E. Suraniti, A.G. Mark, J. Roche, H. Richter, A. Kuhn, P. Fischer, N. Mano

L’Actualité Chimique 2018, 427-428,127-128

Une micro-source d’énergie intégrée permettrait à des implants biomédicaux miniatures de fonctionner de façon autonome. Les piles ou batteries conventionnelles sont peu adaptées à cette utilisation car difficiles à miniaturiser. Des biopiles enzymatiques peuvent produire l’énergie in situ par la transformation électrochimique de glucose et d’oxygène. Une micro-biopile intégrée peut donc alimenter un microcircuit électronique pour des applications biomédicales.

2018 05

A. Kuhn

L’Actualité Chimique 2018, 426,19-24

L’analyse et la synthèse des composés chiraux est d’une importance cruciale dans de nombreux domaines de la société et de la science, y compris la médecine, la biologie, la chimie, la biotechnologie et l’agriculture. Ainsi, il existe un intérêt fondamental dans le développement de nouvelles approches pour la détection et la production d’énantiomères. Cet article décrit l’utilisation de structures métalliques mésoporeuses codées avec une information chirale pour la reconnaissance et l’induction électrochimique d’une asymétrie moléculaire. Le métal mésoporeux chiral, obtenu par réduction électrochimique de sels de platine en présence d’une phase cristal liquide et de la molécule chirale modèle, conserve parfaitement l’information chirale après élimination du moule moléculaire. Les films métalliques obtenus permettent premièrement de différencier deux énantiomères et provoquent également un excès énantiomérique supérieur à 90 % au cours de l’électroréduction d’un composé prochiral.

2018 4

Haidong Li, Silvia Voci, Valérie Ravaine and Neso Sojic

J. Phys. Chem. Lett., 2018, 9, 340–345

Luminescent and redox properties of stimuli-responsive hydrogel materials have been modulated by different external stimuli which trigger swelling or collapse of the polymer matrix. There is a very rapid development in the field of such “smart” materials particularly combined with other sensing functionalities. Here, a poly(N-isopropylacrylamide) matrix incorporating covalently-bound phenylboronic acids as a saccharide sensing unit and a redox-active [Ru(bpy)3]2+ luminophore was designed and exhibited multi-stimuli responsive electrochemical and luminescent switching behaviors. Redox activity of the films is reversibly changed by sequential stimuli (fructose and temperature) which control the swelling and the collapse of the films. Finally, electrogenerated chemiluminescence (ECL) is enhanced by a ~16-fold factor during the film collapse induced by the temperature whereas the swelling due to fructose provokes the decrease of the light emission. We demonstrate for the first time that ECL response correlates intrinsically with the swelling ratio and is finely modulated by both stimuli. The multi-stimuli responsive characteristics of such ECL-active hydrogels should find promising applications in biosensing, new luminescent materials, and logic gates in bioelectronic devices.

TOC JPCL2018

Nanoscale 2018, 10, 2018, 3060-3067.

If the factors controlling the decay in single-molecule electrical conductance G with molecular length L could be understood and controlled, then this would be a significant step forward in the design of high-conductance molecular wires. For a wide variety of molecules conducting by phase coherent tunnelling, conductance G decays with length following the relationship G = AeβL. It is widely accepted that the attenuation coefficient β is determined by the position of the Fermi energy of the electrodes relative to the energy of frontier orbitals of the molecular bridge, whereas the terminal anchor groups which bind to the molecule to the electrodes contribute to the pre-exponential factor A. We examine this premise for several series of molecules which contain a central conjugated moiety (phenyl, viologen or α-terthiophene) connected on either side to alkane chains of varying length, with each end terminated by thiol or thiomethyl anchor groups. In contrast with this expectation, we demonstrate both experimentally and theoretically that additional electronic states located on thiol anchor groups can significantly decrease the value of β, by giving rise to resonances close to EF through coupling to the bridge moiety. This interplay between the gateway states and their coupling to a central conjugated moiety in the molecular bridges creates a new design strategy for realising higher-transmission molecular wires by taking advantage of the electrode–molecule interface properties.

TOC RSC Nano 2018

B. Gupta, B. Goudeau, P. Garrigue, A. Kuhn

Adv. Funct. Mater. 2018, 1705825

see also video clip in Zeste de Science

Bipolar electrochemistry can be used in different ways to induce motion of an object, for example by generating gas bubbles in an asymmetric way or by a wireless self-regeneration mechanism due to the intrinsic symmetry breaking of this concept. Here a complementary approach is explored on the basis of conducting polymer objects addressed in solution by an electric field. The presence of the latter results in a differential polarization of the polymer, thus enabling its oxidation at one extremity and its reduction at the opposite side. This triggers different degrees of swelling and shrinking, leading to important deformations of the object. Combined with an additional asymmetry in the polymer surface morphology, a periodic switching of the electric field orientation allows exploiting these deformations to induce directed crawling motion. This first example of a wireless biomimetic crawler based on conducting polymers opens interesting long-term perspectives in several areas such as for example wireless valves, pumps and (micro)robotics.

2017 25