Near-infrared excitation of CdTe quantum dots based on fluorescence resonance energy transfer and their use as fluorescent sensors

Most of the traditional II-VI quantum dots (QDs) are only excited under short-wavelength light below 600 nm, which limits their applications. We herein report the near-infrared (NIR) excitation of CdTe QDs based on fluorescence resonance energy transfer (FRET). In the FRET systems (UCQDs), UCNPs and QDs were used as energy donors and acceptors, respectively. For UCQDs with different CdTe QDs as acceptors, the new broad QD emission bands were observe under 980 nm excitation, which was due to the FRET from UCNPs to QDs. In addition, the UCQDs were used as fluorescent sensors for dopamine (DA) detection. Experimental results showed that the FRET-sensitized QD emission intensity (at 630 nm, F630) was quenched gradually with the introduction of DA, which was the result of the inhibition of FRET between UCNPs and QDs. Importantly, the F630 was linearly proportional to the DA concentrations in the range from 10 to 300 nM, with a detection limit of 8 nM (S/N = 3), which showed better performance than traditional QDs with UV excitation. Therefore, the results presented in this study not only offer an approach to realizing NIR excitation of QDs but also show good potential for biosensor applications.