CdSe/ZnS quantum dots with interface states as biosensors

The paper presents the brief review of published results as well as the original study of photoluminescence (PL) and Raman scattering of core-shell CdSe/ZnS quantum dots (QDs) with radiative interface states. First commercially available CdSe/ZnS QDs with emission at 525 nm (2.36 eV), 565 nm (2.20 eV), 605 nm (2.05 eV) and 640 nm (1.96 eV) covered by PEG polymer have been compared in nonconjugated states. PL spectra of nonconjugated QDs are characterized by a superposition of PL bands related to exciton emission in CdSe cores and to hot electron-hole emission via high energy states (2.00, 2.20, 2.37, 2.75 and 3.04 eV). The high energy states were studded using QDs of different sizes and at different temperatures. It is shown that these PL bands related to interface states. Then the CdSe/ZnS QDs with the color emission 525nm and 605 nm have been conjugated with bio-molecules - ovarian cancer (OC 125) and anti Interleukin 10 (IL-10) antibodies, respectively. It is revealed that the PL spectrum of bioconjugated QDs has changed dramatically with essential decreasing the hot electron-hole recombination flow via interface states. The variation of PL spectra at the bioconjugation is explained on the base of electrostatic interaction and re-charging of QD interface states. The Raman scattering study of nonconjugated and bioconjugated QDs has shown that mentioned antibodies are characterized by the dipole moment that provokes the surface enhance Raman scattering effect in bioconjugated QD samples as well.