Application of CdTe/CdS core-shell quantum dots in a DNA fluorescence probe

CdTe/CdS core-shell quantum dots (QDs) with 12 nm in diameters were synthesized in water, and Au nanoparticles (AuNPs) with 25nm in diameters were prepared by reduction of sodium citrate. Compared with the fluorescent of CdTe core QDs, the fluorescent of CdTe/CdS core-shell QDs was increased about one times, which suggested the advantage of CdTe/CdS core-shell QDs in fluorescence application. It was confirmed that the fluorescence emission spectrum of CdTe/CdS QDs and the UV-Vis absorption spectrum of AuNPs had an obvious overlap, which indicated that a novel DNA probe based on fluorescence resonance energy transfer (FRET) from CdTe/CdS QDs donors to AuNPs acceptors could be designed. 3'-SH-DNA were assembled onto the surface of AuNPs by Au-S bond (Au-DNA), and CdTe/CdS QDs were linked to 5'-NH2-DNA (partly complementary with 3'-SH-DNA) by Schiff's reaction (CdTe/CdS-DNA). Then, the distance between donors and acceptors of DNA probe was controlled within 1-10 nm by hybridization of CdTe/CdS-DNA and Au-DNA, which resulted in a FRET from CdTe/CdS QDs to AuNPs according to Forster theory, so the fluorescent of probe was extremely decreased compared with CdTe/CdS-DNA. The detection ability of this novel probe was investigated by fluorescence emission spectrum when target DNA (completely complementary with 3'-SH-DNA) existed.

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