2018/06/12 by Fumagalli, L., Esfandiar, A., Fabregas, R. +10 · 13 citations
#Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Soft Condensed Matter (cond-mat.soft)
paper · doi:10.48550/arxiv.1806.04486
The dielectric constant of interfacial water has been predicted to be smaller than that of bulk water (= 80) because the rotational freedom of water dipoles is expected to decrease near surfaces, yet experimental evidence is lacking. We report local capacitance measurements for water confined between two atomically-flat walls separated by various distances down to 1 nm. Our experiments reveal the presence of an interfacial layer with vanishingly small polarization such that its out-of-plane dielectric constant is only approximately 2. The electrically dead layer is found to be two to three molecules thick. These results provide much needed feedback for theories describing water-mediated surface interactions and behavior of interfacial water, and show a way to investigate the dielectric properties of other fluids and solids under extreme confinement.