CdTe semiconductor nanocrystals with 2.5 nm in diameters, as energy donors, were prepared in water. Narrow-disperse
Au nanoparticles with 16 nm in diameters, as energy acceptors, were prepared from gold chloride by reduction. It was
confirmed that the emission spectrum of CdTe ODs and the absorption spectrum of AuNPs had an appreciable overlap.
Therefore, a DNA fluorescence probe system based on fluorescence resonance energy transfer (FRET) from CdTe
quantum dots donors to gold nanoparticles acceptors was designed. CdTe QDs were linked to 5'-NH2-DNA through 1-
ethyl-3-(dimethylaminopr opyl) carbodi-imide hydrochloride (EDC) as a linker, and the 3'-SH-DNA was self-assembled
onto the surface of Au nanoparticles. The hybridization of complementary DNA bound to the QDs and Au nanoparticles
(CdTe-DNA-Au) determined the FRET distance of CdTe QDs and Au nanoparticles. Compared with the fluorescence of
CdTe-DNA, the fluorescence of CdTe-DNA-Au conjugates decreased extremely, which indicated that the FRET
occurred between CdTe ODs and Au nanoparticles. The fluorescence change of this conjugates was depended on the
ratio of Au-DNA and CdTe-DNA, when the AuNPs-DNA to QD-DNA ratio is 5:1, the FRET efficiency reached a
maximum. If a complementary single stranded DNA was add to the CdTe-DNA-Au conjugates, the fluorescence of the
probe system would have a certain degree recovery, this showed that the distance between CdTe QDs and Au
nanoparticles was increased.