The molecular ionic surface structure and charge of the electric double layer around a
nanodroplet and its structural change induced by hydrophobic effects are measured using
vibrational coherent surface scattering spectroscopy, second harmonic scattering, and
electrokinetic mobility measurements. Tetraalkylammonium chloride salts were added to
negatively charged nanoscopic oil droplets in water. When we vary the alkyl chain length of
the cation from CH3 to C4H10, both the size of the cation and its hydrophobic interaction are …