Open AccessWater Structure at the Hydrophobic Nanodroplet Surface Revealed by Vibrational Sum Frequency Scattering Using Isotopic Dilution
Author(s) -
Saranya Pullanchery,
S. P. Kulik,
Sylvie Roke
Publication year - 2022
Publication title -
the journal of physical chemistry. b (1997 : online)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 392
eISSN - 1520-6106
pISSN - 1520-5207
DOI - 10.1021/acs.jpcb.2c01987
Subject(s) - hydrogen bond , sum frequency generation spectroscopy , chemistry , dilution , chemical physics , spectroscopy , scattering , molecule , analytical chemistry (journal) , intramolecular force , infrared spectroscopy , sum frequency generation , chromatography , organic chemistry , optics , thermodynamics , laser , physics , quantum mechanics , nonlinear optics
The water structure at the hydrophobic/water interface is key toward understanding hydrophobicity at the molecular level. Herein, we characterize the hydrogen-bonding network of interfacial water next to sub-micron-sized hydrophobic oil droplets dispersed in water using isotopic dilution vibrational sum frequency scattering (SFS) spectroscopy. The relative intensity of different modes, the frequency shift of the uncoupled O-D spectrum, and a low-frequency shoulder (2395 cm -1 ) reveal that water forms an overall stronger hydrogen-bonding network next to hydrophobic droplets compared to bulk water and the air/water interface. Half of the spectral width of the oil droplet SFS spectrum is determined by inter- and intramolecular coupling of water molecules. Isotopic dilution also confirms the presence of a broad distribution (ca. 2640-2745 cm -1 ) of non-water-hydrogen-bonded O-D modes that are red-shifted and broadened compared to similar species at the air/water interface. This band corroborates the presence of charge transfer between water and oil.