Efficient Synthesis of Yellow-Green Carbon Quantum Dots as a Sensitive Fluorescent Probe of Folic Acid.

Bright yellow-green carbon quantum dots (YGCDs) have been successfully synthesized by a simple and efficient hydrothermal method. Their luminescent absolute quantum yield reached 30.0% in 4 h. Compared with commonly reported solvothermal methods, the synthesis time was reduced by more than 70% by using tin oxide nanoparticles as a catalyst. Moreover, the fluorescence of YGCDs could be selectively quenched by folic acid (FA) molecules, and the relative fluorescence intensities of F/F0 was fitted perfectly in line decay curve versus the concentration of FA in the range of 2.0×10-8  mol/l to 1.0×10-5  mol/l (R2 =0.9988). The detection limit of FA was below 2.0×10-8  mol/l, suggesting a promising fluorescent probe of folic acid.