Single molecule tracking (SMT) and emission polarization (SMEP) measurements are used to study the translational and orientational motions of fluorescent molecules dispersed within ordered, oriented mesoporous silica.  Our goal is to better understand the mechanisms of molecular diffusion within these materials, at the single-pore level.  Mesoporous films are prepared by spin coating of surfactant-templated silica sols.  SMT results, employing perylene diimide (PDI) dyes, depict a predominance of one-dimensional translational motion, reflecting confinement of the dye within aligned, cylindrical mesopores.  Simultaneously acquired SMEP data show that the orientational motions of the PDI dyes are also confined.  Wobbling angles can be measured to within �7o from the SMEP data, allowing for the effective diameter of individual pores to be estimated to within �0.4 nm.  Ensemble averaged results show the effective pore size is much smaller than expected.  Strong confinement of PDI orientational motions is attributed to nanostructuring of the pore filling medium.

Super-resolution single-molecule measurements of effective pore size in mesoporous silica films

248th National Meeting (2014)

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