Publications by authors named "Olivier Spalla"

37 Publications

Metabolomic and proteomic investigations of impacts of titanium dioxide nanoparticles on Escherichia coli.

PLoS One 2017 1;12(6):e0178437. Epub 2017 Jun 1.

Université Paris Diderot, Sorbonne Paris Cité, IPGP, UMR 7154, Paris Cedex 13 France.

In a previous study, it was demonstrated that the toxic impact of titanium dioxide nanoparticles on Escherichia coli starts at 10 ppm and is closely related to the presence of little aggregates. It was also assumed that only a part of the bacterial population is able to adapt to this stress and attempts to survive. Proteomic analyses, supported by results from metabolomics, reveal that exposure of E. coli to nano-TiO2 induces two main effects on bacterial metabolism: firstly, the up-regulation of proteins and the increase of metabolites related to energy and growth metabolism; secondly, the down-regulation of other proteins resulting in an increase of metabolites, particularly amino acids. Some proteins, e.g. chaperonin 1 or isocitrate dehydrogenase, and some metabolites, e.g. phenylalanine or valine, might be used as biomarkers of nanoparticles stress. Astonishingly, the ATP content gradually rises in relation with the nano-TiO2 concentration in the medium, indicating a dramatic release of ATP by the damaged cells. These apparently contradictory results accredit the thesis of a heterogeneity of the bacterial population. This heterogeneity is also confirmed by SEM images which show that while some bacteria are fully covered by nano-TiO2, the major part of the bacterial population remains free from nanoparticles, resulting in a difference of proteome and metabolome. The use of combined-omics has allowed to better understand the heterogeneous bacterial response to nano-TiO2 stress due to heterogeneous contacts between the protagonists under environmental conditions.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0178437PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5453534PMC
September 2017

Interaction of TiO nanoparticles with proteins from aquatic organisms: the case of gill mucus from blue mussel.

Environ Sci Pollut Res Int 2017 May 7;24(15):13474-13483. Epub 2017 Apr 7.

LIONS, NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191, Gif-sur-Yvette, France.

To better understand the mechanisms of TiO nanoparticle (NP) uptake and toxicity in aquatic organisms, we investigated the interaction of NPs with the proteins found in gill mucus from blue mussels. Mucus is secreted by many aquatic organisms and is often their first line of defense against pathogens, xenobiotics, and other sources of environmental stress. Here, five TiO NPs and one SiO NP were incubated with gill mucus and run out on a one-dimensional polyacrylamide gel for a comparative qualitative analysis of the free proteins in the mucosal solution and the proteins bound to NPs. We then used nanoscale liquid chromatography coupled with tandem mass spectrometry to identify proteins of interest. Our data demonstrated dissimilar protein profiles between the crude mucosal solution and proteins adsorbed on NPs. In particular, extrapallial protein (EP), one of the most abundant mucus proteins, was absent from the adsorbed proteins. After thermal denaturation experiments, this absence was attributed to the EP content in aromatic amino acids that prevents protein unfolding and thus adsorption on the NP. Moreover, although the majority of the protein corona was qualitatively similar across the NPs tested here (SiO and TiO), a few proteins in the corona showed a specific recruitment pattern according to the NP oxide (TiO vs SiO) or crystal structure (anatase TiO vs rutile TiO). Therefore, protein adsorption may vary with the type of NP. Graphical abstract Proteins with adsorption selectivity as identified from isolated bands.
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http://dx.doi.org/10.1007/s11356-017-8801-3DOI Listing
May 2017

Multipod-like silica/polystyrene clusters.

Nanoscale 2016 Mar;8(10):5454-69

CNRS, Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac, France.

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.
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http://dx.doi.org/10.1039/c5nr07613gDOI Listing
March 2016

Gold Nanoparticle Internal Structure and Symmetry Probed by Unified Small-Angle X-ray Scattering and X-ray Diffraction Coupled with Molecular Dynamics Analysis.

Nano Lett 2015 Sep 17;15(9):6088-94. Epub 2015 Aug 17.

CEA Saclay, DSM/IRAMIS/NIMBE/LIONS, UMR CEA/CNRS 3685 , 91191 Gif-sur-Yvette CEDEX, France.

Shape and size are known to determine a nanoparticle's properties. Hardly ever studied in synthesis, the internal crystal structure (i.e., particle defects, crystallinity, and symmetry) is just as critical as shape and size since it directly impacts catalytic efficiency, plasmon resonance, and orients anisotropic growth of metallic nanoparticles. Hence, its control cannot be ignored any longer in today's research and applications in nanotechnology. This study implemented an unprecedented reliable measurement combining these three structural aspects. The unified small-angle X-ray scattering and diffraction measurement (SAXS/XRD) was coupled with molecular dynamics to allow simultaneous determination of nanoparticles' shape, size, and crystallinity at the atomic scale. Symmetry distribution (icosahedra-Ih, decahedra-Dh, and truncated octahedra-TOh) of 2-6 nm colloidal gold nanoparticles synthesized in organic solvents was quantified. Nanoparticle number density showed the predominance of Ih, followed by Dh, and little, if any, TOh. This result contradicts some theoretical predictions and highlights the strong effect of the synthesis environment on structure stability. We foresee that this unified SAXS/XRD analysis, yielding both statistical and quantitative counts of nanoparticles' symmetry distribution, will provide new insights into nanoparticle formation, growth, and assembly.
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http://dx.doi.org/10.1021/acs.nanolett.5b02924DOI Listing
September 2015

The role of solvent swelling in the self-assembly of squalene based nanomedicines.

Soft Matter 2015 Jun;11(21):4173-9

CEA Saclay, DSM/IRAMIS/NIMBE/LIONS, UMR CEA/CNRS 3299, 91191 Gif sur Yvette, France.

Squalene based nanoparticles obtained via nanoprecipitation are promising candidates as efficient anti-cancer drugs. In order to highlight their preparation process and to facilitate further clinical translation, the present study enlightens the paramount role of the solvent in the formation of these nanomedicines. Three different squalene-based nanoparticles, i.e. squalenic acid, deoxycytidine squalene and gemcitabine squalene, have been investigated before and after organic solvent evaporation. Size and structural analysis by Small Angle Neutron Scattering revealed that droplets' size was uniquely controlled by the solvent composition (ethanol-water), which evolved during their gradual formation. The particles were preferably swollen by water and the swelling increased when less ethanol was present. Either coalescence or fragmentation was observed depending on the increase or decrease of the ethanol content, supporting an equilibrium control of the size. Moreover, a high water swelling was observed for the three local organization of the nanodroplets (hexagonal for gemcitabine squalene, cubic for deoxycytidine and not structured for squalenic acid) and could be the source of the previously reported efficiency of related anti-cancer squalene based nanomedicines.
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http://dx.doi.org/10.1039/c5sm00592bDOI Listing
June 2015

The challenge of studying TiO2 nanoparticle bioaccumulation at environmental concentrations: crucial use of a stable isotope tracer.

Environ Sci Technol 2015 Feb 28;49(4):2451-9. Epub 2015 Jan 28.

CEA Saclay, DSM/IRAMIS/NIMBE/LIONS, UMR CEA-CNRS 3299, 91191 Gif-sur-Yvette, France.

The ecotoxicity of nanoparticles (NPs) is a growing area of research with many challenges ahead. To be relevant, laboratory experiments must be performed with well-controlled and environmentally realistic (i.e., low) exposure doses. Moreover, when focusing on the intensively manufactured titanium dioxide (TiO2) NPs, sample preparations and chemical analysis are critical steps to meaningfully assay NP's bioaccumulation. To deal with these imperatives, we synthesized for the first time TiO2 NPs labeled with the stable isotope (47)Ti. Thanks to the (47)Ti labeling, we could detect the bioaccumulation of NPs in zebra mussels (Dreissena polymorpha) exposed for 1 h at environmental concentrations via water (7-120 μg/L of (47)TiO2 NPs) and via their food (4-830 μg/L of (47)TiO2 NPs mixed with 1 × 10(6) cells/mL of cyanobacteria) despite the high natural Ti background, which varied in individual mussels. The assimilation efficiency (AE) of TiO2 NPs by mussels from their diet was very low (AE = 3.0 ± 2.7%) suggesting that NPs are mainly captured in mussel gut, with little penetration in their internal organs. Thus, our methodology is particularly relevant in predicting NP's bioaccumulation and investigating the factors influencing their toxicokinetics in conditions mimicking real environments.
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http://dx.doi.org/10.1021/es504638fDOI Listing
February 2015

Behavior and determination of titanium dioxide nanoparticles in nitric acid and river water by ICP spectrometry.

Anal Chem 2014 Apr 13;86(7):3453-60. Epub 2014 Mar 13.

Commissariat à l'Energie Atomique et aux Energies Alternatives, CEA Saclay, DSM/IRAMIS/NIMBE/LIONS, CNRS UMR 3299, 91191 Gif Sur Yvette, France.

ICP spectrometry (ICPMS, ICPOES) are classical techniques for the determination of solubilized or suspended elements. Unfortunately, their relevance for nanoparticles at low concentration (below 10 ppm) is rarely called into question, even if literature reports are not always coherent. This work is a systematic study based on the measurement of TiO2 nanoparticle suspensions, as a model of quasi-insoluble material, by plasma spectrometry. It studies both sample treatment and measurement in the 10 ppb to 30 ppm concentration range. Realized on a set of four engineered nanoparticles suspensions at low concentration, it shows the existence of three different regimes of stability that affect concentration measurement. Above a C(S) stability concentration value, suspensions are stable in time; below a low-concentration C(E) value, the signal loss is at a maximum, and a final partition is reached between the container walls and the suspension. Between these two regimes, the suspension aging varies with concentration. C(E) and C(S) depend on nanoparticle characteristics and the suspension medium, whereas the evolution kinetic is volume-dependent. Because TiO2 nanoparticles are present in the environment at concentrationd below C(S), it is then necessary to find a way to rehomogenize the suspension between sampling and analyzing. Soft sonication, minimizing the sample temperature, and trapping of free radicals is proposed and evaluated. Homogenization is traced by the addition of an internal standard before storage. The procedure is applied to a real sample, Seine River water. The amount of total titanium found, 48.7 ppb, is in good agreement with the result of the reference method.
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http://dx.doi.org/10.1021/ac403926rDOI Listing
April 2014

Amorphous to crystal conversion as a mechanism governing the structure of luminescent YVO4:Eu nanoparticles.

ACS Nano 2014 Mar 13;8(3):2602-8. Epub 2014 Feb 13.

Groupe de Chimie du Solide, Laboratoire de Physique de la Matière Condensée, UMR CNRS 7643, École Polytechnique , 91128 Palaiseau, France.

The development of functional materials by taking advantage of the physical properties of nanoparticles needs an optimal control over their size and crystal quality. In this context, the synthesis of crystalline oxide nanoparticles in water at room temperature is a versatile and industrially appealing process but lacks control especially for "large" nanoparticles (>30 nm), which commonly consist of agglomerates of smaller crystalline primary grains. Improvement of these syntheses is hampered by the lack of knowledge on possible intermediate, noncrystalline stages, although their critical importance has already been outlined in crystallization processes. Here, we show that during the synthesis of luminescent Eu-doped YVO4 nanoparticles a transient amorphous network forms with a two-level structuration. These two prestructuration scales constrain topologically the nucleation of the nanometer-sized crystalline primary grains and their aggregation in nanoparticles, respectively. This template effect not only clarifies why the crystal size is found independent of the nucleation rate, in contradiction with the classical nucleation models, but also supports the possibility to control the final nanostructure with the amorphous phase.
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http://dx.doi.org/10.1021/nn4062534DOI Listing
March 2014

Exopolysaccharides protect Synechocystis against the deleterious effects of titanium dioxide nanoparticles in natural and artificial waters.

J Colloid Interface Sci 2013 Sep 4;405:35-43. Epub 2013 Jun 4.

CEA Saclay, DSM/IRAMIS/SIS2M/LIONS, UMR CEA-CNRS 3299, 91191 Gif sur Yvette, France.

We have studied the effect of TiO2 nanoparticles (NPs) on the model cyanobacteria Synechocystis PCC6803. We used well-characterized NPs suspensions in artificial and natural (Seine River, France) waters. We report that NPs trigger direct (cell killing) and indirect (cell sedimentation precluding the capture of light, which is crucial to photosynthesis) deleterious effects. Both toxic effects increase with NPs concentration and are exacerbated by the presence of UVAs that increase the production of Reactive Oxygen Species (hydroxyl and superoxide radicals) by TiO2 NPs. Furthermore, we compared the responses of the wild-type strain of Synechocystis, which possesses abundant exopolysaccharides surrounding the cells, to that of an EPS-depleted mutant. We show, for the first time, that the exopolysaccharides play a crucial role in Synechocystis protection against cell killing caused by TiO2 NPs.
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http://dx.doi.org/10.1016/j.jcis.2013.05.061DOI Listing
September 2013

Influence of exopolysaccharides on the electrophoretic properties of the model cyanobacterium Synechocystis.

Colloids Surf B Biointerfaces 2013 Oct 25;110:171-7. Epub 2013 Apr 25.

CEA Saclay, DSM/IRAMIS/SIS2M/LIONS, UMR CEA-CNRS 3299, 91191 Gif sur Yvette, France.

The influence of extracellular polymeric substances (EPS) on cell electrokinetics was investigated in the model cyanobacterium Synechocystis, in wild-type strains and in ten EPS-depleted mutants. The charge density and the softness of the EPS polyelectrolyte layer were calculated from the dependence of the electrophoretic mobility values of the cells with the ionic strength of the surrounding fluid. Electrophoretic mobility data showed that the eleven Synechocystis strains investigated behave as soft particles and cannot be adequately described by classical electrokinetic models of rigid particles. EPS surrounding the cells, especially those released in the growth medium, significantly increased the softness of the cell surface. Furthermore, the anionic nature of EPS resulted in negative surface charge densities, which appeared to be strongly dependent on the composition of the suspending fluid, as documented by a strong reduction of their absolute values in the presence of calcium cations. These finding stresses the importance of the physicochemical properties of EPS and cell surfaces of cyanobacteria, for both cell-to-medium and cell-to-cell communications. In turn, these results emphasize that, whenever possible, natural waters should be used for meaningful ecotoxicological analyses of potential toxics.
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http://dx.doi.org/10.1016/j.colsurfb.2013.03.057DOI Listing
October 2013

Multidisciplinary evidences that Synechocystis PCC6803 exopolysaccharides operate in cell sedimentation and protection against salt and metal stresses.

PLoS One 2013 6;8(2):e55564. Epub 2013 Feb 6.

UMR8221, CEA, CNRS, Université Paris-Sud, iBiTec-S, LBBC, Bat 142 CEA-Saclay, F-91191 Gif sur Yvette Cedex, France.

Little is known about the production of exopolysaccharides (EPS) in cyanobacteria, and there are no genetic and physiological evidences that EPS are involved in cell protection against the frequently encountered environmental stresses caused by salt and metals. We studied four presumptive EPS production genes, sll0923, sll1581, slr1875 and sll5052, in the model cyanobacterium Synechocystis PCC6803, which produces copious amounts of EPS attached to cells (CPS) and released in the culture medium (RPS) as shown here. We show that sll0923, sll1581, slr1875 and sll5052 are all dispensable to the growth of all corresponding single and double deletion mutants in absence of stress. Furthermore, we report that sll0923, sll1581 and slr1875 unambiguously operate in the production of both CPS and RPS. Both sll1581 and slr1875 are more important than sll0923 for CPS production, whereas the contrary is true for RPS production. We show that the most EPS-depleted mutant, doubly deleted for sll1581 and slr1875, lacks the EPS mantle that surrounds WT cells and sorbs iron in their vicinity. Using this mutant, we demonstrate for the first time that cyanobacterial EPS directly operate in cell protection against NaCl, CoCl(2), CdSO(4) and Fe-starvation. We believe that our EPS-depleted mutants will be useful tools to investigate the role of EPS in cell-to-cell aggregation, biofilm formation, biomineralization and tolerance to environmental stresses. We also suggest using the fast sedimenting mutants as biotechnological cell factories to facilitate the otherwise expensive harvest of the producer cell biomass and/or its separation from products excreted in the growth media.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0055564PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3566033PMC
August 2013

Microsecond time-resolved energy-dispersive EXAFS measurement and its application to film the thermolysis of (NH₄)₂[PtCl₆].

Sci Rep 2012 21;2:1018. Epub 2012 Dec 21.

Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, BP 48 91192 Gif sur Yvette Cedex, France.

Microsecond (μs) time-resolved extended X-ray absorption fine structure spectroscopy (EXAFS) has been developed using an energy-dispersive EXAFS (EDE) setup equipped with a silicon Quantum Detector ULTRA. The feasibility was investigated with a prototypical thermally driven redox reaction, the thermal decomposition of (NH₄)₂[PtCl₆]. EXAFS data were collected with snapshots every 60 μs during the course of the thermolysis reaction, then averaged for 100 times along the reaction to get better signal to noise ratio which reduces the time resolution to 6 millisecond (ms). Our results provide direct structural evidence of cis-PtCl₂(NH₃)₂ as the intermediate, together with continuous electronic and geometric structure dynamics of the reactant, intermediate and final product during the course of the thermolysis of ((NH₄)₂[PtCl₆]. The thermal effect on EXAFS signals at high temperatures is considered in the data analysis, which is essential to follow the reaction process correctly. This method could also be applied to other reaction dynamics.
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http://dx.doi.org/10.1038/srep01018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3527826PMC
June 2013

Stabilization of TiO2 nanoparticles in complex medium through a pH adjustment protocol.

Environ Sci Technol 2013 Jan 26;47(2):1057-64. Epub 2012 Dec 26.

CEA Saclay, DSM/IRAMIS/SIS2M/LIONS UMR3299, 91191 Gif-sur Yvette, France.

Preparing TiO(2) nanoparticle (NP) suspensions displaying well-defined and reproducible dispersion state is a key feature to perform relevant toxicity experiments for environmental, animal, or human concerns. Relying on the evolution of surface charge with pH, and interactions between nanoparticles in their medium, we developed an optimized dispersion protocol involving a pH adjustment before addition of bovine serum albumin (BSA). It yielded highly dispersed and stable concentrated stock suspensions of TiO(2) NP at pH 7. It was designed for four kinds of manufactured TiO(2) nanomaterials and can be extended to a wide range of TiO(2) NP. The suspensions studied here were characterized by small-angle X-ray scattering (SAXS), using a model quantitatively describing fractal aggregates. Results were correlated with dynamic light scattering (DLS) measurements. Moreover, the stability in a typical biological medium was assessed by diluting stock suspensions in Luria-Bertani (LB) medium. It resulted in highly dispersed and stable working suspensions. No sedimentation, followed by in situ DLS, was observed over 17 h for both the concentrated stock suspensions prepared according to the pH adjusted-BSA protocol and their dilution into LB medium.
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http://dx.doi.org/10.1021/es3040736DOI Listing
January 2013

Understanding of the size control of biocompatible gold nanoparticles in millifluidic channels.

Langmuir 2012 Nov 1;28(45):15966-74. Epub 2012 Nov 1.

CEA Saclay, DSM/IRAMIS/SIS2M/LIONS, UMR CEA/CNRS 3299, 91191 Gif sur Yvette, France.

The size control of gold nanoparticles synthesized in surfactant free water with a continuous flow mode was elucidated and used to produce higher concentration (3 mM) of stabilized gold nanoparticles. The originality of the synthesis was to finely modulate the initial pH of the reducing agent instead of the gold precursor to modify the kinetic of the reaction. The acceleration of the kinetic (~1 s) prevents the modification of the gold precursors ensuring the control of the final size (from 3 to 25 nm) of the nanoparticles with a low polydispersity for aqueous surfactant free solution. The accurate measure of the size distribution by small angle X-ray scattering was combined to the use of a model based on the coupling of nucleation and growth equations together with a progressive injection of monomers. The results on the final state show that the size of the nanoparticles is indeed controlled by the kinetic of reduction of gold atoms. A millifluidic setup equipped with a homemade mixer offers a robust way of rapid mixing to obtain a reproducible production of large amounts of nanoparticles.
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http://dx.doi.org/10.1021/la303439fDOI Listing
November 2012

Interaction between Escherichia coli and TiO2 nanoparticles in natural and artificial waters.

Colloids Surf B Biointerfaces 2013 Feb 31;102:158-64. Epub 2012 Aug 31.

CEA Saclay, DSM/IRAMIS/SIS2M/LIONS, UMR CEA-CNRS 3299, 91191 Gif sur Yvette, France.

Seine River water was used as a natural environmental medium to quantify the ecotoxicological impact of three types of manufactured titanium dioxide (TiO(2)) nanoparticles toward the model bacterium Escherichia coli. Under ambient light, a significant toxicity starting at 10 ppm of TiO(2) in water was observed. Presence of the anatase polymorph slightly increased the toxicity in comparison to pure rutile samples. Furthermore, the toxicity was found to be lower at pH 5 compared to Seine water (pH 8). To assess the nanoparticles state of dispersion and their interactions with bacteria, cryogenic transmission electron microscopy (TEM) and zeta potential measurements were performed. A higher sorption of nanoparticle aggregates on cells is observed at pH 5 compared to Seine water. This allows concluding that the observed toxicity is not directly linked to the particles sorption onto the cell surfaces. In spite of stronger interaction between cells and nanoparticles at pH 5, a bacterial subpopulation apparently non-interacting with nanoparticles is evidenced by both TEM and zeta potential measurements. Such heterogeneities in cell populations can increase global bacterial resistance to TiO(2) nanoparticles.
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http://dx.doi.org/10.1016/j.colsurfb.2012.08.034DOI Listing
February 2013

Spheres growing on a sphere: a model to predict the morphology yields of colloidal molecules obtained through a heterogeneous nucleation route.

Langmuir 2012 Aug 25;28(31):11575-83. Epub 2012 Jul 25.

CEA Saclay, IRAMIS, Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire, Gif sur Yvette, France.

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.
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http://dx.doi.org/10.1021/la301857hDOI Listing
August 2012

Competition between ligands for Al2O3 in aqueous solution.

J Phys Chem A 2012 Jun 8;116(25):6511-8. Epub 2012 May 8.

CEA Saclay, IRAMIS/SIS2M/LIONS-UMR3299, 91191 Gif sur Yvette, France.

The adsorption of two classes of carboxylic ligands (i.e., aliphatic and aromatic small molecules), onto α-alumina nanoparticles was investigated. A new methodology was used whereby two molecules were simultaneously equilibrated with the inorganic material. A two-dimensional representation of the adsorption of the two complexing molecules enables us to differentiate between pairs of ligands with (i) independent adsorption on different sites of the alumina particles, (ii) competing adsorption on the same sites, or (iii) a mix thereof. Both the highest affinity ligands (tetracarboxylic acid, citric acid, and tiron), and the way they compete with lower affinity ligands have been identified. The combination of carbon skeleton and complexing groups required to produce the ligand of highest affinity at pH 5 has been recognized. In particular, the role of the OH in the α position of a carboxylic group and the role of the distance between two carboxylic groups are emphasized.
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http://dx.doi.org/10.1021/jp212359qDOI Listing
June 2012

Physico-chemical control over the single- or double-wall structure of aluminogermanate imogolite-like nanotubes.

J Am Chem Soc 2012 Feb 13;134(8):3780-6. Epub 2012 Feb 13.

CEA Saclay, IRAMIS, Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire, 91191 Gif-sur-Yvette cedex, France.

It is known that silicon can be successfully replaced by germanium atoms in the synthesis of imogolite nanotubes, leading to shorter and larger AlGe nanotubes. Beside the change in morphology, two characteristics of the AlGe nanotube synthesis were recently discovered. AlGe imogolite nanotubes can be synthesized at much higher concentrations than AlSi imogolite. AlGe imogolite exists in the form of both single-walled (SW) and double-walled (DW) nanotubes, whereas DW AlSi imogolites have never been observed. In this article, we give details on the physicochemical control over the SW or DW AlGe imogolite structure. For some conditions, an almost 100% yield of SW or DW nanotubes is demonstrated. We propose a model for the formation of SW or DW AlGe imogolite, which also explains why DW AlSi imogolites or higher wall numbers for AlGe imogolite are not likely to be formed.
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http://dx.doi.org/10.1021/ja209756jDOI Listing
February 2012

Surfactant (bi)layers on gold nanorods.

Langmuir 2012 Jan 14;28(2):1453-9. Epub 2011 Dec 14.

Departamento de Quimica Fisica, Universidade de Vigo, 36310 Vigo, Spain.

Gold nanorods in aqueous solution are generally surrounded by surfactants or capping agents. This is crucial for anisotropic growth during synthesis and for their final stability in solution. When CTAB is used, a bilayer has been evidenced from analytical methods even though no direct morphological characterization of the precise thickness and compactness has been reported. The type of surfactant layer is also relevant to understand the marked difference in further self-assembling properties of gold nanorods as experienced using 16-EO(1)-16 gemini surfactant instead of CTAB. To obtain a direct measure of the thickness of the surfactant layer on gold nanorods synthesized by the seeded growth method, we coupled TEM, SAXS, and SANS experiments for the two different cases, CTAB and gemini 16-EO(1)-16. Despite the strong residual signal from micelles in excess, it can be concluded that the thickness is imposed by the chain length of the surfactant and corresponds to a bilayer with partial interdigitation.
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http://dx.doi.org/10.1021/la203451pDOI Listing
January 2012

Nucleation of silica nanoparticles measured in situ during controlled supersaturation increase. Restructuring toward a monodisperse nonspherical shape.

Langmuir 2011 Oct 16;27(20):12304-11. Epub 2011 Sep 16.

Commissariat à l'Energie Atomique, DSM/IRAMIS/SIS2M/LIONS, UMR CEA/CNRS 3299, 91191 Gif-sur-Yvette, France.

The first stages of the nucleation and growth of silica nanoparticles are followed in situ using both SAXS and Raman spectroscopy. Coupling these two techniques allows the determination of the fractions of soluble and solid silica as a function of the reaction time. SAXS also enables demonstrating that major modifications of the structure occur after the initial precipitation period, inducing an increase of the precipitate density. These structural modifications have important implications in the initial nucleation growth stages, which have never been introduced either in classical models or in more recent kinetic nucleation theories. Such restructuration stages could contribute to explain the monodispersity of the obtained silica nanoparticles that is not predicted by classical models.
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http://dx.doi.org/10.1021/la2013842DOI Listing
October 2011

Macroscopic dynamics as reporter of mesoscopic organization: the Belousov-Zhabotinsky reaction in aqueous layers of DPPC lamellar phases.

J Phys Chem A 2011 Apr 24;115(15):3227-32. Epub 2011 Mar 24.

Departement of Chemistry, University of Sassari, Sassari (SS), Italy.

The propagation of traveling chemical waves in the excitable Belousov-Zhabotinsky (BZ) system when performed in the presence of 1,2-dipalmitoyl-sn-glycero-3-phosphatidyl choline (DPPC) bilayers responds sensitively to the phospholipid content. The characteristic features of wave propagation, such as spiral pitch, rotation period, and size of the spiral core region, show two regions of different behavior, one below and the other above a DPPC content of 12.5% (w/w) thus suggesting a transition in the organization of the lipid domains at a DPPC content of ∼12.5% (w/w). This transition is supported by small-angle X-ray scattering data, which show pronounced changes in the coherence lengths of the lyotropic smectic domains. Thus, the dynamics of the chemical system occurring at a macroscopic length scale reflects the organization of the water/lipid domains which extend over mesoscopic lengths. These findings indicate that in the BZ/DPPC system, there is an interaction between processes that occurs at length scales differing by as much as 3 orders of magnitude.
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http://dx.doi.org/10.1021/jp2004375DOI Listing
April 2011

Growth kinetic of single and double-walled aluminogermanate imogolite-like nanotubes: an experimental and modeling approach.

Phys Chem Chem Phys 2011 Feb 9;13(7):2682-9. Epub 2010 Dec 9.

CEA, IRAMIS, Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire, 91191 Gif-sur-Yvette, France.

Atomic Force Microscopy (AFM) and in situ Small Angle X-ray Scattering (SAXS) were used to investigate the evolution of the aluminogermanate imogolite-like nanotubes concentration and morphology during their synthesis. In particular, in situ SAXS allowed quantifying the transformation of protoimogolite into nanotubes. The size distribution of the final nanotubes was also assessed after growth by AFM. A particular attention was focused on the determination of the single and double walled nanotube length distributions. We observed that the two nanotube types do not grow with the same kinetic and that their final length distribution was different. A model of protoimogolites oriented aggregation was constructed to account for the experimental growth kinetic and the length distribution differences.
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http://dx.doi.org/10.1039/c0cp01851aDOI Listing
February 2011

Nanorods versus nanospheres: a bifurcation mechanism revealed by principal component TEM analysis.

Langmuir 2010 May;26(10):6887-91

IRAMIS-SIS2M-LIONS, CEA Saclay, 9191 Gif-sur-Yvette, France.

A quantitative analysis of object populations obtained by TEM images is performed for the classical scheme of aqueous seedless synthesis of nanorods. Using an effective way to represent nanoparticle size distributions, we unravel that spheres, usually considered to be a side-product, are in fact coming from a competing route during nanorod formation. The differentiation between spheres and rods appears above a critical size of 5 nm and is due to different growth rates between faces. The initial repartition of faces on nuclei or on the nanoparticles at the critical size can be the source for the final differentiation between globules and rods. The efficiency of the selection is strongly influenced by the production of the initial seeds and, in particular, by the amount of borohydride added in the present scheme.
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http://dx.doi.org/10.1021/la100843kDOI Listing
May 2010

SAXS exploration of the synthesis of ultra monodisperse silica nanoparticles and quantitative nucleation growth modeling.

J Colloid Interface Sci 2010 Jun 26;346(1):79-86. Epub 2010 Feb 26.

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire, IRAMIS, CEA Saclay, F-91191 Gif-sur-Yvette, France.

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.
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http://dx.doi.org/10.1016/j.jcis.2010.02.052DOI Listing
June 2010

Evidence of double-walled Al-Ge imogolite-like nanotubes. a cryo-TEM and SAXS investigation.

J Am Chem Soc 2010 Feb;132(4):1208-9

CEA, IRAMIS, Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire 91191 Gif-sur-Yvette, France.

It has been recently discovered that the synthesis of Al-Ge imogolite-like nanotubes is possible at high concentration. Despite this initial success, the structure of these Al-Ge imogolite-like nanotubes remains not completely understood. Using high resolution cryo-TEM and Small Angle X-ray Scattering, we unravel their mesoscale structure in two contrasted situations. On the one hand, Al-Ge imogolite nanotubes synthesized at 0.25 M are double-walled nanotubes of 4.0 +/- 0.1 nm with an inner tube of 2.4 +/- 0.1 nm. Moreover, SAXS data also suggest that the two concentric tubes have an equal length and identical wall structure. On the other hand, at higher concentration (0.5M), both SAXS and cryo-TEM data confirm the formation of single-walled nanotubes of 3.5 +/- 0.15 nm. Infrared spectroscopy confirms the imogolite structure of the tubes. This is the first evidence of any double-walled imogolite or imogolite-like nanotubes likely to renew interest in these materials and associated potential applications.
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http://dx.doi.org/10.1021/ja908707aDOI Listing
February 2010

Insight into silicate-glass corrosion mechanisms.

Nat Mater 2008 Dec 26;7(12):978-83. Epub 2008 Oct 26.

CEA, DEN, Laboratoire d'étude du Comportement à Long Terme, 30207 Bagnols-sur-Cèze, France.

The remarkable chemical durability of silicate glass makes it suitable for a wide range of applications. The slowdown of the aqueous glass corrosion kinetics that is frequently observed at long time is generally attributed to chemical affinity effects (saturation of the solution with respect to silica). Here, we demonstrate a new mechanism and highlight the impact of morphological transformations in the alteration layer on the leaching kinetics. A direct correlation between structure and reactivity is revealed by coupling the results of several structure-sensitive experiments with numerical simulations at mesoscopic scale. The sharp drop in the corrosion rate is shown to arise from densification of the outer layers of the alteration film, leading to pore closure. The presence of insoluble elements in the glass can inhibit the film restructuring responsible for this effect. This mechanism may be more broadly applicable to silicate minerals.
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http://dx.doi.org/10.1038/nmat2301DOI Listing
December 2008

Cetyltrimethylammonium bromide silver bromide complex as the capping agent of gold nanorods.

Langmuir 2008 Sep 9;24(17):9219-22. Epub 2008 Aug 9.

IRAMIS-SCM-LIONS, CEA Saclay, 9191 Gif-sur-Yvette, France.

A complex between cetyltrimethylammonium bromide (CTAB) surfactant and silver bromide (CTASB) is recognized by NMR and X-ray photoelectron spectroscopy (XPS) to be the entity at the surface of gold nanorods, resulting from an in situ formation in the classical scheme of synthesis. It can thus be introduced directly along with the initial reactants in place of silver(I) salt to produce a new effective synthesis of these objects. Complementary XPS and quartz crystal microbalance (QCM) measurements on macroscopic gold surfaces confirm a strong adsorption of CTASB that is higher than that of CTAB and any other CTAX surfactants. The role of CTASB as a rod inducing agent by surface complexation is stressed.
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http://dx.doi.org/10.1021/la801711qDOI Listing
September 2008

Gold nanoparticle superlattice crystallization probed in situ.

Phys Rev Lett 2008 Mar 19;100(11):115504. Epub 2008 Mar 19.

LIONS, Service de Chimie Moléculaire, IRAMIS, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France.

The nucleation and growth of three-dimensional superlattices of gold nanoparticles has been followed directly in situ by means of small angle x-ray scattering. These assemblies spontaneously form in a dilute solution providing the particles are large enough to generate a van der Waals driven attraction sufficient to counterbalance the thermal energy. The superlattices nucleate very soon after the birth of the individual particles and their growth kinetics is slower than predicted by a mechanism of simple diffusion of the nanoparticles towards the superlattices. The superlattices are first limited in size (170 nm in diameter) and have a globular shape with a low polydispersity. They present a fcc inner structure with nanoparticles being separated by a capping agent bilayer yielding a low gold internal volume fraction (phi SL = 0.33). In a second stage, these superlattices coalesce with time.
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http://dx.doi.org/10.1103/PhysRevLett.100.115504DOI Listing
March 2008

Time resolved alteration process of oxide glasses.

J Colloid Interface Sci 2008 Mar 22;319(1):214-25. Epub 2007 Nov 22.

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire CEA/DRECAM CEA Saclay, 91191 Gif sur Yvette, France.

Dissolution of oxide glasses by water has been studied by small angles X-ray scattering. It is shown that the altered residual surface layer due to dissolution and recondensation of Si atoms is a porous material with nanometer size pores. Based on five elements oxide glass (18NaO2-17B2O3-4CaO-yZrO2-(61-y)SiO2 with y=0, 1, 2, 4 and 8) the experiment highlights a strong influence of insoluble element on both the kinetic of alteration and the structure of the altered layer. It is shown that above 2% Zr content, the fraction of porous volume and the surface of exchange in the altered layer pass through a maximum value in the first hours of alteration corresponding to an overshoot of Si lixiviation without recondensation as the saturation limit is not reached. When the saturation limit is reached the porous volume fraction is just below the fraction of volume occupied primarily by the sodium and the boron.
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http://dx.doi.org/10.1016/j.jcis.2007.10.065DOI Listing
March 2008

Small angle scattering and zeta potential of liposomes loaded with octa(carboranyl)porphyrazine.

J Phys Chem B 2007 Sep 14;111(35):10357-64. Epub 2007 Aug 14.

University of Firenze, Department of Chemistry, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy, Laboratoire des Colloïdes, Verres et Nanomatériaux (LCVN), Université Montpellier II, 34095 Montpellier Cedex 05 France.

In this work, the physicochemical characterization of liposomes loaded with a newly synthesized carboranyl porphyrazine (H2HECASPz) is described. This molecule represents a potential drug for different anticancer therapies, such as boron neutron capture therapy and for photodynamic therapy or photothermal therapy. Different loading methods and different lipid mixtures were tested. The corresponding loaded vectors were studied by small angle scattering, light scattering, and zeta potential. The combined analysis of structural data at various lengths of scales and the measurement of the surface charge allowed us to obtain a detailed characterization of the investigated systems. The mechanisms underlying the onset of differences in relevant physicochemical parameters (size, polydispersity, and charge) were also critically discussed.
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http://dx.doi.org/10.1021/jp0731710DOI Listing
September 2007