Radiative interface state study in CdSe/ZnS quantum dots covered by polymer

The paper presents the transformation of photoluminescence (PL) spectra of nonconjugated and bioconjugated core/shell CdSe/ZnS QDs covered by PEG polymer at the aging in ambient air. Studied QDs are characterized by the sizes: (i) 3.6-4.0 nm and color emission with the maxima at 560-565 nm (2.19-2.25 eV) and (ii) 5.2-5.3 nm and with emission at 605-610 nm (2.02-2.08 eV). The part of 565 nm CdSe/ZnS QDs has been bioconjugated to the mouse anti PSA (Prostate-Specific Antigen) antibodies and the part of 605 nm QDs has been bioconjugated to the antihuman IL10 (Interleukin 10) antibodies using the commercially available 565 nm and 605 nm QD conjugation kits. It is revealed that the aging process in ambient air has the very strong impact on PL spectra of nonconjugated core/shell CdSe/ZnS QDs covered with PEG polymer. The aging process relates to the polymer modification in ambient air that is accompanied by the three effects: (i) polymer transparency increasing for the emission of CdSe cores (2.03 or 2.20 eV), (ii) the intensity stimulation of high energy PL bands (2.37, 2.73 and 3.06 eV) related to the interface states at the ZnS/PEG polymer interface and (iii) the elastic strain modification in QD systems. The concentration of interface states at the ZnS/polymer interface increases at the aging of PEG polymer in ambient air.