fig3

Figure 3. (A) Schematic diagram of ratiometric fluorescence for visualizing THC and its metabolite; (B) A smartphone-based portable fluorescence capture device; (C) Signal response of the sensor upon exposure to different target concentrations. THC: Tetrahydrocannabinol; THC-COOH: 11-nor-9-carboxy-tetrahydrocannabinol; QDs: quantum dots.