Electropolymerization of Polypyrrole by Bipolar Electrochemistry in an Ionic Liquid

Bipolar electrochemistry has been recently explored for the modification of conducting micro- and nanoobjects with various surface layers. So far, it has been assumed that such processes should be carried out in low-conductivity electrolytes in order to be efficient. We report here the first bipolar electrochemistry experiment carried out in an ionic liquid, which by definition shows a relatively high conductivity. Pyrrole has been electropolymerized on a bipolar electrode, either in ionic liquid or in acetonitrile. The resulting polymer films were characterized by scanning electron microscopy and by contact profilometry. We demonstrate that the films obtained in an ionic liquid are thinner and smoother than the films synthesized in acetonitrile. Furthermore, a well-defined band of polypyrrole can be obtained in ionic liquid, in contrast to acetonitrile for which the polypyrrole film is present on the whole anodic part of the bipolar electrode

Wireless Synthesis and Activation of Electrochemiluminescent Thermoresponsive Janus Objects Using Bipolar Electrochemistry

In this work, bipolar electrochemistry (BPE) is used as a dual wireless tool to generate and to activate a thermoresponsive electrochemiluminescent (ECL) Janus object. For the first time, BPE allows regioselective growth of a poly­(<i>N</i>-isopropylacrylamide) (pNIPAM) hydrogel film on one side of a carbon fiber. It is achieved thanks to the local reduction of persulfate ions, which initiate radical polymerization of NIPAM. By controlling the electric field and the time of the bipolar electrochemical reactions, we are able to control the length and the thickness of the deposit. The resulting pNIPAM film is found to be swollen in water at room temperature and collapsed when heated above 32 °C. We further incorporated a covalently attached ruthenium complex luminophore, Ru­(bpy)₃²⁺, in the hydrogel film. In the second time, BPE is used to activate remotely the electrogenerated chemiluminescence (ECL) of the Ru­(bpy)₃²⁺ moieties in the film. We take advantage of the film responsiveness to amplify the ECL signal. Upon collapse of the film, the ECL signal, which is sensitive to the distance between adjacent Ru­(bpy)₃²⁺ centers, is strongly amplified. It is therefore shown that BPE is a versatile tool to generate highly sophisticated materials based on responsive polymers, which could lead to sensitive sensors

Electrokinetic Assembly of One-Dimensional Nanoparticle Chains with Cucurbit[7]uril Controlled Subnanometer Junctions

One-dimensional (1D) nanoparticle chains with defined nanojunctions are of strong interest due to their plasmonic and electronic properties. A strategy is presented for the assembly of 1D gold-nanoparticle chains with fixed and rigid cucurbit­[<i>n</i>]­uril-nanojunctions of 9 Å. The process is electrokinetically accomplished using a nanoporous polycarbonate membrane and controlled by the applied voltage, the nanoparticle/CB­[<i>n</i>] concentration ratio, time and temperature. The spatial structure and time-resolved analysis of chain plasmonics confirm a growth mechanism at the membrane nanopores