UMR 8640 : Electrochimie

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Theory and Simulations for the Electron-Transfer/Ion-Transfer Mode of Scanning Electrochemical Microscopy in the Presence or Absence of Homogenous Kinetics

ChemElectroChem 2017

 

 

The electron transfer/ion transfer (ET/IT) mode of the scanning electrochemical microscopy (SECM) was developed recently and applied to studies of heterogeneous reactions at the substrate surface. The charged products or intermediates are detected by measuring the ion transfer current of this species across the liquid/liquid interface supported at the tip of a nanopipette. In this article, we developed the theory for this technique and explored its potential advantages and limitations. Using COMSOL Multiphysics package, the approach curves were simulated for three commonly encountered experimental situations, viz., the surface generated ionic species is either chemically stable or participates in a first or second order homogeneous reaction. The simulation results are generalized in the form of analytical approximations derived under limiting conditions. 

Mechanism and analyses for extracting photosynthetic electrons using exogenous quinones – what makes a good extraction pathway?

Photochem. Photobiol. Sci., 2016,15, 969-979

 

Plants or algae take many bene!ts from oxygenic photosynthesis by converting solar energy into chemical energy through the synthesis of carbohydrates from carbon dioxide and water. However, the overall yield of this process is rather low (about 4% of the total energy available from sunlight is converted into chemical energy). This is the principal reason why recently many studies have been devoted to extraction of photosynthetic electrons in order to produce a sustainable electric current. Practically, the electron transfer occurs between the photosynthetic organism and an electrode and can be assisted by an exogenous mediator, mainly a quinone. In this regard, we recently reported on a method involving "uorescence measurements to estimate the ability of di#erent quinones to extract photosynthetic electrons from a mutant of Chlamydomonas reinhardtii. In the present work, we used the same kind of methodology to establish a zone diagram for predicting the most suitable experimental conditions to extract photoelectrons from intact algae (quinone concentration and light intensity) as a function of the purpose of the study. This will provide further insights into the extraction mechanism of photosynthetic electrons using exogenous quinones. Indeed "uorescence measurements allowed us to model the capacity of photosynthetic algae to donate electrons to an exogenous quinone by considering a numerical parameter called “open center ratio” which is related to the Photosystem II acceptor redox state. Then, using it as a proxy for investigating the extraction of photosynthetic electrons by means of an exogenous quinone, 2,6-DCBQ, we suggested an extraction mechanism that was globally found consistent with the experimentally extracted parameters.

Interview Christian Amatore : The Electrochemical Society

Christian Amatore has given an interview at The Electrochemical Society in the ECS Podcast context.

 

Astrocyte-derived adenosine is central to the hypnogenic effect of glucose

Scientific Reports 6, Article number: 19107 (2016)

 

Sleep has been hypothesised to maintain a close relationship with metabolism. Here we focus on the brain structure that triggers slow-wave sleep, the ventrolateral preoptic nucleus (VLPO), to explore the cellular and molecular signalling pathways recruited by an increase in glucose concentration. We used infrared videomicroscopy on ex vivo brain slices to establish that glucose induces vasodilations specifically in the VLPO via the astrocytic release of adenosine. Real-time detection by in situ purine biosensors further revealed that the adenosine level doubles in response to glucose, and triples during the wakefulness period. Finally, patch-clamp recordings uncovered the depolarizing effect of adenosine and its A2A receptor agonist, CGS-21680, on sleep-promoting VLPO neurons. Altogether, our results provide new insights into the metabolically driven release of adenosine. We hypothesise that adenosine adjusts the local energy supply to local neuronal activity in response to glucose. This pathway could contribute to sleep-wake transition and sleep intensity.

 

Three-electrode analytical and preparative electrochemistry in micro-volume hanging droplets

Electrochem. Commun. 54 (2015) 41

 

Three-electrode micro-cells equipped with a conventional reference electrode (SCE) were easily constructed based on micro-volume droplets suspended by capillary forces to the fritted glass of the SCE bridge. Working and counter electrodes were simply inserted through the droplet surface, allowing classical electrochemistry to be readily performed in minute samples.