A sol-gel approach including partially removing capping agents, depositing SiO2 monomers, and growing a SiO2 shell was developed to generate a bio-compatible functionalization on CdTe quantum dots (QDs). The QDs retained their high photoluminescence (PL) efficiency after coating with a SiO2 shell (22.5%) by controlling the surface state of the QDs to decrease PL degradation during a sol-gel preparation. Furthermore, the CdTe QDs with a SiO2 shell were conjugated with IgG using 3-sulfo-N-hydroxysuccinimide or streptavidin-maleimide as linkers. The biotin-streptavidin linker resulted in a high PL efficiency retained (only similar to 23% lower than the initial value of the QDs), which is crucial for bio-applications. (c) 2010 Elsevier Inc. All rights reserved.