Raman spectra and emission of CdSe/ZnS quantum dots bioconjugated to OC125 antibodies

This paper presents the analysis of photoluminescence (PL) and Raman scattering spectra of CdSe/ZnS quantum dots (QDs) covered by the amine (NH ₂)-derivatized PEG polymer nonconjugated and bioconjugated to ovarian cancer (OC 125) antibodies and localized on the Si substrate. Commercial CdSe/ZnS QDs used are characterized by the color emission with the maxima at 525 nm (2.36 eV) and 605 nm (2.05 eV) at 300 K. PL spectra of nonconjugated 525 nm QDs can be presented as a superposition of PL bands related to exciton emission in CdSe cores (2.36 eV) and to hot electron-hole emission via interface states (2.04, 2.20, 2.71 and 3.06 eV) localized at the CdSe/ZnS or ZnS/polymer interfaces. It is revealed that PL spectra of bioconjugated 525 nm QDs have changed dramatically with essential decreasing the hot electron-hole recombination flow via interface states. This effect is explained on the base of the model deals with re-charging QD interface states at the bioconjugation to OC125 antibodies. Raman scattering spectra of bioconjugated QDs can be presented as a superposition of Raman lines related to the silicon substrate. Raman lines deal with the vibration of COH, CH and OH groups of PEG polymer, which covered QDs, were detected additionally in nonconjugated QDs. It is revealed that the QD bioconjugation to OC 125 antibodies is accompanied by the changes in the intensity of all types of Raman lines. The explanation of details of bioconjugation effects has been proposed and discussed.