Highly efficient incorporation of amino-reactive dyes into silica particles by a multi-step approach

Simultaneous hydrolysis and condensation of the dye-APS (3-aminopropyltriethoxysilane) precursor and tetraethoxysilane (TEOS) has been developed as a conventional method to incorporate the amino-reactive dyes into silica particles. In this method, doping efficiency of the dyes is usually low (ca. 10%) due to the competitive hydrolysis and condensation of the precursor and TEOS. In this work, we developed a multi-step approach for efficient incorporation of the amino-reactive dyes into silica particles. First, APS was modified on surface of the pre-prepared silica particles and then the dyes were covalently coupled with the amino groups of APS on the particle surface. After further growth of silica protection layer, the dye-doped silica particles showed good colloidal stability, bright luminescence and excellent anti-leaking ability. Doping efficiency of the typical amino-reactive dye such as fluorescein isothiocyanate (FITC) was as high as 91% attributed to the complete separated hydrolysis and condensation processes of APS and TEOS. Such an approach is also applicable to the preparation of the multicolor dye-doped silica particles by the simultaneous coupling of two or more amino-reactive dyes onto surface of the APS modified silica particles.