Fig. 1. TEM images of BP nanosheets

Fig. 2. Fluorescence intensity of DNA aptamer labeled with different fluorescence concentrations

Fig. 3. Fluorescence quenching effects of BP nanosheets with different concentrations on CdTe quantum dots

Fig. 4. Effect of cell number on restoration of fluorescence intensity

Fig. 5. Fluorescence intensities at 520 nm under different number of cells

Fig. 6. Fluorescence intensities under different conditions

Fig. 7. Schematic of fluorescence quenching and restoration. (a) Fluorescence of specific DNA-aptamer can be restored with the addition of target cells; (b) fluorescence of random-DNA sequence can not be restored with the addition of target cells