Effect of infrared radiation on interfacial water at hydrophilic surfaces
Paper published Mar 24, 2021
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Hydrophilic materials such as Nafion can nucleate the buildup of interfacial water, which shows features different from bulk water. We investigated the effect of infrared (IR) light on a negatively charged, interfacial exclusion zone (EZ) and a positively charged proton zone (PZ) formed in the vicinity of Nafion. After irradiation for 5 min by mid-IR light, EZ size increased with an expansion ratio of 1.41. A significant expansion was also found in the size of PZ, equivalent to an increment of about 1.39 × 1016 molecules of hydronium ions. Thus, IR radiation not only builds EZ, but at the same time drives release of protons from the growing EZ to bulk water. Near-IR illumination also showed expansion of EZ and PZ water. These results imply that incident IR light not only promotes the build-up of interfacial water at the hydrophilic surface, but also provides a driving force for charge separation.