http://www.cd-bioparticles.com/p/DiagNano™-Blue-Fluorescent-Carboxyl-Silica-Particles-500-nm_258_262_293_3976.html500 nm fluorescent silica particles with carboxylic acid groups (COOH) on the surface. Fluorescence dyes are covalently bound in the silica matrix and availbale with blue fluorescence (excitation: 354 nm, emission: 450 nm).