Characterization of as-synthesized mesoporous silica using NMR and solid-state fluorescence spectroscopy

In this study, as-synthesized mesoporous silica preloaded with pyrene was synthesized, and then its physical properties and molecular state of pyrene were evaluated. The product had mesoporous structure from small-angle X-ray scattering and scanning electron microscopy measurements. Nitrogen gas adsorption and solid-state NMR measurements confirmed that the pore spaces were filled with Pluronic P123 (P123) and pyrene. Mobility of P123 inside the pore was investigated by solid-state NMR measurement. Mobility of hydrophilic PEO chain decreased in the pore. Solid-state fluorescence measurement was used to examine the encapsulation state of pyrene. Molecular state of pyrene was compared before and after the calcination process. At a low loading amount, pyrene-loaded calcined mesoporous silica showed the superior excimer emission, whereas pyrene-loaded as-synthesized mesoporous silica gave the predominant monomer emission. The results revealed that the presence of P123 could contribute to the dispersion improvement of pyrene at the molecular level.