It has been widely recognized that local environment has important effects on the behavior of molecules in condensed phases. These effects may be even more important within nanoconfined systems where spatially constrained guest molecules interact with their hosts and co-encapsulated solvent. In this study, the effects of local environment on guest molecules confined within the pores of MCM-41 type mesoporous silica nanoparticles (MSN) were investigated. Different types of local environments were created within the pores of MSN via co-condensation of tetraethoxysilane with organosilanes having varying dipole moments. The local polarities produced within the pores of MSN were then probed using the solvatochromic dye Prodan. The varying degrees of stabilization of the zwitterionic excited state of Prodan by microsolvation led to changes in the fluorescence emission of the dye. These changes were employed as indicators of the polarity of the mesopores. Local polarity was determined by comparison with fluorescence measurements of the dye in different solvents, deriving values based on solvent polarity scales. Computational studies were carried out to further understand the interaction of the dye with the functionalized silica surfaces. Two other solvatochromic probes, Nile Red and Pyrene, gave results consistent with those obtained with Prodan suggesting that mesopore polarity could indeed be controlled by co-condensation of organosilanes. We believe that fine-tuning mesopore polarity of MSNs will enhance their scope of applications in many different fields.

Investigation on the local environment of functionalized mesoporous silica nanoparticles using fluorescence instrumentation

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.