http://www.cd-bioparticles.com/p/DiagNano™-Blue-Coloured-Amine-Silica-Particles-15-μm_258_262_294_4018.html15 μm silica particles are available with covalently bound blue dye in the silica matrix. These particles have a hydrophilic surface with terminal Si-OH bonds and are supplied in water without any surfactants.