C. Picard, P. Garrigue, M.C. Tatry, V. Lapeyre, S. Ravaine, V. Schmitt, V. Ravaine

Langmuir, 2017, 33, 7968-7981

Poly(N-isopropylacrylamide) (pNIPAM) microgels are soft and deformable particles, which can adsorb at liquid interfaces. In the present paper, we study the two-dimensional organization of charged and quasi-neutral microgels with different cross-linking densities, under compression at the air−water interface and the transfer of the microgel monolayer onto a solid substrate at different surface pressures. At low cross-linking densities, the microgels form highly ordered hexagonal lattices on the solid substrate over large areas, with a unique lattice parameter
that decreases continuously as the surface pressure increases. We thus prove that the microgel conformation evolves at the air−water interface. The microgels undergo a continuous transition from a highly flattened state at low surface coverage, where the maximal polymer segments are adsorbed at the interface, to entangled flattened microgels, and finally the thickening of the layer up to a dense hydrogel layer of compacted microgels. Moreover, two batches of microgels, with and without charges, are compared. The contribution of electrostatic interactions is assessed via changing the charge density of the microgels or modulating the Debye length. In both cases, electrostatics does not change the lattice parameter, meaning that, despite the microgel different swelling ratio, charges do not affect neither interactions between particles at the interface nor microgels adsorption. Conversely, the cross-linking density has a strong impact on microgel packing at the interface: increasing the cross-linking density strongly decreases the extent of microgel flattening and promotes the occurrence of coexisting hexagonally ordered domains with different lattice parameters.

Langmuir vr 43

C. Wattanakit, T. Yutthalekha, S. Asssavapanumat, V. Lapeyre, A. Kuhn

Nature Comm. 2017, 8, 2087

see also CNRS press release

Asymmetric synthesis of molecules is of crucial importance to obtain pure chiral compounds, which are of primary interest in many areas including medicine, biotechnology, and chemistry. Various methods have been used very successfully to increase the enantiomeric yield of reaction pathways, but there is still room for the development of alternative highly enantioselective reaction concepts, either as a scientific challenge of tremendous fundamental
significance, or owing to the increasing demand for enantiopure products, e.g., in the pharmaceutical industry. In this context, we report here a strategy for the synthesis of chiral compounds, based on pulsed electrochemical conversion. We illustrate the approach with the stereospecific electroreduction of a prochiral model molecule at chiral mesoporous metal structures, resulting in an enantiomeric excess of over 90%. This change of paradigm opens up promising reaction schemes for the straightforward synthesis of high-added-value molecules.

2017 26

V. Eßmann, S. Voci, G. Loget, N. Sojic, W. Schuhmann, A. Kuhn

 

Bipolar electrochemistry has been shown to enable and control various kinds of propulsion of non‑wired conducting objects: translation, rotation, and levitation. There is a very rapid development in the field of controlled motion combined with other functionalities. Here, we integrate two different concepts in one system to generate wireless electrochemical motion of a specifically designed rotor and track its polarization simultaneously by electrochemical light emission. Locally produced hydrogen bubbles at the cathodic pole of the bipolar rotor are the driving force of the motion, whereas [Ru(bpy)3]Cl2 and tripropylamine react at the anodic extremity, thus generating an electrochemiluminescence signal with an intensity directly correlated with the orientation of the rotor arms. This allows in a straightforward way the qualitative visualization of the changing interfacial potential differences during rotation, and shows for the first time that light emission can be coupled to autonomously rotating bipolar electrodes.

2017 24

Giovanni Valenti, Sabina Scarabino, Bertrand Goudeau, Andreas Lesch, Milica Jovic, Elena Villani, Milica Sentic, Stefania Rapino, Stephane Arbault, Francesco Paolucci, and Neso Sojic

J. Am. Chem. Soc., 2017,DOI: 10.1021/jacs.7b09260

We report here the development of coreactant-based electrogenerated chemiluminescence (ECL) as a surface-confined microscopy to image single cells and their membrane proteins. Labeling the entire cell membrane allows to demon-strate that, by contrast with fluorescence, ECL emission is only detected from fluorophores located in the immediate vicinity of the electrode surface (i.e. 1-2 µm). Then, to present the potential diagnostic applications of our approach, we selected carbon nanotubes (CNT)-based inkjet-printed disposable electrodes for the direct ECL imaging of a labeled plasma receptor over-expressed on tumor cells. The ECL fluorophore was linked to an antibody and enabled to localize the ECL generation on the cancer cell membrane in close proximity to the electrode surface. Such a result is intrinsically associated to the unique ECL mechanism and is rationalized by considering the limited lifetimes of the electrogenerated coreactant radicals. The electrochemi-cal stimulus used for luminescence generation does not suffer from background signals, such as the typical auto-fluorescence of biological samples. The presented surface-confined ECL microscopy should find promising applications in ultrasensitive single cell imaging assays.JACS TOC ECL cell

Soft Matter, 2017,13, 6293-6296

We design polystyrene–poly(N′-isopropylacrylamide-co-acrylic acid) core–shell particles that exhibit dynamically tunable scattering. We show that under normal solvent conditions the shell is nearly index-matched to pure water, and the particle scattering is dominated by Rayleigh scattering from the core. As the temperature or salt concentration increases, both the scattering cross-section and the forward scattering increase, characteristic of Mie scatterers. The magnitude of the change in the scattering cross-section and scattering anisotropy can be controlled through the solvent conditions and the size of the core. Such particles may find use as optical switches or optical filters with tunable opacity.

Clogging by sieving in microchannels: application to the detection of contaminants in colloidal suspensions
Friday, 08 April 2016
A. Sauret, E. C. Barney, A. Perro, E. Villermaux, H. A. Stone and E. Dressaire  Applied Physics Letters 2014, 105, 074101  We report on a microfluidic method that...
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Readily Prepared Dynamic Hydrogels by Combining Phenyl Boronic Acid- and Maltose-Modified Anionic Polysaccharides at Neutral pH
Friday, 19 December 2014
D. Tarus, E. Hachet, L. Messager, B. Catargi, V. Ravaine, R. Auzély-Velty Macromol. Rapid. Commun. 2014, 35, 2089 -2095 Dynamic covalent hydrogels are facilely prepared from biocompatible...
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Impact of Electrostatics on the Adsorption of Microgels at the Interface of Pickering Emulsions
Friday, 19 December 2014
P. Masse, E. Sellier, V. Schmitt, and V. Ravaine Langmuir, 2014, 30 (49), pp 14745–14756 The importance of electrostatics on microgel adsorption at a liquid interface is studied, as well as its...
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Wireless Electrosampling of Heavy Metals for Stripping Analysis with Bismuth-Based Janus Particles
Wednesday, 19 November 2014
H. Sopha, J. Roche, I. Švancara, A. Kuhn Anal.Chem. 2014, 86, 10515–10519 In this contribution, a wireless method for the electrolytic sampling of heavy metals at special bismuth-modified...
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Wireless powering of e-swimmers
Tuesday, 21 October 2014
J. Roche, S. Carrara, J. Sanchez, J. Lannelongue, G. Loget, L. Bouffier, P. Fischer, A. Kuhn Sci. Rep. 2014, 4, 6705 Miniaturized structures that can move in a controlled way in solution and...
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Stimuli-responsive microgels for electrochemiluminescence amplification
Tuesday, 07 October 2014
F. Pinaud, N. Sojic, V. Ravaine L'Actualité Chimique, 2014, 390. In the present work, redox thermoresponsive microgels bearing ruthenium complex were synthesized. Investigation of electrogenerated...
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Physico-chemical Milling for controlled Size Reduction of Metal Beads
Thursday, 28 August 2014
J. Roche, E. Gianessi, A. Kuhn Phys. Chem. Chem. Phys. 2014, 16, 21234-21236. Here we report a new physico-chemical method based on bipolar electrochemistry for producing spherical metal beads with a...
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Asymmetric Modification of TiO2 Nanofibers with Gold by Electric-Field-Assisted Photochemistry
Thursday, 31 July 2014
M. Ongaro, J. Roche, A. Kuhn, P. UgoChem. Electro. Chem. 2014, 2048-2051 We present a new procedure for the site-specific deposition of metal on semiconductor nanofibers (NF). The semiconductor NFs...
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Electrochemiluminescent Swimmers for Dynamic Enzymatic Sensing
Monday, 30 June 2014
M. Sentic, S. Arbault, B. Goudeau, D. Manojlovic, A. Kuhn, L. Bouffier, N. SojicChem. Commun. 2014, 50, 10202-10205. An electrochemiluminescent (ECL) swimmer driven by bipolar electrochemistry is...
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Monitoring Electrochemically the Early Events of Hydrogen peroxide Production by Mitochondria
Thursday, 22 May 2014
E. Suraniti, S. Ben-Amor, P. Landry, M. Rigoulet, E. Fontaine, S. Bottari, A. Devin, N. Sojic, N. Mano, S. ArbaultAngew. Chem. Int. Ed. 2014, 126, 6773-6776.Mitochondria consume oxygen at the...
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Electropolymerization of Polypyrrole by Bipolar Electrochemistry in an Ionic Liquid
Tuesday, 13 May 2014
S. Kong, O. Fontaine, J. Roche, L. Bouffier, A. Kuhn, D. ZigahLangmuir 2014, 30, 2973−2976 Bipolar electrochemistry has been recently explored for the modification of conducting micro- and...
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Adsorption of Microgels at an Oil–Water Interface: Correlation between Packing and 2D Elasticity
Friday, 25 April 2014
F. Pinaud, K. Geisel, P. Massé, B. Catargi, L. Isa, W. Richtering, V. Ravaine, V. SchmittSoft Matter, 2014, in press. The aim of this paper is to determine how microgels adsorb at a model...
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Imaging Redox Activity at Bipolar Electrodes by Indirect Fluorescence Modulation
Friday, 21 March 2014
Bouffier L., Doneux T., Goudeau B., Kuhn A.Anal. Chem. 2014, 86(8) 3708-3711. Bipolar electrochemistry (BPE) is nowadays well-known but relatively underexploited and still considered as...
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Site-Selective Synthesis of Janus-type Metal-Organic Framework Composites
Thursday, 06 March 2014
Yadnum S., Roche J., Lebraud E., Négrier P., Garrigue P., Bradshaw D., Warakulwit C., Limtrakul J., Kuhn A. Angew. Chem. Int. Ed. 2014, 126, 4082-4086. Herein, bipolar electrochemistry is applied in...
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Mapping the Electrogenerated Chemiluminescence Reactivity in Space: Mechanistic Insight into Model Systems Used in Immunoassays
Monday, 03 March 2014
Sentic, M., Milutinovic, M., Kanoufi, F., Manojlovic, D., Arbault S., Sojic, N.Chem. Sci. 2014, 5, 2568-2572. The remarkable characteristics of electrogenerated chemiluminescence (ECL) as a readout...
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Enantioselective Recognition at Mesoporous Chiral Metal Surfaces
Wednesday, 19 February 2014
Wattanakit C., Bon Saint-Côme Y., Lapeyre V., Bopp P., Heim M., Yadnum S., Nokbin S., Warakulwit C., Limtrakul J., Kuhn A.Nature Comm. 2014, 5, article 3325. Chirality is widespread in natural...
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Straight-forward Synthesis of Ringed Particles
Thursday, 23 January 2014
Roche J., Loget G., Zigah D., Fattah Z., Goudeau B., Arbault S., Bouffier L., Kuhn A.Chem. Sci. 2014, 5, 1961-1966 Particles with sophisticated surface patterns have many potential applications...
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Impact of pNIPAM Microgel Size on their Ability to stabilize Pickering Emulsions
Wednesday, 22 January 2014
Destribats M., Lapeyre V., Sellier E., Varga I., Ravaine V., Schmitt V.Langmuir 2014, 30, 1768-1777. We study the influence of the particle size on the ability of poly(N-isoprolylacrylamide)...
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Asymmetrical Modification of Carbon Microfibers by Bipolar Electrochemistry in Acetonitrile
Friday, 10 January 2014
Ongaro M., Gambirasi A., Favaro M., Kuhn A., Ugo P.Electrochim. Acta 2014, 116, 421. This contribution presents the asymmetrical modification of carbon microfibers (CMF) with gold and polythiophene...
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Thiol-ene Clickable Hyaluronans: from Macro- to Nanogel
Wednesday, 25 December 2013
Hachet E., Sereni N., Pignot-Paintrand I., Ravaine V., Szarpak-Jankowska A., Auzély-Velty R.J. Coll. Interface Sci. 2014, 419, 52-55. The fabrication of hyaluronic acid (HA) nanogels using a...
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Enhanced Detection of Hydrogen Peroxide with Platinized Microelectrode Arrays for Analyses of Mitochondria Activities
Sunday, 01 December 2013
Ben-Amor S., Vanhove E., Sékli Belaïdi F., Charlot S., Colin D., Rigoulet M., Devin A., Sojic N., Launay J., Temple-Boyer P., Arbault S. Electrochimica Acta 2014, ASAP article Black...
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Electrochemical Transduction of DNA Hybridization at Modified Electrodes by using an Electroactive Pyridoacridone Intercalator
Thursday, 12 September 2013
Bouffier L., Wang B. S., Roget A., Livache T., Demeunynck M., Mailley P.Anal. Bioanal. Chem. 2014, 406(4), 1163-1172. A synthetic redox probe structurally related to natural pyridoacridones was...
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Optical Microwell Array for Large Scale Studies of Single Mitochondria Metabolic Responses
Sunday, 28 July 2013
Vajrala V. S., Suraniti E., Garrigue P., Goudeau B., Rigoulet M., Devin A., Sojic N., Arbault S.Anal. Bioanal. Chem. 2014, 406, 931-941. Forefront Paper Microsystems based on microwell arrays have...
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Lighting up Redox Propulsion with Luminol Electrogenerated Chemiluminescence
Monday, 08 July 2013
Bouffier L., Zigah D., Adam C., Sentic M., Fattah Z., Manojlovic D., Kuhn A., Sojic N.ChemElectroChem 2014, 1(1), 95-98. A blue-light-emitting swimmer driven by bipolar electrochemistry is reported...
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