The local environments at liquid-solid interfaces can be affected by covalently binding organic functionalities on the surface of the solid. Those functionalities may induce solvent-like effects on molecules that reach the surface. To better understand the environmental effects of tethered organic groups at such interfaces, we developed a series of structure–property relationships between functional groups on the pore surface of MCM-41 type mesoporous silica nanoparticles and Stokes shifts of adsorbed solvatochromic dye Prodan. We produced a local polarity scale for functionalized pores by correlating the shifts of the dye inside the pores with its shifts in solvents of known polarities. To validate the scale, we studied the effect of pore polarity on the quenching of Nile Red fluorescence and on the vibronic band fine structure of Pyrene. Because the measurements were done in aqueous suspensions of the loaded particles, we concluded that the dielectric properties inside the organofunctionalized pores are different from those of the bulk solvent. Our findings indicate that the dielectric properties at liquid-solid interfaces are controlled by the nature and density of surface groups and their interactions with the solvent.

Control and quantification of local polarity in nano-confined systems

253rd National Meeting (2017)

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