Ratiometric sensor based on imprinted quantum dots-cationic dye nanohybrids for selective sensing of dsDNA.

A ratiometrically responsive sensor for dsDNA is reported, based on molecularly imprinted polymer coated quantum dots (MIP-QDs). A new platform is described for probing dsDNA by tracing the "turn on" fluorescence signal of malachite green (MG) as a cationic dye and "turn off-on" room temperature phosphorescence (RTP) signal of MIP-QDs/MG nanohybrids. The interaction between MIP-QDs surface and MG discloses an intense quenching in RTP (turning off) by a phosphorescence resonance energy transfer (PRET) process. After the addition of dsDNA, MG molecules escape from the MIP-QDs surface and intercalate into the dsDNA, resulting in the restoration of RTP intensity of MIP-QDs (turning on) and also enhancing in fluorescence of MG. This outcome hereby can be employed for the selective sensing of dsDNA via optical response. The ratio of fluorescence enhancement of MG to RTP intensity of MIP-QDs is proportional to the concentration of dsDNA in the range of 0.089-1.79 μg/mL with a detection limit (3σ/K) of 19.48 ng/mL under the optimized experimental conditions.