Electron transfer is a process by which an atom donates an electron to another atom. It is the foundation of all chemical reactions, and is of intense research because of the implications it has for chemistry and biology. When two molecules interact, electron transfer takes place in a few quadrillionths (10-15) of a second, or femtoseconds (fsec), meaning that studying this event requires very time-sensitive techniques like ultrafast spectroscopy. However, the transfer itself is often influenced by the solution in which the molecules are studied (e.g. water), and this must be taken into account when such experiments are designed. In a recent Nature Communications paper, EPFL scientists have visualized for the first time how electron transfer takes place in one of the most common solvents, water.
For over twenty years, scientists have been trying to understand how an electron departs from an atom or molecule, travels through space in a solvent, and finally connects to an acceptor atom or molecule. Until now, experimental efforts have not borne much fruit, mostly because of the extremely short time periods involved in electron transfer. The problem is further complicated when we consider that the molecules of the commonest reaction solvent, water, are polar, which means that they respond to electron movement by influencing it. Understanding the real-time impact of the solvent is crucial, because it directly affects the outcome and efficiency of electron-transfer chemical reactions.
Majed Chergui's group at EPFL's Laboratory of Ultrafast Spectroscopy (LSU) employed a world-unique setup in their lab to observe the evolution of electron movement with unprecedented time-resolution. The scientists excited iodide in water with ultraviolet light, causing the ejection of an electron from the iodine atom. Using a technique called ultrafast fluorescence spectroscopy they observed the departure of the electron over different times between 60 fsec an
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Ecole Polytechnique Fdrale de Lausanne