Fluorescent hybrid assembled with Rhodamine B entrapped in hierarchical vesicular mesoporous silica

Abstract

Vesicular mesoporous silica (VMS) was synthesized using cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulfate (SDS) as co-surfactant templates and then functionalized with (3-aminopropyl)triethoxysilane (APTES) as the silylation reagent through a post-synthesis grafting method. The results showed that the particle size and hierarchical structure of VMS could be modified by adjusting the anionic–cationic surfactant molar ratio and 1,3,5-triisopropylbenzene (TIPB) concentration. Changes in the molar ratio of SDS/CTAB generated a regular VMS comprising a hierarchical structure and two unique inter-cores. Fluorescent hybrid materials assembled with Rhodamine B (Rh B) on VMS or aminopropyl-functionalized VMS (NH2-VMS) were prepared. The hybrid materials were well characterized by Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectra, N2 adsorption–desorption experiments, elemental analysis, 29Si and 13C cross-polarization and magic angle spinning nuclear magnetic resonance, and fluorescence spectra. Rh B was used as a fluorescence unit to study the effect of aminopropyl functionalization on the fluorescence intensity of hybrid materials. We found that the fluorescence intensity of VMS-Rh B was significantly weaker than that of NH2-VMS-Rh B. In addition, compared to VMS2-Rh B and VMS4-Rh B, NH2-VMS2-Rh B and NH2-VMS4-Rh B exhibited blue shifts of fluorescence emission spectra from 588nm to 565nm and 578nm, respectively.