Abstract
Two-dimensional infrared spectroscopy (2D-IR) was used to investigate the sensitivity of a vibrational mode to spectral diffusion on the nanometer length scale. A confined volume within a porous silica nanoparticle was used as the model system. Utilizing a novel grafting technique, silane probes were covalently secured to the pore surface for a series of templated mesoporous silica nanoparticles with variable pore sizes. 2D-IR measurements determined that isopropanol exhibited two dominant time scales of ultrafast motions within the pores with time scales of a few picoseconds and tens of picoseconds. The unique perspective of the probe on a surface revealed that the vibrational dynamics of the reporting mode were perturbed by molecules up to μ5 nm away. The data were modeled well by a 1/d2 distance dependence for the coupling of solvent dynamics to frequency fluctuations and a logistic radial distribution of fast and slow dynamic populations.
Original language | English (US) |
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Pages (from-to) | 25135-25144 |
Number of pages | 10 |
Journal | Journal of Physical Chemistry C |
Volume | 119 |
Issue number | 45 |
DOIs | |
State | Published - Nov 12 2015 |
Bibliographical note
Publisher Copyright:© 2015 American Chemical Society.