Nadège Reverdy-Bruas

Freestanding redox buckypaper electrodes from multi-wall carbon nanotubes for bioelectrocatalytic oxygen reduction via mediated electron transfer

An efficient and easy way of designing free standing redox buckypaper electrodes via the elegant combination of multi-walled carbon nanotubes (MWCNTs) and a bis-pyrene derivative is reported. This bis-pyrene 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (bis-Pyr-ABTS) acts as a cross-linker between the nanotubes and assures the formation of a mechanically reinforced buckypaper, obtained by a classical filtration technique of a MWCNT suspension in the presence of bis-Pyr-ABTS. In addition, the ABTS derivative assures a mediated electron transfer to laccase. The electroactive buckypapers were characterized in terms of morphology, conductivity, and electrochemical properties. Two setups were evaluated. The first consisted of the immobilization and wiring of laccase enzymes via an inclusion complex formation between the hydrophobic cavity of laccase and the pyrene groups of bis-Pyr-ABTS that are not π-stacked to the nanotubes. The second approach was to evaluate the mediated electron transfer using laccase in solution. For this setup, the developed mediator electrodes demonstrated high performances with maximum currents up to 2 mA ± 70 μA and an excellent operational stability for two weeks with daily one hour discharges using refreshed laccase solutions.

Flexography Printing of Silver Tracks on LTCC Tapes – Effect of Printing Direction on Line Properties

The originality of this work is to print with flexography process conductive silver lines suitable for Low Temperature Co-fired Ceramics (LTCC) multilayer systems. Screen printing conductive paste with 65% silver flake particles was optimised for flexography process. Patterns with different line widths – from 100 to 600 μm – were printed in two directions, parallel and perpendicular to printing orientation. Printed lines withstood temperature as high as 875°C for one hour, relative to conventional sintering profile of LTCC multilayer systems. Line width, thickness and roughness decreased after sintering. A minimum line width of 153 μm was measured on sintered lines. Line thickness varied from 1.8 to 3.8 μm and line roughness from 0.7 to 0.9 μm after sintering. Conductive silver lines along 34 cm length were accomplished after sintering. Very low values of electrical resistivity were measured on the sintered lines. This study demonstrates the huge potential of flexography printing for LTCC multilayer systems.