This article presents the analysis of photoluminescence (PL) spectra of CdSe/ZnS quantum dots (QDs) with and without bioconjugation to biomolecules, Interleukin 10 (IL10) antibodies. Commercial CdSe/ZnS QDs used in the study are characterized by the color emission with the maximum at 605 nm (2.05 eV). It is shown that PL spectra of nonconjugated QDs can be presented as a superposition of PL bands dealing with exciton emission in the CdSe core and electron-hole emission via defect states at the CdSe/ZnS interface. The comparison of PL spectra of such type of CdSe/ZnS QDs with and without bioconjugation gives the opportunity to detect the bioconjugation without mistake. Moreover the electrostatic mechanism of bioconjugation process follows from the analyses of PL spectra of CdSe/ZnS QDs. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3032904]