http://www.cd-bioparticles.com/p/DiagNano™-Red-Fluorescent-Silica-Particles-1-μm_258_262_293_3906.html1 µm silica particles with fluorescence dye covalently bound in the silica matrix are availbale with red fluorescence (excitation: 569 nm, emission: 585 nm). These particles have a hydrophilic surface with terminal Si-OH bonds.