Carboxyl-functionalized eFluor® Nanocrystals, composed of either CdSe or cadmium-free InGaP, are functionalized nanocrystals that can be easily conjugated to proteins, oligonucleotides and other biomolecules of interest using simple binding chemistries and easy-to-complete protocols. The straightforward procedures are designed to allow the user to apply eFluor® Nanocrystal technology in a wide variety of assay types, such as immunoassays, protein interaction assays, and other fluorescence-based detection assays.