G. Salinas, B. A. Frontana-Uribe, S. Reculusa, P. Garrigue, A. Kuhn
Highly ordered macroporous electrodes of the conducting polymer poly-3,4-ortho-xylendioxythiophene (PXDOT) are presented as a sensitive analytical tool for heavy metal ion quantification due to a controlled gain in electroactive area. They were designed by using colloidal crystal templates. A direct correlation between the final number of porous layers and the deposition charge (Qd) employed for electropolymerization is observed. All the electrodes exhibit a surface-templated structure due to an interaction between the radical cation, formed during the electropolymerization, and the surface groups of the silica beads. The voltamperometric response of the macroporous PXDOT electrodes shows a rather fast electron transfer with ΔEp values between 70 mV and 110 mV. Square wave anodic stripping voltammetric (SWASV) analysis of Cu2+ as a representative heavy metal ion shows a linear response in the subppm range. As a model application, the efficient quantification of Cu2+ in a commercial mezcal sample is validated by the standard addition method and the results correlate adequately with the values obtained by atomic absorption spectroscopy.
E. Suraniti, P. Merzeau, J. Roche, S. Gounel, A. G. Mark, P. Fischer, N. Mano, A. Kuhn
see also CNRS press release
Chemical systems do not allow the coupling of energy from several simple reactions to drive a subsequent reaction, which takes place in the same medium and leads to a product with a higher energy than the one released during the first reaction. Gibbs energy considerations thus are not favorable to drive e.g., water splitting by the direct oxidation of glucose as a model reaction. Here, we show that it is nevertheless possible to carry out such an energetically uphill reaction, if the electrons released in the oxidation reaction are temporarily stored in an electromagnetic system, which is then used to raise the electrons’ potential energy so that they can power the electrolysis of water in a second step. We thereby demonstrate the general concept that lower energy delivering chemical reactions can be used to enable the formation of higher energy consuming reaction products in a closed system.
A. de Poulpiquet, B. Goudeau, P. Garrigue, N. Sojic, S. Arbault, T. Doneux, L. Bouffier.
The coupling between electrochemistry and fluorescence confocal laser scanning microscopy (FCLSM) allows deciphering the electrochemical and/or redox reactivity of electroactive fluorophores. This is demonstrated with phenoxazine electrofluorogenic species frequently used in bioassays by mapping the variation of fluorescence intensity with respect to the distance from the electrode. The electrochemical conversion of resorufin dye (RF) to non-fluorescent dihydroresorufin (DH) leads to a sharp decrease of the fluorescence signal in the vicinity of the electrode. In contrast, the direct reduction of resazurin (RZ) to DH leads to an unexpected maximum fluorescence intensity localized further away from the surface. This observation indicates that the initial electron transfer (heterogeneous) is followed by a chemical comproportionation step (homogeneous), leading to the formation of RF within the diffusion layer with a characteristic concentration profile. Therefore, in situ FCLSM affords a direct way to monitor such chemical reactivity in space and to decipher a new redox pathway that cannot be resolved solely by electrochemical means.
V. Pirenne, G. Kurtay, S. Voci, L. Bouffier, N. Sojic, F. Robert, D. M. Bassani, Y. Landais.
Eosin-Y (EY)-mediated alkylsulfonyl cyanation of olefins was shown to afford alkylsulfonyl nitriles in good yields. On the basis of transient absorption spectroscopy, the reaction was shown to proceed via photoinduced electron transfer from 3EY* to an O-cyanated derivative of the photocatalyst, formed in situ, with generation of the corresponding sulfinate that is oxidized by EY•+ into a sulfonyl radical. Addition of the latter on the olefin, followed by a radical cyano group transfer, then furnished the nitrile along with a RSO2 radical sustaining the radical chain.
D. Kos, H. P. A. G. Astier, G. D. Martino, J. Mertens, H. Ohadi, D. De. Fazio, D. Yoon, Z. Zhao, A. Kuhn, A. C. Ferrari, C. J. B. Ford, J. J. Baumberg
Nanoactuators are a key component for developing nanomachinery. Here, an electrically driven device yielding actuation stresses exceeding 1 MPa with integrated optical readout is demonstrated. Electrolyte films of 10-nm-thick Al2O3 are sandwiched between graphene and Au electrodes that allow reversible room-temperature solid-state redox producing Al metal and O2 gas in a memristive-type switching device. The resulting high-pressure oxygen microfuel reservoirs are encapsulated under the graphene, swelling to heights of up to 1 μm, which can be dynamically tracked by plasmonic rulers. Unlike in standard memristors where the memristive redox reaction occurs in single or few conductive filaments, the mechanical deformation forces the constant creation of new filaments over the whole area of the inflated film. The resulting on–off resistance ratios are exceptionally high, reaching 108 in some cycles. The synchronization of nanoactuation and memristive switching in these devices is compatible with large-scale fabrication and has potential for precise and electrically monitored actuation technology.
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