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 Stöber‐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. The formation of fluorescent coreshell silica nanoparticles with diameters