Publications by authors named "Jean-Pierre Boilot"

34 Publications

Monitoring the orientation of rare-earth-doped nanorods for flow shear tomography.

Nat Nanotechnol 2017 09 19;12(9):914-919. Epub 2017 Jun 19.

Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, CNRS, Université Paris-Saclay, 91128 Palaiseau, France.

Rare-earth phosphors exhibit unique luminescence polarization features originating from the anisotropic symmetry of the emitter ion's chemical environment. However, to take advantage of this peculiar property, it is necessary to control and measure the ensemble orientation of the host particles with a high degree of precision. Here, we show a methodology to obtain the photoluminescence polarization of Eu-doped LaPO nanorods assembled in an electrically modulated liquid-crystalline phase. We measure Eu emission spectra for the three main optical configurations (σ, π and α, depending on the direction of observation and the polarization axes) and use them as a reference for the nanorod orientation analysis. Based on the fact that flowing nanorods tend to orient along the shear strain profile, we use this orientation analysis to measure the local shear rate in a flowing liquid. The potential of this approach is then demonstrated through tomographic imaging of the shear rate distribution in a microfluidic system.
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http://dx.doi.org/10.1038/nnano.2017.111DOI Listing
September 2017

Pressure Control of Cuprophilic Interactions in a Luminescent Mechanochromic Copper Cluster.

Inorg Chem 2015 Oct 29;54(20):9821-5. Epub 2015 Sep 29.

Laboratoire de Physique de la Matière Condensée (PMC), CNRS, Ecole Polytechnique , 91128 Palaiseau Cedex, France.

For the development of applications based on mechanochromic luminescent materials, a comprehensive study of the mechanism responsible for the emission changes is required. We report the study of a mechanochromic copper iodide cluster under hydrostatic pressure, which allows control of crystal packing via modification of the intermolecular interactions. In situ single-crystal powder X-ray diffraction analysis and emission measurements under pressure permit one to establish a direct correlation between the molecular structure and luminescence properties and, in particular, to demonstrate that cuprophilic interactions are responsible for the stimuli-responsive luminescence properties of such multinuclear coordination compounds.
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http://dx.doi.org/10.1021/acs.inorgchem.5b01546DOI Listing
October 2015

Electric field induced birefringence in non-aqueous dispersions of mineral nanorods.

Soft Matter 2015 Sep;11(33):6595-603

Centre de Recherche Paul-Pascal, CNRS - Université de Bordeaux, 115 Avenue Schweitzer, 33600 Pessac, France.

Lanthanum phosphate (LaPO4) nanorods dispersed in the non-aqueous solvent of ethylene glycol form a system exhibiting large intrinsic birefringence, high colloidal stability and the ability to self-organize into liquid crystalline phases. In order to probe the electro-optical response of these rod dispersions we study here the electric-field-induced birefringence, also called Kerr effect, for a concentrated isotropic liquid state with an in-plane a.c. sinusoidal electric field, in conditions of directly applied (electrodes in contact with the sample) or externally applied (electrodes outside the sample cell) fields. Performing an analysis of the electric polarizability of our rod-like particles in the framework of Maxwell-Wagner-O'Konski theory, we account quantitatively for the coupling between the induced steady-state birefringence and the electric field as a function of the voltage frequency for both sample geometries. The switching time of this non-aqueous transparent system has been measured, and combined with its high Kerr coefficients and its features of optically isotropic "off-state" and athermal phase behavior, this represents a promising proof-of-concept for the integration of anisotropic nanoparticle suspensions into a new generation of electro-optical devices.
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http://dx.doi.org/10.1039/c5sm01427aDOI Listing
September 2015

Geometry flexibility of copper iodide clusters: variability in luminescence thermochromism.

Inorg Chem 2015 May 10;54(9):4483-94. Epub 2015 Apr 10.

⊗Science et Technologies, Université Lille, F-59000 Lille, France.

An original copper(I) iodide cluster of novel geometry obtained by using a diphosphine ligand is reported and is formulated [Cu6I6(PPh2(CH2)3PPh2)3] (1). Interestingly, this sort of "eared cubane" cluster based on the [Cu6I6] inorganic core can be viewed as a combination of the two known [Cu4I4] units, namely, the cubane and the open-chair isomeric geometries. The synthesis, structural and photophysical characterisations, as well as theoretical study of this copper iodide along with the derived cubane (3) and open-chair (2) [Cu4I4(PPh3)4] forms, were investigated. A new polymorph of the cubane [Cu4I4(PPh3)4] cluster is indeed presented (3). The structural differences of the clusters were analyzed by solid-state nuclear magnetic resonance spectroscopy. Luminescence properties of the three clusters were studied in detail as a function of the temperature showing reversible luminescence thermochromism for 1 with an intense orange emission at room temperature. This behavior presents different feature compared to the cubane cluster and completely contrasts with the open isomer, which is almost nonemissive at room temperature. Indeed, the thermochromism of 1 differs by a concomitant increase of the two emission bands by lowering the temperature, in contrast to an equilibrium phenomenon for 3. The luminescence properties of 2 are very different by exhibiting only one single band when cooled. To rationalize the different optical properties observed, density functional theory calculations were performed for the three clusters giving straightforward explanation for the different luminescence thermochromism observed, which is attributed to different contributions of the ligands to the molecular orbitals. Comparison of 3 with its [Cu4I4(PPh3)4] cubane polymorphs highlights the sensibility of the emission properties to the cuprophilic interactions.
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http://dx.doi.org/10.1021/acs.inorgchem.5b00321DOI Listing
May 2015

Mechanochromic luminescence of copper iodide clusters.

Chemistry 2015 Apr 5;21(15):5892-7. Epub 2015 Mar 5.

Laboratoire de Physique de la Matière Condensée, UMR 7643, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France).

Luminescent mechanochromic materials are particularly appealing for the development of stimuli-responsive materials. Establishing the mechanism responsible for the mechanochromism is always an issue owing to the difficulty in characterizing the ground phase. Herein, the study of real crystalline polymorphs of a mechanochromic and thermochromic luminescent copper iodide cluster permits us to clearly establish the mechanism involved. The local disruption of the crystal packing induces changes in the cluster geometry and in particular the modification of the cuprophilic interactions, which consequently modify the emissive states. This study constitutes a step further toward the understanding of the mechanism involved in the mechanochromic luminescent properties of multimetallic coordination complexes.
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http://dx.doi.org/10.1002/chem.201500251DOI Listing
April 2015

Single YVO4:Eu nanoparticle emission spectra using direct Eu3+ ion excitation with a sum-frequency 465-nm solid-state laser.

Opt Express 2014 Aug;22(17):20542-50

We report emission spectrum measurements on single YxEu(1-x)VO4 nanoparticles. The inhomogeneous widths of the emission peaks are identical for single nanoparticles and for ensembles of nanoparticles, while being broader than those of the bulk material. This indicates that individual nanoparticles are identical in terms of the distribution of different local Eu3+ sites due to crystalline defects and confirms their usability as identical, single-particle oxidant biosensors. Moreover, we report a 465 nm solid-state laser based on sum-frequency mixing that provides a compact, efficient solution for direct Eu3+ excitation of these nanoparticles. Both these two aspects should broaden the scope of Eu-doped nanoparticle applications.
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http://dx.doi.org/10.1364/OE.22.020542DOI Listing
August 2014

Multifunctional rare-Earth vanadate nanoparticles: luminescent labels, oxidant sensors, and MRI contrast agents.

ACS Nano 2014 Nov 20;8(11):11126-37. Epub 2014 Oct 20.

Laboratoire d'Optique et Biosciences, Ecole Polytechnique , CNRS UMR 7645-INSERM U696, 91128 Palaiseau Cedex, France.

Collecting information on multiple pathophysiological parameters is essential for understanding complex pathologies, especially given the large interindividual variability. We report here multifunctional nanoparticles which are luminescent probes, oxidant sensors, and contrast agents in magnetic resonance imaging (MRI). Eu(3+) ions in an yttrium vanadate matrix have been demonstrated to emit strong, nonblinking, and stable luminescence. Time- and space-resolved optical oxidant detection is feasible after reversible photoreduction of Eu(3+) to Eu(2+) and reoxidation by oxidants, such as H2O2, leading to a modulation of the luminescence emission. The incorporation of paramagnetic Gd(3+) confers in addition proton relaxation enhancing properties to the system. We synthesized and characterized nanoparticles of either 5 or 30 nm diameter with compositions of GdVO4 and Gd0.6Eu0.4VO4. These particles retain the luminescence and oxidant detection properties of YVO4:Eu. Moreover, the proton relaxivity of GdVO4 and Gd0.6Eu0.4VO4 nanoparticles of 5 nm diameter is higher than that of the commercial Gd(3+) chelate compound Dotarem at 20 MHz. Nuclear magnetic resonance dispersion spectroscopy showed a relaxivity increase above 10 MHz. Complexometric titration indicated that rare-earth leaching is negligible. The 5 nm nanoparticles injected in mice were observed with MRI to concentrate in the liver and the bladder after 30 min. Thus, these multifunctional rare-earth vanadate nanoparticles pave the way for simultaneous optical and magnetic resonance detection, in particular, for in vivo localization evolution and reactive oxygen species detection in a broad range of physiological and pathophysiological conditions.
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http://dx.doi.org/10.1021/nn504170xDOI Listing
November 2014

Polymorphic copper iodide clusters: insights into the mechanochromic luminescence properties.

J Am Chem Soc 2014 Aug 30;136(32):11311-20. Epub 2014 Jul 30.

Laboratoire de Physique de la Matière Condensée (PMC), CNRS - Ecole Polytechnique, 91128 Palaiseau Cedex, France.

An in-depth study of mechanochromic and thermochromic luminescent copper iodide clusters exhibiting structural polymorphism is reported and gives new insights into the origin of the mechanochromic luminescence properties. The two different crystalline polymorphs exhibit distinct luminescence properties with one being green emissive and the other one being yellow emissive. Upon mechanical grinding, only one of the polymorphs exhibits great modification of its emission from green to yellow. Interestingly, the photophysical properties of the resulting partially amorphous crushed compound are closed to those of the other yellow polymorph. Comparative structural and optical analyses of the different phases including a solution of clusters permit us to establish a correlation between the Cu-Cu bond distances and the luminescence properties. In addition, the local structure of the [Cu4I4P4] cluster cores has been probed by (31)P and (65)Cu solid-state NMR analysis, which readily indicates that the grinding process modifies the phosphorus and copper atoms environments. The mechanochromic phenomenon is thus explained by the disruption of the crystal packing within intermolecular interactions inducing shortening of the Cu-Cu bond distances in the [Cu4I4] cluster core and eventually modification of the emissive state. These results definitely establish the role of cuprophilic interactions in the mechanochromism of copper iodide clusters. More generally, this study constitutes a step further into the understanding of the mechanism involved in the mechanochromic luminescent properties of metal-based compounds.
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http://dx.doi.org/10.1021/ja500247bDOI Listing
August 2014

Photoactive hybrid gelators based on a luminescent inorganic [Cu4I4] cluster core.

Chemistry 2013 Nov 21;19(47):15831-5. Epub 2013 Oct 21.

Laboratoire de Physique de la Matière Condensée - CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France), Fax: (+33) 169334799.

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http://dx.doi.org/10.1002/chem.201303567DOI Listing
November 2013

How to prepare the brightest luminescent coatings?

ACS Appl Mater Interfaces 2013 Nov 1;5(21):11315-20. Epub 2013 Nov 1.

Laboratoire de Physique de la Matière Condensée, UMR CNRS 7643 - Ecole Polytechnique , 91128 Palaiseau Cedex, France.

We address here the question of studying the parameters affecting the brightness of luminescent nanoparticulate coatings, among which are the absorption rate, the internal quantum yield of the phosphor nanoparticles, and the extraction factor of the emitted light in a solid angle perpendicular to the substrate. Experimental investigations are achieved on spray-deposited YVO4:Eu particles, a system whose synthesis and properties are well documented so that particles of different sizes and microstructure can be considered. This allows a quantitative evaluation of the factors affecting film brightness. Considering a film made from raw colloidal particles, this work shows that its brightness is limited by a factor of 5 due to altered quantum yield of nanoparticles, a factor of 1.75 by dielectric effects and a factor of 2.4 by light extraction issues. This investigation, through providing quantitative evaluations of these different parameters, opens the way toward a possible rational design of inorganic luminescent coatings, with a possible improvement of brightness that could reach a factor of 30 as compared to simple films made directly from colloidal suspensions.
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http://dx.doi.org/10.1021/am4035448DOI Listing
November 2013

Optically anisotropic thin films by shear-oriented assembly of colloidal nanorods.

Adv Mater 2013 Jun 13;25(24):3295-300. Epub 2013 May 13.

Laboratoire de Physique de la Matière Condensée, CNRS-Ecole Polytechnique, 91128, Palaiseau, France.

Device-scale thin films of highly oriented (in-plane) colloidal nanorods are made available by using a simple coating process involving thixotropic rod gel suspensions. Application of this process to LaPO₄ nanorods leads to films exhibiting outstanding anisotropic optical properties, such as a remarkably large birefringence (Δn = 0.13) associated with high transparency, and sharply polarized fluorescence spectra when doped with europium.
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http://dx.doi.org/10.1002/adma.201300594DOI Listing
June 2013

Photolithographic processing of silver loaded dielectric coatings based on preformed colloidal TiO2 nanoparticles dispersed in a mesoporous silica binder.

Nanotechnology 2012 Dec 29;23(50):505206. Epub 2012 Nov 29.

Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique-CNRS, Palaiseau, F-91128, France.

Titanium dioxide is a well known photocatalyst for reactions involving surface trapped photogenerated carriers. Noble metal photo-reduction may be used for the processing of silver/TiO(2) nanocomposite coatings that may exhibit interesting optical and electrical properties. We present here results of our investigations performed on an original system consisting of preformed colloidal TiO(2) nanoparticles homogeneously dispersed within a mesoporous silica host matrix. Light irradiation of samples immerged in an aqueous silver salt solution leads to the homogeneous deposition of silver islands in the vicinity of the TiO(2) particles and throughout the film thickness. The silver volume fraction is directly controlled by the irradiation dose up to a value of about 16 vol.%. Films exhibit tunable plasmonic properties that correspond to silver nanoparticles in interaction, and a percolation threshold is observed at 8-10 vol.%, leading to films with a conductivity of about 40 S cm(-1). The major interest of this method lies in the high silver reduction quantum efficiency (about 50%) and the possibility to modulate optical and electronic properties by light irradiation while the low temperature of processing permits the photolithographic deposition of metallic patterns on organic flexible substrates.
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http://dx.doi.org/10.1088/0957-4484/23/50/505206DOI Listing
December 2012

Observing the confinement potential of bacterial pore-forming toxin receptors inside rafts with nonblinking Eu(3+)-doped oxide nanoparticles.

Biophys J 2012 May 15;102(10):2299-308. Epub 2012 May 15.

Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale U696, Palaiseau, France.

We track single toxin receptors on the apical cell membrane of MDCK cells with Eu-doped oxide nanoparticles coupled to two toxins of the pore-forming toxin family: α-toxin of Clostridium septicum and ε-toxin of Clostridium perfringens. These nonblinking and photostable labels do not perturb the motion of the toxin receptors and yield long uninterrupted trajectories with mean localization precision of 30 nm for acquisition times of 51.3 ms. We were thus able to study the toxin-cell interaction at the single-molecule level. Toxins bind to receptors that are confined within zones of mean area 0.40 ± 0.05 μm(2). Assuming that the receptors move according to the Langevin equation of motion and using Bayesian inference, we determined mean diffusion coefficients of 0.16 ± 0.01 μm(2)/s for both toxin receptors. Moreover, application of this approach revealed a force field within the domain generated by a springlike confining potential. Both toxin receptors were found to experience forces characterized by a mean spring constant of 0.30 ± 0.03 pN/μm at 37°C. Furthermore, both toxin receptors showed similar distributions of diffusion coefficient, domain area, and spring constant. Control experiments before and after incubation with cholesterol oxidase and sphingomyelinase show that these two enzymes disrupt the confinement domains and lead to quasi-free motion of the toxin receptors. Our control data showing cholesterol and sphingomyelin dependence as well as independence of actin depolymerization and microtubule disruption lead us to attribute the confinement of both receptors to lipid rafts. These toxins require oligomerization to develop their toxic activity. The confined nature of the toxin receptors leads to a local enhancement of the toxin monomer concentration and may thus explain the virulence of this toxin family.
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http://dx.doi.org/10.1016/j.bpj.2012.03.072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3352999PMC
May 2012

Siloxanol-functionalized copper iodide cluster as a thermochromic luminescent building block.

Inorg Chem 2012 Jan 23;51(2):794-8. Epub 2011 Dec 23.

Laboratoire de Physique de la Matière Condensée, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex, France.

A copper iodide cluster bearing reactive silanol groups exhibits thermochromic luminescence properties sensitive to its chemical environment and is thus a suitable building block for the synthesis of optically active materials.
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http://dx.doi.org/10.1021/ic200672rDOI Listing
January 2012

Thermochromic luminescence of copper iodide clusters: the case of phosphine ligands.

Inorg Chem 2011 Nov 29;50(21):10682-92. Epub 2011 Sep 29.

Laboratoire de Physique de la Matière Condensée (PMC), CNRS-Ecole Polytechnique, 91128 Palaiseau Cedex, France.

Three copper(I) iodide clusters coordinated by different phosphine ligands formulated [Cu(4)I(4)(PPh(3))(4)] (1), [Cu(4)I(4)(Pcpent(3))(4)] (2), and [Cu(4)I(4)(PPh(2)Pr)(4)] (3) (PPh(3) = triphenylphosphine, Pcpent(3) = tricyclopentylphosphine, and PPh(2)Pr = diphenylpropylphosphine) have been synthesized and characterized by (1)H and (31)P NMR, elemental analysis and single crystal X-ray diffraction analysis. They crystallize in different space groups, namely, monoclinic P21/c, cubic Pa ̅3, and tetragonal I ̅42m for 1, 2, and 3, respectively. The photoluminescence properties of clusters 1 and 3 show reversible luminescence thermochromism with two highly intense emission bands whose intensities are temperature dependent. In accordance to Density Functional Theory (DFT) calculations, these two emission bands have been attributed to two different transitions, a cluster centered (CC) one and a mixed XMCT/XLCT one. Cluster 2 does not exhibit luminescence variation in temperature because of the lack of the latter transition. The absorption spectra of the three clusters have been also rationalized by time dependent DFT (TDDFT) calculations. A simplified model is suggested to represent the luminescence thermochromism attributed to the two different excited states in thermal equilibrium. In contrast with the pyridine derivatives, similar excitation profiles and low activation energy for these phosphine-based clusters reflect high coupling of the two emissive states. The effect of the Cu-Cu interactions on the emission properties of these clusters is also discussed. Especially, cluster 3 with long Cu-Cu contacts exhibits a controlled thermochromic luminescence which is to our knowledge, unknown for this family of copper iodide clusters. These phosphine-based clusters appear particularly interesting for the synthesis of original emissive materials.
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http://dx.doi.org/10.1021/ic201128aDOI Listing
November 2011

Photonic crystal patterning of luminescent sol-gel films for light extraction.

Nanotechnology 2011 Sep 11;22(36):365701. Epub 2011 Aug 11.

Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique/CNRS UMR7643, Palaiseau, France.

Structured luminescent thin films are investigated in the context of improved light extraction of phosphors for solid-state-lighting applications. Thin films composed of a sol-gel titania matrix doped with europium chelates are studied as a model system. These films, patterned with a square photonic lattice by soft nanoimprint lithography, are characterized by angle-resolved fluorescence. Modeling of this simple technique is shown to fit well the experimental data, revealing in great detail the guided modes of the film and their extraction parameters. An eightfold extraction enhancement factor of the film emission is measured. To further improve the extraction efficiency, we investigate the role of an additional low-index mesoporous silica underlayer through its influence on the guided modes of different polarizations and their interactions with the photonic crystal. Results obtained on model systems open the way towards the optimization of light-emitting devices, using a strategy of dielectric microstructure engineering using the sol-gel process.
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http://dx.doi.org/10.1088/0957-4484/22/36/365701DOI Listing
September 2011

A protected annealing strategy to enhanced light emission and photostability of YAG:Ce nanoparticle-based films.

Nanoscale 2011 May 8;3(5):2015-22. Epub 2011 Mar 8.

Physique de la Matière Condensée, CNRS, Ecole Polytechnique, Palaiseau, France.

A significant obstacle in the development of YAG:Ce nanoparticles as light converters in white LEDs and as biological labels is associated with the difficulty of finding preparative conditions that allow simultaneous control of structure, particle size and size distribution, while maintaining the optical properties of bulk samples. Preparation conditions frequently involve high-temperature treatments of precursors (up to 1400 °C), which result in increased particle size and aggregation, and lead to oxidation of Ce(iii) to Ce(iv). We report here a process that we term protected annealing, that allows the thermal treatment of preformed precursor particles at temperatures up to 1000 °C while preserving their small size and state of dispersion. In a first step, pristine nanoparticles are prepared by a glycothermal reaction, leading to a mixture of YAG and boehmite crystalline phases. The preformed nanoparticles are then dispersed in a porous silica. Annealing of the composite material at 1000 °C is followed by dissolution of the amorphous silica by hydrofluoric acid to recover the annealed particles as a colloidal dispersion. This simple process allows completion of YAG crystallization while preserving their small size. The redox state of Ce ions can be controlled through the annealing atmosphere. The obtained particles of YAG:Ce (60 ± 10 nm in size) can be dispersed as nearly transparent aqueous suspensions, with a luminescence quantum yield of 60%. Transparent YAG:Ce nanoparticle-based films of micron thickness can be deposited on glass substrates using aerosol spraying. Films formed from particles prepared by the protected annealing strategy display significantly improved photostability over particles that have not been subject to such annealing.
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http://dx.doi.org/10.1039/c0nr01000fDOI Listing
May 2011

Mechanochromic and thermochromic luminescence of a copper iodide cluster.

J Am Chem Soc 2010 Aug;132(32):10967-9

Laboratoire de Physique de la Matière Condensée (PMC), CNRS - Ecole Polytechnique, 91128 Palaiseau Cedex, France.

The mechanochromic and thermochromic luminescence properties of a molecular copper(I) iodide cluster formulated [Cu(4)I(4)(PPh(2)(CH(2)CH=CH(2)))(4)] are reported. Upon mechanical grinding in a mortar, its solid-state emission properties are drastically modified as well as its thermochromic behavior. This reversible phenomenon has been attributed to distortions in the crystal packing leading to modifications of the intermolecular interactions and thus of the [Cu(4)I(4)] cluster core geometry. Notably, modification of the Cu-Cu interactions seems to be involved in this phenomenon directly affecting the emissive properties of the cluster.
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http://dx.doi.org/10.1021/ja103431dDOI Listing
August 2010

Electrostatic grafting of diamond nanoparticles: a versatile route to nanocrystalline diamond thin films.

ACS Appl Mater Interfaces 2009 Dec;1(12):2738-46

Laboratoire de Physique de la Matiere Condensee (PMC), CNRS - Ecole Polytechnique, F-91128 Palaiseau cedex, France.

Nanodiamond (ND) seeding is a well-established route toward the CVD (chemical vapor deposition) synthesis of diamond ultrathin films. This method is based on the deposition onto a substrate of diamond nanoparticles which act as pre-existing sp(3) seeds. Here, we report on a straightforward method to disperse diamond nanoparticles on a substrate by taking advantage of the electrostatic interactions between the nanodiamonds and the substrate surface coated with a cationic polymer. This layer-by-layer deposition technique leads to reproducible and homogeneous large-scale nanoparticle deposits independent of the substrate's nature and shape. No specific functionalization of the nanoparticles is required, and low concentrated solutions can be used. The density of NDs on the substrate can be controlled, as shown by in situ ATR-FTIR (attenuated total reflection Fourier transform infrared) analysis and QCM (quartz crystal microbalance) measurements. Highly dense and compact ND deposits can be obtained, allowing CVD growth of nanocrystalline diamond ultrathin films (70 nm) on various substrates. The synthesis of 3D structured and patterned diamond thin films has also been demonstrated with this method.
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http://dx.doi.org/10.1021/am900458gDOI Listing
December 2009

Plasmon-induced modification of fluorescent thin film emission nearby gold nanoparticle monolayers.

Langmuir 2010 Jun;26(11):8842-9

Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique-CNRS, 91128 Palaiseau, France.

When placed in the vicinity of metal nanoparticles, fluorophore molecules can have their fluorescence intensity enhanced. In order to engineer highly fluorescent thin films, surface plasmon enhancement fluorescence was studied on macroscopic systems composed of gold nanoparticles deposited on a substrate and coated by a dye-containing polymer film. We developed a simple method based on surface silanization to get a good dispersion of up to 100 nm gold nanoparticles on a substrate. While controlling the nanoparticle size and the fluorophore concentration, we measured the fluorescence enhancement factors of systems doped with dyes possessing different quantum yields. We evidenced experimentally that a fluorescence enhancement factor of 4 could be reached for a low-quantum yield dye and that the fluorophore quantum yield affects significantly the enhancement factor. We then discussed how our experimental results agree with previously developed models.
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http://dx.doi.org/10.1021/la904612rDOI Listing
June 2010

Single europium-doped nanoparticles measure temporal pattern of reactive oxygen species production inside cells.

Nat Nanotechnol 2009 Sep 9;4(9):581-5. Epub 2009 Aug 9.

Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS, INSERM U696, Palaiseau, France.

Low concentrations of reactive oxygen species, notably hydrogen peroxide (H(2)O(2)), mediate various signalling processes in the cell. Production of these signals is highly regulated and a suitable probe is needed to measure these events. Here, we show that a probe based on a single nanoparticle can quantitatively measure transient H(2)O(2) generation in living cells. The Y(0.6)Eu(0.4)VO(4) nanoparticles undergo photoreduction under laser irradiation but re-oxidize in the presence of oxidants, leading to a recovery in luminescence. Our probe can be regenerated and reliably detects intracellular H(2)O(2) with a 30-s temporal resolution and a dynamic range of 1-45 microM. The differences in the timing of intracellular H(2)O(2) production triggered by different signals were also measured using these nanoparticles. Although the probe is not selective towards H(2)O(2), in many signalling processes H(2)O(2) is, however, the dominant oxidant. In conjunction with appropriate controls, this probe is a powerful tool for unravelling pathways that involve reactive oxygen species.
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http://dx.doi.org/10.1038/nnano.2009.200DOI Listing
September 2009

High temperature strategy for oxide nanoparticle synthesis.

ACS Nano 2008 Dec;2(12):2505-12

Groupe de Chimie du Solide, Laboratoire de Physique de la Matiere Condensee, CNRS, Ecole Polytechnique, 91128 Palaiseau cedex, France.

Compared with noble metals and quantum dots, dielectric complex oxide nanoparticles are significantly less popular due to their high crystallization temperature, making difficult their synthesis in the 10-100 nm range for which surface effects are reduced. We report here an original process permitting thermal annealing of complex oxide nanoparticles at high temperature without aggregation and growth. Thus, after thermal treatment, these annealed particles can be dispersed in water, leading to concentrated aqueous colloidal dispersions containing isolated highly crystalline particles. This contrasts with usual colloidal techniques for which the production of particles in the 10-100 nm range generally leads to poorly crystallized particles, especially for multicomponent oxides. From two examples, we show some possibilities offered by this type of process. This concerns the synthesis of lanthanide-doped oxide nanoparticles exhibiting a bulk behavior for their luminescence properties and the control of the composition in nitrogen-doped titanium oxide particles without sintering and size change.
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http://dx.doi.org/10.1021/nn8005784DOI Listing
December 2008

Organic functionalization of luminescent oxide nanoparticles toward their application as biological probes.

Langmuir 2008 Oct 5;24(19):11018-26. Epub 2008 Sep 5.

Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, CNRS, Route de Saclay, 91128 Palaiseau, France.

Luminescent inorganic nanoparticles are now widely studied for their applications as biological probes for in vitro or in vivo experiments. The functionalization of the particles is a key step toward these applications, since it determines the control of the coupling between the particles and the biological species of interest. This paper is devoted to the case of rare earth doped oxide nanoparticles and their functionalization through their surface encapsulation with a functional polysiloxane shell. The first step of the process is the adsorption of silicate ions that will act as a primary layer for the further surface polymerization of the silane, either aminopropyltriethoxysilane (APTES) or glycidoxypropyltrimethoxysilane (GPTMS). The amino- or epoxy- functions born by the silane allow the versatile coupling of the particles with bio-organic species following the chemistry that is commonly used in biochips. Special attention is paid to the careful characterization of each step of the functionalization process, especially concerning the average number of organic functions that are available for the final coupling of the particles with proteins. The surface density of amino or epoxy functions was found to be 0.4 and 1.9 functions per square nanometer for GPTMS and APTES silanized particles, respectively. An example of application of the amino-functionalized particles is given for the coupling with alpha-bungarotoxins. The average number (up to 8) and the distribution of the number of proteins per particle are given, showing the potentialities of the functionalization process for the labeling of biological species.
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http://dx.doi.org/10.1021/la8015468DOI Listing
October 2008

Counting the number of proteins coupled to single nanoparticles.

J Am Chem Soc 2007 Oct 29;129(42):12592-3. Epub 2007 Sep 29.

Laboratoire d'Optique et Biosciences and Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, CNRS, 91128 Palaiseau, France, and INSERM U696, 91128, Palaiseau, France.

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http://dx.doi.org/10.1021/ja0731975DOI Listing
October 2007

Coupling of liquid crystals to silica nanoparticles.

J Am Chem Soc 2007 Aug 11;129(30):9274-5. Epub 2007 Jul 11.

Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, CNRS, Palaiseau, France.

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http://dx.doi.org/10.1021/ja0735608DOI Listing
August 2007

Functionalized sol-gel coatings for optical applications.

Acc Chem Res 2007 Sep 2;40(9):895-902. Epub 2007 Mar 2.

Groupe de Chimie du Solide, Laboratoire de Physique de la Matière Condensée, CNRS, Ecole Polytechnique, 91128 Palaiseau cedex, France.

Sol-gel processing is well-known to be a powerful technique for designing materials for optical applications. Here, some recent applications of functionalized sol-gel coatings in optics are briefly reviewed. Lanthanide-doped oxide nanocrystals form a new promising class of nanophosphors allowing the easy sol-gel preparation of transparent and luminescent films for the development of light-emitting devices. Recent experiments on organized mesoporous films show their potential applications in optics, such as stable low-index layers in interferential antireflective devices or as silica binders in TiO 2-photocatalytic devices.
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http://dx.doi.org/10.1021/ar600025jDOI Listing
September 2007

Stabilization of well-organized transient micellar phases in CTAB-templated silica and organosilica thin films.

Soft Matter 2007 Jan;3(2):223-229

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

The influence of some previously reported critical parameters (aging of the silica sol, humidity, % of trivalent precursor) controlling the nature and the degree of organization of mesophases is studied in detail for CTAB-templated silica and organosilicate films prepared by rapid evaporation techniques. It is shown that all of these parameters directly influence the silica-condensation kinetics. Concerning films with the 2D-hexagonal structure belonging to the CTAB-water phase diagram, the mesophase is mainly stabilized by interactions between cylindrical micelles, and the reactivity of the silica sol does not drastically modify the extent of the order in films. In contrast, the formation of a rigid silica network just after the micellar organization appears to be crucial to prepare well-organized films with the 3D-hexagonal or the cubic transient structure. In the latter case, the size and reactivity of silica clusters have to be controlled to obtain rapid gelation in the deposited sol.
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http://dx.doi.org/10.1039/b612408aDOI Listing
January 2007

Single lanthanide-doped oxide nanoparticles as donors in fluorescence resonance energy transfer experiments.

J Phys Chem B 2006 Oct;110(39):19264-70

Laboratory for Optics and Biosciences, CNRS UMR7645, INSERM U696, Ecole Polytechnique, F-91128 Palaiseau Cedex, France.

We used lanthanide-ion doped oxide nanoparticles, Y(0.6)Eu(0.4)VO(4), as donors in fluorescent resonance energy transfer (FRET) experiments. The choice of these nanoparticles allows us to combine the advantages of the lanthanide-ion emission, in particular the long lifetime and the large Stokes shift between absorption and emission, with the detectability of the nanoparticles at the single-particle level. Using cyanine 5 (Cy5) organic molecules as acceptors, we demonstrated FRET down to the single-nanoparticle level. We showed that, due to the long donor lifetime, unambiguous and precise FRET measurements can be performed in solution even in the presence of large free acceptor concentrations. Highly efficient energy transfer was obtained for a large number of acceptor molecules per donor nanoparticle. We determined FRET efficiencies as a function of Cy5 concentration which are in good agreement with a multiple acceptor-multiple donor calculation. On the basis of the donor emission recovery due to acceptor photobleaching, we demonstrated energy transfer from single-nanoparticle donors in fluorescence microscopy experiments.
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http://dx.doi.org/10.1021/jp063229vDOI Listing
October 2006