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revised on 19.02.2019 and posted on 19.02.2019by Haoyuan Wang, Wenfan Chen, Jackson Wagner, Wei Xiong
We report, for the first time, observations of mesoscopically
homogeneous but macroscopically heterogenous water dynamics in self-assembled
materials by a new, spatially resolved infrared (IR) pump vibrational sum
frequency generation (VSFG) probe microscope. Using this new technique, we spatially
resolved dynamics of water bounded by host-guest, self-assembled sheets comprised
of sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD). We found that the strong hydrogen-bond interactions
and nearby water not only template nearby water networks to adopt the chirality
but also allow resonant energy transfer from β-CD to nearby water. More interestingly, the resonant
energy transfer dynamics are heterogeneous among domains, while remaining
uniform within domains. This surprising result indicates that the water near
self-assembled materials can be templated uniformly across micron domains. Because
SDS@2β-CD is a synthetic analogue that parallels the morphology, rigidity and
crystallinity of protein assemblies, similar mesoscopic ordering of water
structure and dynamics could also exist in biological soft materials. The
advancement of adding spatial resolution to ultrafast molecular vibrational
spectroscopy opens a new way to probe mesoscopic molecular structure ordering
and relaxation dynamics in biological systems, and hydro-responsive
self-assembly materials for micro-optics and electronics.