Molecular Nature of Structured Water in the Light-Induced Interfacial Capacitance Changes at the Bioelectric Interface.

Uncovering the function of structured water in the interfacial capacitance at the molecular level is the basis for the development of the concept and model of the electric double layer; however, the limitation of the available technology makes this task difficult. Herein, using surface-enhanced infrared absorption spectroscopy combined with electrochemistry, we revealed the contribution of the cleavage of loosely bonded tetrahedral water to the enhancement of model membrane capacitance. Upon further combination with ionic perturbation, we found that the interface hydrogen bonding environment in the stern layer was greatly significant for the light-induced cleavage of tetrahedral water and thus the conversion of optical signals into electrical signals. Our work has taken an important step toward gaining experimental insight into the relationship between water structure and capacitance at the bioelectric interface.