particle, the high-yield achievement of hybrid colloidal molecules with a well-controlled multipod-like morphology was recently demonstrated. However, as the formation mechanism of these colloidal molecules has not been completely understood yet, some opportunities remain to reduce the tedious empirical process needed to optimize the chemical recipes. In this work, we propose a model to help understand the formation mechanism of almost pure suspensions of well-defined colloidal molecules. The outcomes of the model allow proposing probable nucleation growth scenario able to explain the experimental results. Such a model should make easier the determination of the optimal recipe parameters for a targeted morphology. The reasonably good agreements between the model and the experimental results show that the most important processes have been captured. It is thus a first step toward the rational design of large quantities of chemically prepared colloidal molecules.
miscs by Désert Anthony
Presented at the 8th European Coating Symposium, September 7-9, 2009, Karlsruhe
phdtheses by Désert Anthony
Les molécules colloïdales peuvent être décrites comme des agrégats robustes de particules sphériq... more Les molécules colloïdales peuvent être décrites comme des agrégats robustes de particules sphériques prenant la forme de certaines molécules simples. La préparation de suspensions de molécules colloïdales est étudiée afin d'obtenir de hauts rendements en morphologie et des distributions étroites en taille des objets, conditions indispensables pour envisager de futures applications comme leur assemblage et l'élaboration de matériaux. La stratégie repose sur l'introduction de germes de silice fonctionnalisés dans une polymérisation en émulsion du styrène, menant à la nucléation-croissance d'un nombre restreint de nodules sphériques de latex ancrés à la surface de la silice.Les travaux proposent une optimisation des voies de préparation (i) des germes de silice par voie sol-gel et (ii) des particules de latex de PS par polymérisation en émulsion. Les structures des clusters silice/PS sont caractérisées par cryo-tomographie électronique et leur formation fait l'objet de discussions notamment en s'appuyant sur des modèles géométriques connus et en proposant un nouveau modèle de croissance des nodules. Enfin, une étude préliminaire est menée afin de recouvrir ces clusters d'une couche d'oxyde (SiO2 et TiO2).
inproceedings by Désert Anthony
One-dimensional polymer-based nano-structures such as nanowires (NWs) and nanotubes (NTs) are now... more One-dimensional polymer-based nano-structures such as nanowires (NWs) and nanotubes (NTs) are nowadays intensively investigated since they promote enhanced properties, as well as new paradigms for electronic, optical, optoelectronic, and photonic devices. Here, we propose a review of recent developments achieved in our group with collaborations on polymer based nanowires and nanotubes. Various polymer based NWs and NTs were synthesized by template strategies with advanced architectures designed for improving their functionality (waveguiding, color control of photoluminescence, photoconductivity and mechanical reinforcement,…). Both conjugated polymers (CPs) and photoresists containing photo-active species (transition metal compound clusters, single-walled-carbon nanotubes SWCNTs) were involved. The focus is made on the emerging strategies for understanding and controlling the behavior of charges, excitons and photons, as well as light propagation in sub-wavelength nanostructures.
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Papers by Désert Anthony
dilute) dispersion of nanoparticles and concentrate the dispersion until a solid made of densely packed
nanoparticles grows and totally invades the microfluidic geometry. The growth process can be rationalized
as an interplay between evaporation-induced flow and kinetic and thermodynamic coefficients which are
system-dependent; this yields limitations to the growth process illustrated here on two main cases:
evaporation- and transport-limited growth. Importantly, we also quantify how colloidal stability may hinder the growth and show that care must be taken
as to the composition of the initial dispersion, especially regarding traces of ionic species that can destabilize the suspension upon concentration. We define
a stability chart, which, when fulfilled, permits us to grow and shape-up solids, including superlattices and extended and thick arrays of nanoparticles made
of unary and binary dispersions, composites, and heterojunctions between distinct types of nanoparticles. In all cases, the geometry of the final solid is
imparted by that of the microfluidic device.
KEYWORDS: densley packed nanoparticles . microfluidic-induced growth . extended arrays
miscs by Désert Anthony
phdtheses by Désert Anthony
inproceedings by Désert Anthony
dilute) dispersion of nanoparticles and concentrate the dispersion until a solid made of densely packed
nanoparticles grows and totally invades the microfluidic geometry. The growth process can be rationalized
as an interplay between evaporation-induced flow and kinetic and thermodynamic coefficients which are
system-dependent; this yields limitations to the growth process illustrated here on two main cases:
evaporation- and transport-limited growth. Importantly, we also quantify how colloidal stability may hinder the growth and show that care must be taken
as to the composition of the initial dispersion, especially regarding traces of ionic species that can destabilize the suspension upon concentration. We define
a stability chart, which, when fulfilled, permits us to grow and shape-up solids, including superlattices and extended and thick arrays of nanoparticles made
of unary and binary dispersions, composites, and heterojunctions between distinct types of nanoparticles. In all cases, the geometry of the final solid is
imparted by that of the microfluidic device.
KEYWORDS: densley packed nanoparticles . microfluidic-induced growth . extended arrays