Large Stokes-Shift Fluorescent Silica Nanoparticles with Enhanced Emission Over Free Dye for Single Excitation Multiplexing

We describe a polycondensation reaction of silica precursors in a modified Stober-type basic ethanol solution to produce graded Stokes-shift core-shell silica nanoparticles providing bright and spectrally multiplexed sets of fluorescent tags that are excitable using a single excitation source. Dynamic light scattering and scanning electron microscopy demonstrate particle sizes in the sub-10 nm regime. Absorption matched emission comparisons between encapsulated and free dyes in aqueous solution reveal about an order of magnitude per-dye brightness enhancements that are apparent by simply looking at the solutions under laser illumination conditions.