The confined orientational motions of fluorescent dye molecules diffusing along one dimension (1D) within individual silica mesopores are investigated by simultaneous single molecule tracking and single molecule emission dichroism methods.  Perylene diimide dyes have been reported to exhibit strong orientational confinement as they diffuse within the nanometer-sized one-dimensional pores of cetyltrimethylammonium bromide (CTAB)-templated mesoporous silica films. It is expected that the Perylene diimide dye molecules are confined to the most hydrophobic regions of the surfactant micelles, and that formation of a water-rich solvent layer at the silica/surfactant boundary may also contribute but evidence for the actual location of the dye molecules is crucial. The polarity sensitive dye Nile Red is employed in spectroscopic single molecule tracking studies to determine the exact location of the dye and Polarization-dependent single molecule tracking is used to show that the Nile Red molecules exhibit the similar orientational confinement as Perylene diimide dye molecules. The spectroscopic single molecule tracking data reveal that the majority of 1D diffusing Nile Red molecules, as well as immobile and 2D diffusing populations are predominantly found in highly nonpolar environments. These results are most consistent with confinement of both the Nile Red and Perylene diimide dyes to the hydrophobic micelle core regions in the center of the pores.<br/>

Spectroscopic single-molecule tracking reveals the one-dimensional diffusion pathways in surfactant-templated mesoporous silica

253rd National Meeting (2017)

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