BESSY II Finds Electron-Transfer Path in UV Water Radicals
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- BESSY II researchers led by Professor Alexander Föhlisch at HZB developed a new method to investigate hydroxyl radical chemistry in UV-exposed aqueous solutions, using X-ray absorption spectroscopy with a liquid jet sample cell that is, per the team, only possible at BESSY II.
- First author Leo Cordsmeier deployed the radical scavenger molecule TEMPO as a 'sensor' that directly participates in the reaction and can be easily detected, enabling step-by-step tracking of where bonds break and new ones form.
- The team measured an unexpected intermediate state and found the mechanism proceeds through electron transfer rather than a bound intermediate state between TEMPO and the hydroxyl radical — contradicting what Föhlisch called the previously proposed literature model.
- The proton of the hydroxyl radical reacts with TEMPO first, a sequence the researchers reconstructed with precision through the new method.
- The findings are relevant to health and environmental research, including understanding hydroxyl radical formation in rivers and lakes contaminated by nitrogen oxides leaching from over-fertilized agricultural soils, and oxidative stress in human cells.
Why it matters: The new method lets researchers selectively watch radicals form and react in realistic aqueous conditions, directly relevant to oxidative stress in human cells and the photochemistry of nitrogen-oxide-polluted waterways. By overturning the textbook bound-intermediate model in favor of an electron-transfer mechanism, the work reshapes how scientists model radical scavenging in both biological and environmental systems.
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