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.

Redox- and pH-Responsive Nanogels Based on Thiolated Poly(aspartic acid)
Monday, 25 July 2016
Enikő Krisch, Léa Messager, Benjámin Gyarmati, Valérie Ravaine, and András Szilágyi Macromol. Mater. Eng. 2016, 301(3), 260–266 Nanogels loaded with fluorescent dextran as a model drug are...
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Wall slip across the jamming transition of soft thermoresponsive particles
Monday, 25 July 2016
Thibaut Divoux, Véronique Lapeyre, Valérie Ravaine, and Sébastien Manneville Phys. Rev. E 2015, 92, 060301(R) Flows of suspensions are often affected by wall slip, that is, the fluid velocity Vf...
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Differential Photoluminescent and Electrochemiluminescent Behavior for Resonance Energy Transfer Processes in Thermoresponsive Microgels
Monday, 25 July 2016
Florent Pinaud, Romain Millereux, Pierre Vialar-Trarieux, Bogdan Catargi, Sandra Pinet, Isabelle Gosse, Neso Sojic, Valérie Ravaine J. Phys. Chem. B, 2015, 119 (40), pp 12954–12961...
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One-Step Preparation of Bifunctionalized Surfaces by Bipolar Electrografting
Wednesday, 30 December 2015
L. Koefoed, K. Shimizu, S. U. Pedersen, K. Daasbjerg, A. Kuhn, and D. Zigah RSC Adv., 2015, DOI: 10.1039/c5ra20156j Bipolar electrochemistry (BPE) is widely used to trigger electrochemical reactions...
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Original Dual Microelectrode: Writing and Reading a local click reaction with Scanning Electrochemical Microscopy
Thursday, 05 November 2015
V. Badets, D. Duclos, D. Quinton, O. Fontaine, D. Zigah Electrochimica Acta, 2015, doi:10.1016/j.electacta.2015.10.066 A dual gold-copper microelectrode (diameter 25 μm) was fabricated to be...
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Electrogenerated Chemiluminescence of Cationic Triangulene Dyes: Crucial Influence of the Core Heteroatoms
Thursday, 05 November 2015
C. Adam, A. Wallabregue, H. Li, J. Gouin, R. Vanel, S. Grass, J. Bosson, L. Bouffier, J. Lacour and N. Sojic. Chem. Eur. J., 2015, 21, 19243-19249. Trianguleniums are fascinating conjugated...
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Solid-State Bipolar Electrochemistry: Polymer-Based Light-Emitting Electrochemical Cells
Thursday, 05 November 2015
S. Chen, G. Wantz, L. Bouffier and J. Gao. ChemElectroChem, 2016, 3, 392-398. We present solid-state, polymer-based, light-emitting electrochemical cells incorporating bipolar electrodes (BPEs)...
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Guiding pancreatic beta-Cells to target Electrodes in a whole-cell Biosensor for Diabetes
Friday, 25 September 2015
E. Pedraza, A. Karajić, M. Raoux, R. Perrier, A. Pirog, F. Lebreton, S. Arbault, J. Gaitan, S. Renaud, A. Kuhn, J. Lang Lab Chip, 2015, 15, 3880–3890 We are developing a cell-based bioelectronic...
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The EChemPen: A Guiding Hand To Learn Electrochemical Surface Modifications
Wednesday, 23 September 2015
M. Valetaud, G. Loget, J. Roche, N. Hüsken, Z. Fattah, V. Badets, O. Fontaine, D. Zigah. J. Chem. Educ., 2015, 92 (10), pp 1700–1704. The Electrochemical Pen (EChemPen) was developed as an...
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Bipolar Electrografting on the Inner Wall of Carbon Nanotubes
Wednesday, 23 September 2015
C. Kumsapaya, J. Limtrakul, A. Kuhn, D. Zigah, C. Warakulwit. ChemElectroChem, 2016, 3, 410-414. Vertically aligned carbon nanotubes were grown over the inner wall of the pores of an anodic aluminum...
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Single-Step Screening of the Potential Dependence of Metal Layer Morphologies Along Bipolar Electrodes
Monday, 07 September 2015
G. Tisserant, J. Gillion, J. Lannelongue, Z. Fattah, P. Garrigue, J. Roche, D. Zigah, B. Goudeau, A. Kuhn and L. Bouffier.  ChemElectroChem, 2016, 3, 387-391. The preparation of surface...
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Enantioselective Recognition of DOPA by mesoporous Platinum imprinted with Mandelic acid
Friday, 24 July 2015
T. Yutthalekha, C. Warakulwit, J. Limtrakul, A. Kuhn Electroanalysis, 2015, Special Issue Advanced Materials, in press Chiral imprinted mesoporous platinum was electrochemically synthesized in the...
Bottom-up Generation of Miniaturized Coaxial Double Electrodes with tunable Porosity
Friday, 24 July 2015
A. Karajić, S. Reculusa, M. Heim, P. Garrigue, S. Ravaine, N. Mano, A. Kuhn Adv. Mater. Interfaces, 2015, in press We report the bottom-up design of a fully integrated and miniaturized...
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3D electrogenerated chemiluminescence: from surface-confined reactions to bulk emission
Thursday, 11 June 2015
M. Sentic, S. Arbault, L. Bouffier, D. Manojlovic, A. Kuhn and N. Sojic.   Chem. Sci., 2015, 6, 4433-4437.   Among luminescence techniques, electrogenerated chemiluminescence (ECL) provides...
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Synthesis of conducting asymmetric hydrogel particles showing autonomous motion
Thursday, 28 May 2015
A. Srinivasan, J. Roche, V. Ravaine and A. KuhnSoft Matter, 2015, 11, 3958-3962 In the present work, we introduce a new approach for the synthesis of asymmetric particles made from electrically...
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Shearforce Positioning of Nanoprobe Electrode Arrays for Scanning Electrochemical Microscopy Experiments
Tuesday, 12 May 2015
C. Adam, F. Kanoufi, N. Sojic and M. Etienne. Electrochim. Acta, 2015, in press. Shearforce detection was applied to the controlled positioning of nanotip arrays at air/solid and liquid/solid...
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Generation of Metal Composition Gradients by Means of Bipolar Electrodeposition
Wednesday, 18 March 2015
G. Tisserant, Z. Fattah, C. Ayela, J. Roche, B. Plano, D. Zigah, B. Goudeau, A. Kuhn and L. Bouffier.  Electrochim. Acta, 2015, 179, 276-281. Bipolar electrochemistry is an unconventional...
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Effects of 50 Hz Magnetic Fields on Gap Junctional Intercellular Communication in NIH3T3 Cells
Wednesday, 18 February 2015
Y. Percherancier, B. Goudeau, R. Charlet de Sauvage, F. Poulletier de Gannes, E. Haro, A. Hurtier, N. Sojic, I. Lagroye, S. Arbault, and B. Veyret Bioelectromagnetics, 2015, 36, 4, 287-293. The...
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Synthesis of Multivalent Silica Nanoparticles combining both Enthalpic and Entropic Patchiness
Friday, 16 January 2015
C. Hubert, C. Chomette, A. Désert, M. Sun, M. Treguer, S. Mornet, A. Perro, E. Duguet, S. Ravaine Faraday Discuss., 2015, 181, 139-146 Silica particles with a controlled number of entropic patches,...
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Linking Glucose Oxidation to Luminol-based Electrochemiluminescence using bipolar Electrochemistry
Wednesday, 10 December 2014
V. Eßmann, D. Jambrec, A. Kuhn, W. Schuhmann Electrochem. Comm. 2015, 50, 77–80. The range of potential analytes for bipolar electrochemistry can be significantly extended by modification of...
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