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Surfaces, Particles, and Structured Liquids - Ultrafast Nonlinear Experiments

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[Technical Report, Final Report]

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Ultrafast infrared nonlinear experiments, particularly two dimensional infrared 2D IR spectroscopy and polarization selective pump-probe PSPP experiments were used to investigate the dynamics of very thin films of room temperature ionic liquids RTIL. The films range in thickness from a few tens of nanometers to two hundred nanometers. The experiments were conducted using an IR probe molecule that reports on the structural dynamics of the films.The dynamics of the films are highly dependent on thickness, with structural rearrangement slowing dramatically as the films are made thinner. Experiments were conducted to study of dependence of the film dynamics on the alkyl chain length of the RTIL cation. The films are spin coated onto functionalized SiO2 coated CaF2 substrates. It was shown that the film dynamics can be controlled by the thickness of the surface functionalized network. The thicker the network, the slower the dynamics for the same film thickness. In another study, the dynamics of water in the nanopores of porous SiO2 particles were investigated with 2D IR, PSPP, and simulations. Pore sizes from 2.8 nm to 8 nm were investigated. The dynamics slow dramatically as the pores become smaller.

Subject Categories:

  • Inorganic Chemistry
  • Test Facilities, Equipment and Methods

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[A, Approved For Public Release]