Design of doped hybrid xerogels for a controlled release of brilliant blue FCF

We investigate a controlled release of brilliant blue FCF (BBF)(1) from doped hybrid xerogels by considering the effects of release media, precursors, and dopants. The three release media used are acidic, neutral, and basic solutions. In the xerogel preparation, tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), vinyltriethoxysilane (VTES), propyltriethoxysilane (PTES), and phenyltriethoxysilane (PhTES) are used as precursors, and cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and hydroxypropyl cellulose (HPC) as dopants. Our experimental results suggest that BBF release can easily be controlled by using organosilanes as well as TEOS as precursors and/or by adding dopants. The released amount of BBF from organically modified xerogels is usually lower than that from TEOS-based xerogels. For different dopants, the released amount is in the order of SDS > HPC similar to without dopant > CTAB. We find that the experimental results can be well explained by considering the textural properties of the xerogels and the electrostatic, hydrophobic, and aromatic-aromatic interactions between BBF and xerogel matrices/ dopants. (C) 2004 Elsevier B.V. All rights reserved.