The resultant suspensions prepared in Section 2.4 and Section 2.5 were mixed at different ratios. CdTe/SiO2-ssDNA and AuNPs-ssDNA were hybridized in a buffer solution of 20 mM Tris-HCl, 50 mM NaCl, and 5 mM MgCl2 (pH = 8.0) at 37 °C, for 12 h under shaking. For detection, an amount of target ssDNA was introduced into the detection solution under shaking for 12 h. The fluorescence spectra of the probe system were measured with an F-7000 Luminescence Spectrometer (Hitachi, Japan). According to Foster’s theory, the FRET efficiency (quenching efficiency, Qe) can be measured experimentally and is commonly defined as [16 (link)]:
where FDA is the integrated fluorescence intensity of the donor in the presence of the acceptor(s) and FD is the integrated fluorescence intensity of the donor alone (no acceptors present).
When the complementary DNA was present, the hybridized structure of probes opens and the fluorescent intensity of detection system recovers. The fluorescent recovery efficiency (Fr) is given as:
where F0 is the fluorescent intensity of the DNA probe, and F is the fluorescent intensity of the DNA probe with target ssDNA.
where FDA is the integrated fluorescence intensity of the donor in the presence of the acceptor(s) and FD is the integrated fluorescence intensity of the donor alone (no acceptors present).
When the complementary DNA was present, the hybridized structure of probes opens and the fluorescent intensity of detection system recovers. The fluorescent recovery efficiency (Fr) is given as:
where F0 is the fluorescent intensity of the DNA probe, and F is the fluorescent intensity of the DNA probe with target ssDNA.