N. Sojic, A. Ismail, S. Voci, L. Descamps, A. Buhot, L. Leroy, A. Bouchet-Spinelli
This work depicts the original combination of electrochemiluminescence (ECL) and bipolar electrochemistry (BPE) to map in real-time the oxidation of silicon in microchannels. We fabricated model silicon-PDMS microfluidic chips, optionally containing a restriction, and monitored the evolution of the surface reactivity using ECL. BPE was used to remotely promote ECL at the silicon surface inside microfluidic channels. The effects of the fluidic design, the applied potential and the resistance of the channel (controlled by the fluidic configuration) on the silicon polarization and oxide formation were investigated. A potential difference down to 6V was sufficient to induce ECL, which is two orders of magnitude less than in classical BPE configurations. Increasing the resistance of the channel led to an increase in the current passing through the silicon and boosted the intensity of ECL signals. Finally, the possibility to achieve electrochemical reactions at predetermined locations on the microfluidic chip was investigated using a patterning of the silicon oxide surface by etched micrometric squares. This ECL imaging approach opens exciting perspectives for the precise understanding and implementation of electrochemical functionalization on passivating materials. In addition, it may help the development and the design of fully integrated microfluidic biochips paving the way for development of original bioanalytical applications.
L. Bouffier, D. Zigah, N. Sojic, A. Kuhn
Annu. Rev. Anal. Chem. 2021, 14, 65-86
This contribution gathers a selection of the most recent studies with respect to the use of bipolar electrochemistry in the frame of analytical chemistry. Despite the fact that the concept is not new, with several important studies dating back to the middle of the last century, completely novel and very original approaches have emerged over the last decade. This current revival illustrates that scientists still (re)discover some exciting virtues of this approach, useful in many different areas, and especially for tackeling analytical challenges in an unconventional way. In several cases, this “wireless” electrochemistry strategy enables carrying out measurements that are simply not possible with classic electrochemical approaches. This review will hopefully stimulate new ideas and trigger scientists to integrate some aspects of bipolar electrochemistry in their work in order to drive the topic into so-far unexplored and eventually completely unexpected directions.
L. Bouffier, D. Zigah, N. Sojic, A. Kuhn
Encyclopedia of Electrochemistry, Bard et al. (Eds.), Wiley, 2021
Bipolar electrochemistry is a technique that involves two opposite chemical processes, namely an oxidation and a reduction, occurring simultaneously on the surface of a conducting object, usually without connection to a power supply. The basic phenomenon has already been described and used for many decades but regained a lot of interest in recent years, thanks to several attractive features for developing new applications in various areas ranging from materials science and analytical chemistry to catalysis and even life science. Consequently, bipolar electrochemistry has experienced a substantial growth in the number of users and publications. This is mostly due to several advantages over classic electrochemistry, such as the absence of an ohmic contact, the generation of a directional gradient of electroactivity on the object, and the possibility to address simultaneously thousands of objects, which opens the door for high throughput screening of (electro)chemical properties. Also, some features of this “wireless” electrochemistry allow performing experiments that cannot be achieved with a classic electrochemical set-up. Last but not least, only rather low-cost equipment is needed.
The objective of the present contribution is to introduce first some fundamental aspects of bipolar electrochemistry, and then to illustrate its different developments, highlighting not only the historic landmark achievements, but also the most recent findings, especially in the context of micro- and nanoscience. The chapter will illustrate the singularities and advantages of this straightforward approach and hopefully convince the reader of the power of this interesting electrochemical concept.
A. A. Melvin, B. Gupta, K. Tieriekhov, W. Nogala, P. Garrigue, S. Reculusa, A. Kuhn
Adv. Funct. Mater. 2021, 31, 2101171
Actuators controlled by external stimuli have received a lot of attention in recent years. Herein we report a polymer based dual stimuli actuator, triggered by light and an electric field. This allows a better control of actuation, enlarging the field of potential applications, like e.g. in the frame of soft robotics. The actuator is composed of polypyrrole (PPy) and TiO2 modified with methylene blue (MB). In aqueous solution, the resulting freestanding hybrid film shows reversible actuation due to the synergy of light and an applied electric field. Illumination with light produces electron-hole pairs in the TiO2 layer, which are shuttled to the opposite ends of the actuator by the potential gradient present in solution. This results in electrochemical oxidation and reduction reactions at the two extremities and consequently in site selective swelling of the polymer, which finally leads to a controlled motion of the actuator, following the principles of logic gate operations. Such synergistically induced switching allows developing original actuation schemes for performing complex mechanical tasks triggered by more than one stimulus.
S. Butcha, S. Assavapanumat, S. Ittisanronnachai, V. Lapeyre, C. Wattanakit, A. Kuhn
Editors’ Highlights in Catalysis
The design of efficient chiral catalysts is of crucial importance since it allows generating enantiomerically pure compounds. Tremendous efforts have been made over the past decades regarding the development of materials with enantioselective properties for various potential applications ranging from sensing to catalysis and separation. Recently, chiral features have been generated in mesoporous metals. Although these monometallic matrices show interesting enantioselectivity, they suffer from rather low stability, constituting an important roadblock for applications. Here, a straightforward strategy to circumvent this limitation by using nanostructured platinum-iridium alloys is presented. These materials can be successfully encoded with chiral information by co-electrodeposition from Pt and Ir salts in the simultaneous presence of a chiral compound and a lyotropic liquid crystal as asymmetric template and mesoporogen, respectively. The alloys enable a remarkable discrimination between chiral compounds and greatly improved enantioselectivity when used for asymmetric electrosynthesis (>95 %ee), combined with high electrochemical stability.
- Pickering emulsions stabilized by thermoresponsive oligo(ethylene glycol)-based microgels: Effect of temperature-sensitivity on emulsion stability
- Versatile template-directed synthesis of highly-symmetrical gold nanocages with predefined number of the openings
- Electrochemiluminescence microscopy of cells: essential role of the surface regeneration
- Electrochemiluminescence loss in photobleaching